Clinical evaluation of Er:YAG laser in the treatment of chronic periodontitis in comparison with that of hand and ultrasonic treatment A thesis Submitted to The College of Dentistry - University of Baghdad In partial fulfillment of requirements for the Degree of Master in science in Periodontics By Fahad M. Al Dabbagh B.D.S. Prof. Dr. Khulood A. Al Safi B.D.S., M.Sc., Ph.D. IRAQ – BAGHDAD 1431 A.H. 2010 A.D.
126
Embed
Clinical evaluation of Er:YAG laser in the treatment of ...
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Clinical evaluation of Er:YAG laser in the
treatment of chronic periodontitis in comparison
with that of hand and ultrasonic treatment
A thesis Submitted to
The College of Dentistry - University of Baghdad
In partial fulfillment of requirements for the Degree of
Master in science in Periodontics
By
Fahad M. Al Dabbagh
B.D.S.
Prof. Dr. Khulood A. Al Safi
B.D.S., M.Sc., Ph.D.
IRAQ – BAGHDAD
1431 A.H. 2010 A.D.
Clinical evaluation of Er:YAG laser in the
treatment of chronic periodontitis in comparison
with that of hand and ultrasonic treatment
A thesis Submitted to
The College of Dentistry - University of Baghdad
In partial fulfillment of requirements for the Degree of
Master in science in Periodontics
By
Fahad M. Al Dabbagh
B. D. S.
Prof. Dr. Khulood A. Al Safi
B. D. S., M. Sc., Ph. D.
IRAQ – BAGHDAD
1431 A.H. 2010 A.D.
بسم االله الرحمن الرحيم
﴿إن في خلق السـمـوت والأرض وٱختلــف الليل والنهار لأيـــت لأولي
الألبــب﴾ صدق االله العظيم
191- 190 ٱل عمران
Supervisor Declaration
This is to certify that the organization and preparation of this thesis have
been made by the graduate student Fahad Maizar Al Dabbagh under my
supervision in College of Dentistry, University of Baghdad in partial
fulfillment for the degree of Master of Science in Periodontics.
Signature:
Prof. Dr. Khulood A. Al Safi
B.D.S., M.Sc., Ph.D.
College of Dentistry
University of Baghdad
Supervisor
Committee Declaration
We are the examination committee certify that we have read this thesis and
have examine the graduated student Fahad Maizar Al Dabbagh in its
content and that in our opinion, it meets the standard of a thesis for the
degree of Master of Science in Periodontics.
Approval of the dean of the College of Dentistry, University of Baghdad
Signature:
Prof. Dr. Abdullatif A.H. Abbas Aljuboury
B.D.S., M.Sc., Ph.D., Ph.D
Chairman of the examination committee
Signature:
Prof. Dr. Ali H. AlKhafaji
BDS. MSc. D. (UK)
Dean of the College of
Dentistry.
University of Baghdad
Signature:
Assist. Prof. Dr. Kadhem J. Hanau
B.D.S., M.Sc.
Member
Signature:
Lecturer Dr. Aida Z. Khaleel
B.D.S., M.Sc., Ph.D.
Member
Dedication To our great messenger Mohammed
(God bless be upon him)
To the persons who give me all they have to be the best,
My Father and my Mother,
To my brothers and sisters in Islam who guide me and
support me,
To everyone how work's hard to get knowledge;
I dedicate this work
Fahad Al Dabbagh
I
ACKNOWLEDGEMENT In the beginning I thank my God for inspiring me with willingness,
strength and patience to finish this work in a good manner, and I pray to
keep me as he will.
Then I would like to express my sincere thanks and deep
appreciation to my supervisor Prof. Dr. Khulood A. Al Safi - Head of
periodontics department in college of dentistry, University of Baghdad -
whom I fortunate to be under her supervision.
Special thank to Dr. Hussain A. Jawad - Dean of laser institution for
postgraduate studies - and institution's staff for helping me to understand
the laser science.
I want to express my appreciation to Dr. Aida F. Zaki for her support
and advices regarding laser aspect of this work.
My grateful thanks and respect to Dr. Sindis Hashim – head of
endodontics and laser unit in al Jumhory dental specialist center - for their
assistance and support especially in practical part of research, also I would
like to thank the staff of center for giving me the permission to conduct my
research in their institution
I would like to thank the seniors of periodontics department, college
of dentistry - University of Baghdad, for their advices and scientific
support; Also those of periodontics unit in college of dentistry - University
of Mosul for their cooperation in collecting research samples.
I want to extend my thanks to my patients, who participated in the
study, follow my instruction carefully and be patience until we complete
the study, so my deep appreciation for them.
II
Finally I would never forget the encouragements and support of my
family, friends and my soul twins, whom their efforts are invaluable, and
thanks for every one helped me in some way or another throughout my
study
III
ABSTRACT UBackgroundU: The use of lasers for treatment of periodontal diseases has
become a topic of much interest and is a promising field in periodontal
therapy, based on its various characteristics, such as tissue ablation,
homeostasis, and sterilization effect; recently an attention has been paid to
the clinical applicability of Erbium-doped: Yttrium-Aluminum- Garnet
(Er: YAG) with a 2.94µm wavelength, as it is capable of ablation in both
soft and hard tissues.
UMaterials and MethodsU: A total of 96 periodontal pockets were first
selected for conducting the initial study. Here the pockets randomly
categorized into six groups. Three energies with two pulse repetition rate
settings of Er:YAG laser were used to determine the most efficient laser
setting for treatment of chronic periodontitis, based on comparison of the
periodontal clinical parameter before treatment (base line) and after three
month of treatment. The results indicate that laser energy setting of 160mJ
and pulse repetition rate of 15Hz is the most efficient setting for this
purpose.
