Pain Perception at Different Stages of Orthodontic Treatment

Doctoral dissertation

To be presented by permission of the Faculty of Medicine of the University of Kuopio

for public examination in Auditorium L22, Snellmania building, University of Kuopio,

on Saturday 19th September 2009, at 12 noon

Faculty of MedicineInstitute of Biomedicine, Department of Physiology

University of Kuopio

FARSHAD DALILI

Pain Perception at DifferentStages of Orthodontic Treatment

JOKAKUOPIO 2009

KUOPION YLIOPISTON JULKAISUJA D. LÄÄKETIEDE 452KUOPIO UNIVERSITY PUBLICATIONS D. MEDICAL SCIENCES 452

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Series Editors: Professor Esko Alhava, M.D., Ph.D. Institute of Clinical Medicine, Department of Surgery Professor Raimo Sulkava, M.D., Ph.D. School of Public Health and Clinical Nutrition Professor Markku Tammi, M.D., Ph.D. Institute of Biomedicine, Department of Anatomy

Author´s address: Sii l injärvi and Maaninka, Health Centre Department of Dentistry Kasurilantie 3 FI-71850 SIILINJÄRVI FINLAND

Supervisors: Professor Matti Närhi, DDS., Ph.D. Institute of Biomedicine, Physiology Section University of Kuopio

Professor T. Maija Laine-Alava, DDS., M.Sc., Ph.D. Secretary General, Finnish Dental Society Helsinki

Reviewers: Professor Will iam Proffit , DDS., M.Sc., Ph.D. School of Dentistry, University of North Carolina, Chapel Hil l , North Carolina, U.S.A.

Professor Mauno Könönen, DDS., M.Sc., Ph.D. School of Dentistry, Department of Physiology and Prosthetics University of Helsinki

Opponent: Professor Timo Peltomäki, DDS., M.Sc., Ph.D. School of Dentistry, Department of Orthodontics and Pediatric Dentistry University of Zurich, Switzerland

ISBN 978-951-27-1172-7ISBN 978-951-27-1209-0 (PDF)ISSN 1235-0303

KopijyväKuopio 2009Finland

Dalili, Farshad. Pain perception at different stages of orthodontic treatment. Kuopio University Publications D. Medical Sciences 452. 2009. 99 p. ISBN 978-951-27-1172-7 ISBN 978-951-27-1209-0 (PDF) ISSN 1235-0303 ABSTRACT The purpose of the present study was to assess pain experience as reported by the patients during different stages of orthodontic treatment. Further, the aim was to examine the extent of which the sensitivity of the dental pulp might be affected by orthodontic treatment and if such changes could explain the mechanisms and origins of the pain symptoms. The study group consisted of 64 voluntary patients, 46 females and 18 males, with a mean age of 26.4 (SD 11.1) years. Patients were requested to fill out a structured questionnaire for three consecutive days after the insertion of orthodontic separators, after the initial archwire placement, and after the archwire activation. The intensity (mild, moderate, severe), quality (sore, shooting, dull, ache) and the duration (short, long) of the pain symptoms in connection with seven items were evaluated, namely: eating sweets, having hot or cold food/drink, tooth brushing, mastication of food, fitting anterior and fitting posterior teeth together. Clinical study regarding tooth sensitivity included measurements of the electrical thresholds with a constant current stimulator and cold sensitivity with an electrothermal device at 0ºC and 15ºC. A 100 mm Visual Analogue Scale (VAS) was used to assess the intensity of the cold responses to cold. Tooth movement/s were measured using the irregularity index (Little 1975) for the anterior teeth (canine to canine), in addition to tooth movements (mm) into the extraction spaces after three months of orthodontic force application. Proportion of the patients who had experienced pain was 70% after insertion of the separators, 96% after placement of the initial archwire and 69% after archwire activation, with the highest proportions during the first day after each procedure. The intensity of pain was mostly reported to be mild 62.5%, followed by moderate 28.5% and severe 9%, respectively. Regarding the quality the sensory experience was described as sore, shooting, dull and ache in 63.5%, 14.3%, 14.3% and 7.9% of the reports, respectively. Duration of pain was mostly short, in 85% of the sample. Regarding the listed items, mastication of food, fitting anterior and posterior teeth together, tooth brushing, cold and hot food/drink and sweets, in descending order, gave the most frequent pain reports. Dental electrical thresholds were generally unchanged before, during and after different orthodontic procedures. Proportion of teeth responding to the cold sensitivity tests as well as the intensity of the pain responses were higher at 0ºC than 15ºC, and were associated with the pain experienced at different stages of orthodontic treatment. In general the differences in the prevalence of the pain and the tooth movement with regards to anterior crowding, between the two different fixed orthodontic appliances were small. However, there was a difference in tooth movements into extraction spaces between the two fixed orthodontic appliances. It is concluded that 1) pain symptoms are common and the prevalence of such experiences varies at different stages of orthodontic treatment, insertion of the initial archwire being the most painful stage, 2) the intensity of the experienced pain was mostly mild followed by moderate pain reports and less frequently severe pain, 3) the induced pain is mostly due to periodontal nociceptor responses which is reflected by the frequent pain reports during mastication and fitting teeth together, 4) increased dental sensitivity to cold due to sensitization of the pulpal nerves suggests also pulpal involvement which seems to partly explain the origin of the pain symptoms in connection with orthodontic treatment, and finally 5) slight differences in the applied forces, due to the use of different initial archwires, provoked no apparent increase either in the pain experienced by the patients or in the dental sensitivity.

National Library of Medicine Classification: WU 400, WL 704 Medical Subject Headings: Dentistry; Orthodontics; Tooth Movement; Pain; Facial Pain; Toothache; Analgesia; Pain Measurement; Questionnaires

ACKNOWLEDGMENTS I would like to express my deepest gratitude to the supervisors of this study, Professor Matti Närhi DDS., Ph.D., for his discerning professional advice in many theoretical and practical matters. He always has had time for my questions and guided this work with warmth and supporting encouragement. My sincere thanks to Professor T. Maija. Laine-Alava DDS., MSc., Ph.D., for the supporting optimism and professional guidance until the end. Helping me realize the importance of pain control in orthodontics. I wish to extend appreciations to Professor William Proffit DDS., MSc., Ph.D., of the University of North Carolina, USA, the official reviewer of this study who blessed me with his constructive comments and criticism of the manuscript. My thanks to Professor Mauno Könönen DDS., Ph.D., of the University of Helsinki, the official reviewer for his constructive comments. This study was carried out at the Departments of Orthodontics and Physiology of University of Kuopio and at the Department of Oral Development and Orthodontics, Institute of Dentistry, University of Turku, and finalized at the Institute of Biomedicine, Physiology Section, University of Kuopio, Finland. I am grateful to Professor Juha Varrela DDS., MSc., Ph.D., Head of the Department of Oral Development and Orthodontics of University of Turku, Finland, for his support. To the personnel of the Orthodontic Department and all the patients and their parents who volunteered to participate in this study I owe my warmest thanks. The orthodontic materials of this work have been supported partly by Ormco and GAC international, which I acknowledge with gratitude. Many thanks to Dr. Anthony Viazis DDS., MSc., of Dallas, Texas, USA, for introduction of his approach to fixed orthodontic therapy. My thanks to Seppo Lammi, Head of the Department of Computer Sciences of the University of Kuopio for his guidance and advice with the statistical analyses. I owe my special thanks to Riitta Myllykangas for all the efforts she has put in to this study. I wish to thank my teachers and colleagues at the University of Kuopio for their support. Dr. Veijo Miettinen former head of the Dental Clinic, acting Professor Dr. Pauli kilpeläinen Ph.D., Dr. Armando Gale Associate professor, Dr. Riitta Pahkala Ph.D., Associate professor. Many thanks to my dear family for their loving support during this work. To my lovely sons Niku and Sam who have provided me with the encouragement for all strivings in my life. I owe my warmest thanks to my dear wife Dr. Najin Atashkari DDS., MSc., who has been strongest supporter of this study by taking care of every other detail in our lives to provide me the precious time I needed to finalize this research. September 2009, Farshad Dalili

CONTENTS ACKNOWLEDGMENTS 1. INTRODUCTION 2. REVIEW OF LITERATURE 2.1. Mechanism of the pain symptoms related to orthodontic treatment 2.2. Optimal forces for tooth movements 2.3. Dental pulp reactions to orthodontic forces 2.4. Variation of the perceived orthodontic pain with age and gender 2.5. Measurement of tooth sensitivity 2.6. Management of orthodontic pain 3. AIMS OF THE PRESENT STUDY 4. SUBJECTS AND METHODS 4.1. Subjects 4.2. Orthodontic mechanotherapies used for the study subjects 4.3. The questionnaire 4.4. Clinical examination 4.4.1. Dental electrical threshold measurement 4.4.2. Testing thermal sensitivity of the teeth 4.5. Measurement of tooth movement from hard stone casts 4.6. Study protocol 4.7. Statistical methods 5. RESULTS 5.1. Subjective pain experience during orthodontic treatment as reported in

the questionnaires 5.1.1. Prevalence of the pain 5.1.2. The intensity, quality and duration of the pain 5.1.3. Pain experienced during the three days subsequent to each orthodontic procedures 5.1.4. Pain experienced in relation to different stimuli of the questionnaire 5.1.5. The relationship between subjective pain reports and the analgesic consumption 5.1.6. Relationship between subjective pain reports and age, gender, extraction(s) and the extent of treatment 5.2. Clinical study 5.2.1. Responses to cold stimulation 5.2.1.1. Correlations between the VAS ratings to cold stimulation at

0 and 15ºC

5.3. Comparison of two different orthodontic mechanotherapies 5.3.1. Dental cold sensitivity and electrical thresholds in two different orthodontic mechanotherapies 5.3.2. Tooth movements in two different orthodontic mechanotherapies 6. DISCUSSION 6.1. Study subjects 6.2. Measurement of the experienced pain 6.2.1. The questionnaire 6.2.2. Subjective pain symptoms related to different orthodontic procedures 6.2.3. Intensity, quality and duration of the pain symptoms 6.2.4. Analgesic consumption 6.2.5. Dental pain sites 6.2.6. The relationships between the pain symptoms during initial tooth movement and age, gender, and treatment approach 6.3. Clinical study 6.3.1. Electrical tooth stimulation 6.3.2. Cold sensitivity tests 6.3.3. Comparison of different fixed oerthdontic appliances 7. SUMMARY AND CONCLUSIONS REFERENCES APPENDIX

1. INTRODUCTION

Pain is perhaps even older than mankind. There is a reason to believe that it is inherent in any life

linked with consciousness. Evidence indicates that man has suffered this affliction since his

beginning, for one finds testimony to the existence of pain in the chronicles of all races (Fulöp-

Miller 1938). The international Association of the Study of Pain has defined pain as: “an

unpleasant sensory and emotional experience associated with actual or potential tissue damage or

described in terms of such damage” (Wall and Melzack 1994).

Accordingly, pain is a complex experience that includes sensations evoked by noxious stimuli and

the reactions to such stimuli. The subjective reactions vary among individuals and can depend on a

person’s cultural background, past experiences, and other forms of psychologic input that give

meaning to a situation in which pain occurs (Burstone 1985).

Pain and pain control are important to dental profession, since general perception of public is that

dental treatment and pain are inseparable and go hand in hand. Orthodontic tooth movement

requires application of force to the tooth, which generally causes pain (Walker et al. 1987) although

not much knowledge exists on the intensity and quality of such pain symptoms. Because of its

obvious importance in orthodontics, one would assume a large volume of research on the treatment

of the related pain, which unfortunately is not the case. The intensity of the pain symptoms has been

studied to some extent (Tayer and Burek 1981, Ngan et al. 1989 and 1994, Brown and Moerenhout

1991, Jones and Chan 1992, Scheurer et al. 1996). However, there is little knowledge on the quality

and duration of such symptoms and their significance regarding the treatment.

The discomfort related to tooth movement is a subject little discussed by clinicians and given little

attention in orthodontics. There are reports that one of the discouraging factors for seeking

orthodontic treatment is the individual’s fear for the related pain and discomfort (Oliver and Knap-

man 1985). In most cases, the quality and extent of the information about orthodontic treatment and

the related discomfort seems to be satisfactory, but still many people report not having been well-

informed prior to the procedures (Oliver and Knapman 1985).

The control of pain in orthodontic therapy should include adjusting the forces to a level below the

pain thresholds. Unfortunately, such low forces would have very little if any effect on the tooth

movement. To alleviate the pain and discomfort clinicians have tried different approaches: a

conventional pharmacological analgesia (Simmons and Brandt 1992), physiologically by having

9

patients to chew on something fairly hard for example a plastic wafer (Furstman and Bernick 1972),

analgesic chewing gums (White 1984), transcutaneous electrical nerve stimulation (TENS, Roth

and Thrash 1986), low level laser therapy (Lim et al. 1995), and magnetic force fields (Blechman

1998).

The initial pain/discomfort experienced during orthodontic treatment for the first couple of days

after force application is a generally accepted observation. Many factors have been thought to affect

the extent of the symptoms, namely the intensity and duration of forces applied, age, gender, the

degree of crowding of the arch/es, patient’s psychological background and past experiences. There

is a traditional belief of the existence of a causal relationship between the amount of the force

applied to the tooth and the severity of the pain experience.

It seems to be a general assumption that the only sources for the pain in connection with orthodontic

treatment are the periodontal tissues or, more generally, tissues outside the tooth pulp. However,

many studies indicate that the pulp circulation and tissue metabolism and even vitality may be

affected or compromised by the applied forces (Butcher and Taylor 1952, Stenvik and Mjör 1970,

Biesterfield et al. 1979, Hamersky et al. 1980, Labat et al. 1980, Unterselher et al. 1987). Dental

electrical thresholds as an indicator of tooth vitality have been studied, however, not as a measure of

possible sensitivity changes in the pulpal nerves. The possible changes in the pulp nerve sensitivity

and their connection to orthodontic pain symptoms have evoked little attention.

Technological advances have long influenced orthodontic mechanotherapy approaches.

Introduction of superelastic, heat-activated archwires to orthodontics, claims to enable the

practitioner to reduce the treatment time by combining different stages of orthodontic treatment

done separately earlier, namely alignment, leveling and tooth movement (Viazis 1993, 1995, 1998).

The extent of which such approach might affect the type and amount of the tooth movement, the

perception of pain and discomfort experienced, and also the tooth responses, is not known. The

orthodontic profession needs critical clinical data on the relative efficiencies of different

biomechanical strategies of tooth movement. From a cost-benefit point of view, orthodontic

treatment should be performed as quickly as possible without jeopardizing the affected tissues. A

major question is which approach provides minimum discomfort, the most rapid orthodontic tooth

movement with the least damage to the teeth and the supporting structures.

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2. REVIEW OF LITERATURE

2.1. Mechanism of the pain symptoms related to orthodontic treatment.

Nociceptive afferents transmit their messages to the central nervous system at different rates,

depending on the size and type of the axons. Both myelinated (A-type) and unmyelinated (C-type)

nerve fibers enter the pulp and periodontium (Reader and Foreman 1981, Holland and Robinson

1983, Byers 1984). A δ-fibers have diameters that vary between 2-4 and 20 microns with the

conduction velocity of upto 30 meters per second. A -fibers are present in somatic and visceral

nerves. They carry mechnoreceptive signals, pressure and proprioceptive impulses at the speed that

may exceed 100 meter per second. The unmyelinated C-fibers have a smaller diameter, up to 2

microns. Majority of them carry nociceptive signals but at a lower speed, approximately 0.5-2.5

meters per second.

Functional differences between, as well as their differences in the character of the tooth pain

associated with pulpal A- and C-fibers have been reported (Närhi 1985a, b, Jyväsjärvi and Kniffki

1987, Närhi et al. 1992a, b). Hydrodynamic mechanism, which is believed to activate A-fibers, is

most probably responsible for dentin sensitivity. C-fibers are activated by a direct effect of thermal,

mechanical and chemical irritants, for example, by bradykinin and histamine (Närhi 1985, Närhi et

al.1992). Heat stimulation induces an immediate sharp pain, which is due to A δ-fiber activation,

and a delayed dull pain indicative of C-fiber activity (Närhi et al. 1982a, 1984, Närhi 1985a,

Jyväsjärvi and Kniffki 1987). A δ-fibers are thought to be involved in the mediation of pain in the

initial phases of pulpal inflammation (sharp pain), the dull pain induced during the later phases is

probably due to C-fiber activation (Mumford 1982, Närhi 1985, Olgart 1985).

Release of neuropeptides has been suggested to be related to the activation of C-fibers and some

small diameter A δ-fibers (Byers et al. 1992b, Närhi et al. 1994, Byers and Närhi 1999).

