Spring-loaded bite-blocks for early correction of skeletal open bite associated with thumb sucking

Spring-loaded bite-blocks for early correction of skeletal open bite associated with thumb suckingSpring-loaded bite-blocks for early correction of skeletal open bite associated with thumb sucking
Umal H. Doshia and Wasundhara A. Bhadb
Nagpur, Maharashtra, India
From Denta aForm bAsso The a ucts o Reprin van C rediff Subm 0889- Copyr doi:10
Skeletal open-bite malocclusion is frequently discussed in orthodontics. Diagnosis, treatment, and retention can be difficult because this malocclusion has numerous correlated etiologic factors. The earlier this malocclusion is corrected, the better the prognosis will be, especially when the problem is skeletal. This article presents a patient with a skeletal open bite and a thumb-sucking habit who was treated in the mixed dentition with an orthodontic appliance that included an acrylic occlusal splint along with spring-loaded blocks to guide the vertical force against the posterior teeth and the alveolar process. The usefulness of the appliance as a habit-breaking therapy is also highlighted. (Am J Orthod Dentofacial Orthop 2011;140:115-20)
In the study of the formation of malocclusion, vertical facial dysplasia is treated with special deference. This attitude is a by-product of many decades of clinical,
experimental, and morphologic investigations and re- flects the rich variety of opinions concerning the nature of vertical dysplasia. The vertical problem varies from a deep or an excessive overbite to the opposite extreme, an open bite.
Even though the prevalence of open bite is low (3.5% in patients aged 8-17 years1), correcting the problem has proven to be extremely challenging. The cause of an an- terior open bite is multifactorial and can be attributed to a combination of skeletal, dental, and soft-tissue effects.
A patient with a skeletal open bite has superimposed craniofacial dysplasia. Development of a skeletal open bite has been attributed to lack of coordination between condylar-glenoid fossa growth (horizontal factor) and vertical growth of the maxilla and the dentoalveolar pro- cesses (vertical factor). Increased expression of vertical factors rather than horizontal factors results in clockwise rotation of the mandible, leading to skeletal anterior open bite.2,3 This type of disturbance could also be
the Department of Orthodontics and Dentofacial Orthopedics, Government l College and Hospital, Nagpur, Maharashtra, India. er Postgraduate student. ciate professor and head. uthors report no commercial, proprietary, or financial interest in the prod- r companies described in this article. t requests to: Umal H. Doshi, 68, Builder’s Housing Society, Near Nandan- olony, Aurangabad, Maharashtra, India 431002; e-mail, Umal_16@ mail.com. itted, revised and accepted, August 2009. 5406/$36.00 ight 2011 by the American Association of Orthodontists. .1016/j.ajodo.2009.08.033
produced by a long-standing finger-sucking habit, con- verting a dental open bite into a skeletal open bite.4
According to Brodie,5 patterns of facial growth are established early in development. But the use of ortho- dontic appliances to correct an open bite in the decidu- ous dentition is not indicated because there is no reason to change a habit or move teeth if the situation will spontaneously correct. However, if the open bite is a re- sult of a skeletal discrepancy of the maxilla in a patient with a long face, spontaneous correction might not oc- cur. The ideal period to begin treatment is during the mixed dentition; if the malocclusion is corrected during the deciduous dentition, it will recur because of contin- ued growth changes. In the mixed dentition, the most important step in correcting an open bite associated with abnormal habits is to eliminate the habits with behavior-modification techniques, accompanied by speech therapy; if necessary, a removable functional ap- pliance with a vertical crib can be used. It is important to present this treatment to the child as an aid and not as a punishment. In about half of the patients, thumb suck- ing ceases immediately, and the anterior open bite closes relatively quickly. After the habit is eliminated, it is im- portant to maintain the appliance for 3 to 6 months.6
However, when the open bite is associated with skeletal features such as an increased mandibular plane angle, anterior face height, and extruded posterior teeth, it is necessary to redirect maxillary growth with molar intru- sion, to rotate the mandible in an upward and forward direction.6
Many approaches have been suggested to modify this early developmental pattern, but only posterior bite- blocks proved to be effective in producing condylar growth and forward rotation of mandible.7-15 To
116 Doshi and Bhad
actively intrude the posterior teeth, Iscan et al12 and Ak- kaya and Haydar14 suggested the use of a spring-loaded bite-block.