Another 72 periodontal pockets were selected for prime study and
randomly grouped into three groups; the first group treated by Er:YAG
laser (160mJ – 15Hz), the second group treated by ultrasonic scaling device
Chapter one: Review of literatures (1-1) History of laser 14 (1-2) Classification of laser 19 (1-3) Laser types and typical lasing media 21 (1-4) Laser thermal effect on biological tissues 24 (1-5) Types of laser hazards 27 (1-6) Laser safety classes 28 (1-7) Current lasers commonly used in clinical dentistry 30 (1-8) Current application of Erbium lasers 32 (1-9) Advantages and disadvantages of laser periodontal therapy 36
Chapter two: Materials and Methods
(1-1) Basic properties of KaVo Key laser III 39 (2-2) Equipments and instruments used 42 (2-3) Silness and loe plaque index 44 (2-4) Groups and pockets distribution in initial study 46 (2-5) Groups and pockets distribution in main study 47
Chapter three: Results
(3-1) Descriptive statistics of Plaque Index – Initial study 59 (3-2) Paired sample t-test of Plaque Index for six groups at the second
visit – Initial study 59
(3-3) Percentage of Bleeding On Probing at two visits – Initial study 60 (3-4) Chi-Square test of Bleeding On Probing for six groups – Initial
study 60
(3-5) Descriptive statistics of Probing Pocket Depth – Initial study 61 (3-6) Paired sample t-test of pocket depth for six groups at the second
visit – Initial study 61
(3-7) Descriptive statistics of Relative Attachment Level – Initial study 62 (3-8) Paired sample t-test of Relative Attachment Level for six groups at
the second visit – Initial study 62
(3-9) Initial study conclusion 63 (3-10) Descriptive statistics of Plaque Index – Main study 66 (3-11) Paired sample t-test of Plaque Index for three groups at the second
visit – Main study 66
(3-12) Percentage of Bleeding On Probing at two visits – Main study 67 (3-13) Chi-Square test of Bleeding On Probing for six groups – Main
study 67
XI
(3-14) Descriptive statistics of Probing Pocket Depth – Main study 68 (3-15) Paired sample t-test of pocket depth for three groups – Main study 68 (3-16) Descriptive statistics of Relative Attachment Level – Main study 69 (3-17) Paired sample t-test of Relative Attachment Level for three groups
at the second visit 69
(3-18) Mean of pain score for three groups – Main study 70 (3-19) Paired sample t-test of Pain Level for three groups – Main study 70 (3-20) Main study conclusion 71
XII
LIST OF FIGURES Table Title Page
Chapter one: Review of literatures (1-1) Biofilm structure 6 (1-2) Piezoelectric and magnetostrictive scalers 10 (1-3) Electromagnetic Spectrum 15 (1-4) Stimulated absorption, spontaneous emission and stimulated
emission 17
(1-5) Laser device elements 18 (1-6) Laser – tissue interactions 21 (1-7) Absorption spectrum for water of various lasers 23 (1-8) Hard tissue ablation by Er: YAG laser irradiation 26 (1-9) Section of human eye 29
Chapter two: Materials and Methods
(2-1) KaVo Key Laser 51 (2-2) Fibro optic handpiece 51 (2-3) Diagnostic and periodontal instruments 51 (2-4) Gracey and Universal curettes 51 (2-5) Materials used in study 52 (2-6) Materials and devices used in fabrication of stent 52 (2-7) Dental unit 52 (2-8) Ultrasonic scaler device 53 (2-9) Ultrasonic scaler tips 53
(3-1) Difference of Plaque Index means for six groups between two visits – Initial study
59
(3-2) Difference of Bleeding On Probing percentage for six groups between two visits – Initial study
60
(3-3) Difference of pocket depth mean for six groups between two visits – Initial study
61
(3-4) Difference of Relative Attachment Level mean for six groups 62
XIII
between two visits – Initial study (3-5) Difference of Plaque Index mean for three groups between two
visits – Main study 66
(3-6) Difference of Bleeding On Probing percentage for six groups between two visits – Main study
67
(3-7) Difference of pocket depth mean for three groups between two visits – Main study
68
(3-8) Difference of Relative Attachment Level mean for three groups between two visits – Main study
69
(3-9) Difference of Pain Level for three groups - Main study 70
XIV
LIST OF ABBREVIATIONS No. Abbreviation Word 1 µm Micro Meter 2 ηm Nano Meter 3 ADA American Dental Association 4 BOP Bleeding On Probing 5 C0 Degree centigrade 6 CAL Clinical attachment Level 7 CFUs Colonies Forming Units 8 CO2 Carbon dioxide 9 CW Continuous Wave
10 DL Diode laser 11 EM Electromagnetic 12 Er,Cr:YSGG Erbium-chromium doped: yttrium-scandium-gallium garnet 13 Er:YAG Erbium-doped: Yttrium-Aluminum- Garnet 14 GaAlAs Gallium - Aluminum - Arsenide 15 GaAs Gallium - Arsenide 16 GIC Glass Ionomer Cement 17 GN Gallium - Neodymium 18 HeNe Helium Neon 19 Hz Hertz 20 InGaAsP Indium - Gallium - Arsenide - Phosphid 21 IL-3 Interleukin – three 22 IL-6 Interleukin – six 23 kHz Kilo Hertz 24 Laser Light amplification by stimulated emission of radiation 25 LGAC Laser – generated airborne contaminants 26 mJ Mili Joule 27 mW Mili Watt 28 MMP-8 Matrix Metallo Proteinases – eight 29 Nd:YAG Neodymium-doped: Yttrium-Aluminum- Garnet 30 NRS Numerical Rating Scale 31 P Probability value 32 PI Plaque Index 33 PPD Probing Pocket Depth 34 PRR Pulse Repetition Rate 35 PPS Pulse per second 36 Q Quality 37 RAL Relative Attachment Level
XV
38 S Second 39 SD Standard of Deviation 40 SE Standard of Error 41 SPSS Software Package of Statistical 42 SRP Scaling and Root Planing 43 Ti Titanium 44 t-test Student Paired sample t-test 45 V Volt 46 VUS Vector ultrasonic System 47 W Watt
XVI
LIST OF VOCABULARIES 1 Chronic periodontitis إلتهاب الأنسجة المحيطة بالأسنان المزمن2 Microbial dental plaque الصفيحة السنية الجرثومية 3 Dental calculus الكلس السني 4 Scaling التقليح 5 Root planing (جعله أملس) تسحجة الجذر 6 Curette ( or curet) المجرفة 7 Hand scaler المقلحة اليدوية 8 Ultrasonic scaler المقلحة بالأمواج فوق الصوتية 9 Er:YAG laser ليزر الأيربيوم ياك المشوب بالياتيريوم- ألمنيوم - غارنيت 10 Pulse repetition rate (frequency) (التردد) معدل تكرار النبضة 11 Laser Energy طاقة الليزر
INTRODUCTION
INTRODUCTION
1
INTRODUCTION Periodontal diseases are among the most common infectious diseases
of humans and are characterized by bacterial-induced inflammatory
destruction of tooth supporting tissues including alveolar bone; with
progression of destruction of the tooth supporting tissues, pockets form
between the teeth and the surrounding detached periodontal tissue, and teeth
may become loose and may eventually be lost .(Jin. , 2003)
Scaling and root planing (SRP) is generally the first treatment
employed for periodontitis and it is considered as a nonsurgical procedure,
root planing involves cleaning and smoothing the root surface of an infected
tooth so that the gingival tissue can heal, shrinking the tissue and reducing the
depth of the pocket that had formed, thus making the root surfaces
biologically compatible with optimal healing and reattachment of epithelium
to the root surface, scaling may be performed with hand instruments alone or
with the aid of an ultrasonic scaler. (Bonito et al, 2004)
However, such instrumentation calls for advanced clinical skills and
sometimes, the anatomy of the root often complicates the achievement of the
desired biologically compatible root, also extensive cementum removal may
lead to increased surface roughness in both supra- and sub-gingivally located
areas, which might enhance plaque retention. (Schwarz et al, 2006)
Recently, the use of laser light has been suggested as an alternative to
the conventional mechanical treatment, it was proposed that laser-based root
surface treatment might lead to improved periodontal therapy due to
relatively conservative removal of tooth substance as well as to the
bactericidal effect towards perio-pathogenic bacteria, also it has been
annotated in the literature that application of laser in periodontal treatment
provides a more comfortable patient experience with less trauma and post-
operative complications as well as a decreased healing time. (Kelbauskiene
et al, 2007)
INTRODUCTION
2
The Erbium-doped: Yttrium–Aluminum–Garnet laser (Er: YAG),
emitting at a wavelength of 2940 nm, possesses suitable properties not only
for soft tissue therapy but also for hard tissue treatment due to its
characteristic wavelength that is highly absorbed by water. (Takasaki, 2007)
The erbium laser group has emerged as a promising laser system for
periodontal indications as several in vitro and clinical studies have already
demonstrated an effective application of the Er: YAG laser for calculus
removal and decontamination of the diseased root surface in periodontal non-
surgical and surgical procedures. (Ishikawa, 2008)
AIMS OF THE STUDY
3
AIMS OF THE STUDY: 1- Determination of the most efficient energy and pulse repetition rate (PRR)
(frequency) values for Er:YAG laser for treatment of chronic periodontitis,
based on clinical evaluation of affected teeth before and after treatment, using
clinical measures (Plaque Index (PI), Bleeding On Probing (BOP), Probing
Pocket Depth (PPD) and Relative Attachment Level (RAL).
2- Evaluation of the efficiency of Er:YAG laser in comparison with that of
ultrasonic and hand instruments regarding treatment of chronic periodontitis,
based on clinical evaluation of affected teeth before and after treatment, using
clinical parameters (PI, BOP, PPD and RAL).
3- Evaluation of the pain level that the patient experience during each type of
nonsurgical periodontal treatment (Er:YAG laser, ultrasonic and hand
instruments).