Prostaglandins have been shown to increase intradental nociceptor sensitivity to thermal stimulation

and cause hyperalgesia (Ahlberg 1978) as do some other inflammatory mediators activated or

released in connection with tissue injury (Närhi et al. 1992, 1994). It is probable that inflammatory

reactions and nerve sensitization also take place in the periodontal tissues (Yamaguchi and Kasai

2005), although such responses in the PDL have been much less studied than the pulp nerve

reactions. Thus, tissue injury and consequent inflammation of gingival and periodontal tissues

during orthodontic treatment could lower pain threshold by inducing nociceptor sensitization. These

11

tissues may then become responsive to stimuli that would not ordinarily evoke any pain reaction

(Ngan 1994).

During orthodontic tooth movement the collagen fibers of periodontal ligament are disrupted, with

some part of the ligament undergoing compression and others tension. Initial healing of wounds in

the periodontal ligament begins with blood clot and granulation tissue formation subsequent to

necrosis regardless of the type of the periodontal challenge (Sismanidou et al. 1996). Organization

of granulation tissue follows, during which vascular and nervous components (Parlange and Sims

1993) as well as new periodontal connective tissue (Melcher 1970, 1976, Line et al. 1974, Caton

and Nyman 1980, Harison and Jurronsky 1991, Wikesjo et al. 1992) enter the area.

It has been suggested that the periodontal ligament nociceptive nerve fibers perform two main

functions: transmission of pain impulses centrally (Mengel, Jyväsjärvi and Kniffki 1992, 1993) and

release of neuropeptides peripherally (Davidovitch 1991). Närhi (1978) recording from the single

pulpal nerve fibers, found that an increase in the tissue pressure increases sensory nerve activity.

However, our knowledge regarding the function of the periodontal nociceptors is limited. It has

been shown, however, that they respond to strong forces applied to the tooth (Mengel, Jyväsjärvi

and Kniffki 1992, 1993). Khayat et al. (1988) suggested that after pulp tissue injury sprouting of the

nerve fibers in the pulp and apical periodontium might potentiate dental pain sensitivity by

multiplying the receptor sites.

The increase in the expression of Calcitonin Gene-Related Peptide (CGRP) and Substance P (SP)

during the first two days after application of an orthodontic force in the rat (Kvinnsland et al. 1990,

Norevall et al. 1995) is interesting, considering the findings in clinical human studies that show pain

symptoms reaching the peak approximately one to two days after force application (Furstman and

Bernick 1972, Wilson et al. 1989, Ngan et al. 1989, 1994, Jones and Chan 1992).

Pain connected to orthodontic tooth movement most probably originates from the periodontal

tissues due to mechanical injury and consequent inflammatory reaction. However, also intradental

nociceptive nerves may be involved because periodontal inflammatory reactions may spread to the

pulp due to formation and diffusion of various inflammatory mediators, and neurogenic

inflammation mediated by branching axons, which are known to innervate both the pulp and

periodontal ligament (Byers 1984, 1985, 1994, Byers et al. 1992b, Yamaguchi and Kasai 2005).

Moreover, as already mentioned, nerve sprouting also takes place within the pulp in response to

orthodontic forces, which may affect the functional properties of the intradental nerves. Also,

12

possible impairment of the pulpal blood flow due to vessel compression may play a role.

As already mentioned due to the neurogenic effects transmitted by branching axons innervating

both the pulp and PDL, the effects of periodontal tissue injury may also be reflected in the pulp. To

what extent pulpal inflammatory reactions and consequent increase in intradental nerve sensitivity

play a role in the pain responses to orthodontic tooth movement is not known.

2.2. Optimal forces for tooth movement

Many investigators have reported a relationship between the magnitude of applied force and

different types of tooth movement (Smith and Storey 1952, Reitan 1957, 1960, Burnstone and

groves 1961, Andreasen and Johnson 1967, Hixon et al. 1969, 1970, Mitchell et al. 1973,

Andreasen and Zwanziger 1980, Maltha et al. 1993, Owman-Moll et al. 1995, 1996, Bergius et al.

2002).

The term optimum orthodontic force is usually regarded as meaning the force that moves teeth most

rapidly, with the least discomfort to the patient and least damage to the teeth and their investing

tissues. In 1932 Schwarz stated that biologically the most favorable treatment is that which works

with forces not greater than the pressure in the blood capillaries. Oppenheim (1944) and Reitan

(1959) have also reported the optimal force levels based on capillary blood pressure in the

periodontal membrane. Schwartz (1932) in his experience, recommended light, continuous forces

because he was of the opinion that this prevents the formation of resorption-resistant osteoid bone

and certain reparative processes on the side toward which tooth moves. Burstone (1985)

characterized optimal force by maximal cellular response from the tooth supporting tissues,

including apposition and resorption of alveolar bone, at the same time as the maintenance of the

vitality of these tissues is secured. Thus, the amount of tooth movement is not the only indicator of

optimal force.

Light differential forces for tooth movement have been recommended, the assumption being that a

differential movement of the teeth can generally be achieved. Moreover, it is generally thought that

light forces are somewhat more efficient and more biologic and, hence, less painful (Storey and

Smith 1952, Reitan 1956). Reitan (1957, 1960, 1964, 1985) has always been a spokesman for light

forces, especially at the initial stages of tooth movement, to minimize adverse tissue reaction.

However, Hixon et al. (1969) found such a wide variation in response of individuals´ teeth to forces

applied that they suggested ideal light differential forces to be a myth. With respect to canine

13

retraction they found that higher forces were generally more efficient. Boester and Johnston (1974)

suggested that out of the three most common arguments favoring light forces, namely efficiency,

anchorage preservation and comfort, none could be substantiated in the exact sense of their original

proposal. Gianelly and Goldman (1971) questioned that larger forces cause greater periodontal

compression and result in greater pain. They also questioned the validity of using the pain response

as a guide to the amount of hyalinization of the periodontal ligament.

Yamaguchi and Nanda (1991, 1992) have shown that the same degree of forces results in varying

changes in blood flow and indicated that the change may be subject to deformation of the tissue but

not the degree of force. They concluded that tooth displacement has a closer relationship to the

decreased blood flow than to the degree of force.

Jones and Richmond (1985) have reported that the degree of crowding in the arches reflect the

overall forces being applied to the teeth in the arches examined, and demonstrated no correlation

between the magnitude of the force and the discomfort experienced. Owman-Moll et al. (1995) in a

clinical study showed that buccal tipping of maxillary first premolars was less efficiently performed

with an interrupted force than with a continuous one, and found no difference in the number or

severity of areas of root resorption between the two force systems. In an interrupted force system

with rest periods one would, however, assume less tissue strain and possibly more tooth movement

with less root resorption. Owman-Moll et al. (1996), and Bergius et al. (2008), suggested that

individual responses might have more impact than the increase in the amount of force or length of

experimental period on both the tooth movement achieved and occurrence of root resorption.

Generally, the use of light continuous force is thought to be the key factor for orthodontic tooth

movement. However, the connection between the different recommended ranges of such light

forces and the pain experience is not clear, and the picture seems to become more complex when

the type and amount of the tooth movement is considered.

2.3. Dental pulp reactions to orthodontic forces

The blood flowing through the tooth is confronted with a unique environment. The dental pulp is

incased within a rigid, non-compliant chamber and its survival is dependent on the blood circulation

and vessels that access the interior of the tooth through the apical foramen or multiple foramina

(Barwick and Ramsay 1996).

Understanding the effect of orthodontic force on the pulp is of particular importance, because it

14

interferes with pulpal circulation and, thus, the metabolic activity and the respiration rate of the pulp

tissue (Hamerski et al. 1980, Unterseher et al. 1987). The effects can be reflected as disruption of

the odontoblast layer (Stenvik and Mjör 1970, Anstendig and Kronman 1974), pulpal obliteration

by secondary dentin formation (Marshall 1933, Cywk et al. 1984), root resorption (Spurrier et al.

1990, King and Fischlschweiger 1982, Reitan 1964, Vardimon et al. 1991), and even pulpal

necrosis (Butcher and Taylor 1952, Cwyk et al. 1984, Årtun and Urbye 1988), which have all been

associated with orthodontic treatment. Additionally, the indirect effect of orthodontic forces through

neurogenic interactions may play an important role (Yamaguchi and Kasai 2005).

Reversible pulpal injury is a common response to orthodontic treatment (Stenvik and Mjör 1970,

Hamersky et al. 1980, Labat et al. 1980, Unterseher et al. 1987). Ikeda et al. (1998) monitoring

dental pain thresholds in response to electrical stimulation, demonstrated that light premature

contacts resulting in abnormal loading of teeth were capable of increasing tooth sensitivity, and that

after elimination of such interferences, tooth response returned to the base line and clinical

symptoms disappeared. In animal studies such an injury has been induced, and the severity of the

changes depends on the intensity and duration of the irritation and the resistance of the pulp

(Biesterfield, Taintor and Marsh 1979). Butcher and Taylor (1952) reported that experimental

retraction of the lower incisors with 250 gram of force for 3 to 20 days in rhesus monkey produced

early pulpal changes ranging from partial blood flow stasis to necrosis.

Intrusive forces have also been considered to have deleterious effects on teeth. Stanley et al. (1978)

suggested that a too powerful depressive force may shut off the arterial supply and thus produce

devitalization of the pulp. Stenvik and Mjör (1970) reported that with intrusive force on human

premolars for 4 to 35 days, the main pulpal changes were circulatory disturbances. Further, the

effects of traumatic occlusion and excessive stress of orthodontic forces have been reported to cause

extravasations of blood and necrosis of the pulp tissue in human teeth (Seltzer and Bender 1975).

Experimental data using respiratory activity (oxidation of organic fuels by molecular oxygen) as an

indicator of pulpal injury, have indicated that a 72-hour orthodontic force can cause a 27%

reduction of pulp metabolism in human premolars. The respiratory rates remained depressed for at

least one week after the force was discontinued. The metabolic effects were significantly smaller in

younger subjects with more patent root apices than in older people (Hamersky et al. 1980). One

factor contributing to this apparent decrease in respiration rate could be a strangulation of the blood

vessels and stasis of blood flow to the pulp (Marshall 1933, Orban 1936, Oppenheim 1937,

Stuteville 1938, Butcher and Taylor 1951, 1952, Langeland 1957, Anstending and Kronman 1974,

15

Guevara et al. 1977). Another interesting finding by Hamerski et al. (1980) was that as the age of

the subjects increased, the relative amount of depression in the pulpal respiratory rate also

increased. These results seem to indicate a relationship between the biologic effect of orthodontic

force and the maturity of the tooth. Accordingly, large apical foramina result in a reduction of

detrimental effects from orthodontic force.

Regulations of the blood flow by sensory nerve fibers, and the related neurogenic inflammatory

reactions have been described in the dental pulp (Gazelius et al. 1987, Olgart 1985, 1990).

Neurogenic inflammation effects include the release of vasoactive peptides from the nerve endings

and consequent vasodilation, increased vascular permeability and hyperalgesia. Furthermore, it has

been shown that sensory nerve fibers sprout in the inflamed pulp tissue, which may affect its

sensitivity (Kimberly and Byers 1988, Taylor et al.1988, Byers et al. 1990b, Michelotti et al. 1999,

Yamaguchi and Kasai 2005).

2.4. Variation of the perceived pain during orthodontic treatment with age and

gender

Relation of age and the perceived pain during orthodontic therapy is not clear, partly because a

critical comparison of the various studies is impossible due to differences in experimental designs

and methods.

Ngan (1989) found significant interaction between the age and duration of force implemented.

Patients 16 years of age and younger experienced more discomfort at 4 hours, whereas patients

older than 16 years of age experienced more discomfort at 24 hours and at the 7th day. Brown and

Moerenhout (1991), however, reported that adolescents of 14-17 years of age were more vulnerable

to the undesirable psychological effects of treatment and had higher levels of pain than younger and

older patients. Scheurer et al. (1996) also reported that 13-16 years old patients had the highest

prevalence of pain. Jones and Richmond (1984) have shown that adults experienced more pain than

adolescents, however, pain experiences do not appear to differ between the genders. Differences

between study designs and methodologies may partly explain these different conclusions. Ngan et

al. (1989) reported no difference in the perception of pain from orthodontic appliances between

males and females. According to Scheurer et al. (1996), however, girls reported a higher impact on

daily life, and significantly greater pain intensity and analgesic consumption than boys in response

to fixed appliances. The changes with age on the perceived pain may relate to the differences in the

tissue compliance and tissue repair. However, there is a wide range of individual variations in the

16

pain experienced during orthodontic treatment, which is affected, by patients past experiences,

cultural background and other forms of psychological input (Burstone 1985).

2.5. Measurement of tooth sensitivity

For the measurement of tooth sensitivity it is necessary that the stimulus intensity needed to evoke a

sensory response can be determined accurately and reliably. Different stimuli have been used for

the purpose. These include; mechanical, thermal, osmotic, dehydrating and electrical stimulation.

The sensitivity can be different depending on the type of stimuli used (Lilja 1980, Närhi 1985a,

Orchardson and Collins 1987b).

The measurement of tooth sensitivity during orthodontic treatment is technically complicated. On

one hand, bonding materials, brackets and archwires limit the accessibility to the tooth surface for

stimulation and, on the other hand, open dentinal tubules which may be the basis for pain induction

with some stimuli may not be found as often in orthodontic patients as in patients with, for example,

dentin hypersensitivity.

A preferred method of stimulating dental pulp for induction of pain is cold stimulation. It has been

found to be the most potent (Flynn et al. 1985, Orchardson and Collins 1987b) and also better

tolerated by dental pulp than for example hot stimuli (Pashley 1990). Fulling and Andreasen (1976)

reported consistent responses from the teeth, which had stainless steel crown using cold stimulation

with carbon dioxide snow. Electrical stimulation of the teeth was reliable only when the

stimulator’s electrode was directly in contact with the enamel, thus, controlling the electrical

current leakage.

The sensitivity of electric pulp testers for detection of different stages of pulpal inflammation has

been questioned (Seltzer et al. 1963, Mumford 1982). Nevertheless, higher accuracy in the

measurement of the applied stimulus by electrical rather than natural stimuli has been noted

(Mumford 1982). According to Närhi (1985) since electrical stimulation affects any excitable cell

membrane, it could as well activate intradental axons as peripheral receptors, and thus would not be

a valid measure of the pulpal nociceptor sensitivity.

Markus (1946) reported that teeth became more responsive to electric pulp testing immediately

following orthodontic activation while Burnside et al. (1974) found that in general the experimental

17

teeth showed higher pain threshold values to electrical stimulation than did the controls indicating

reduced sensitivity. It must be mentioned that in the study of Burnside et al. (1974) the comparison

was made between the orthodontic patients who had fixed orthodontic appliances for a minimum of

four months prior to the test, and the control group had no appliances. Longitudinal studies would

be needed to find out the effects of orthodontic tooth movement on the dental pulp sensitivity.

McGill Pain Questionnaire (MPQ) measures both the intensity and quality of pain. This verbal

rating scale has been used previously for evaluation of pain symptoms in orthodontics, and shown

to have high reliability (Brown and Moerenhout 1991). However, vocabulary limitations (Gracely et

al.1978) and insufficiency of pain-word questionnaires have been noted (Curro 1990). The Visual

Analogue Scale (VAS) is a direct pain intensity scaling method in which the subjects evaluate the

level of pain by making a mark on a continuous line. One end of the line means “no pain and the

other end “intolerable pain” es of using the VAS over

observational, self-report, behavioral, physiological or verbal rating scales, are the higher

sensitivity, reproducibility and reliability of the direct scaling techniques (Melzack, Torgerson

1971, Uskisson 1974, Scott and Huskisson 1979, Huskisson 1983, Seymour et al. 1985, McGrath

1986, Duncan et al. 1989). It also allows the use of parametric statistical tests (Bhat 1986). On the

other hand, the limitation of VAS is that the recorded values are mostly related to the intensity

component of pain.

( uskisson 1983). The advantag H

2.6. Management of orthodontic pain

Pain caused by orthodontic treatment can be a major negative component of the entire therapy.

Theoretically, the ideal way to control pain during orthodontic treatment would simply be to keep

the applied force levels to a minimum, below the pain threshold. This approach, however, is

contradictory for the purpose if the force levels should be kept too low to result in any tooth

movement (Simmons and Brandt 1992).

Conventional analgesics have been used to alleviate orthodontic pain. According to Simmons and

Brandt (1992) these drugs should be taken prior to the installation of an active orthodontic

appliance and for a minimum of 24 hours following the procedure. However, Ngan et al. (1994)

reported that single dose given at the moment of orthodontic appliance insertion was sufficient for

prevention of pain symptoms.