Our objective was to present an alternative treatment for anterior skeletal open bite associated with thumb sucking during the mixed dentition with a removable mandibular acrylic occlusal splint and a spring-loaded block, based on the appliance designed by Woodside and Linder-Aronson.16 This modified appliance guides the vertical force against the posterior teeth and the al- veolar process. The effectiveness of the appliance as a habit-breaking therapy is highlighted.
CASE REPORT
A boy, aged 9 years 4 months, was initially referred by his pediatrician to an orthodontic department (Figs 1 and 2). The clinical examination showed a skeletal open-bite malocclusion associated with a thumb- sucking habit. There was no history of respiratory prob- lems. The patient had all the cephalometric features of skeletal open bite, including steep mandibular plane an- gle, obtuse gonial angle, increased lower anterior face height, and excessive posterior dental heights (Table I). Clinically, the open bite was 7 mm.
The main problem was the anterior open bite, which was of skeletal origin, as confirmed by cephalometric analysis; it impaired his dental esthetics. The severe ver- tical skeletal dysplasia was most likely hereditary, but the sucking habit probably contributed to the development or exacerbation of the malocclusion.
Therefore, the following objectives were established: (1) eliminate the sucking habit and redefine perioral muscular function, (2) establish a normal overbite, (3) improve facial appearance and labial balance, (4) reduce the vertical skeletal dysplasia, and (5) align and level the teeth with corrective orthodontics, if necessary, in the permanent dentition.
Orthodontic alternatives were limited because of the patient’s age. The treatment objective for the maxilla in- cluded altering the vertical position through posterior
July 2011 Vol 140 Issue 1 American
impaction. The following options were discussed with the patient’s family: early treatment with removable appliances or fixed-appliance treatment after all perma- nent teeth had erupted.
For removable therapy, 2 options were given to the patient: extraoral appliance (high-pull headgear or ver- tical pull chincup) and modified posterior bite-blocks. The patient refused the extraoral appliance. Modified posterior bite-blocks had several advantages. They would (1) normalize the open bite, (2) prevent extrusion of the posterior teeth, (3) prevent an increase of the open bite, and (4) prevent downward and backward mandib- ular rotation. But this alternative also had several disad- vantages: the treatment time would not be shorter, and success would depend on patient compliance.
Journal of Orthodontics and Dentofacial Orthopedics
Table I. Cephalometric data
Measurement Pretreatment Posttreatment 1 year after retention
Sagittal \SNA () 80 80.5 81 \SNB () 75 77.5 78 \ANB () 5 3 3
Vertical \SN-GoGn () 36 33.5 33 \Ar-Go-Me () 132 129 128 N-Me (mm) 110 107 106 S-Go/N-Me 3 100% 58 61.5 62
Dental Maxillary incisor-NA (mm)
Overjet (mm) 4.5 2 2 Overbite (mm) 7 1 1.5
\Angular measurement; ^perpendicular linear measurement.
Doshi and Bhad 117
The second alternative was fixed appliances in the permanent dentition. This treatment would normalize the open bite, but we would have to wait for all perma- nent teeth to erupt. Treatment costs would be greater, and orthognathic surgery might be required.
After we discussed the treatment options with the patient and his parents, it was decided to use the modified bite-blocks. Although posterior bite-blocks had been used previously for control of vertical dimensions, their useful- ness in controlling the sucking habit has not been consid- ered.6-15 By virtue of its spring action, the appliance stimulates continuous masticatory movements: ie, an oral gymnastic effect. It was thought that this oral gymnastic effect could also act as a habit-breaking ther- apy by diverting the patient’s attention toward holding the appliance in the mouth. Hence, the option of a spring-loaded bite-block was discussed with the patient and his parents, and informed consent was obtained.
To study the treatment effects, study models, cepha- lograms, and electromyograph recordings of the masse- ter and temporalis muscles at rest and at maximal clenching were taken at the start of treatment and after closure of the open bite.
The construction bite was taken by hinging the man- dible open about 3 to 4 mm beyond the rest position in centric relation. This resulted in 6 to 8 mm of vertical opening in the second premolar region. Working models
American Journal of Orthodontics and Dentofacial Orthoped
were then mounted on the 3-point articulator with the wax construction bite in place.
The appliance had 2 parts: a mandibular removable plate with occlusal coverage and an acrylic bite-block, occlusal to the mandibular plate (Fig 3). The mandibular plate acrylic was extended incisally to the cingulum of the incisors to prevent their supraeruption.