CHAPTER ONE
REVIEW OF LITERATURES
CHAPTER ONE REVIEW OF LITERATURES
4
1.1. Periodontal diseases: 1.1.1. Definition:
The periodontal disease is a chronic, degenerative disease which is
localized in the gingiva, periodontal ligament, cementum and alveolar bone.
(Kesic, 2008)
1.1.2. Classification of periodontal diseases:
The currently used classification of periodontal diseases was introduced
by the 1999 International Work-shop for a classification of periodontal
diseases and conditions and encompasses eight main categories, namely:
I- Gingival diseases
II- Chronic periodontitis
III- Aggressive periodontitis
IV- Periodontitis as a manifestation of systemic diseases
V- Necrotizing periodontal diseases
VI- Abscesses of periodontium
VII- Periodontitis associated with endodontic lesions
VIII- Developmental or acquired deformities and conditions. (American
Academy of Periodontology, 1999)
1.1.3. Etiology of periodontal diseases:
The primary etiologic factor of periodontal disease is the bacterial
biofilm, where gram-positive and gram-negative bacteria possess a plethora of
structural or secreted components that may cause direct destruction to
periodontal tissues or stimulate host cells to activate a wide range of
inflammatory responses, these responses are intended to eliminate the
microbial challenge, but may often cause further tissue damage. (Madianos,
2005)
CHAPTER ONE REVIEW OF LITERATURES
5
The critical mass of bacteria probably provide triggers that up regulate
inflammatory and degradative processes associated with chronic periodontitis
leading to tissue destruction, possibly by way of three different pathways:
1. Pathogens may release their own proteolytic enzymes that could degrade
periodontal structures directly.
2. Pathogens may elaborate products (e.g. lipopolysaccharide) that could
subsequently trigger host cell populations to express degradative enzymes.
3. Pathogens may stimulate an immune response resulting in release of pro-
inflammatory cytokines such as interleukin 1and 6 (IL-1, IL-6), and tumor
necrosis factor14 that indirectly induce increases in levels of degradative
enzymes which include matrix metalloproteinases such as matrix
metalloproteinases (MMP-8), and elastase, both of which target the principal
connective tissue proteins of the periodontium. (Tenenbaum, 2007)
1.1.3.1 Dental plaque:
Dental plaque can be defined as an organized mass, consisting mainly
of microorganisms that adheres to teeth, prostheses and oral surfaces and is
found in the gingival crevice and periodontal pockets, other components
include an organic, polysaccharide-protein matrix consisting of bacterial by-
products such as enzymes, food debris, desquamated cells and inorganic
components such as calcium and phosphate. (American Academy of
Periodontology, 2001)
This biofilm showed as a thin basal layer on the substratum, in contact
with, and occasionally penetrating, the acquired enamel pellicle, and with
columnar mushroom-shaped multibacterial extensions into the lumen of the
solution, separated by regions “channels” seemingly empty or filled with
extracellular polysaccharide, figure (1-1), the bacteria in a biofilm
communicate with each other by sending out chemical signals, these chemical
signals trigger the bacteria to produce potentially harmful proteins and
enzymes. (Dumitrescu, 2010)
CHAPTER ONE REVIEW OF LITERATURES
6
Figure (1-1): Biofilm structure
The different regions of plaque are significant to different processes
associated with diseases of the teeth and periodontium, as marginal plaque is
of prime importance in the development of gingivitis, while supragingival
plaque and tooth-associated subgingival plaque are critical in calculus
formation and root caries, whereas tissue-associated subgingival plaque is
important in the soft tissue destruction that characterizes different forms of
periodontitis. (Newman, 2009)
The most important and most prevalent anaerobic gram-negative
bacteria in the subgingival area are Actinobacillus Actinomycetemcomitans,
Porphyromonas gingivalis, Prevotella intermedia, these bacteria play an
important role in the onset and subsequent development of periodontitis,
participating in the formation of the periodontal pocket, connective tissue
destruction, and alveolar bone resorption by means of an immunopathogenic
mechanism and once periodontitis has been established an inflammatory
infiltrate is formed consisting of different kinds of cells, such as macrophages
and lymphocytes that will produce different cytokine subtypes, biological
mediators which are responsible for the immunopathology of different
illnesses. (Bascones and Figuero, 2005)
CHAPTER ONE REVIEW OF LITERATURES
7
1.1.3.2. Dental calculus:
Calculus is a hard deposit that forms by mineralization of dental plaque
and is generally covered by a layer of unmineralized plaque, hence, does not
directly come into contact with the gingival tissues, therefore calculus is a
secondary etiologic factor for periodontitis. (Newman, 2009)
Supragingivally, calculus can be recognized as a creamy-whitish to
dark yellow or even brownish mass of moderate hardness, while
subgingivally calculus is frequently dark brown or green in color due to the
inclusion of haem, a blood breakdown product (Lindhe, 2008)
Calculus is a local environmental factor for periodontal disease because:
- It has a rough surface always covered with pathogenic bacteria.
- The contour changes produce overhangs and increase plaque retention.
- It is almost impossible to control periodontal disease in the presence of
calculus. (Ireland, 2006)
1.1.4. Chronic periodontitis:
1.1.4.1. Definition:
The chronic periodontitis is defined as inflammation of the gingiva
extending into the adjacent attachment apparatus, the disease is characterized
by loss of clinical attachment due to destruction of the periodontal ligament
and loss of the adjacent supporting bone. (American Academy of
Periodontology, 2000)
Chronic periodontitis is caused by an opportunistic microflora, and this
infection triggers host inflammatory responses resulting in the destruction of
the tooth supporting tissues. (Renvert and Persson 2002)
1.1.4.2. Characteristics:
The main characteristics of chronic periodontitis, according to
classification of periodontal diseases 1999, are:
CHAPTER ONE REVIEW OF LITERATURES
8
1- Most common in adults, but can occur in children, the prevalence and
severity of the disease increase with age.
2- Slow to moderate rate of progression.
3- Amount of microbial deposits consistent with the severity of
periodontal tissue destruction.
4- Subgingival calculus is frequent finding.
5- Amount of destruction is consistent with the presence of local factors
(e.g., tooth –related or iatrogenic).
6- May be modified by and /or associated with systemic disease (e.g.,
diabetes mellitus).
7- Can be modified by factors other than systemic diseases (e.g., smoking,
emotional stress).
8- Variable distribution of periodontal destruction; no discernible pattern.
9- No marked familial aggregation. (Dumitrescu and Kobayashi, 2010)
1.1.5. Diagnosis of periodontal disease:
To arrive at a periodontal diagnosis, the dentist must rely upon such factors: 1- Presence or absence of clinical signs of inflammation (e.g., bleeding upon
probing).
2- Probing depths.
3- Extent and pattern of loss of clinical attachment and bone.
4- Patient’s medical and dental histories.
5- Presence or absence of miscellaneous signs and symptoms, including pain,
ulceration and amount of observable plaque and calculus. (American
Academy of Periodontology, 2003)
1.1.6. Treatment of periodontal diseases:
1.1.6.1. Scaling and root planing:
Scaling is the process by which plaque and calculus are removed from
both supragingival and subgingival tooth surfaces without any attempt to
CHAPTER ONE REVIEW OF LITERATURES
9
remove tooth substances along with the calculus; while root planing is the
process by which residual embedded calculus and portion of cementum are
removed from the roots to produce a smooth, hard and clean surface.