18

”

In addition to the conventional analgesics more physiological approaches for the treatment or

prevention of pain have been applied. Chewing something fairly hard -a plastic wafer, for example-

within the first two hours after arch wire adjustment may act to reduce the ischemia and

inflammation in the periodontal ligament (Furstman and Bernick 1972). Stimulation of vascular and

lymphatic circulation would prevent the build-up of metabolic products, which are known to

stimulate pain receptors (Proffit 1986).

In a study on 93 orthodontic patients, White (1984) found that 63% of their subjects reported less

discomfort after chewing analgesic gum, however, lack of control group in this study raises the

question of whether the reduction of pain was due to the analgesics or the chewing function.

Transcutaneous electrical nerve stimulation (TENS) is another technique for pain control in

orthodontics which according to Roth and Thrash (1986) dramatically decreased the delayed (more

than 12 hours after arch wire adjustment) pain response. Unfortunately, there was not any

significant reduction of pain within the first 12 hours using this method. Low level laser has been

claimed by many investigators to produce analgesic effects in various therapeutic and clinical

applications (Plog 1980, Midda and Renton-Harper 1991). The mechanism of laser analgesia has

not been established, but it has been attributed to its anti-inflammatory effects (Harris 1991). Low

level laser therapy has been applied for the treatment of pain related to orthodontic activations but

without success (Lim et al. 1995). Blechman (1998) reported of the possibility of pain free and

mobility free orthodontics using magnetic force fields. Magnetic field is hypothesized to accelerate

osteogenic rate and therefore, reduce tooth mobility and the related pain. However, the assumption

is based only on several reports by different clinicians. Up to date there is no systematic study

published comparing the pain experience, tooth mobility and sensitivity between the tooth

movements in the conventional approach and under magnetic fields. Further studies on the different

mechanisms of pain induction during tooth movement are needed to provide the essential

knowledge for its possible management.

19

3. AIMS OF THE PRESENT STUDY

The purpose of the present study was to assess the prevalence and significance of the pain

experience reported by the patients at different stages of orthodontic treatment. It was also

examined to what extent the dental pulp sensitivity might be changed or affected by the treatment,

and if such changes could explain part of the pain symptoms complained by patients. It was

hypothesized that the pain experienced during orthodontic tooth movement is strongest at the initial

phase of the therapy and that it gradually decreases with time. Also it was presumed that the amount

of tooth movement as a response to orthodontic forces is related to the tooth sensitivity as

perception of pain experienced by the patients.

The specific objectives were to study:

1. The prevalence, intensity, quality and duration of pain/discomfort experienced by patients at

different stages of orthodontic treatment during different functions used as stimuli, by using a

structured questionnaire,

2. The effect of orthodontic treatment/forces on electrical thresholds and cold sensitivity of the

dental pulp,

3. The relationship between the subjective pain perception as reported in the questionnaire and pain

responses in the clinical sensitivity tests,

4. The relation of the subjective pain perception and the clinically assessed sensitivity to the amount

of tooth movement.

20

4. SUBJECTS AND METHODS

4.1. Subjects

The study group consisted of 64 patients, 46 females and 18 males, with a mean age 26.4 years (SD

11.1). The distribution of the age and gender of the subjects is shown in Table 1.

Table 1. Age and gender distribution of the subjects.

Age (yrs) Female

(n=46)

Male

(n=18)

Total

(n=64)

Mean

SD

Range

27.8

11.7

10.8-49.3

22.9

9.0

11.8-40.6

26.4

11.2

10.8-49.3

The study subjects were not pre-selected but the sample was formed by consecutive cases from

patients who were willing to participate. Patients were included in this study at the beginning of

their active orthodontic treatment before the insertion of fixed appliances. The deciduous teeth of

patients who were in the late mixed dentition stage were not included in the measurements. The ap-

pliances inserted were complete banded/bonded appliance of either one or both dental arches. No

additional elements of fixed appliances, extraoral or functional appliances were used during the

study. The study protocol was approved by the ethics committee of the Medical Faculty, University

of Kuopio, Kuopio, Finland.

4.2. Orthodontic mechanotherapies used for the study subjects

Three different fixed appliances were used: Standard edgewise technique for six patients, Wick

Alexander technique for 30 patients and Viazis technique for 28 patients. Because of the small

number of participants in the standard edgewise bracket group (n=6), this group was not included in

the comparison of different techniques but for all other comparisons.

21

Elastics for separating the first molars before banding (3M Unitek, Alastik Separator Modules) were

placed and left at the mesial and distal contacts of the first permanent molars in each of the four

quadrants for a three day period.

The three different types of fixed appliances used a 0.018″ bracket slot size, were: the Viazis

(OrthoSystem Inc., Plano, TX), the Alexander MINI WICK (Ormco Corporation), and the Standard

edgewise (Unitek/3M) brackets. The characteristics of the different mechanotherapies in producing

orthodontic tooth movement have been described (Viazis 1995, 1998, Alexander 1986)

- Viazis Bioefficient therapy (Viazis 1995) with a triangular bracket design, which is a combination

of a twin bracket at the lower half and a single bracket type at the upper half. The bracket slot is

elevated so that the wire may come in contact with the extensions (the bracket elbows), thus

providing control for tipping movements. The longer the interslot distance, the lower the wire

stiffness. The Viazis mechanotherapy incorporated a square initial archwire, 0.018″ x 0.018″ Heat

activated, Ionguard (Nitrogen substitution of the top 3 μmm of Nickel of the archwire surface),

Bioforce Sentalloy (GAC International, Inc.). These archwires have been described to demonstrate

a differential force delivery increasing progressively from 80 grams of force anteriorly, up to 320

grams of force in the posterior region. Heat activated property refers to that a decrease in

temperature allows the archwire to be in the martensinic phase, which provides ease of handling

during the archwire engagement to the bracket. At the oral temperature, austensinic phase resumes

the original arch form (shape memory). Additionally, in this technique in premolar extraction cases

Niti closed coil springs, Tension w/hooks M (GAC International, Inc.) were used in conjunction

with the initial archwire. The closed coil delivers 150 grams of force for canine retraction (GAC

International, Inc.). The objective of this mechanotherapy is to start the space closure as soon as

possible and to make the transition towards the finishing stainless steel wire within four to six

months of active therapy.

- Alexander technique has a twin bracket design for the maxillary incisors in combination with

single brackets with wings on the rest of maxillary and mandibular dentition. A round 0.016″

Superelastic Thermalloy Niti initial archwire (RMO) was used. This archwire has been described to

have a force delivery of 80 grams of force throughout the arch (Alexander 1986). In both extraction

and non-extraction treatments it is recommended the initial archwire to be activated for the next two

or three appointments before changing to an archwire with higher forces, for example, a round

0.016″ stainless steel wire, to continue the alignment and leveling or the sliding mechanics for

canine retraction.

22

- Standard edgewise technique, incorporated the same initial archwire and mechanotherapy

approach as that of the Alexander technique, the difference being the types of the brackets used.

The age and gender distribution of the subjects in the Alexander technique (n=30) and the Viazis

(n=28) technique is shown in Table 2.

Table 2. Age and gender distribution of the subjects treated with the two different types of fixed

appliances.

Alexander technique Viazis technique

Age (yrs) Female

(n=23)

Male

(n=7)

Total

(n=30)

Female

(n=19)

Male

(n=9)

Total

(n=28)

Mean

SD

Range

28.8

11.3

10.8-45.9

27.4

9.5

12.3-40.6

28.5

10.7

10.8-45.9

25.9

11.6

11.4-45.4

21.5

7.9

11.8-33.2

24.5

10.6

11.4-45.4

4.3. The questionnaire

The intensity, quality and duration of pain symptoms subsequent to the placement and activation of

the orthodontic appliances were assessed in a longitudinal series of questionnaires. The question-

naires (Appendix I) were given to each patient with a request to return them for the next

appointment. The patients were given oral as well as written instructions on how to complete the

questionnaire. Neither prescription for pain medication nor analgesics were dispensed to the

patients. However, they were free to take any medication they felt necessary. They were asked to

mark at the top of the questionnaire the brand name, dose and timing of the medication they had

possibly taken. In the questionnaire the occurrence of pain in connection with seven different

stimuli related to everyday life was included, namely: cold food/drink, hot food/drink, sweets, tooth

brushing, mastication of food, fitting the anterior teeth together and fitting the posterior teeth to-

gether. The patients were requested to fill out the questionnaire every morning for three days after

insertion of orthodontic separators, after initial archwire insertion and after activation of the

23

archwire. The pain intensity was scored on a 0-3 scale on each of the first three days after the three

aforementioned stages of the orthodontic treatment (see protocol page 32). The scores were defined

as follows:

0 = No pain,

1 = Mild pain,

2 = Moderate pain,

3 = Severe/intolerable pain.

The descriptors which were used to indicate the quality of pain in the questionnaire were as follow;

1) sore, 2) shooting, 3) dull and 4) ache. Duration of pain was divided into two groups of short (S)

(lasting not more than a few seconds) and long (L) lasting pain (clearly outlasting the time of the

stimulus).

The pain experience related to each stimulus was estimated for its intensity, quality and duration

(Table. 3).

Stimulus Sore Shooting Dull Ache

Fitting

front teeth

together

0

1

2

3

Duration

S

L

0

1

2

3

Duration

S

L

0

1

2

3

Duration

S

L

0

1

2

3

Duration

S

L

Table 3. An example of a patient’s response to pain from fitting the front teeth together after the

insertion of the initial archwire. The patient reported that the teeth were sore and the evoked

sensation was mild and short lasting.

The intensity of pain related to each pain descriptor was calculated on the basis of all responses

given by the patients in all questionnaires and each stimuli. The mean values for each descriptor are

presented in Figure 1. Although not statistically significant, there was a clear trend, the order of the

intensity scores for different descriptors was: sore<shooting<dull<ache. Figure 2 shows the relation

between the intensity and the duration of the reported pain.

24

0

1

2

3

sore shooting dull ache

Quality of pain

Inte

nsity

of p

ain

Figure 1. The overall relations between the quality and the intensity of the reported pain.

0

1

2

3

short long

Duration of pain

Inte

nsity

of p

ain

(0-3

)

Figure 2. The relations between the overall intensity and duration of the reported pain.

25

On the basis of this comparison the pain quality descriptors were arranged in the following order

from the least intense to the most intense one; 1= sore, 2= shooting, 3= dull and 4= ache.

Correspondingly, pain described as being of either short or long duration was given values of 1 and

2, respectively. They were given these numerical values for the further analyses and used to form a

total pain score.

For statistical analyses, an index describing the pain experience was formed by multiplying the

numerical values of the intensity (0-3), the quality (1-4), and the duration (1, 2) of pain.

Thus the maximum pain scores were as follows:

1) 3 x 4 x 2=24 PIS Pain Index for each Stimuli (one questionnaire)

2) 24 x 7=168 PIQ Pain Index for one Questionnaire (seven stimulus)

3) 24 x 7 x 3=504 PIStage Pain Index for one treatment Stage (three questionnaires)

4) 24 x 6=144 PI2Stages Pain Index for each Stimuli at Two stages

(six questionnaires)

5) 24 x 9=216 TPIS Total Pain Index for each Stimuli at three stages

(nine questionnaires) 6) 24 x 7 x 9=1512 TPI Total Pain Index (seven stimuli and nine questionnaires)

4.4. Clinical examination

A total of 907 teeth of the 64 subjects were examined in the clinical sensitivity tests, which included

measurements of the dental electrical thresholds and cold sensitivity. The teeth were dried and

isolated with cotton rolls. The measurements were performed for each tooth starting from the

maxillary right first molar and ending up with the mandibular right first molar (maximum of 24

teeth per patient). Thus five to ten minutes of recovery period was allowed between stimulus appli-

cations for each tooth. Any enamel/dentin irregularities or caries/fillings were avoided as sites of

stimulation. The tooth number and the surface were noted on the patients´ chart so that the same

spot could be stimulated during all appointments. Teeth with crowns, root canal fillings and/or with

extensive fillings were excluded. If the molars were to be banded, they were excluded from the

sensitivity tests after banding due to the difficulties in finding an exact spot for stimulation. Thus

those cases were included only in the first set of the questionnaire involving the separation of the -

molar and patient’s response during the following three days. Altogether 5-7 hours was spent

collecting the data from each patient.

26

4.4.1. Dental electrical threshold measurement

Electrical thresholds were measured with a constant current electrical stimulator (Bofors Pulp

Tester, Bofors, Sweden) in µA, (Fig.3). The stimulator gives 10 ms cathodal square wave pulses at

5 Hz frequency. The stimulator tip was 2 mm in diameter and made of conductive rubber. The tip of

the stimulator was placed in contact with the incisal third of the lingual/palatal surfaces of the

incisors and lingual/palatal cusp tip of the premolars and the mesiolingual/palatal cusps of the first

molars (Fig. 4). Stimulation of the cervical third close to the gingiva was avoided because of the

danger of the current leakage to the soft tissues with low resistance (Mumford and Björn 1962,

Matthews and Searle 1974, 1976, Mumford 1982). Patients were instructed to stop the electrical

current by pushing the button on the handle as soon as they felt any sensation (prepain). The

electrical threshold of each tooth was measured twice, and the mean value of the two measurements

was used for further analysis of data. In cases in which the difference between the two readings was

more than 5 µA in incisors, 15 µA in canines and premolars and 25 µA in molars, the lower

values were selected.

27

Figure 3. The constant current electrical stimulator used to measure the dental electrical thresholds

(Bofors Pulp Tester, Bofors, Sweden).

Figure 4. The electrical stimulator probe in contact with the incisal third of the palatal surface of a

maxillary central incisor.

28

Figure 5. The thermal stimulator used to test the cold sensitivity of the studied teeth.

Figure 6. The cold stimulator probe in contact with the cervical third of the facial surface of a

maxillary lateral incisor.

29

4.4.2. Testing thermal sensitivity of the teeth

Methods for testing sensitivity of tooth, originally developed for studies on dentin hypersensitivity

(Kontturi-Närhi 1993, Kontturi-Närhi and Närhi 1993), were adopted for examination and evalu-

ation of the tooth responses to orthodontic forces. An electrothermal device constructed in the

Technical Center of the University of Kuopio was employed for the purpose (Fig.5). The

stimulator´s probe had a feedback circuit for the control of the tip temperature at an accuracy of

0.1ºC. The tip diameter was 2mm. Cold stimuli at 15ºC and 0ºC were applied to the teeth under

examination. The tip of the probe was precooled to the desired temperature and then placed on the

cervical third of the facial surface of each tooth (Fig. 6). In each stimulation trial the cold probe was

kept in contact with the tooth for a maximum of 2 seconds. No extra pressure was exerted on the

tooth surface. Prior to testing, patients were instructed to raise the right hand at the instant he/she

felt the first sensation. As soon as the patient gave a positive response, the stimulation of the tooth

was discontinued.

The intensity of the induced pain was assessed with a 100 mm Visual Analogue Scale (VAS)

(Huskisson 1983, McGrath 1986). The left end of the scale indicated "no pain" and the right end

"intolerable pain" (Fig. 7). Patients were requested to place a vertical mark on the VAS

corresponding to the intensity of the pain they experienced. They were able to see only one VAS at

a time.

The distance of the mark from the left end of the scale was then taken to represent the VAS pain

score.

No pain Intolerable pain

Fig. 7. The visual analogue scale (VAS) used in the present study. The length of the scale was 100

mm.

4.5. Measurement of tooth movement from hard stone casts

Dental casts were made from alginate impressions taken before the treatment and a second set three

months after the placement of the initial archwire. Severity of malocclusion was then measured

using the Irregularity Index, defined as the summed displacement of adjacent anatomic contact

30

points (Little 1975) for the maxillary and mandibular anterior segments (canine-canine).

Furthermore, in extraction cases the movement of the teeth moved into extraction space was

measured. The measurements were carried out with a Mitutoyo digital caliper (Mitutoyo Mfg. Co.,

Ltd., Japan) to the nearest 0.1 mm. For intraexaminer consistancy, the measurements included the

Irregularity Index as well as the amount of tooth movement into the extraction spaces, twenty

randomly selected dental casts were measured three times with a three weeks intervals. The

intraclass correlation coefficient (Selkäinaho 1983) was used for the three repeated measurements

of the dental casts. The values of ICC were high for both measurements (ICC 0.99, 95% CI 0.998,

.0999). There was no statistically significant difference between the two groups with regards to the

anterior crowding prior to the orthodontic treatment (by t-test).