The occlusal bite-block extended from the mandibu- lar first premolar and first deciduous molar region to the maxillary last erupted molar. These parts were connected by 2 helical springs (buccal and lingual) made from 0.9-mm high-strength stainless steel wire. The springs were positioned with the helices facing the premolars. The lower end of the buccal spring was soldered to the Adams clasp (0.8-mm stainless steel), and the occlusal end was embedded completely in the occlusal bite- block. The lingual spring had its lower end embedded in the lower plate and the upper end embedded in the occlusal bite-block. Both buccal and lingual springs were parallel to each other.
A hook made from 0.9-mm stainless steel wire was embedded in the occlusal bite-block in the molar region on the buccal side to measure the amount of activation. The force activation was measured by compressing the springs until contact between the 2 acrylic bite-blocks was achieved. This was done by using a Dontrix gauge (Ortho Organizers, Carlsbad, Calif).
The patient was instructed to wear the appliance for 24 hours a day except during meals and brushing. He was recalled every 4 weeks, and the appliance was activated at every appointment. The helical springs were activated progressively to maintain the forces between 250 and 300 g.
TREATMENT PROGRESS
There were no breakages during the treatment, and full closure of the open bite was obtained in 8 months (Figs 4 and 5). At this time, he was also free of the sucking habit. The cephalometric analysis (Table I) showed intrusion of the maxillary molars by 1.5 mm and the mandibular molars by 0.5 mm, causing autoro- tation of the mandible. This led to decreases in the mandibular plane angle and anterior face height. Elec- tromyographically (Table II), there were increases in muscle activity of the masseter and the temporalis at rest and at maximal clenching. An increase in muscle strength could be a positive factor for retention of the results, if the muscle strength does not decline after treatment.
After closure of the open bite, patient was kept on re- tention using the passive posterior bite-block appliance for 6 months. One year after retention (Figs 6 and 7), the
ics July 2011 Vol 140 Issue 1
Fig 3. Spring-loaded bite-block.
Table II. Electromyographic recordings: peak-to-peak amplitude (mV)
Muscle Pretreatment Posttreatment Masseter Rest 5 9 Maximal clenching 234 457
Temporalis Rest 11 17 Maximal clenching 412 983
118 Doshi and Bhad
July 2011 Vol 140 Issue 1 American
patient had a Class I molar relationship with 1.5 mm of overbite and was free of the sucking habit.
DISCUSSION
Anterior open bite is a term used if there is localized absence of occlusion when the remaining teeth are in occlusion.17,18 This lack of occlusion of at least 1 tooth with its antagonist in the opposite arch occurs because of interference during normal dental eruption and in alveolar development. The principal causes are mechanical interference in the eruption of teeth and in alveolar growth, such as digital sucking habits,4,19,20
and vertical skeletal dysplasia.3,17,18
Clinically, anterior open bite is grouped into 2 main categories: dental or acquired open-bites, which have no distinguishing craniofacial malformations, and
Journal of Orthodontics and Dentofacial Orthopedics
Fig 7. Superimposition of cephalometric tracings before treatment (red) and 1 year after treatment (black).
Fig 6. One year after treatment.
Doshi and Bhad 119
skeletal open bite with superimposed craniofacial dysplasia.17,18
The study of this anomaly is important during the de- ciduous and mixed dentition because of its relationship with the period of growth and development, and with common oral habits during this phase. The treatment of this anomaly is not exclusive to orthodontics. If the skeletal relationship is the primary cause of the anterior open bite and control of the sucking habit is limited, the prognosis is poor.4,17,18 The treatment of choice for this problem is to reduce the vertical dimension by reducing the height of the posterior teeth.
The difficulty of managing anterior open-bite maloc- clusions is not only in obtaining the correct diagnosis, but also in treating to a successful facial and dental re- sult. The orthodontist’s challenge is to minimize molar extrusion during treatment to prevent downward and backward mandibular rotation.
The early treatment strategy of skeletal open bite is based on inhibition of the vertical development or intru- sion of the buccal dentoalveolar structures by means of bite-blocks or extraoral appliances, thus producing up- ward and forward rotation of the mandible into a more horizontal growth direction, rather than vertical. Early interception offers psychological benefits and the potential for condylar growth. Nonsurgical options usu- ally require longer treatment times and more patient compliance.
Although attempts to limit the increase in vertical di- mensions by at least 1 of the above approaches were done by orthodontists, posterior bite-blocks proved to be effective in producing condylar growth and forward rotation of the mandible. To actively intrude the poste- rior teeth, active components in the form of magnets and springs have been suggested.6-16
The design of spring-loaded bite-blocks was first de- scribed by Woodside and Linder-Aronson.16 These blocks are activated from time to time, and they supply additional force in the neuromuscular system, in addi- tion to the forces of the masticatory muscles that are
American Journal of Orthodontics and Dentofacial Orthoped
exerted by the passive posterior bite-blocks. Because of its peculiar design, it was thought that the same appli- ance could also act as a habit-breaking appliance. With this appliance, the patient must apply active force to close his mouth, and this acts as a distraction therapy.