(Newman, 2009)
SRP are the bases of non-surgical therapy in the treatment of
periodontitis. (Herrera et al., 2002)
In patients with chronic periodontitis, subgingival debridement (in
conjunction with supragingival plaque control) is an effective treatment in
reducing probing pocket depth and improving the clinical attachment level, In
fact it is more effective than supragingival plaque control alone. (Van der,
2002)
1.1.6.2. Instruments and instrumentation:
The ideal goal of periodontal instrumentation is to effectively remove
plaque and calculus without causing root surface damage; scaling and root
planing are the basis of periodontal therapy and various instruments have
been designed to achieve this goal; ultrasonic scaler and curettes are the
instruments used for surgical and non-surgical periodontal therapy and have
shown similar results as for biological response, plaque/calculus removal and
elimination of endotoxin. (Corrêa, 2009)
1.1.6.2.1. Hand instruments:
Hand instruments are available in various designs, described as
curettes, hoes or scalers; they all have a sharp working tip, which is used to
mechanically break the bond between deposit and tooth. (Walmsley et al.,
2008)
The parts of each instrument, referred to as the working end, shank and
handle. (Newman, 2009)
CHAPTER ONE REVIEW OF LITERATURES
10
1.1.6.2.1.1. Characteristics of hand instruments therapy: The process is time consuming and physically demanding, but is seen
as the treatment of choice as it is believed that the clinician has direct tactile
control over the hand instrumentation process compared with the use of
powered devices. (Walmsley et al., 2008)
The instruments are cheaper to buy and maintain, also there are no aerosols.
(Ireland, 2006)
1.1.6.2.2. Powered instrument:
Powered instruments are those instruments whose working tip is driven
to oscillate at either sonic (6–8 kHz) or ultrasonic (25–42 kHz) frequencies;
these tip oscillations of sonic devices are generated by the passage of
compressed air over an eccentric rod that vibrates, and these vibrations are
transmitted to the working tip, while the tip vibrations of ultrasonic
instruments may be generated through a process of either piezoelectricity or
magnetostriction, figure (1-2). (Lea and Walmsley, 2009)
Figure (1-2): Piezoelectric (top) and magnetostrictive (bottom) scalers, the working end
for both instruments is similar but the method of vibration generation is quite different.
The nickel-based stack of the magnetostrictive scaler is shown.
CHAPTER ONE REVIEW OF LITERATURES
11
1.1.6.2.2.1. Mechanism of action of powered instruments:
1- Chipping action: scaling tip of the instrument oscillating in a
longitudinal mode and mechanically removing the deposits by chipping
action.
2- Cavitational activity: encompasses all of the linear oscillatory motions
of gas and/or vapor filled bubbles in an acoustic field, these motions
may vary within one acoustic cycle from cavitation where the bubbles
are oscillating without fragmentation, to transient cavitation, where
there is rapid growth and collapse of the bubble; cavitational activity
will cause fracture of the attached deposits through the resultant shock
waves.
3- Acoustic micro streaming (turbulence): which produced by the
oscillatory action of the ultrasonic scaling tip within water, so the
forces generated by streaming will shear the plaque away from itself
and from the tooth surface. (Laird and Walmsle, 1991)
1.1.6.2.2.2. Characteristics of ultrasonic periodontal therapy:
Currently, the use of the ultrasonic scaler has appeared as an important
alternative for daily clinical use due to its several advantages such as access to
furcation, less operator tiredness, pocket penetration and less time required for
scaling and root planning (Corrêa et al, 2009)
During the use of powered instruments irrigant (normally water) flows
over the working tip, where it helps to reduce the frictional heat generated
during the cleaning process, this water has further benefits which include
helping to clear the treatment site of debris, thus aiding the operator's field of
view; the irrigant may also act as a site for the generation of biophysical
processes commonly associated with ultrasonic powered instruments, namely
cavitation and streaming which may also aid in the cleaning process. (Lea et
al, 2003), (Lea et al, 2005)
CHAPTER ONE REVIEW OF LITERATURES
12
Powered instruments are believed to provide less sensitive tactile
feedback to the clinician than hand instruments, although recent research has
suggested that the loss of tactile control reported for powered instruments
may only be temporary and that the operator regains sensation with time.
(Tunkel et al, 2002), (Ryan et al, 2005)
In 2000, the Research, Science and Therapy Committee of the
American Academy of Periodontology performed a detailed literature review
to produce a position paper concerning the use of powered instruments in
periodontics and these are conclusions of this paper:
• Sonic and ultrasonic instruments attain similar results to hand instruments in
terms of plaque, calculus and endotoxin removal.
• Instrument width may mean that manual scalers provide less access to
furcations than ultrasonic instruments.
• A disadvantage of powered scalers is the production of contaminated
aerosols. (Drisko et al, 2000)
So when compared with hand scalers, power-driven instruments have
the advantage of being easier to use and may take significantly less time than
hand instruments, also requires minimal stroke pressure; it is not dependent
on permanently sharp instruments and finally precision-thin tips have been
shown to penetrate deeper than hand instruments, but on other hand the
powered instrument has the potential to damage the root surface producing
indentations and unwanted scratches on the hard tissue surface. (Walmsley et
al., 2008) (Ireland, 2006)
CHAPTER ONE REVIEW OF LITERATURES
13
1.2. LASER: 1.2.1. Definition:
Laser is an acronym for Light Amplification by Stimulated Emission of
Radiation. (Godett, 2009)
A laser system is that one which amplifies light and produces a highly
directional, high intensity beam that most often has a very pure frequency or
wavelength. (Silfvast, 2004)
1.2.2. History of laser:
Table (1-1) summarizes the history of laser. (Silfvast, 2004);
(Bertolotti, 2005); (Gross and Herrmann, 2007)
CHAPTER ONE REVIEW OF LITERATURES
14
Table (1-1): History of laser
Date Name Achievement 1916 Albert Einstein Theory of light emission. Concept of
stimulated emission
1947 Willis E Lamb
R C Rutherford
Induced emission suspect in hydrogen spectra.
First demonstration of stimulated emission.
1951
Charles H Townes
The inventor of the MASER (Microwave
Amplification of Stimulated Emission of
Radiation) at Columbia University – First
device based on stimulated emission, awarded
Nobel prize 1964.
1957 Gordon Gould First document defining a LASER
1960
Theodore Maiman
Invented first working LASER based on Ruby.
May 16th 1960, Hughes Research
Laboratories.
1960
Ali Javan,
William Bennett
Donald Herriot
First helium-neon LASER at Bell Labs Dec.
1960, First gas laser and first CW laser
1961 Leo F. Johnson,
K. Nassau
First neodymium crystal LASER at Bell Labs
1962 Robert Hall Invention of semi-conductor LASER at
General Electric Labs.
1963 Robert Keyes
Theodore Quist
First diode pumped solid state LASER,
uranium doped calcium fluoride at MIT
Lincoln Labs
1964 Kumar N Patel Inventor of CO2 LASER at Bell Labs.
1965 George Pimentel
J V V Kasper
First chemical LASER at University of
California, Berkley.
1966 Peter Sorokin
John Lankard
First dye LASER action demonstrated at IBM
Labs.
CHAPTER ONE REVIEW OF LITERATURES
15
1.2.3. Electromagnetic radiations:
Electromagnetic (EM) radiation includes all forms of radio waves,
microwaves, infrared radiation, visible light, ultraviolet radiation, x-rays and
gamma rays. (Csele, 2004)
EM radiation, which is produced by lasers, requires no medium for its
transmission because it can travel through the vacuum of space; it can also
travel through matter in the form of gases, liquids or solids, but the speed and
the direction of the propagation of radiation will be changed upon the
transition from one medium to another in the form of heat. (Berger and Eeg
2006 a)
The EM spectrum is traditionally divided into the seven regions shown
in figure (1-3). (Andrews and Hill, 2009)
Figure (1-3): Electromagnetic Spectrum
1.2.4. Properties of laser:
Laser light has some unique characteristics that don't appear in the light
from other sources, these characteristics are:
1- Directionality: All laser light traveling in very nearly the same
direction, resulting in directionality of laser beam which can be focused
to a very small spot, greatly increasing its intensity.
CHAPTER ONE REVIEW OF LITERATURES
16
2- Monochromaticity: laser light has far greater purity of color than the
light from other sources.