31

4.6. Study protocol The examination of the subjects was divided into five stages (I-V) as shown in the following table:

Stage Orthodontic procedure Cold sensitivity and

electrical pulp tests

Questionnaire

I Orthodontic separators

(S)

Initial (T1), before

separation of molars

Three (one/day, S1, S2, S3)

II

(3 days after stage I)

Banding/Bonding &

initial archwire (W)

Second (T2) Three (one/day, W1, W2, W3)

III

(3 days after stage II)

Third (T3)

IV

(A month after stage III)

Before activation of the

archwire (A)

Fourth (T4) Three (one/day, A1, A2, A3)

V

(3 days after stage IV)

Final (TF)

T1 corresponds to the measurements of the cold sensitivity and electrical pulp tests, before the

insertion of orthodontic separators. T2 is the pulpal tests after three days of orthodontic separation of

molars. T3 is the pulpal tests after three days of bonding orthodontic appliances. T4 is the pulpal

tests before activation of archwires and TF is the final pulpal tests, three days after activation of

archwires.

32

4.7. Statistical methods

In analyzing data from the questionnaire, chi-square test and Z-test were applied in comparing the

frequencies of the categorical variables at different stages of orthodontic treatment. The Wilcoxon

matched-pairs signed-ranks test was used to compare the changes in the pain intensity (0-3), quality

(1-4) and duration (1,2), at different days (1,2,3) and stages (separation of the first molars, initial

archwire insertion and the archwire activation) of the orthodontic treatment. The differences

between the means of the parametric variables were analyzed by Student’s t-test. Pearson

correlation coefficient was used when analyzing the relationships between the clinical measurements

(cold sensitivity at 15ºC and 0ºC, electrical thresholds), and the subjective responses to the

different orthodontic procedures (separation of the first molars, initial archwire insertion and the

archwire activation). Multiple regression analysis was used to estimate the associations between the

scores of the index of the reported pain and clinical measurements for each tooth including cold

stimulation (VAS values in mm) and the electrical thresholds in µA, considering the possible

effects of age (years), gender (0=female, 1=male), type of brackets (1=Alexander, 2=Viazis) and the

use of analgesics (0=no, 1=yes), one or both jaws treatment (0=one, 1=both), and extraction (1=no,

2=yes). In analyzing the clinical data (questionnaire study excluded), and measurements Student’s t-

test, paired t-test and Pearson correlation coefficients were used. The statistical significance level

was taken at p≤0.05, in all the tests performed.

33

5. RESULTS

5.1. Subjective pain experience during orthodontic treatment as reported in the

questionnaires

The overall response rate for the questionnaires was 98.6%. Altogether seven questionnaires were

missing, four from the initial archwire placement and three from the activation phase. Throughout

the entire study, five appointments were compromised for two days interval instead of three because

of the adult patients´ working schedules (for these patients only the available data were used and

analyzed). Two patients were excluded, one moved abroad and the other had difficulties in

complying with the study requirements. Thus the number of subjects included in the analyses was

64. There was a financial incentive (50% discount of the total orthodontic treatment costs), for those

who participated in the study. We were able to recruit 66 subjects (two did not complete the study)

out of 68 (that is 97% of the total). Subjects reflect a reasonable representation of our practice.

5.1.1. Prevalence of pain

Prevalence of reported pain during the first three days after different orthodontic procedures for

different stimuli are shown in Table 4. The prevalence was higher after initial archwire insertion

(W1, W2, W3) than after separation of molars (S1, S2, S3) and archwire activation (A1, A2, A3), in

connection with all the stimuli except for sweets at S1 compared to W1. In general, the prevalence

decreased from the first through the second to the third day. The exceptions were for cold

food/drink and fitting posterior teeth together between A1 and A2, for sweets, mastication of food,

and fitting anterior teeth together between W1 and W2, and also for tooth brushing between A2 and

A3. Prevalence of pain was more clearly highest for mastication of food and fitting anterior teeth

together during the second day after the initial archwire, in 93.2% and 89.9%, respectively. Pain

was also very common for fitting the posterior teeth together during W1 and W2, 83% and 81%,

respectively. There were no statistically significant differences except for W1/W3 in cold

food/drink and S1/S3 in tooth brushing (p<0.05= Z value at 1.2-3.8).

The highest frequency of pain was reported after the insertion of initial archwire, in relation to all

items namely, mastication of food in 93.2%, fitting anterior teeth in 82.7%, fitting posterior teeth in

78.6%, tooth brushing in 47.6%, cold in 27.4%, hot in 22.3% and sweets in 9.8% of all subjects.

The differences in the prevalence of the reported pain between the first three corresponding days of

34

different orthodontic procedures (Table 5) related to all other items except for sweets and hot

food/drink at W1/A1, and sweets at S1/W1, were statistically significantly higher at the first day

after initial archwire insertion (W1) compared to both the first days after separation of molars (S1)

and the archwire activation (A1). The prevalence of the experienced pain (Table 5) was quite

similar on the first days after molar separation (S1) and archwire activation (A1) with only two

items, namely, fitting anterior and posterior teeth together showing statistically significant

differences.

Table 4. The prevalences of pain reported by 64 orthodontic patients during the first three days after

each orthodontic procedure, namely, separation of the molars (S1, S2 and S3), initial archwire

placement (W1, W2 and W3), and the first archwire activation (A1, A2 and A3) for different items

of the questionnaire.

Stimulus Days after separation

Days after initial archwire

Days after activation of archwire

S1 %

S2 %

S3 %

W1 %

W2 %

W3 %

A1 %

A2 %

A3 %

Cold food/drink

14.3 11.6 9.5 35.6 28.8 17.9 13.5 16.7 9.8

Hot food/drink

9.5 7.0 2.4 25.4 23.7 17.9 12.1 8.3 6.6

Sweets

9.5 7.0 7.1 8.5 11.9 8.9 6.9 5.0 4.9

Tooth brushing

28.6 20.9 11.9 50.8 49.2 42.9 34.1 20.0 24.6

Mastication of food

50.0 55.8 42.9 88.1 93.2 89.3 56.9 53.3 49.2

Fitting anterior teeth

14.3 14.0 11.9 79.7 89.8 78.6 51.7 43.3 41.0

Fitting posterior teeth

61.9 58.1 45.2 83.1 81.4 71.4 27.6 30.0 24.6

35

Table 5. The statistical significance of the differences in the prevalence of the reported pain

between the first three days of different orthodontic procedures. By Z-test. (P<0.05, Z value 1.2-3.8

and P<0.01, Z value 3.8-5.6 and P<0.001, Z value>5.6).

S1/W1

S2/W2

S3/W3

S1/A1

S2/A2

S3/A3

W1/A1

W2/A2

W3/A3

Cold food/drink

P<0.01 P<0.05 P>0.05 P>0.05 P>0.05 P>0.05 P<0.01 P>0.05 P>0.05

Hot food/drink

P<0.05 P<0.01 P<0.001 P>0.05 P>0.05 P>0.05 P>0.05 P<0.05 P<0.05

Sweets

P>0.05 P>0.05 P>0.05 P>0.05 P>0.05 P>0.05 P>0.05 P>0.05 P>0.05

Tooth brushing

P<0.01 P<0.001 P<0.001 P>0.05 P>0.05 P>0.05 P<0.001 P<0.001 P<0.05

Mastication of food

P<0.001 P<0.001 P<0.001 P>0.05 P>0.05 P>0.05 P<0.001 P<0.001 P<0.001


P<0.001 P<0.001 P<0.001 P<0.001 P<0.001 P<0.001 P<0.001 P<0.001 P<0.001


P<0.01 P<0.01 P<0.01 P<0.001 P<0.01 P<0.05 P<0.001 P<0.001 P<0.001

36

5.1.2. The intensity, quality and duration of the reported pain

Based on all pain reports, pain intensity was most frequently reported to be mild (62.5%) followed

by moderate (28.5%) and severe (9%) pain respectively. The distribution of the intensity of the

reported pain symptoms during the first three days after different orthodontic procedures, in relation

to each stimuli included in the questionnaire, is presented in Table 6. During the three days after the

insertion of initial archwire the corresponding distribution of the reported pain intensity was mild

52.7%, moderate 33.9% and severe 13.4%. There were no reports of severe pain during the first

three days after separation of molars and wire activation in connection with cold and hot food/drink,

sweets and tooth brushing. This coincides with the high "no pain" reports related to the

abovementioned items. The highest prevalence of severe pain was found after the initial archwire

insertion, namely on the first day after the procedure mastication of food was reported to cause

severe pain most frequently, by 25.4% of the subjects. Generally reports of the severe pain were

mostly related to the three most frequently reported items: mastication of food, and fitting anterior

and posterior teeth together respectively.

37

Table 6. The distribution of orthodontic patients who experienced pain according to the intensity of

the experienced pain during the first three days after each orthodontic procedure, separation of

molars (S1, S2 and S3), initial archwire (W1, W2 and W3), archwire activation (A1, A2 and A3).

Days after separation


Days after activation of the archwire

S1 n

S2 n

S3 n

W1 n

W2 n

W3 n %

A1 n %

A2 n %

A3 n % % % % % %

Cold food/drink(n) 11 10 9 35 18 11 10 78.0 22.0

0

10 80.1 19.9

0

6 mild pain moderate pain severe pain

83.2 16.8

0

100 100 61.8 23.9 14.3

70.5 23.6 5.9

90.0 0

10.0

100 0 0

0 0

0 0

Hot food/drink(n) 9 7 5 16 15 11 8 85.8 14.2

0

5 100 0 0


100 100 100 53.6 40.0 6.7

64.3 35.7

0

100 100 0 0

0 0

0 0

0 0

0 0

Sweets(n) 9 7 8 5 7 5 4 100 0 0

3 100 0 0


50.0 50.0

0

0 100

66.6 33.4

0

40.0 0

60.0

71.4 0

28.6

60.0 40.0

0

100 0

0 0 Tooth brushing(n) 19 14 8 33 32 27 15

71.4 28.6

0

13 83.5 16.5

0


83.2 16.8

0

89.0 11.0

0

80.0 20.0

0

70.0 16.7 13.3

58.6 37.9 3.5

70.9 24.9 4.2

86.6 13.4

0 Mastication of food(n) 32 36 28 56 60 57 36

62.8 21.0 16.2

34 74.9 21.9 3.2


63.9 24.4 11.7

53.1 32.7 14.2

77.6 11.2 11.2

23.0 48.1 28.9

29.0 51.0 20.0

40.0 48.0 12.0

80.0 20.0

0 Fitting anterior teeth(n) 9 8 7 51 57 50 33

63.4 30.0 6.6

28 65.3 30.7 4.0


49.6 33.6 16.8

83.4 16.6

0

80.0 20.0

0

42.5 44.7 12.8

52.8 32.0 15.2

52.3 34.0 13.7

88.0 12.0

0 Fitting posterior teeth(n) 40 37 29 53 52 46 18

68.8 31.2

0

19 72.3 27.7

0

16

mild pain moderate pain severe pain

61.6 34.6 3.8

68.0 32.0

0

79.0 21.0

0

61.2 28.5 11.3

64.6 28.5 11.3

62.5 27.5 10.0

86.6 15.4

0

The quality of the reported pain as indicated by the pain descriptors during the first three days

after each orthodontic procedure, regarding each item included in the questionnaire is presented

in Table 7. According to the reports sore (65%) was the most frequent descriptor followed by

dull (15.5%), shooting (9.5%) and ache (9.5%). During the three days after the insertion of

initial archwire the corresponding distribution of the pain descriptors were 65.2% for sore,

14.6% for shooting, 12.1% for dull and 8.1% for ache.

Regarding the duration of the reported pain during the first three days after different orthodon-

tic procedures, for different stimuli, in general pain was mostly short lasting in 85% of the

reports (Table 8). During the three days after the insertion of initial archwire the proportion of

38

short and long lasting pain were 75.2% and 24.8% respectively. The differences in the reported

duration of pain (short vs. long), were statistically significant when comparing the three days

after archwire insertion to the corresponding days after archwire activation in all items except

for cold at W2/A2 and sweets at W3/A3.

Wilcoxon Matched-Pairs Signed-Ranks Test was used to study the differences of the intensity,

quality and duration of the reported pain in connection with each item between the first three

days after each orthodontic procedure (Table. 9). No statistically significant difference was

found between S1/S2 in the pain reports of any item. In general most of the significant

differences between the days examined in connection with the intensity, quality and duration of

the reported pain were found between W1/W3 followed by W2/W3 and S1/S3 and S2/S3,

respectively. Differences in the intensity, quality and duration of the reported pain in

connection with cold food/drink were highest and found to be statistically significant between

W1/W3 and W2/W3. Comparison between the differences of the reported pain during the first

three days after archwire activation (A1, A2 and A3) showed statistically significant differences

only with regards to fitting front teeth together. Taking sweets was the only item with no

statistically significant differences of the reported pain between the days tested.

Wilcoxon Matched-Pairs Signed-Ranks Test was also used to study the differences of the

intensity, quality and duration of the reported pain in connection with each item between the

first three days of different orthodontic procedures (Table. 10). Taking sweets was the only

item with no statistically significant differences in the reported pain between the days tested. In

general most of the significant differences were found between W1/A1 followed closely by

S3/W3, W3/A3, S1/W1, S2/W2 and W3/A3, respectively. Comparison between the differences

of the reported pain during the first three days after archwire activation and separation of

molars (S1/A1, S2/A2 and S3/A3) showed statistically significant differences only with regards

to fitting anterior and posterior teeth together.

39

Table 7. The distribution of the quality of experienced pain of 64 orthodontic patients who

experienced pain during the first three days after each orthodontic procedure, separation of molars

(S1, S2 and S3), initial archwire (W1, W2 and W3), archwire activation (A1, A2 and A3).




S1 n %

S2 n %

S3 n %

W1 n %

W2 n %

W3 n %

A1 n %

A2 n %

A3 n %

Cold food/drink (n) sore shooting dull ache

9 49.6 32.5 17.9

0

7 60.0 40.0

0 0

6 25.0 50.0 25.0

0

23 42.8 42.8 4.8 9.6

18 41.2 41.2 11.7 5.9

11 39.7 30.2 20.1 10.0

10 22.0 44.5 33.5

0

11 19.9 50.0 19.9 10.2

6 16.3 50.0 33.7

0 Hot food/drink (n) sore shooting dull ache

6 74.7

0 25.3

0

4 100 0 0 0

2 100

0 0 0

16 53.3 20.0 20.0 6.7

15 50.0 28.6 21.4

0

11 59.8 20.1 10.1 10.0

8 28.3 28.3 43.4

0

5 20.5 39.7 39.7

0

4 24.6 50.8 24.6

0 Sweets (n) sore shooting dull ache

6 74.7 25.3

0 0

4 67.1 32.9

0 0

4 66.6 33.4

0 0

5 80.0 20.0

0 0

8 85.7 14.3

0 0

5 79.8 20.2

0 0

4 100 0 0 0

3 100 0 0 0

3 100 0 0 0

Tooth brushing (n) sore shooting dull ache

18 83.2 8.4 8.4 0

13 89.0

0 11.0

0

8 79.8

0 20.2

0

33 80.0

0 10.0 10.0

31 82.7 10.4 6.9 0

27 79.2 16.6 4.2 0

15 57.3 7.1

14.1 21.5

13 66.5

0 25.0 8.5

16 67.0 6.5

20.0 6.5

Mastication of food (n) sore shooting dull ache

32 45.9 14.2 19.0 20.9

36 49.9 12.5 29.2 8.4

24 66.6 5.6

16.5 11.3

56 59.6 5.8

13.5 21.1

60 69.0 3.6

14.6 12.8

57 72.0 7.9

14.0 6.1

36 72.8 3.0

15.1 9.1

34 65.5 3.2

21.9 9.4

31 76.6

0 16.6 6.8

Fitting anterior teeth (n) sore shooting dull ache

9 49.6

0 33.6 16.8

9 66.8

0 16.6 16.6

9 33.6 16.8 49.6

0

51 57.4 6.4

17.0 19.2

58 60.3 7.6

15.1 17.0

50 77.2 4.6

11.3 6.9

33 50.0 10.0 16.6 23.4

28 65.3 7.6

15.5 11.6

26 68.0 3.9

20.0 8.1

Fitting posterior teeth (n) sore shooting dull ache

40 57.7 7.7

15.3 19.3

37 59.9 8.1

19.9 12.1

29 57.8 5.3

31.5 5.4

53 59.2

0 28.5 12.3

52 70.8 2.1

16.7 10.4

46 70.0 5.0

15.0 10.0

27 81.5

0 12.3 6.2

19 94.3

0 5.7 0

16 80.1

0 13.4 6.5

40

Table 8. The distribution of the duration of experienced pain of 64 orthodontic patients who

experienced pain during the first three days after each orthodontic procedure, separation of

molars (S1, S2 and S3), initial archwire (W1, W2 and W3), archwire activation (A1, A2 and

A3).