3- Coherence: monochromaticity and directionality together with the
phase consistency of laser light are combined into a single descriptive
term; coherence makes laser light different from the light produced by
any other source.
4- Intensity (Irradiance): by focusing the laser beams to small spot sizes
one can obtain very high intensities. (Hitz et al., 2001), (Kishen and
Asundi, 2007)
1.2.5. Fundamentals of laser: Stimulated absorption which denotes to process in which an atomic or
a molecular system subjected to an electromagnetic field of frequency (ʋ )
absorbs energy from the photon and as a result of the absorption the atom or
the molecule is raised from lower state (n) to the upper state (m) of higher
energy; this process occurs only when the energy of the photon precisely
matches the energy separation of the participating pair of energy states (where
(En) and (Em) are the energies of the initial state (n) and the final state (m),
(w) is the circular frequency of the incident radiation, and (ħ) is Planck’s
constant). (Abramczyk, 2005)
Light emission takes place by two processes; one is spontaneous
emission wherein an atom in excited state returns to a lower energy state on
its own by emission of a photon with energy equal to the difference of the
energies of the two atomic energy levels; in this process the atoms radiate
randomly and independent of each other leading to incoherent light as in the
light from all conventional sources of it. (Kishen and Asundi, 2007)
When the pumping source is strong, emission can take place not only
spontaneously but also under stimulation by the field, and this kind of
emission is called stimulated emission, so the molecule will already be in an
CHAPTER ONE REVIEW OF LITERATURES
17
excited state, then an incoming photon, for which the energy is equal to the
energy difference between its present level and the lower level, can
‘‘stimulate’’ a transition to that lower state, which produce a second photon of
the same energy; in contrast to spontaneous emission, stimulated emission
exhibits coherence with the external radiation field; this control on emission
of individual atoms through the control on stimulating photons is the essence
of laser operation, figure (1-4). (Abramczyk, 2005)
Figure (1-4): Scheme of a two-level system illustrating stimulated absorption,
spontaneous emission and stimulated emission phenomena. To produce cascade of identical photons, stimulated emission must be
more likely than absorption, more of the atoms must be in the higher energy
state than are in the lower one, and since this is the reverse of the usual case;
so it is called a population inversion.(Giambattista et al. , 2008)
1.2.6. Elements of laser device:
in its simplest form, a laser consists of a gain or amplifying medium
(where stimulated emission occurs) and a set of mirrors to feed the light back
into the amplifier for continued growth of the developing beam; the three
basic components , as seen in figure (1-5): (Berger and Eeg, 2006 a)
CHAPTER ONE REVIEW OF LITERATURES
18
A laser always includes the following parts:
1- Energy source (power supply): the types of energy supply depends
on the structure of the medium, thus the energy source may be an
electrical current, optical radiation from flash lamb or another
pumping laser as, radio waves, microwave or chemical reaction;
2- Lasing (amplifying ) medium: it could be either solid , liquid or gas
medium; the lasing medium must be able to store the energy
supplied, by a process of population inversion; the lasing medium is
generally elongated in shape, often in the form of a channel ( gas
laser) or a narrow rod (solid state lasers) or doped channel
(semiconductor lasers);
3- Resonating cavity (mirrors): these mirrors are fitted at both ends of
the medium, one of these mirror is fully reflected while the other is
partially reflected, making the light produced in the lasing medium
reflected back into it several times and stimulates new light
production, thus the resonating cavity is of two fold importance: it
increase the lasing medium's amplification and makes the light
more coherent. (Tuner and Hode, 2004)
Figure (1-5): Laser device elements.
CHAPTER ONE REVIEW OF LITERATURES
19
1.2.7. Manner of operation of laser:
Lasers operate in one of three different manners:
1- Continuous wave (CW): if the partially transmitting end allows a
fraction of the light energy that strikes it to escape, and if energy can
be pumped into the lasing medium at such a rate that the laser output
can be maintained uninterruptedly then we have a CW laser.
2- Pulsed (long pulse or normal pulse): which occur when the laser
device deliver their output in bursts of light whose duration range from
femtoseconds (10−15
3- Q-switched (or Q-spoiled): is an acousto-optical or electro-optical
device within the optical cavity that is analogous to a shutter; it
prevents laser emission until it is opened, and because of the
combination of high energy and narrow pulse width, very high powers,
on the order of megawatts, are readily attainable with
Q-switched lasers. (Cember and Johnson, 2009)
seconds) to 0.25 seconds.
1.2.8. Types of laser:
Laser systems can be classified using many different criteria, table
(1-2) list most common classifications of laser systems. (Ishikawa et al.,
2004) Table (1-2): Classification of laser.
CHAPTER ONE REVIEW OF LITERATURES
20
1- Solid state laser:
The oldest technology is that of the optically pumped solid-state
laser, it (not to be confused with semiconductor lasers) consist of a
crystal of glasslike material doped with a small concentration of a
lasing ion such as chromium (in the case of ruby) or neodymium (in the
case of YAG); for many solid state lasers the technology has not
changed much, but in recent years more efficient materials with lower
pumping thresholds have been used, and compact solid-state lasers
have been developed that are pumped by semiconductor laser diodes
instead of lamps. (Csele, 2004)
2- Liquid lasers:
The most common and familiar liquid lasers are those based on
strongly absorbing organic dye molecules in an organic solvent; the
very broad emission and gain spectra of organic dyes lead to tunable
laser output typically over several tens of nanometers, because of this
property, dye lasers are used extensively in wavelength selective
spectroscopy. (Weber, 2001)
3- Gas lasers:
Comprise the largest number of lasing transitions over 12000,
gas lasers may be categorized as neutral atom, ionic, or molecular;
molecular lasers can be further divided or characterized by the nature of
the transitions involved in the stimulated emission process, that is, the
transitions may be between electronic, vibrational, or rotational energy
levels; the output of many lasers may consist of several lines of varying
intensities. Table (1-3). (Cember and Johnson, 2009)
CHAPTER ONE REVIEW OF LITERATURES
21
Table (1-3): Laser types and typical lasing media. (Weber, 2001)
1.2.9. Laser tissue interactions:
1.2.9.1. Light propagation in biological tissues:
Four basic interactions can take place when laser energy interacts with
a target material or tissue including reflection, scatter, transmission or
absorption, figure (1-4). (Berger and Eeg, 2006 b)
Figure (1-6): Laser – tissue interactions. When it reaches biological tissue, the laser light can be reflected, 1; transmitted to the surrounding tissues, 2; scattered, 3; or be
absorbed, 4. (Schwarz, 2009)
The strength of the individual effect essentially depends on the
wavelength of the incident light, the index of refraction and the attenuation
and scattering coefficients of the tissue, together, they determine the total
transmission of the tissue at a certain wavelength; on the other hand, the
following parameters are given by the laser radiation itself: wavelength,
Laser type Typical lasing medium
Typical excitation methods
Gas He–Ne, CO2 Electrical Semiconductor GaAlAs, GaN Electrical Solid State YAG, Ti:sapphire Optical Dye Rhodamine 6G Optical Metal Vapor Copper Electrical
CHAPTER ONE REVIEW OF LITERATURES
22
exposure time, applied energy, focal spot size, energy density and power
density. (Haberth"ur, 2002)
a- Reflection and Refraction
Reflection is defined as the returning of electromagnetic
radiation by surfaces upon which it is incident, while reflecting surface
is the physical boundary between two materials of different indices of
refraction such as air and tissue; it originates from a change in speed of
the light wave, changing its wavelength, direction and thus the speed of
light will reduced according to the index of refraction of the medium,
as expressed:
Vm = c / n Where:
Vm
b- Absorption
is the velocity of light in medium
c is the speed of light in space,
n is the index of refraction;
In biological tissue, absorption is mainly due to the presence of
free water molecules, proteins, pigments and other macromolecules;
during absorption, the intensity of an incident electromagnetic wave is
attenuated in passing through a medium; it is due to a partial
conversion of light energy into heat motion or certain vibrations of
molecules of the absorbing material; the absorbance of a medium is
defined as the ratio of absorbed and incident intensities, and the ability
of a medium to absorb electromagnetic radiation depends on a number
of factors, mainly the electronic constitution of its atoms and
molecules, the wavelength of radiation, the thickness of the absorbing
layer and internal parameters such as the temperature or concentration
of absorbing agents. (Niemz, 2007)
CHAPTER ONE REVIEW OF LITERATURES
23
The process of absorption of laser energy by a tissue is the key to
effective laser to tissue interaction, as this photonic energy is absorbed,
it transfers its energy potential to the target tissue, thus inducing a
change in that tissue; water is the most abundant substance within
tissue and is a strong absorber of light in the near-infrared and
ultraviolet wavelengths, but has highest absorption at mid-infrared
wavelengths; there is negligible absorption of visible light by water,
water absorbs light maximally at 2,940 nm, which is the characteristic
wavelength of the Er: YAG laser. Figure (1-7) (Ishikawa et al., 2009)
Figure (1-7): Absorption spectrum for water of various lasers, such as
Argon, Diode, neodymium-doped yttrium aluminium garnet (Nd: YAG), CO2
Er,Cr:YSGG and erbium-doped yttrium aluminium garnet (Er:YAG). The
Er: YAG laser has the best absorption coefficient of water among these laser
systems.
c- Scattering
When elastically bound charged particles are exposed to
electromagnetic waves, the particles are set into motion by the electric
field; if the frequency of the wave equals the natural frequency of free
vibrations of a particle, resonance occurs being accompanied by a
considerable amount of absorption, while scattering takes place at
frequencies not corresponding to those natural frequencies of particles,
Er: YAG 2.940nm
CO2 10.600nm
Er,Cr: YSGG 2.780nm
Nd: YAG 1.064nm
Argon 488nm
Diod 810nm
CHAPTER ONE REVIEW OF LITERATURES
24
thus resulting oscillation is determined by forced vibration. (Niemz,
2007)
1.2.9.2. Optical Processing of Tissue
The diagnostic applications of lasers are based on scattered or reemitted
light. Surgical and therapeutic applications depend on absorption of light. The
absorbed laser energy can broadly lead to three effects:
a- Photothermal Effects
Most of the surgical applications of lasers exploit laser induced
photothermal effect that is a rise in tissue temperature subsequent to
absorption of laser radiation, the biological effect depends on the level of rise
in tissue temperature which is determined by two factors, the tissue volume in
which a given laser energy is deposited and the time in which the energy is
deposited via the thermal relaxation time (the inverse of which determines the
rate of flow of heat from heated tissue to the surrounding cold tissue, so if the
rate of deposition of energy is faster than that required for boiling of water,
the tissue is superheated and can be thermally ablated; thermal ablation or
explosive boiling is similar to what happens when cold water is sprinkled on a
very hot iron. Table (1-4) shows the thermal effect on biological tissues.
(Kishen and Asundi, 2007) Table (1-4): Laser thermal effect on biological tissues
Temperature Biological effect 37 oC Normal 45 oC Hyperthermia 50 oC Reduction in enzyme activity, cell immobility 60 oC Denaturation of protein and collagen, coagulation 80 oC Permeabilization of membranes
At high intensities associated with lasers operating in short pulse duration
(nanosecond 10-9, picoseconds 10-12
c- Photochemical Effects
) absorption of laser-radiation may lead to
generation of pressure waves or shock waves; the localized absorption of
intense laser radiation can also lead to very large temperature gradients,
resulting in enormous pressure waves and localized photomechanical
disruption; at high intensities, the electric field strength of radiation is also
very large, the resulting plasma absorbs energy and expands creating shock
waves, which can shear off the tissue, these plasma-mediated shock waves are
used for breaking stones in the kidney or urethra (lithotripsy) and in posterior
capsulotomy for removal of opacified posterior capsule of the eye lens.
(Kishen and Asundi, 2007)
For laser irradiation at power levels where there is no significant rise in
temperature of the tissue, the photothermal and photomechanical effects are
not possible, in such a situation, only photochemical effects can take place
provided the energy of laser photon is adequate to cause electronic excitation
of biomolecules, which can be either endogenous or externally injected; the
photo-excitation of molecules and the resulting biochemical reactions can
lead to either bio-activation exploited in various phototherapies or generation
of some free radicals or toxins, which are harmful for the host tissue and so
there will be a mild rise in the tissue temperature and the tissue removal can
be achieved in an extremely precise manner. (Kishen and Asundi, 2007)
1.2.9.3. Mechanism of tissue ablation by Er:YAG laser:
A mechanism of biological tissue ablation with the Er:YAG laser has
been proposed based on the optical properties of its emission wavelength and
morphologic features of the surface ablated by Er: YAG laser which
concluded that during Er:YAG laser irradiation, the laser energy is absorbed
CHAPTER ONE REVIEW OF LITERATURES
26
selectively by water molecules and hydrous organic components of biological
tissues causing evaporation of water and organic components and resulting in
thermal effects due to the heat generated by this process ‘photothermal
evaporation’; moreover, in hard tissue procedures, the water vapor production
induces an increase of internal pressure within the tissue, resulting in
explosive expansion called ‘micro explosion’, these dynamic effects cause
mechanical tissue collapse and resulting in a ‘thermo-mechanical’ or
‘photomechanical’ ablation ; this phenomenon has also been referred to as
‘water-mediated explosive ablation’. Figure (1-8). (Aoki et al., 2004)
Figure (1-8): Hard tissue ablation by Er: YAG laser irradiation. W: water molecules. BA: biological apatites. PM: protein matrix. (Sasaki KM et al., 2002)
CHAPTER ONE REVIEW OF LITERATURES
27
1.2.10. Laser safety:
Lasers and laser systems emit beams of optical radiation (ultraviolet,
visible and infrared which is termed as non-ionizing radiation to distinguish it
from ionizing radiation such as X-rays or gamma rays); eye hazards and/or
skin hazards are the primary concerns associated with optical radiation, table
(1-5). (Western Ontario University, 2006)
Table (1-5) summarizes the possible hazards that laser could cause: Table (1-5): types of laser hazards
Category Type of hazard
Physical
1- Electrical hazards.
2- Collateral and plasma radiation.
3- Noise and mechanical hazards from very high
energy lasers.
4- Cryogenic coolant hazards.
5- X radiation from faulty high-voltage (>15 kV)
power supplies.
6- Explosions from faulty optical pumps and lamps.
7- Fire hazards.
Chemical
1- Laser-generated airborne contaminants (LGAC).
2- Compressed gases, dyes and solvents. (hazardous
and/or contain toxic substances)
3- Biological agents include airborne infectious
materials and microorganisms
The American National Standard for Safe Use of Lasers (ANSL) has
four hazard classifications, which is used to describe the capability of the
laser or laser system to produce injury to personnel; higher-class numbers
indicate greater potential hazards. Brief descriptions of each laser class are as
follows: (U.S. Department of energy, 2005)
CHAPTER ONE REVIEW OF LITERATURES
28
Table (1-6): laser safety classes
Class Description
Class 1 (Exempt Lasers)
Emit low levels of energy that are not hazardous to the eyes or skin. Class 1 products are safe during normal operation, but may contain higher class lasers (a possible hazard only during service or maintenance). Examples include laser printers and compact disc players.
Class 2a and 2b
(Low-Power Lasers)
Visible lasers that require the use of caution, which can injure the eye if viewed for longer than the aversion response time of 0.25 seconds but will not produce a skin burn. An example is a store barcode scanner.
Class 3a
(Low-Risk Lasers)
Visible lasers that can produce spot blindness and other possible eye injuries under certain conditions. Examples include laser pointers, alignment lasers, survey equipment and laser levels.