S1 n %

S2 n %

S3 n %

W1 n %

W2 n %

W3 n %

A1 n %

A2 n %

A3 n %

Cold food/drink (n) short long

9

66.5 33.5

7

80.2 19.8

6

100 0

23

76.1 23.9

18

88.2 11.8

11

89.9 10.1

10 100 0

11

89.8 10.2

6

100 0

Hot food/drink (n) short long

6 74.7 25.3

4 100 0

2 100 0

16 79.9 20.1

15 92.8 7.2

11 89.9 10.1

8 100 0

5 100 0

4 100 0

Sweets (n) short long

6 74.7 25.3

4 100 0

4 100 0

5 40.0 60.0

8 71.4 28.6

6 100 0

4 100 0

3 100 0

3 100 0

Tooth brushing (n) short long

18 100 0

13 100 0

8 100 0

33 76.6 23.4

31 86.2 15.8

27 91.6 8.4

15 85.9 14.1

13 91.5 8.5

16 100 0

Mastication of food (n) short long

32 81.0 19.0

36 83.3 16.7

27 94.4 5.6

57 53.8 46.2

60 65.6 34.4

57 82.0 18.0

36 94.0 6.0

34 96.8 3.2

31 96.7 3.3

Fitting anterior teeth (n) short long

9 66.4 33.6

9 83.4 16.6

9 100 0

51 68.0 32.0

57 79.3 20.7

50 86.4 13.6

33 86.6 13.4

28 96.1 3.9

26 100 0

Fitting posterior teeth (n) short long

30 73.0 27.0

37 84.0 16.0

29 94.7 5.3

53 79.6 20.4

52 87.5 12.5

46 85.0 15.0

18 93.8 6.2

19 100 0

16 100 0

41

Table 9. The statistical significance of the differences in the intensity, quality and duration of

the reported pain during the first three days after each orthodontic procedure, separation of


A3). By Wilcoxon Matched-pairs Signed-Ranks Test.

S1/S2 S1/S3 S2/S3 W1/W2 W1/W3 W2/W3 A1/A2 A1/A3 A2/A3

Cold food/drink

Intensity .41 .18 .56 .06 .003 .029 .70 .06 .06

Quality .50 .58 1.0 .18 .032 .48 .46 .19 .10

Duration .52 .15 .41 .07 .005 .032 .41 .08 .06

Hot food/drink

Intensity .32 .18 .32 .61 .025 .012 .18 .16 .56

Quality .32 .16 .32 .56 .37 .75 .18 .17 .41

Duration .16 .16 .32 .78 .16 .10 .16 .18 .56

Sweets

Intensity .16 .59 .58 1.0 .16 .10 .32 .56 1.0

Quality .08 .74 1.0 .16 1.0 .16 .32 .56 1.0

Duration .18 .48 1.0 .65 .18 .10 .32 .56 1.0

Tooth brushing

Intensity .16 .019 .08 .83 .11 .09 .16 .36 .41

Quality .16 .019 .08 .000 .10 .036 .13 .35 .32

Duration .18 .014 .08 .28 .033 .16 .28 .36 .70

Mastication of food

Intensity .44 .18 .014 .65 .07 .023 .47 .11 .85

Quality .86 .038 .011 .006 .040 .31 .85 .12 .12

Duration .74 .09 .011 .54 .016 .002 .25 .052 .26


Intensity .27 .75 .35 .60 .07 .36 .08 .005 .050

Quality .71 1.0 .68 .09 .012 .71 .021 .015 .87

Duration .71 .46 .71 .81 .08 .040 .041 .023 .46


Intensity .11 .002 .027 .46 .48 .16 .64 .18 .22

Quality .21 .09 .08 .000 .013 .08 .65 .77 .79

Duration .07 .005 .033 .32 .06 .27 .77 .38 .38

42

Table 10. The statistical significance of the differences in the intensity, quality and duration of

the reported pain during the first three days after each orthodontic procedure, separation of


A3). By Wilcoxon Matched-pairs Signed-Ranks Test.

S1/W1 S2/W2 S3/W3 W1/A1 W2/A2 W3/A3 S1/A1 S2/A2 S3/A3

Cold food/drink

Intensity .006 .027 .41 .009 .09 .09 .80 .56 .56

Quality .034 .18 .59 .054 .64 .20 .72 .28 .41

Duration .028 .11 .31 .003 .09 .09 .55 1.0 .56

Hot food/drink

Intensity .021 .005 .034 .015 .005 .034 1.0 .65 1.0

Quality .22 .13 .033 .16 .16 .09 1.0 1.0 1.0

Duration .058 .005 .035 .025 .007 .035 .48 .65 1.0

Sweets

Intensity .70 .68 .70 .46 .20 .41 .33 .21 .48

Quality .56 .70 .70 .70 1.0 .41 .48 .48 .48

Duration .70 .65 .56 .46 .21 .56 .48 .65 .65

Tooth brushing

Intensity .003 .000 .000 .000 .000 .017 .87 1.0 .09

Quality .002 .67 .002 .10 .59 .39 .25 .55 .08

Duration .001 .000 .000 .000 .000 .034 .76 1.0 .10

Mastication of food

Intensity .000 .000 .000 .000 .000 .000 .28 .24 .08

Quality .09 .83 .001 .001 .21 .003 .67 .41 .89

Duration .000 .000 .000 .000 .000 .000 .82 .20 .82


Intensity .000 .000 .000 .000 .000 .000 .019 .012 .012

Quality .000 .000 .000 .008 .051 .015 .003 .010 .06

Duration .000 .000 .000 .000 .000 .000 .013 .026 .012


Intensity .11 .050 .001 .000 .000 .000 .014 .036 .13

Quality .21 .57 .042 .000 .002 .001 .004 .004 .12

Duration .27 .08 .011 .000 .000 .000 .007 .022 .19

43

The intensity in relation to different pain descriptors and duration of the reported pain is shown in Figure 8. Results are based on the combination of the scores, from the seven items throughout three days of the three stages of the treatment (Total Pain Index, TPI, page 26 ), thus describing the pain experienced during the study period.

0

1

2

3

sore shooting dull acheQuality of pain

ain

f p

y o short

sit

long en

Int

Figure 8. The relationship between the intensity, quality and duration of the pain reports given by the subjects (Total Pain Index, score = 0-1512, page 26) during orthodontic treatment. The intensity values are based on (0=no pain, 1=mild pain, 2=moderate pain, 3=severe pain). 5.1.3. Pain experienced during the three days subsequent to each orthodontic procedures The pain scores (Pain Index for one Questionnaire, PIQ, score=0-168, page 26) for each of the first three days after different stages of the orthodontic treatment are shown in Fig. 9. The pain scores after each different treatment stages decreased during the first three days: after separation of molars from 13.6 for S1, to 10.6 for S2 and further to 7.9 for S3. After initial archwire insertion the pain

44

scores were 28.6 for W1, 23.5 for W2 and 16.8 for W3. The pain scores after the activation of archwire were 12.6 for A1, 9.6 for A2 and 7.9 for A3, respectively. Reduction of reported pain symptoms from the first day to the third was evident at all the stages, suggesting that the first day is the most painful. Additionally, the initial archwire insertion was by far the most painful stage of the treatment. The differences in the pain scores were statistically significant (z-test) for the combined three days, between separation of the first molars and initial archwire insertion and between initial archwire insertion and its activation, the difference between the separation of molars and the archwire activation stage was not statistically significant. The differences in the pain scores were statistically significant within each treatment stage between; S1 and S2 (p=.040), S1 and S3 (p=.008), W1 and W3 (p=.000), W2 and W3 (p=.005), A1 and A3 (p=.008) and among different days in different stages of treatment as follows: S1 and W1 (p=.002), S2 and W2 (p=.000), S3 and W3 (p=.001), W1 and A1 (p=.000), W2 and A2 (p=.000), W3 and A3 (p=.005). 0

5

10

15

20

25

30

S1 S2 S3 W1 W2 W3 A1 A2 A3

fitting back teethfitting front teethmasticationtooth brushingsweethotcold

Figure 9. Total index values (Pain Index for one Questionnaire, PIQ, score=0-168, page 26) of the perceived pain for seven items for each of the three days after separation of the molars (S1, S2, S3), after initial archwire insertion (W1, W2, W3) and after wire activation (A1, A2, A3).

45

5.1.4. Pain experienced in relation to different stimuli of the questionnaire The pain scores for each of the seven stimuli combined for different stages of orthodontic treatment (Total Pain Index for one Stimuli, TPIS, score=0-216, page 26) are presented in Figure 10. Sweets gave the lowest score 1.7, followed by hot food/drink 6.2, cold food/drink 10.0 and tooth brushing 10.4. The highest pain scores were found in response to mastication of food and fitting front or back teeth together, 33.8, 27.0 and 24.6, respectively.

separationinitial archwire1st activation

co

ld hotsw

eet

tooth bru

shing

mastica

tion

fitting fr

ont teeth

fitting bac

k teeth

Figure 10. The reported pain for each of the seven items combined for different stages of treatment (Total Pain Index for one Stimuli, TPIS, score=0-216, page 26).

46

10

0

20

30

40

50

5.1.5. The relationship between subjective pain reports and the analgesic consumption The proportion of subjects taking analgesics during the first three days after different stages of treatment is presented in Figure 11. Overall analgesic consumption in the sample was limited to two patients in the separation stage and archwire activation stages and to 15 patients after the initial archwire placement. More analgesics were consumed on the second day after both the separation of molars and the initial archwire than on the first day. During the W3 the use of the analgesics dropped, and none was needed during S3 and A3.

0

5

10

15

20

Separation Initialarchwire

Firstactivation

%

1st day2nd day3rd day

Figure 11. Percentage of the patients (n=64) taking analgesics during the first days after separation of the molars, after initial archwire insertion and archwire activation.

47

Proportion of subjects taking analgesics and that of subjects reporting any pain during each studied day after different stages of orthodontic treatment are shown in Figure 12. Patients responding to any of the items were included, therefore the results from the questionnaire reflects either if there was discomfort associated with different orthodontic procedures or not (yes or no). A correlation (r=0.35) between these two variables was low although statistically significant (p=.006).

0

20

40

60

80

100

S 1st S 2nd S 3rd W 1st W2nd

W 3rd A 1st A 2nd A 3rd

Analgesic cosumptionPain reports

%

.

Figure 12.The proportion (%) of subjects reporting pain and using analgesics during the first three days after separation of molars (S), initial archwire insertion (W) and wire activation (A), (n=64). Patients who had taken medication, reported higher pain scores in connection with all items of the questionnaire except for sweets when compared to those without medication, these differences were statistically significant (t-test) only in fitting front (p=.006) and back (p=.026) teeth together.

48

5.1.6. Relationship between subjective pain reports and age, gender, ext-raction(s) and extent of treatment The difference between the Total Pain Index, TPI, maximum score=1512, of the patients under and above 16 year of age was not statistically significant. However, the older group reported symptoms more frequently and pain was of higher intensity and longer duration in response to mastication on the second day after archwire activation (p=0.047) and initial archwire insertion (p=0.028), respectively. Gender and tooth extractions did not have significant effects on the pain reports. With the treatment of both jaws more discomfort was reported in fitting front and back teeth together, however, the total pain scores between patients with both jaws treated and only one jaw treated did not differ significantly. 5.2. Clinical study 5.2.1. Responses to cold stimulation Proportion of responding teeth to cold stimulation at 15ºC and 0ºC at different stages of the treatment is presented in Table 11. In some of the patients molars were bonded and not separated for the banding procedure. The later measurements from the banded molars were discontinued. A higher proportion of the teeth responded at 0ºC when compared to 15ºC, at all stages of the treatment in all tooth groups examined. Statistically significant differences (Z-test) were found between the proportion of responding teeth in 15ºC and 0ºC at different stages of treatment, namely; incisors and all teeth combined during all the different stages of treatment, premolars and canines during the initial (TI) and three days after the first archwire (TF).

49

Table 11. Proportion of responding teeth to cold stimulation at 15 and 0ºC at different stages of orthodontic treatment. Stages of orthodontic treatment

15ºC % n

0ºC % n

Initial (before treatment) incisors premolars and canines molars all teeth

10.4 33 4.8 21 1.3 2 6.2 56

38.7 122 24.2 104 20.0 30 28.6 256

After separation (S3) molars

3.9 4

22.5 23

Archwire activation (W3) incisors premolars and canines molars all teeth

16.3 45 9.6 36 8.1 11 11.7 92

47.7 132 27.5 103 27.8 37 34.6 272

Before activation incisors premolars and canines molars all teeth

13.3 37 3.5 13 3.1 4 6.9 54

41.2 113 24.3 89 27.6 35 30.9 237

After activation (A3) incisors premolars and canines molars all teeth

17.3 49 6.1 23 2.3 3 9.5 75

38.4 109 23.6 90 19.5 25 28.2 224

In order to study the overall dental cold sensitivity at different stages of orthodontic treatment the

results from maxillary and mandibular teeth were combined and grouped in three; 1) incisors, 2)

canines and premolars, and 3) molars. The mean VAS values in response to cold stimulation at

15ºC for each tooth group at different stages of treatment are shown in Figure 13. The VAS ratings

(SE) at the initial stage were 0.3 (0.3) in molars, 0.65 (0.2) in premolars and canines, 2.1 (0.6) in in-

cisors. The VAS ratings were higher at three days after initial archwire insertion. The mean values

(SE) were 4.0 (0.9) for incisors, 1.9 (0.5) for premolars and canines and 2.2 (1.0) for molars.

50

0

2

4

6

8

10

12

14mm

molars

premolars and caninesincisors

Fig. 13

I II III IV V

Figure 13. The mean VAS pain ratings to cold stimulation at 15ºC in different tooth groups at

different stages of the treatment (I = initial, II = separation of molars, III = three days after

initial archwire insertion, IV = before wire activation and V = three days after activation).

Maxillary and mandibular teeth were combined in each tooth group.





The mean VAS values in response to cold stimulation at 0ºC for each tooth group at different

stages of treatment are shown in Figure 14. The highest VAS ratings were recorded in the

initial archwire insertion stage. The incisors demonstrating increased sensitivity throughout the

study period, 10.7 (1.5) at the initial stage, 14.2 (1.8) at three days after initial archwire

insertion, 13.8 (2.2) at activation and 12.7 (2.1) at three days after activation stage. The

mean,(SE) in the molars increased from the initial 4.45 (1.2) to 9.3 (1.9) three days after initial

archwire activation. Smaller changes were observed in the premolars and canines group during

this study.

The mean VAS values in response to cold stimulation at 0ºC for each tooth group at different

stages of treatment are shown in Figure 14. The highest VAS ratings were recorded in the

initial archwire insertion stage. The incisors demonstrating increased sensitivity throughout the

study period, 10.7 (1.5) at the initial stage, 14.2 (1.8) at three days after initial archwire

insertion, 13.8 (2.2) at activation and 12.7 (2.1) at three days after activation stage. The

mean,(SE) in the molars increased from the initial 4.45 (1.2) to 9.3 (1.9) three days after initial

archwire activation. Smaller changes were observed in the premolars and canines group during

this study.

51

0

2

4

6

8

10

12

14mm

molars premolars and canine

incisors

Fig . 14 I II III IV V



initial archwire insertion, IV = wire activation and V = three days after activation). Maxillary

and mandibular teeth were combined in each tooth group.



initial archwire insertion, IV = wire activation and V = three days after activation). Maxillary

and mandibular teeth were combined in each tooth group.

5.2.1.1. Correlations between the VAS ratings to cold stimulation at 0ºC and 5.2.1.1. Correlations between the VAS ratings to cold stimulation at 0ºC and

15ºC. 15ºC.

The correlation between the VAS ratings to cold stimulation at 0 and 15ºC at different stages of

treatment is presented in Table 12. Using paired t-test for the statistical analysis revealed that

except for molars at the initial stage (p=.131) and three days after activation (p=.083), all other

tooth groups at all the stages were at a statistically significant level.

The correlation between the VAS ratings to cold stimulation at 0 and 15ºC at different stages of

treatment is presented in Table 12. Using paired t-test for the statistical analysis revealed that

except for molars at the initial stage (p=.131) and three days after activation (p=.083), all other

tooth groups at all the stages were at a statistically significant level.

52

Table 12. Correlations (Pearson correlation coefficient) between the VAS values in response of

different groups of permanent teeth to cold at 0 and 15ºC at different stages of orthodontic

treatment.

Treatment phase Molars r

(p)

Premolars and canines

r (p)

Incisors r

(p)

Before treatment After separation of the first molars On the 3rd day after initial arch-wire insertion Before the activation of the archwire On the 3rd day after activation

0.20

(.131)

0.32 (.044) *

0.51

(.000) *

0.30 (.033) *

0.25

(.083)

0.50

(.000) *

0.69 (.000) *

0.54

(.000) *

0.70 (.000) *

0.63

(.000) *

0.40 (.002) *

0.64

(.000) *

0.77 (.000) *

The mean electrical thresholds of each tooth group with the maxillary and mandibular teeth

combined at different stages of the treatment are shown in Figure 15. The mean thresholds (SE) we-

re; 28.2 (2.2), 25.3 (2.3), 24.7 (2.2) and 25.5 (3.2) in molars, 19.3 (1.2), 17.2 (2.0), 17.8 (1.4), 17.1

(1.2), in premolars and canines and 13.2 (0.9), 12.0 (0.9), 12.1 (1.0), 12.7 (1.1) in the incisors, res-

pectively. The difference between the means was statistically significant (p=.031) in incisors

between the archwire activation and three days after wire activation.

53

0

5

10

15

20

25

30

35 µA

F ig. 15

molars

premolars and canines

incisors

I II III IV V

Figure 15. The mean dental electrical thresholds in different tooth groups at different stages of

the treatment (I = initial, II = three days after the separation of molars, III = three days after the



Figure 15. The mean dental electrical thresholds in different tooth groups at different stages of

the treatment (I = initial, II = three days after the separation of molars, III = three days after the



5.3. Comparison of two different orthodontic mechanotherapies 5.3. Comparison of two different orthodontic mechanotherapies

In general the differences in the prevalence of the pain between the two fixed appliances were

small and statistically significant only in connection with some of the questionnaire items

which altogether gave the most frequent pain reports. Such items were mastication, fitting

anterior and posterior teeth together.

In general the differences in the prevalence of the pain between the two fixed appliances were

small and statistically significant only in connection with some of the questionnaire items

which altogether gave the most frequent pain reports. Such items were mastication, fitting

anterior and posterior teeth together.

Differences in the pain scores between different fixed appliances, during the initial archwire

insertion and wire activation stage, in response to each item (Pain Index of one stimuli in two

Stages, page 26) is presented in Table 13. No statistical significant difference was found.

Mastication of food was reported to have the highest score in both fixed appliances in the

combined initial archwire and wire activation stage. Followed by fitting anterior and posterior

teeth together, respectively.

Differences in the pain scores between different fixed appliances, during the initial archwire

insertion and wire activation stage, in response to each item (Pain Index of one stimuli in two

Stages, page 26) is presented in Table 13. No statistical significant difference was found.

Mastication of food was reported to have the highest score in both fixed appliances in the

combined initial archwire and wire activation stage. Followed by fitting anterior and posterior

teeth together, respectively.

54

Table 13. The reported pain scores during the initial archwire and wire activation stage (Pain

Index of one stimuli in two Stages, page 26) for each of the items in different fixed appliances.

Alexander technique Viazis technique p* mean SD mean SD Cold 9.8 14.5 11.9 19.6 .668 Hot 5.5 10.1 8.5 19.7 .507 Sweet 1.5 6.4 0.5 1.3 .486 Tooth brushing 9.4 17.8 12.8 19.8 .521 Mastication 25.9 27.0 31.5 27.5 .474 Fitting anterior teeth 24.3 27.7 30.0 31.4 .508 Fitting posterior teeth 15.8 21.7 20.9 19.1 .386

* by t-test

The reported pain scores from each of the days after the initial archwire (W1, W2, W3) and the

wire activation (A1, A2, A3) were compared and no statistical differences were found in

different fixed appliances. After the initial archwire insertion pain reports were more frequent,

having higher score, in the Viazis technique than the Alexander. However, after the wire

activation stage the pain scores were higher in the Alexander technique.

The changes in the reported pain scores (Index 1, score=0-24) from the first three days after

initial archwire to the corresponding days after wire activation of each item in different fixed

appliances were studied and analyzed further. Difference of the pain reports was calculated by

subtracting the pain scores at the initial archwire insertion from the reported pain scores during

the wire activation. Generally the pain scores from the initial archwire to the wire activation

have reduced more in the Viazis technique, being at a statistically significant level only on the

first days during mastication. There was a reduction of pain scores from the initial archwire

insertion to the archwire activation in response to all items but on the first days in sweets with

Viazis technique also on the second and third days in tooth brushing with Alexander technique.

55

5.3.1. Dental cold sensitivity and electrical thresholds in two different

orthodontic mechanotherapies.

The mean VAS ratings to cold at 15ºC at different stages of treatment in connection with the

two different fixed orthodontic appliances were studied and analyzed further. Already at the

initial stage, before treatment, there was a statistically significant difference between the two

system in premolars and canines (p=.014) and all teeth combined (p=.032). There was a statisti-

cal significant differences in the corresponding values also three days after initial archwire

insertion (p=.013, p=.008) and at the activation of the archwire (p=.039, p=013) respectively.

The mean VAS ratings in response to cold stimulation at 0ºC at different stages of treatment in

reaction to the two different fixed orthodontic appliances were studied and analyzed further. No

statistically significant differences were found between the two systems at the initial stage. The

mean VAS values in the other stages of the treatment (three days after initial archwire, before

activation of archwire and three days after activation) were lower in the Viazis technique

compared to the Alexander. With all the teeth combined the differences were statistically sig-

nificant three days after initial archwire (p=.012), at activation (p=.017) and three days after

activation (p=.003). The differences in the mean VAS ratings were also statistically significant

in premolars and canines three days after initial archwire placement and three days after wire

activation (p=.024, p=.001) respectively and in molars (p=.035) three days after archwire

activation.

The mean dental electrical thresholds related to the two different fixed orthodontic appliances

were studied and analyzed further. There were no statistically significant differences at the

initial stage between the two groups. However, at the activation stage all tooth groups were less

sensitive in the Viazis technique with the difference in the incisors (p=.034), premolars and ca-

nines (p=.005) and all teeth combined (p=.000) being at a statistically significant level. Also a

significant difference was found three days after archwire activation, when the teeth were

combined (p=.020). This might as well point to, increased pulpal disturbances.

56

5.3.2. Tooth movements in two different orthodontic mechanotherapies

The results from tooth movements with different fixed appliances, using the irregularity index,

defined as the summed displacement of adjacent anatomic contact points (Little 1975) for the

anterior (canine to canine) crowding showed no statistically significant difference between the

two techniques, either before or after three months of fixed orthodontic treatment. The mean

crowding values for each patient was used for statistical analysis. In extraction cases, patients

treated with the Viazis technique demonstrated the mean space closure at the third month to be

2.8mm compared to less than 1mm using Alexander technique.

57

6. DISCUSSION

6.1. Study subjects

The sample was formed by consecutive cases from patients who were willing to participate. As seen

in many practices of contemporary orthodontics (Gottlieb and Voges, 1984) the number of adult pa-

tients seeking therapy is increasing. This explains the high mean age of 26.4 years of the study sam-

ple. Because age distribution was rather wide age was included in the statistical analyses as a

confounding factor. Gender distribution was not even in the sample, female subjects were over

presented, as is the case in most orthodontic practices. The effect of gender was also controlled

during the statistical analyses, and proved not to have an effect on the results.

Size of the study sample was adequate for this study design. Because of the small number of

participants, the six patients who were treated with standard edgewise technique were not included

in the statistical analysis as a separate group. When comparing the two different fixed orthodontic

appliances there was no difference between the two study groups as regard to the age and gender.

6.2. Measurement of the experienced pain

6.2.1. The questionnaire

Most of the existing literature on the pain and discomfort related to orthodontic treatment has con-

centrated on the intensity of pain with different evaluating methods, i.e. the Verbal Rating Scale or

the Visual Analogue Scale.

In the present study subjective pain symptoms subsequent to different stages of orthodontic

treatment were recorded using the questionnaire structured to include the intensity, quality and the

duration of the experienced pain. Attempts were made to structure the questionnaire as simple as

possible to minimize the difficulties usually involved with filling out questionnaires especially

regarding the youngest study subjects. To avoid a large volume of questionnaires and patients con-

fusion, considering the longitudinal nature of this study, it was decided to combine the intensity,

quality and duration of the pain symptoms in one questionnaire. The same form was filled out by

the patients during three consecutive days after each orthodontic procedures, namely after

separation of first molars, insertion of the initial archwire and after the first archwire activation.

58

Cooperation from the patients during the study was excellent, especially considering the time and

effort required for the completion of the repeated clinical tests and questionnaires during different

stages of treatment.

Orthodontic tooth movement is believed to cause varying pain and discomfort to patients (SBU

2005). The first day after each orthodontic procedure has been suggested as being associated with

the most discomfort experienced (Tayer and Burek 1981, Brown and Moerenhout 1991, Jones and

Chan 1992, Scheurer et al. 1996, Yozgatian et al. 2008). The time envelope for this perception has

also been reported to peak on the first and second days and to decrease to minor levels after five

days (Jones 1984, Jones and Richmond 1985, Sinclair et al. 1986, Feinmann et al. 1987, Kvam et al.

1987, 1989, Ngan et al. 1989, Wilson et al. 1989, Jones and Chan 1992, Scheurer 1996). Further-

more, Soltis et al. (1971) found that patient’s proprioceptive and discriminatory ability was reduced

four days after the insertion of orthodontic appliances. The patient’s discomfort at onset and during

various stages of treatment was attributed to the lowering of the pain threshold and disruption of the

level of proprioception of the nerve endings in the periodontal ligament (Jones 1984). It seemed

appropriate and was decided to follow the pain experience for three days after each orthodontic

procedure. In this sample, the first day after each procedure was reported to be related to most

discomfort, with systematic relief of the pain experience from the first to the third day.

Questions regarding the occurrence of pain as response to seven different stimuli were included

(Appendix I). The selection of these stimuli is a critical task, since most often and justifiably so; the

variables are chosen to reflect the effects of orthodontic forces on periodontal tissues, such as

mastication of food, fitting anterior and posterior teeth together. Included were also functions that

would provide information to study the possible effects of the orthodontic forces on the dental pulp,

such as the responses to cold and hot food/drink. Eating sweets was included to serve as the control

as well as an indicator of possible responses from exposed dentine. Therefore comparing these

selected stimuli seemed logical because there is a difference in the induction of pain responses for

example from, taking sweets, cold food/drink and mastication of food, which can be related to

exposed dentin, pulpal and/or periodontal inflammation and hypersensitivity. The most frequent

variables describing pain experience related to orthodontic treatment were mastication of food,

fitting anterior and posterior teeth together followed by tooth brushing, cold and hot food or drink,

respectively. Eating sweets only seldom induced any pain or discomfort.

Responses from the TMJ and soft tissues (lips, cheeks, gingiva and tongue) to orthodontic ap-

pliances were not included in the questionnaire. Patients were directed to possibly respond to the

59

sensations evoked by orthodontic appliances to the teeth only. Scheurer et al. (1996) have also

reported that TMJ and soft tissues were not significantly affected by fixed orthodontic appliances,

but the discomfort during orthodontic therapy was mainly localized at the teeth.

There were no questionnaires given to the patients before the treatment, although it could be

hypothesized that the discomfort during the orthodontic treatment may be associated with the

preexisting pathologies and malocclusions. This should be taken into account when considering the

pain symptoms and discomfort which orthodontic treatment may induce. However, during the

process of data collection for diagnostic purposes none of the patients included in the study

indicated to have suffered from any dental pain. Moreover, responses to the questionnaire showed

considerable differences in the pain reports among different stages of treatment.

The method used for assessment of the intensity of pain in this study was a numeric rating scale and

adopted version of the verbal rating scale (Bond 1979). It has been successfully used in previous

studies (Newman 1980, Jones 1984, Kontturi-Närhi 1993). The method proved to be reliable, and

was considered adequate for the purpose of this study, although, it may pay more attention to the

emotional, cognitive and motivational variables that modify the pain or discomfort sensation (Jones

1984).

Estimating quality of the experienced dental pain has been excluded from the pain research in

orthodontics. Evaluating quality of pain symptoms, reflecting also the intensity of pain in

hypersensitive dentin proved to be a reliable method and gave valuable information in a study by

Kontturi-Närhi (1993). Consequently, for the first time in orthodontic literature the present study

included systematic evaluation of the quality of pain symptoms induced by different orthodontic

procedures.

The descriptors of the type or quality and duration of pain have been used earlier (Addy et al.

1987b, Orchardson and Collins 1987a, Kontturi-Närhi 1993). McGill’s Pain Questionnaire MPQ, or

verbal checklist were not used in the present study because of the restrictions due to the length and

the laboriousness of the questionnaire, although this method has advantages like it’s

multidimensional nature and better ability to express the affective aspects of pain (Gracely et al.

1978, Duncan et al. 1989). Even in the MPQ the vocabulary is limited and moreover, it’s use is

time-consuming (Gracely et al. 1978). According to Curro (1990) no pain-word questionnaire has

sufficient properties for an ideal pain measurement.

60

In the studies of pain connected to orthodontic treatment, duration of the pain experience is most

often referred to and usually measured either in hours or days. In addition to the measurement of the

time envelop of the pain related to orthodontic treatment for three consecutive days, it was found in

this study necessary to also evaluate and assess the duration of such immediate pain symptoms as

they occur. Therefore, patients were requested to respond to the duration (short or long) of the

provoked painful sensation. Although, rather crude, it was chosen to keep the questionnaire simple.

A quite similar binary scale for the description of pain duration has been used satisfactorily

(Kontturi- Närhi 1993).

The need to have numerical values for the statistical analyses lead to study a possible relationship

between the intensity, quality and the duration of the experienced pain. Further assessment of the

results revealed the existence of a relationship between the intensity of the different descriptors used

to explain the quality of pain symptoms. The intensity increased from sore to shooting and further

to dull pain, with ache having the highest intensity. Looking at the association between the intensity

and the quality of the pain experienced one might argue that the differences between the intensity of

the pain descriptors were small and not statistically significant. However, the pain descriptor

changes at different stages of treatment (separation of the first molars, initial archwire insertion and

archwire activation) did not exceed 6.5%, with the average changes being at less than 2% level.

Therefore, it could not have affected the results significantly. Long duration pain had reportedly

higher intensity than short lasting pain. Based on the association between the intensity, quality and

duration of pain symptoms an Index (page 26) was formed describing the pain experience. It was

justified to arrange the descriptors of pain in such a way so that the combination of the intensity,

quality and the duration of pain reports would facilitate the use of statistical methods. The

sensitivity and reliability of the Pain Index was confirmed when the results from the prevalence,

intensity, quality and the duration of the pain reports were considered separately. Evaluation of the

results as regards to the Pain Index, therefore, should be handled with caution, since they do not

represent absolute values, rather a combined measure of the intensity, quality and duration of the

pain experienced

6.2.2. Subjective pain symptoms related to different orthodontic procedures

Prevalence of the pain was highest after the placement of the initial archwire in comparison to the

separation of molars and activation of the archwire. Proportion of patients who experienced pain

was 70% after separation of molars, 96% after initial archwire insertion and 69% after archwire

activation. These results are in agreement with the previous investigations, Kvam et al. (1987) re-

61

ported that 95% of all patients experienced from fixed orthodontic appliances (initial archwire),

Scheurer et al. (1996) also reported the prevalence of pain to be at 94% within the first 24 hours.

Similar observations have been made (Wilson et al. 1989, Ngan et al. 1989 and 1994, Jones and

Chan 1992). The pain experienced after each of the three orthodontic procedures had higher pain

score in the first day, which gradually decreased toward the third day. A point worth mentioning

here is that over all, during the initial archwire insertion higher proportion of the subjects had pain -

on the second day than on the first day. However, when considering the intensity, quality and the

duration of pain, the total score for the pain experienced was higher during the first day.

Prevalence of pain experience during the first days after each orthodontic procedure also indicates,

statistically significant differences between the first day after the initial archwire insertion (W1) and

the first days after separation of molars (S1) in connection with all items but sweets, also between

(W1) and the fist day after the archwire activation (A1) except for sweets and hot food/drink.

However, such statistical differences were limited only to fitting teeth together between the

archwire activation (A1) and separation of molars (S1).

6.2.3. Intensity, quality and duration of the pain symptoms

The intensity of the reported pain during the study period (all three stages combined) was most

frequently mild 62.5%, followed by moderate 28.5% and severe pain 9%. However, after the

insertion of initial archwire, which was reported to be the most painful stage of the treatment, the

pain reports showed higher intensities, 52.7% being mild, 33.9% moderate and 13.4% severe pain.