Class 3b
(Medium-Power Lasers)
Visible and invisible lasers that cause an eye hazard from direct and specular reflections. Diffuse reflections may be hazardous if the laser is at full power and viewed close to the source. Many Class 3b lasers are used in research settings.
Class 4 (High-Power Lasers)
Always dangerous. These lasers can produce acute skin and eye damage from direct exposure and generate sufficient power to produce serious eye injuries from reflected light. Class 4 lasers are also a fire hazard, igniting flammable material. Examples include medical lasers, research lasers, industrial lasers, and military lasers.
CHAPTER ONE REVIEW OF LITERATURES
29
Important components of the eye, such as the cornea, lens, and retina,
figure (1-9), are susceptible to damage by laser light. Light enters through the
transparent layers of the cornea and then is focused by the lens onto the retina.
The eye in essence intensifies light energy, particularly the visible and the
near-infrared wavelengths, in some cases as much as 100,000 times.
(Washington University 2007)
Figure (1-9): section of human eye
1.2.11. Laser applications in dentistry:
Lasers were introduced into the field of clinical dentistry with the hope
of overcoming some of the drawbacks posed by the conventional methods of
dental procedures; since its first experiment for dental application in the
1960s, the use of laser has increased rapidly in the last couple of decades; at
present, wide varieties of procedures are carried out using lasers. (Husein,
2006)
A range of lasers is now available for use in dentistry (Walsh, 2003).
Table (1-7) summarizes the lasers of choice for specific indications in laser
dentistry. (Lee, 2007)
Table (1-7): Current lasers commonly used in clinical dentistry
type Active medium Wavelength (nm) Clinical applications company Gas Lasers CO2 10600 Soft tissue incision and ablation
Subgingival curettage
Deka
Lumenis
Diode
Lasers
InGaAsP
GaAlAs
GaAs
655
810
980
Caries and calculus detection
Soft tissue incision and ablation
Subgingival curettage
Bacterial decontamination
Biolase
Elexxion
KaVo
Odyssey, Sirona
Solid-state
Lasers
Nd:YAG 1064 Soft tissue incision and ablation
Subgingival curettage
Bacterial decontamination
Deka
Fotona
Periolase
Er:YAG 2940 Soft tissue incision and ablation
Subgingival curettage
Scaling and root debridement
Fotona
Hoya, KaVo
Lumenis, Syneron
Er,Cr:YSGG 2780 Modification of hard tissue surfaces
Hard tissue ablation
Bacterial decontamination
Biolase
CHAPTER ONE REVIEW OF LITERATURES
31
1.2.12. Laser in nonsurgical periodontics:
In the 1990s the neodymium: yttrium-aluminum-garnet (Nd:YAG)
laser was introduced for periodontal treatment, including removal of
subgingival calculus and pocket curettage, but it was not promising due to
profound thermal effects on hard tissues, including cementum and alveolar
bone. (Hakki, 2010)
Based on the results of studies, it appears at present that the carbon
dioxide (CO2) laser is not suitable for nonsurgical pocket applications
because this laser is less effective for root debridement and has the potential
to produce thermal damage in the periodontal pocket and surrounding tissues.
(Schwarz et al., 2009)
Also it was reported that using diode laser was unsuitable for calculus
removal and it altered the root surface in an undesirable manner, the results
showed that this laser may cause damage to periodontal hard tissues if
irradiation parameters are not adequate. (Schwarz et al., 2003 c)
Among the dental lasers, the Er:YAG laser (2.94 mm) has been
considered to be one of the most promising lasers in periodontal therapy,
because of the emission wavelength that is highly absorbed by water, the
Er:YAG laser possesses an excellent capacity for ablating dental hard tissues
including calculus without producing major thermal side-effects such as
carbonization, melting or cracking of the root substance, which are usually
observed following CO2 and Nd:YAG laser irradiation. (Maruyama et al,
2008)
The popularity of the erbium family of lasers has increased in the last
five years, many researchers have examined erbium lasers in the treatment of
periodontal disease; the published literature has shown that erbium lasers can
be an alternative therapy for root surface debridement because the laser can
ablate calculus without producing major thermal side effects to adjacent
tissue. (Glenn, 2004)
CHAPTER ONE REVIEW OF LITERATURES
32
1.2.13. Er:YAG laser:
Er:YAG laser was introduced in 1974 as a solid-state laser that
generates a light with a wavelength of 2940 nm; of all lasers emitting in the
near- and mid-infrared spectral range, the absorption of the Er:YAG laser in
water is the greatest because its 2940 nm wavelength coincides with the large
absorption band for water, also, as part of the apatite component, OH groups
show a relatively high absorption at 2940 nm, although the maximum
absorption is around 2800 nm. (Featherstone, 2000)
Since the Er:YAG laser is well absorbed by all biological tissue that
contain water molecules, this laser is indicated not only for the treatment of
soft tissues but also for ablation of hard tissues. (Tuner and Hode 2004)
The Er: YAG laser has elemental erbium as dopant; it works in pulsed
mode and the great benefit of this wavelength is that it is not as harmful to the
eyes (unless directly focused on the cornea) as the Nd:YAG laser; compared
to CO2 laser, it is less painful during treatment and healing is somewhat
faster; for avoiding of overheating, a jet of water accompanies the laser beam
in the same way as the conventional drill, application of Er:YAG laser are
listed in table (1-8) (Walsh, 2008)
Table (1-8): Current application of Erbium lasers
Aspect Action
Soft tissue
- Minor soft tissue surgery - Resurfacing of oral mucosa - Removal of gingival melanin pigmentation and gingival
discolourations - Ablative procedures such as gingivoplasty and
peri-implant surgery
Bone
- Cutting bone effectively without burning, melting, or altering the calcium: phosphorus ratio of the irradiated bone.
- Hard tissue crown lengthening - “tunnelling” closed procedure
- Hard tissue crown lengthening - open flap procedure - Milling sites for implant placement15 - Perforating block bone grafts to enhance osseo-induction16
CHAPTER ONE REVIEW OF LITERATURES
33
- Ablation of bony tori - Preparing bone for block grants, e.g. from the ramus - Selective milling of bone, with the ability to incorporate
autopilot systems18 Enamel
and Dentine
- Caries removal - Surface conditioning (etching) - Removal of resin, composite and GIC restorations
Other hard tissue sites
- Ablation of calculus during closed debridement - Removal of granulation tissue during periodontal or
periapical surgery - Debridement and decontamination of implant surfaces - Disinfection of periodontal pockets and root canals - Removal of smear layer from root canals - Root resection
1.2.13.1 Characteristics of Er:YAG nonsurgical periodontal therapy:
1- Clinical parameters:
In controlled, prospective clinical study for treatment of advanced
periodontal disease with a combination of an Er: YAG laser (KEY II, KaVo,
Germany) and SRP with hand instruments to laser alone, Schwarz et al, 2003
a conclude that
- Non-surgical periodontal therapy with both an Er:YAG laser and SRP
and an Er:YAG laser alone may lead to significant improvements in all
clinical parameters investigated.
- The combined treatment Er:YAG laser and SRP did not seem to
additionally improve the outcome of the therapy compared to Er:YAG
laser alone.
2- Calculus removal and effect on root substance:
Jarjess, 2005 mentioned that best results were obtained from the group
treated by laser of 12.60 J/cm2 with frequency of 10 Hz regarding the least
calculus residues, debris and cracks number on the root surface, and conclude
that the Er:YAG laser subgingival calculus removal was more effective that
the manual instrumentation and the ultrasonic techniques.