Pain intensity in the present study cannot be compared directly to the study by Jones (1984).

However, in contrast to his conclusions that out of 30 patients, 23 suffered moderate to severe

discomfort, in the present study mild pain showed by far the highest proportion among the reports.

According to Locker and Grushka (1987), most of the orofacial pain symptoms were reported as

mild and that severe or intolerable orofacial pain was found in 11.5% of their subjects. Gradual de-

crease of the reported intensity of pain from the first to third day was apparent in the present study -

which is in agreement with the previous reports (Jones 1984, Jones and Richmond 1985, Sinclair et

al. 1986, Feinmann et al. 1987, Kvam et al. 1987, 1989, Ngan et al. 1989, Wilson et al. 1989, Jones

and Chan 1992, Scheurer 1996). The results of the present study indicate that the pain experienced

during the initial archwire insertion was the most intense. Also the first day after each orthodontic

treatment stage was connected with the highest discomfort, which was generally of mild to

moderate intensity.

62

The proportions of different types or qualities of the pain symptoms reported during the study

period were 63.5% for sore, 14.3% for shooting, 14.3% for dull and 7.9% for aching pain. The first

day after any of the three orthodontic treatment stages showed the most frequent aching pain

reports, the highest being on the first day after initial archwire insertion. As mentioned earlier the

type or quality of the pain experience did not change significantly between different orthodontic

procedures and during the insertion of initial archwire the distribution of the quality of pain changed

minimally, 65.2% for sore, 14.6% for shooting, 12.1% for dull and 8.1% for ache. The results

suggest that the type or quality of the pain experienced during orthodontic treatment does not

change significantly.

The first day after any of the orthodontic treatment stages had higher frequency of long duration

pain among the three days, with the highest recording being during the first day after initial

archwire insertion. An interesting observation is that the occurrence of the long duration of pain

also declined gradually from the first to the third day.

6.2.4. Analgesic consumption

The individual variation is reflected in the consumption of analgesics because it could be a matter of

whether a person preferred avoiding medicine or was keen on taking analgesics on a preventive

basis. Ideally an analgesic drug provides significant relief across all pain severities, has minimal

side effects, has few drug interactions and is convenient to administer (Altman 2004, Antman et. al

2007, Chang et. al 2005, Savage and Henry 2004, Zelenakas et. al 2004). Although somewhat a

coarse method for pain assessment analgesic consumption showed a similar pattern to the responses

from the questionnaires. In this sample, regression model showed that after the initial archwire

insertion T2 and archwire activation T4, there was a need for pain medication. At the peak of the

reported pain symptoms, during the initial archwire insertion 15 patients, about one in four, reported

the need for pain medication. However, during the separation of molars and wire activation the

corresponding number was only two. At the initial archwire insertion stage about one fourth of

patients reported taking medication with one patient taking three doses during the first day. The

demand for analgesics was limited to the first and second day during the separation of molars and

activation stage with no patient reporting having taken medication on the third day. However,

during the initial archwire insertion 5% of patients took medication for pain relief on the third day,

this is in agreement with the results from Jones (1984) and Scheurer et al. (1996). In contrast to the

findings of Feinmann et al. (1987) who reported no correlation between the pain experience and

analgesic consumption, in the present study a correlation was found between the total pain score

63

and the use of analgesics.

Ngan et al (1994) have reported that after one initial dose of analgesics at the moment of orthodon-

tic appliance insertion, none of the patients needed additional pain relief. Although in the present

study neither prescription for pain medication nor analgesics were dispensed to the patients, it is

possible that some patients consumed the analgesics as a preventive measure.

First and second days after either initial archwire insertion or archwire activation, provoked the

experienced pain and the need for analgesic.

6.2.5. Dental pain sites

Pain connected to orthodontic tooth movement most probably originates from the periodontal

tissues due to mechanical injury and consequent inflammatory reaction. However, also intradental

nociceptive nerves may be involved because periodontal inflammatory reactions may spread to the

pulp due to formation and diffusion of various inflammatory mediators, and neurogenic

inflammation mediated by branching axons, which are known to innervate both the pulp and

periodontal ligament (Byers 1984, 1985, 1994, Byers et al. 1992b). Moreover, as already

mentioned, nerve sprouting also takes place within the pulp in response to orthodontic forces, which

may affect the functional properties of the intradental nerves. Also, possible impairment of the

pulpal blood flow due to vessel compression may play a role.

Chewing something fairly hard -a plastic wafer, for example- within the first two hours after arch

wire adjustment may act to reduce the ischemia and inflammation in the periodontal ligament

(Furstman and Bernick 1972). Stimulation of vascular and lymphatic circulation would prevent the

build-up of metabolic products, which are known to stimulate pain receptors (Proffit 1986).

The pain experienced during separation of the first molars understandably was related to the

mastication of food and fitting posterior teeth together. Interestingly fitting anterior teeth together

although not at a statistically significant level, was also affected to some extent with the placement

of orthodontic separators. Similar observations have been made by Ngan et al. (1989).

At the initial archwire insertion the responses were mostly concentrated in mastication, as well as

fitting anterior and posterior teeth together respectively. This is not surprising since insertion of the

archwire for initial alignment tends to increase the level of discomfort on the front teeth. This

64

finding is in agreement with previous studies (Ngan et al. 1989, Scheurer et al. 1996) and further

demonstrates the sensitivity of the questionnaire used in the present study.

A month later at the activation of archwire, however, the responses were different, fitting anterior

teeth was the most frequently recorded function inducing pain, followed by mastication of food. At

this stage the experienced pain caused by fitting posterior teeth together was at its lowest level,

which may suggest that as the orthodontic treatment progresses, at least during the initial stage,

there is a gradual decrease of the pain symptoms which seems to start from the posterior teeth.

6.2.6. Relationships between the pain symptoms during initial tooth movement

and age, gender, and treatment approach.

Over the years the question of whether or not age has an influence on perceived pain during

orthodontic therapy has remained controversial, partially due to the differences in study designs and

experiments. In this study, the clinical data indicates a higher discomfort experience in patients aged

16 and over than those of under, being at a statistically significant level in connection with incisors,

canines and premolars during activation of the archwire in response to cold stimulation at 15ºC.

This is in agreement with the findings of Jones (1984), Jones and Chan (1992).

It has been suggested previously that pain might be related to gender (Feinmann et al. 1987).

However, in the present study no statistically significant difference was found between genders in

the subsequent pain responses. Earlier reports seem to agree with this finding (Jones 1984, Ngan et

al. 1989, Jones and Chan 1992). However, Kvam et al. (1987), and Scheurer et al (1996), have

observed that females reported a higher impact on daily life from orthodontic appliances than

males.

Pain symptoms did not differ between extraction and non-extraction cases. Some orthodontists may

prefer to initiate the treatment of one arch at a time to alleviate the pain. Except for molars

responses to cold stimulation at 15ºC during the archwire activation indicating less sensitivity when

treating one arch, the results from this study did not indicate that this treatment strategy would

reduce the perceived pain/discomfort. This finding is in line with the findings of Scheurer et al.

(1996), and Jones and Chan (1992).

65

6.3. Clinical study

6.3.1. Electrical tooth stimulation

Electrical pulp testing methods were first developed in the 1860´s and since that time, many

different methods have been used (Lin and Chandler 2008), dealing with faradic current, galvanic

current, direct, alternating, or high frequency alternating current (Burnside et al. 1974). Electrical

stimulation is convenient in that the stimulus intensity needed to evoke a sensory response can be

determined accurately. The end point of electrical stimulus determination is a threshold sensation,

prepain. Mumford (1973) stated, "Electrical stimuli are at once the most natural and the most artifi-

cial of the stimuli applied to the teeth. They are natural in that conduction through the tissues is

electrolytic, depending on ionic movement, and ionic movement is fundamental to nerve excitation.

They are artificial in that electrical stimuli not applied to the teeth in the natural way that thermal

stimuli are when eating and drinking. However, electrical stimuli have the great advantage over

other stimuli that they can be precisely defined by electronic methods."

Constant current stimulator used in the present study had optimal output characteristics with 10 ms

cathodal square wave pulses (Björn 1946, Mumford and Björn 1962, Mumford 1982). Matthews

and Searle (1974) have investigated seven different pulp testers and reported Bofors® pulp tester

(the electrical stimulator used in the present study) to be the most reliable. Constant current

stimulator minimizes the effect of possible variations in the impedance of the stimulation circuit

(Mumford 1982). If the stimulation were not of constant current type, any changes in the impedance

of stimulation circuit would result in a change in the effective (stimulating) current intensity in the

pulp (Kontturi-Närhi 1993). The current density in the area of the nerve fibers is decisive for their

activation (Mumford 1982). Thus, measurement of voltage in the teeth is unsatisfactory, voltage

drop may vary because of variations in electrical resistance of the dental hard tissues. In addition,

cracks, pits, fissures, caries, restorations, and fractures may cause variations in electrical resistance.

Therefore, in order to overcome such variations in resistance, a stimulator that measures current

rather than voltage should be used.

During the stimulation of teeth the electrode was in contact to the incisal/occlusal third on the

lingual surface of the teeth, cervical stimulation was avoided because of the possibility of current

leakage to the soft tissues with the low resistance (Mumford and Björn 1962, Matthews and Searle

1974, Mumford 1982). The lingual surfaces were used for electrical stimulation to avoid possible

interferences from the brackets. In the view of the fact that all efforts on the part of examiner were

made to isolate the teeth from saliva and tongue, there were cases especially in the lower jaw that

66

made this task difficult. Saliva would provide a current leakage to the soft tissues therefore

increasing the readings significantly. Thus each tooth was tested twice at any given session and if

the difference between the two recordings more than 10 µA for incisors, more than 15 µA for

canines and premolars and more than 25 µA for molars the lower value was taken for statistical

analysis instead of taking a mean value.

Teeth which were not fully erupted were excluded from the clinical testing, because the larger the

quantity of pulp tissue the the amount of electrical current

passing through a unit area in the pulp is greatest where the pulp tissue is thinnest (Hargreaves

1973). There was no statistically significant differences between the maxillary and mandibular

dental electrical thresholds, thus they were combined. Teeth were further grouped as recommended

by Mumford (1982) in the following order, 1) incisors, 2) canines and premolars and 3) molars.

smaller is the electrical impedance,

Nordh (1955) used the Björn pulp tester for testing 36 teeth on the same day before and after orth-

odontic band placement and reported no significant difference in the perception thresholds. He also

tested 13 teeth (with a control group of 10) before and after orthodontic space closure and found no

significant differences. Burnside et al. (1974) reported higher pain threshold values to electrical

stimulation in the experimental group, however the comparison was made between patients who

had fixed orthodontic appliances for a minimum of four months prior to testing and a control group

without any appliances.

Effectiveness of an electrical current in stimulating a tooth does not depend on the presence of

receptors at the pulp dentin junction, this activation likely occurs on more central component of the

axons in dental pulp (Mumford 1982, Närhi 1985b). Mumford (1982) has further reported teeth

with hyperemia or acute pulpitis not to have a lower electrical threshold. Therefore, the electrical

threshold determination does not give much if any information on the receptor sensitivity. Kontturi-

Närhi (1993) has also reported similar findings. Because of the longitudinal nature of this study and

tooth responses to orthodontic forces and pulpal tissue reaction to such forces (i.e. hyperemia), an

interesting objective of the present study was to find out if there were any changes in electrical

thresholds of the teeth. However, the results have clearly demonstrated that dental electrical thresh-

olds were generally constant, before, during and after different orthodontic treatment procedures.

67

6.3.2. Cold sensitivity tests

Cold has been reported to be the most potent irritant in inducing pain in hypersensitive teeth

(Naylor 1961, Brännström 1981, Dowel et al. 1985, Flynn et al. 1985, Närhi 1985a, Orchardson and

Collins 1987a,b, Kontturi-Närhi 1993). Extreme cold for pulp vitality test has long been in use.

Saxer (1958) using dry ice or carbon dioxide snow for pulp vitality test, reported in 1000 teeth an

accuracy of 97.5%, compared to 97.2% for electrical pulp testing. Although the temperature of

carbon dioxide snow is -78ºC, Augsburger and Peters (1981) found that the intra pulpal tempera-

ture, as measured in vitro, decreased only by a mean value of 15.6ºC for non-carious teeth. Their

clinical studies indicated that a 2-second exposure was sufficient to produce a sensory response.

The present study is the first in the orthodontic literature to have extensively investigated pulpal

reaction to orthodontic tooth movement. Additionally, it is the first to use an accurate and reliable

electrothermal device for evaluation of the intensity of orthodontic related pain symptoms.

The electorthermal device used in the present study for the cold stimulation was constructed at the

Technical Center of the University of Kuopio, Finland. The reliability of a similar device has been

confirmed previously and cold stimulation was found to be the most suitable for dentin sensitivity

tests (Kontturi-Närhi 1993). The desired temperature could be adjusted with an accuracy of 0.1ºC,

which is more than satisfactory for the clinical tests. The size of the stimulator tip was suitable

having a sufficient thermal capacity and allowing a good access to the teeth. The thermal

stimulator’s tip was flat, the contact area varied considering the shape of the tooth surface. This

may have caused variations in the stimulus applied. However, this variation was acceptable because

of the good correlation between the responses to cold stimulation at the different temperatures

studied.

Visual Analogue Scale (VAS) was used to evaluate the intensity of the induced pain during the cold

stimulations. This method is widely used for measuring pain and has been described by other

investigators as being sensitive and reliable and also having certain advantages over verbal scales

(Uskisson 1974, Huskisson 1983, Seymour et al. 1985, McGrath 1986, Duncan et al. 1989). VAS is

a direct rating scale and offers a continuum of different pain intensity levels (Huskisson 1983) and

accordingly allows the use of parametric statistical tests (Bhat 1986).

Cold stimulation at 0ºC induced more pain than at 15ºC before, during and after application of

orthodontic forces during the study. The pain responses to clinical examinations at 0ºC and 15ºC,

68

interestingly, were corresponding to the fluctuation of the pain experience as reported by the

patients in response to the questionnaire. Also the subjective pain reports indicated the initial

archwire insertion to be the most painful stage of treatment. The cold responses were the most

intense in incisors, canines/premolars and molars respectively. The incisors which were the most

sensitive tooth group to cold showed the most intense pain responses during initial archwire inser-

tion which is in agreement with the questionnaire results.

Although, the proportion of teeth responding to cold stimulation at 15ºC was significantly lower

than at 0ºC, by no means this test is less effective in its ability to distinguish between different

stages of treatment. Using paired t-test revealed that responses of the first molars to cold stimulation at

0ºC, also incisors, canines and premolars at 15ºC were at a statistically significant level when

comparing the initial archwire insertion to other stages of the orthodontic treatment.

An interesting observation was that when considering cold stimulation at 0ºC only molars were

found to be responding at a statistically significant level. However, during cold stimulation at 15ºC

such differences were exclusive for incisors, canines and premolars. One explanation for the

differences could be that two seconds of cold stimulation at 15ºC for molars was not sufficient for

the differentiation of responses considering the thickness of the enamel and dentin of such teeth. On

the other hand cold stimulation at 0ºC was able to differentiate the most sensitive stage (initial

archwire insertion) from all other stages. Looking at the responses from incisors, canines and

premolars, it seems that cold stimulation at 0ºC although evoked more responses overall (28.2%-

34.6%) than 15ºC (6.25%-11.7%), it might have been too strong a stimulus for patients’

discriminatory ability to differentiate among different stages of the treatment. However, cold stimu-

lation of incisors, canines and premolars, at 15ºC was able to differentiate the sensitivity changes

during different procedures of orthodontic therapy.

Although the changes in the dental cold sensitivity during orthodontic treatment were small they

indicate that part of the discomfort and pain experienced by the patients may, in fact, be of pulpal

origin. It has been shown that morphological changes in the pulpal innervations can be induced by

orthodontic forces (Yamaguchi and Kasai 2005). The sensitivity changes found in the present study

may be related to such morphological nerve responses.

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6.3.3. Comparison of different fixed orthodontic appliances

Both techniques under trial in this study used light continuous forces. Aside from the obvious

differences in the bracket designs, there are two major differences between the two approaches.

First, the dimension and the amount of the force delivered by different initial archwires and second,

the use of closed coils in extraction cases.

Using the Irregularity Index there was no statistically significant difference between the two fixed

appliance groups prior to orthodontic treatment.

The decisions for extraction of teeth were made either to relieve the severely crowded dental arches

and/or to reduce the excessive over jet and/or over bite. Although, all extraction spaces were

completely closed by the end of the orthodontic treatment, the study period considers only the tooth

movements, which occurred during the first three months of the treatment, and compared the tooth

movements accordingly.