CHAPTER ONE REVIEW OF LITERATURES
34
Another study conducted on root surfaces instrumented with both
Er:YAG in vivo and Diode laser (DL) in vitro by Schwarz et al in 2003 c
exhibited no detectable surface alterations; in contrast, Er:YAG scaling in
vitro and SRP in vivo/in vitro produced superficial micro changes in root
cementum. However, irradiation with DL in vivo caused severe damages to
the root surface (i.e., crater formation). Er:YAG provided subgingival
calculus removal on a level equivalent to that provided by SRP, while DL was
unsuitable for calculus removal, since macroscopic inspection revealed the
presence of large amounts of subgingival calculus.
Eberhard et al, 2003 study the effectiveness of subgingival calculus
removal from periodontally involved root surfaces with an Er:YAG laser and
compared it to hand instrumentation in situ, demonstrate in vivo capability of
the Er:YAG laser to remove calculus from periodontally involved root
surfaces, although the effectiveness did not reach that achieved by hand
instrumentation; the lack of cementum removal in contrast to SRP may
qualify the laser as an alternative approach during supportive periodontal
therapy.
Schwarz et al, 2006 study, for evaluating the effects of fluorescence
controlled Er:YAG laser radiation, an ultrasonic device or hand instruments
on periodontally diseased root surfaces in vivo, conclude within the limits of
their study, that ERL and Vector ultrasonic system (VUS) enabled
- A more effective removal of subgingival calculus.
- A predictable root surface preservation in comparison with SRP.
The results of Folwaczny and Mehl, 2000 study showed that a
substance removal with Er:YAG laser radiation at lower energy densities is
comparable, in effect, to that after conventional root surface instrumentation
with curettes, and results seem to indicate that calculus removal can be
selectively done using lower radiation energies.
CHAPTER ONE REVIEW OF LITERATURES
35
3- Effect on soft tissue, hard tissues and bactericidal effect:
Ishikawa et al, 2009 have reported in their preclinical report
(Periodontal tissue healing following flap surgery using an Er:YAG laser in
dogs) that degranulation and root debridement were effectively performed
with an Er:YAG laser without major thermal damage and significantly faster
than that with a curet; histologically, the amount of newly formed bone was
significantly greater in the laser group than in the curet group, although both
groups showed similar amounts of cementum formation and connective tissue
attachment.
It was mentioned that Er:YAG laser possesses suitable characteristics
for oral soft and hard tissue ablation, and it has been applied for effective
elimination of granulation tissue, gingival melanin pigmentation, gingival
discoloration and contouring and cutting of bone with minimal damage and
even or faster healing can be performed with this laser; also reported that
irradiation with the Er:YAG laser has a bactericidal effect with reduction of
lipopolysaccharide, high ability of plaque and calculus removal, with the
effect limited to a very thin layer of the surface, and it is effective for implant
maintenance . (Ishikawa et al., 2008)
Bader and Krejci, 2006 reported that the advantages of Er:YAG
applications in periodontology are based on the efficient elimination of
bacteria and endotoxins on root surfaces in combination with the selective
feedback, where the laser arrives to differentiate between calculus and tooth
tissue.
In another study to evaluate the alterations occurring on radicular surfaces
irradiated with the Er:YAG laser, using the rat subcutaneous tissue response
resulting from human dental root specimens implanted at 7, 14, and 28 days
of healing, the results of histological and morphometric analyses showed a
higher number of inflammatory cells in group 4, for the period of 7 days, in
comparison to all the other groups, in groups 1, 2, and 3 some areas showed
CHAPTER ONE REVIEW OF LITERATURES
36
fiber adherence in the favorable angulation to attachment, denoting more
biocompatibility than that in group 4 suggesting that the Er:YAG laser may
represent an alternative approach in periodontal radicular therapy. (group 1-
Er:YAG laser with 60 mJ, 10 pps, for 15 s; group 2- Er:YAG laser with 100
mJ, 10 pps, for 15 s; group 3- scaling and root planning followed by surface
demineralization with citric acid and tetracycline for 3 min; and group 4-
scaling and root planning). (Jacomino et al., 2005)
4- Pain level and Dentine hypersensitivity:
Birang and Poursamimi, 2006 demonstrated that both Er:YAG and
Nd:YAG lasers have an acceptable therapeutic effect regarding minimizing
the pain and observed that effects seemed to last for at least 6 months, but
they concluded that Nd:YAG laser is more effective than Er:YAG laser in
reduction of patient's pain.
1.2.15. Advantages and disadvantages of laser periodontal therapy:
Table (1-9) summarizes common advantages and disadvantages of laser
therapy. (Lee, 2007) Table (1-9): Advantages and disadvantages of laser periodontal therapy
Advantages
- effective and efficient soft and hard tissue ablation
- greater hemostasis
- bactericidal effect
- Minimal wound contraction
- minimal collateral damages with reduced use of
local analgesia
- the small popping sound of the lasers in action with
Er:YAG seems to produce less stress to patients
than the high pitch vibration sound of most of the
ultrasonic devices
CHAPTER ONE REVIEW OF LITERATURES
37
Disadvantages
- require precautions to be taken during clinical
application
- Laser irradiation can interact with tissues even in
the non-contact mode
- the cost and size of laser device still constitute an
obstacle for clinical application of the lasers
CHAPTER TWO
MATERIALS AND METHODS
CHAPTER TWO MATERIALS & METHODS
38
2.1. MATERIALS:
2.1.1. Sample selection and description:
This study included a total of 16 patients, attending periodontics unit in
college of Dentistry - University of Mosul, seeking treatment for their
periodontal problem (chronic periodontitis). The subjects were then allocated
randomly and equally into study groups during a period of three months. The
laser treatment was accomplished at Al Jumhouria specialist dental center at
Mosul medical city.
A total of sixteen male patients (with age range from 25-45 years were
asked to participate in this clinical trial. Study goals and Full description of
the entire procedure were explained to each patient and an informed consent
was obtained from each of them (Appendix 1).
2.1.1.1. Inclusion criteria:
1- Male patient (to obtain maximum standardization of sample and exclude any
possible external variables effect) with chronic periodontitis having at least 6
teeth with pockets of ≥ 5mm.
2- The patients shouldn't have:
- Systemic diseases that could affect the periodontal condition.
- Recent (3 months) periodontal treatment.
- Recent (3 months) antibiotics taking.
2.1.1.2. Study case sheet:
A special case sheet was designed and required information was
collected from each patient (Appendix 2).
CHAPTER TWO MATERIALS & METHODS
39
2.1.2. Laser equipments:
2.1.2.1. Laser system:
The KaVo KEY Laser III upgraded is a universally usable erbium laser
for dentistry in the dental environment for oral, jaw and facial surgery. With
its variable pulse lengths, it is appropriate for treating enamel, bone and for
processing soft tissue (mucosa, muscle and connective tissue). Figure (2-1)
It contains two types of laser:
1- A pilot diode laser of 655nm: red light delivering maximum of
1 mW continues laser radiation with class II laser safety used as
guidance.
2- A therapeutic Er:YAG laser. It adjusted in ranges from
10 - 200mJ in 20mJ steps and 200 - 600 mJ in 50 mJ steps. The PRR is
from 2-30 Hz and divergence of laser beam after leaving the laser
contra-angle handpiece is approximately 5-10o. Table below contains
basic properties of KaVo Key laser III
Table (2-1): Basic properties of KaVo Key laser III
Solid-state laser Er: YAG laser class 4
Wavelength 2.94 μm
Pulse energy Up to 600 mJ
Pulse frequency 2 – 30 Hz
Pilot beam 655 nm/1 mW
Power consumption Max. 2.3 KW
Connection 230 V, 50/60 Hz/12 A
CHAPTER TWO MATERIALS & METHODS
40
2.1.2.2. Hand piece:
The hand piece no. 2061 was used with a prism on its exit end which is
rotatable and can thus be adapted to the respective tooth position.
The exit window of the prism tip is rectangular with dimension of
0.5 X 1.65 mm and thus the laser cross sectional area exiting from the prism
tip is 9.12 X10-3 cm 2. Figure (2-2)
The main characteristics of the 2061 handpiece are;