One difference was the timing of the application of force, for canine retraction in extraction cases.

Because, as shown by Quinn and Yoshikawa (1985), once the force threshold for tooth movement is

reached, the magnitude of the force applied to the teeth becomes less important. Therefore, using

light forces to have a control of the unwanted movement of the anchor teeth is a fact, which was

taken into account and in the sample studied. Although not separately studied, clinically there was

no evidence of anchorage loss.

Generally, the results of the present questionnaire study indicated no statistically significant

differences in terms of the pain experienced, in either of the initial archwires or their activation

stages between the two techniques. Patients inability to distinguish between the two light

continuous force systems used in the study, is in line with the previous findings (Boester and

Johnston 1974, Andreasen and Zwanziger 1980, Jones and Richmond 1985, Jones and Chan 1992,

Scott et al. 2008). Using the Irregularity Index (Little, 1975) for evaluating the anterior crowding

revealed no statistically significant difference between the two techniques. This finding is also

supported by the conclusion of O´Brien et al. (1990). In extraction cases using closed coils at the

initial stage increased tooth movement was observed during the period of three months. It is a fact

that at present no archwire is "ideal" for all type of orthodontic tooth movement. This is not

surprising because the demands of the treatment plan require different characteristic stiffnesses and

ranges (Kusy 1997).

70

Results from the thermal sensitivity tests using Visual Analogue Scale (VAS) have indicated that

the differences between the groups were altogether small and do not as such justify too extensive

comparison of the two techniques.

Ideally the orthodontic forces should be kept to a level below the pain threshold of each individual

patient. Our results indicate that slight difference in the forces applied, assuming it is within the

recommended range, type and duration, during the initial phase of the orthodontic treatment is not

directly related to the pain experienced by the patients and the tooth sensitivity. Obviously, there is

a difference in the timing of the force application in extraction cases between the two techniques,

and the picture becomes more complicated when we consider the type of tooth movement, for

example, tipping and rotation. Further study is necessary to answer these questions. In light of the

present results it is therefore recommended that the bracket design and ligation system should be

modified in such a way that can accommodate and take advantage of the ever changing new

information and wire technology.

71

7. SUMMARY AND CONCLUSIONS

The present study was performed to assess the experienced pain as reported by the patients at

different stages of orthodontic treatment. It was also examined if orthodontic forces and tooth

movement affect the dental pulp sensitivity, and if such sensitivity is related to the pain experience.

The study subjects were 64 orthodontic patients, 46 females and 18 males, with the mean age of

26.4 (SD 11.2) years and range of 10.8-49.3 years. The sample consisted of consecutive cases of

patients who were willing to participate in the study. A structured questionnaire was used to map

the prevalence, intensity, quality and duration of pain/discomfort after separation of first molars,

after the initial archwire insertion and after the first activation of the archwire, for three days after

each stage. Dental electrical thresholds were measured using an electrical pulp tester and thermal

sensitivity measurement was carried out with an electrothermal device at 15ºC and 0ºC. The

intensity of the pain induced by cold stimulation was assessed using a 100 mm Visual Analogue

Scale (VAS). Deciduous teeth were excluded from the clinical measurements. Altogether 907

permanent teeth of 64 patients were measured at all stages of the study. Tooth movement (mm) was

measured from the hard stone casts using the Irregularity Index (Little 1975). Additionally, two

different orthodontic techniques, namely those of the Alexander and the Viazis, were compared for

the pain experienced, dental sensitivity to cold stimulation and electrical thresholds as well as for

the rate of the tooth movement.

The prevalence of the pain reports according to the questionnaire was higher after the initial

archwire insertion (96%) than after the separation of the first molars (70%) or the archwire

activation (69%). The first day after any of the three orthodontic treatment stages had the most

frequent pain experience, the highest being on the first day after initial archwire insertion. The most

common stimuli related to pain during the first three days after the initial archwire insertion were:

1) mastication of food in 90.2% of the subjects 2) fitting anterior teeth together in 82.7% 3) fitting

posterior teeth together in 78.6% 4) tooth brushing in 47.6% 5) cold food/drink in 27.4% 6) hot

food/drink in 22.3% and 7) sweets in 9.8%. Longer duration of the experienced pain was reported

during the first day after any of the orthodontic procedures, the highest being recorded during the

first day after the initial archwire insertion. The perceived pain decreased significantly from the first

to the second and further to the third day after each orthodontic procedure.

The intensity of the reported pain during the study period was most often mild, in 62.5% of the

reports followed by moderate pain in 28.5% and severe pain in 9%. The pain reported by the

patients after different orthodontic procedures was most often described as sore (63.5%), followed

72

by shooting (14.3%), dull (14.3%) and aching (7.9%) pain. Generally, the quality or type of the pain

symptoms remained constant during the initial stage of orthodontic treatment. The duration of the

pain symptoms reported after different orthodontic procedures was usually short, in 85% of the

reports, compared to long duration found in 15%.

The analgesic consumption showed a similar pattern as the prevalence and intensity of the pain

reports. In general, patients who consumed analgesics reported more pain symptoms.

There were no statistically significant differences between the reported pain and gender, extraction

versus none extraction, type of fixed appliance, or treatment of one or both arches. Although, not at

a statistically significant level, the data indicates a higher discomfort experience in patients aged 16

and over, compared to the younger subjects.

The lack of changes in response to dental electrical stimulation during the study period may suggest

a poor relationship between the dental electrical threshold and the possible changes in the dental

pulp after the application of orthodontic forces. However, It is also possible that the extent of which

the dental pulp is affected by the orthodontic forces is simply not enough to change its electrical

thresholds.

The proportion of teeth responding to the cold stimulation at 0ºC was higher than at 15ºC, and the

pain ratings measured using the Visual Analogue Scale were significantly higher for 0ºC. Cold

stimulations at 0ºC and 15ºC, interestingly, correspond to the results from the questionnaire,

indicating the pain experienced after the initial archwire stage to be the most intense. It was

demonstrated that there is a change in cold sensitivity of the dental pulp subsequent to orthodontic

treatment and that such sensitivity is highest after the initial archwire insertion.

Cold stimulation at 0ºC and 15ºC induced pain (all tooth groups combined) in 28.6% and 6.2%

before the treatment, 34.6% and 11.7% three days after the initial archwire insertion followed by

30.9% and 6.9% before the archwire activation stage, and 28.2% and 9.5% three days after

activation, respectively. Incisors were the most sensitive group of teeth, showing the most frequent

response 47.7%, the highest pain scores at 0ºC three days after the initial archwire insertion, which

is in agreement with the questionnaire results. The differences of the first molars VAS scores to

cold stimulation at 0ºC were at a statistically significant level when comparing initial archwire

insertion stage to: initial (p=.024), separation of molars (p=.013), activation (p=.019) and three days

after activation (p=.017), stages. The differences in the incisors responses to cold at 0ºC between

73

initial stage and initial archwire stage, (p=.079) showed a tendency to increase in sensitivity,

although, not at a significant level. Statistically significant differences at 15ºC (paired t-test) were

found between the initial stage and the initial archwire insertion in, incisors (p=.042), canines +

premolars (p=.026), between initial archwire and activation stage in, canines + premolars (p=.002),

between activation and three days after activation in, canines + premolars (p=.036). The incisors

responses between the initial archwire and the activation stage followed the same pattern, although,

the difference was not statistically significant (p=.065).

In general the differences in the prevalence of pain between the two different fixed appliances were

small and statistically significant only in connection with some of the questionnaire items, which

altogether gave the most frequent pain reports. Such items were mastication, as well as fitting

anterior and posterior teeth together. Results from the thermal sensitivity tests using Visual

Analogue Scale (VAS) have indicated that the differences between the groups were altogether small

and do not as such justify too extensive comparison of the two techniques.

Comparing orthodontic tooth movements with different fixed appliances, using the irregularity in-

dex (Little 1975) for the maxillary and mandibular anterior crowdings (canine to canine) showed no

statistically significant difference between the two fixed orthodontic appliances. In extraction cases,

increased orthodontic tooth movement was observed using the closed coils.

74

On the basis of the present study, the following conclusions can be drawn:

Orthodontic treatment generally induces pain and discomfort, which could mostly be categorized as

mild and short lasting. However, some patients do experience severe pain during the treatment even

to the extent that, mastication of food and tooth brushing might be impaired.

Pain is experienced after orthodontic procedures at different stages of treatment. Analgesic

consumption is correlated with the intensity of the pain experienced. Depending on the patients pain

threshold, clinicians should consider prescribing pain medication to alleviate the unpleasant

experience. The pain experienced during orthodontic treatment originates mostly from periodontium, due to

mechanical injury and consequent inflammatory reaction. Pulpal changes do not seem to contribute

significantly to the patient`s overall pain experience. However, sensitivity of teeth to cold

stimulation during the treatment correlates to the pain responses from the questionnaire study,

suggesting that responses in the dental pulp also play a role. No correlation was found between the

electrical stimulation of teeth and the pain responses from the questionnaire study. Inability of patients to distinguish between different light continuous forces during the initial phase

of the orthodontic treatment was observed. Neither the pain experienced by patients nor the tooth

sensitivity was affected by different archwires used in the present study. Amount of tooth

movement, during the initial phase of the orthodontic treatment does not seem to be directly related

to the pain symptoms experienced by the patients.

75

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93

APPENDIX I

The questionnaire used in the present study. Stimulus

Sore

Shooting

Dull

Ache

Sweets

0 Duration 1 S 2 L 3




Hot, Food/Drink

0 1 S 2 L 3

0 1 S 2 L 3

0 1 S 2 L 3

0 1 S 2 L 3

Cold, Food/Drink

0 1 S 2 L 3

0 1 S 2 L 3

0 1 S 2 L 3

0 1 S 2 L 3

Tooth brushing

0 1 S 2 L 3

0 1 S 2 L 3

0 1 S 2 L 3

0 1 S 2 L 3

Mastication of Food

0 1 S 2 L 3

0 1 S 2 L 3

0 1 S 2 L 3

0 1 S 2 L 3

Fitting anterior teeth together

0 1 S 2 L 3

0 1 S 2 L 3

0 1 S 2 L 3

0 1 S 2 L 3

Fitting posterior Teeth together

0 1 S 2 L 3

0 1 S 2 L 3

0 1 S 2 L 3

0 1 S 2 L 3

94

APPENDIX II

Associations between the subjective pain reports and clinical measurements

Assessment of the possible associations between the subjective pain reports (the questionnaire

study), and clinical measurements (cold tests 15/0ºC and electrical vitality tests µA), was

further studied.

Multiple regression analyses were used to estimate the associations between the pain

experienced at different stages of orthodontic treatment (Index 3, 0-504) namely after

separation of the first molars, after initial archwire insertion and after initial archwire activation

and cold sensitivity tests at 15ºC and 0ºC (mean VAS values, 0-100 mm), electrical vitality

tests (mean, 0-125 µA), in different tooth groups (1.Incisors, 2. Canines and Premolars, 3.

Molars), considering the effects of age (1<16, 2≥ 16 years), gender (0=female, 1=male),

extraction of teeth (0=no, 1=yes), fixed appliances used for orthodontic treatment (1=

Alexander, 2=Viazis), analgesic consumption (0=no, 1=yes), one or both jaws treatment

(1=maxillary or mandibular, 2=both jaws). Due to high correlation between different tooth

groups in cold and electrical measurements, as well as, cold measurements between 15ºC and

0ºC, separate regression models were prepared. There were no statistically significant

differences between the pain experienced after separation of molars and the independent

variables (Table.14).

Medication for the management of pain during the first three days after the initial archwire

insertion and the archwire activation was statistically significant in the tooth groups in both of

the models. Pain experienced by patients aged 16 years and over after archwire activation stage

in both incisors, canines and premolars tooth groups, in model A, was statistically significant.

Statistically significant associations were found in relation to all the tooth groups after the

activation of archwire and molars after the initial archwire insertion and cold measurements.

Treatment of both jaws in response to molars was statistically significantly associated with the

model A.

95

Association between the reported pain after the insertion of initial archwire stage, activation of

archwire stage, and independent variables. Cold and electrical measurements are from different

tooth groups; 1) central and lateral incisors, 2) canines and premolars, 3) molars. (Cold

measurements at 15ºC in Model A and at 0ºC in Model B). Only statistically significant

differences are given.

Tooth groups Treatment stage/ Independent variables

Model A Regr. coeff. P

Model B Regr. coeff. P

Incisors

After initial archwire/ Analgesic consumption

49.8

.008

49.8

.008

After archwire activation/ Age

1.5 .045

Analgesic consumption 103.9 .004 76.9 .019 Cold VAS (mm) 2.2 .043 1.3 .003 Canines/premolars After initial archwire/

Analgesic consumption 49.8

.008

49.8

.008

After archwire activation/ Age

1.4 .049

Analgesic consumption 110.6 .002 101.9 .002 Cold VAS (mm) 7.8 .018 3.1 .001 Molars After initial archwire/

Analgesic consumption 45.3

.015

54.7

.007

Cold VAS (mm) 5.5 .019 After archwire activation/

Treatment of one or both jaws 40.5

.008

Analgesic consumption 67.6 .037 104.7 .000 Cold VAS (mm) 2.8 .000

96

APPENDIX III

The mean values of VAS pain ratings to 15ºC cold stimulation at different stages of the

orthodontic treatment are presented. Incisors were the most sensitive during the trial period

followed closely by canines, premolars and molars. No significant statistical differences were

found between maxillary and mandibular teeth responses at different stages of the treatment

using the paired t-test. molars. Statistically significant differences (paired t-test) were found

between initial stage and initial archwire stage in, incisors (p=.042), canines + premolars

(p=.026), between initial archwire and activation stage in, canines + premolars (p=.002),

between activation and three days after activation in, canines + premolars (p=.036). Although,

not statistically significant (p=.065), the incisors responses between the initial archwire and the

activation stage followed the same pattern.

0

25mm

654321

The mean VAS pain ratings to 15ºC cold stimulation at different stages of the orthodontic

treatment (I = initial, II = separation of molars, III = three days after the initial archwire

insertion, IV = before wire activation and V = three days after activation) in maxillary and

mandibular teeth (1 = incisors, 2 = laterals, 3 = canines, 4 = first premolars, 5 = second

premolars and 6 = molars).

maxilla

mandible

25

I II III IV V

97

APPENDIX IV

The mean values from VAS pain ratings to 0ºC at different stages of the treatment are

presented. The VAS pain ratings to cold at 0ºC were higher compare to 15ºC at all the stages of

treatment. Maxillary molars showed a higher VAS ratings than mandibular molars at all the

stages being at a statistically significant level, also mandibular central incisors had VAS ratings

higher than maxillary central incisors at the activation stage (p<.05). Paired t-test revealed that

the difference in the molars responses to cold stimulation (0ºC) were at a statistically signifi-

cant level when comparing initial archwire insertion to: initial stage (p=.024), separation stage

(p=.013), activation stage (p=.019) and three days after activation (p=.017). The incisors

responses to cold at 0ºC between initial stage and initial archwire stage, also showed a

substantial increase in the sensitivity, although the difference was not significant (p=.079).

0

25mm

654321

I II III IV V

25

maxilla

mandible

The mean VAS pain ratings to 0ºC cold stimulation at different stages of the orthodontic

treatment (I = initial, II = separation of molars, III = three days after the initial archwire


mandibular teeth (1 = central incisors, 2 = lateral incisors, 3 = canines, 4 = first premolars, 5 =

second premolars and 6 = molars).

98

APPENDIX V

The dental electrical thresholds at different stages of the treatment are shown. The mean

electrical threshold values at the initial measurement in µA for the maxillary arch, were 28.7 in

molars, 20.5 in second premolars, 18.5 in first premolars, 14.5 in canines, 12.3 in lateral in-

cisors, 11.9 in central incisors, and for the mandibular arch 29.3 in molars, 22.7 in second

premolars, 23.1 first premolars, 19.2 canines, 14.9 in lateral incisors, 15.2 in central incisors.

The differences in the mean thresholds between the maxillary and mandibular teeth were not

statistically significant. Therefore the combined mean electrical threshold values from the

maxillary and mandibular teeth were used for further statistical analysis. As with the cold

responses the results of electrical stimulation were studied with respect to different tooth groups

(1= incisors, 2= premolars and canines, 3= molars).

The mean electrical thresholds of teeth at different stages of orthodontic treatment (I = initial, II

= three days after the separation of the first molars, III = three days after the initial archwire


mandibular permanent teeth (1 = central incisors, 2 = lateral incisors, 3 = canines, 4 = first

premolars, 5 = second premolars and 6 = first molars).

0

30µA

654321

maxilla

mandible

I II III IV V

99

30

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