For our patient, we used posterior bite-blocks with the addition of springs. The main purpose was to restrict the extrusion of the maxillary permanent molars and vertical maxillary growth, along with control of the thumb-sucking habit. By intruding the posterior teeth, the mandible autorotates upward and forward. This form of treatment is advantageous because it corrects the anterior open bite and simultaneously reduces the total anterior facial height. The increase in muscle
ics July 2011 Vol 140 Issue 1
120 Doshi and Bhad
strength because of its oral gymnastic effect ensures a stable result.
Patients treated with this type of appliance should be seen shortly before the pubertal growth spurt, since op- timum improvement is often attainable only during this period, and significant changes are often seen in only a few months. Functional therapy is essentially a process of guiding growth, and this part of the correction can be maximized only during a period of significant growth.
CONCLUSIONS
The treatment plan was simple and ensured a stable and esthetic result for the patient. Favorable skeletal growth and the patient’s cooperation contributed to functional and esthetic improvements. The appliance used to correct the skeletal open bite during the mixed dentition was shown to be efficient, but its correct indi- cation and control are of fundamental importance.
REFERENCES
1. Proffit WR, Fields HW Jr, Moray LJ. Prevalence of malocclusion and orthodontic treatment need in the United States: estimates from the NHANES III survey. Int J Adult Orthod Orthognath Surg 1988;13:97-106.
2. Bjork A. A prediction of mandibular growth rotation. Am J Orthod 1969;55:585-99.
3. Schudy FF. Vertical growth versus anteroposterior growth as related to function and treatment. Angle Orthod 1964;34: 75-93.
4. Cozza P, Baccetti T, Franchi L, Mucedero M, Polimeni A. Sucking habits and facial hyperdivergency as risk factors for anterior open bite in the mixed dentition. Am J Orthod Dentofacial Orthop 2005; 128:517-9.
5. Brodie AG. On the growth pattern of the human head from the third month to the eighth year of life. Am J Anat 1941;68:209-62.
July 2011 Vol 140 Issue 1 American
6. Altuna G, Woodside DG. Response of the midface to treatment with increased vertical occlusal forces. Angle Orthod 1985;55: 251-63.
7. Dellinger EL. A clinical assessment of the active vertical corrector, a nonsurgical alternative for skeletal open bite treatment. Am J Orthod 1986;89:428-36.
8. Woods MG, Nanda RS. Intrusion of posterior teeth with magnets, an experiment in growing baboons. Angle Orthod 1988;58: 136-50.
9. Kalra V, Burstone CJ. Effects of a fixed magnetic appliance on the dentofacial complex. Am J Orthod Dentofacial Orthop 1989;95: 467-78.
10. Kiliaridis S, Egermark I, Thilander B. Anterior open bite treatment with magnets. Eur J Orthod 1990;12:447-57.
11. Barbre RE, Sinclair PM. A cephalometric evaluation of anterior open bite correction with the magnetic active vertical corrector. Angle Orthod 1991;61:93-102.
12. Iscan HN, Akkaya S, Koralp E. The effects of the spring-loaded pos- terior bite-block on the maxillofacial morphology. Eur J Orthod 1992;14:54-60.
13. Kuster R, Ingervall B. The effect of treatment of skeletal open bite with two types of bite-blocks. Eur J Orthod 1992;14:489-99.
14. Akkaya S, Haydar S. Post-retention results of spring-loaded poste- rior bite-block therapy. Aust Orthod J 1996;14:179-83.
15. Iscan HN, Sarisoy L. Comparison of the effects of passive posterior bite-blocks with different construction bites on the craniofacial and dentoalveolar structures. Am J Orthod Dentofacial Orthop 1997;112:171-8.
16. Woodside DG, Linder-Aronson S. Progressive increase in lower an- terior facial height and the use of posterior bite block in its man- agement. In: Graber LW, editor. Orthodontics: state of art, essence of science. St Louis: C. V. Mosby; 1986. p. 200-21.
17. Subtelny JD, Sakuda M. Open-bite: diagnosis and treatment. Am J Orthod 1964;50:337-58.
18. Worms FW,Meskin LH, Isaacson RJ. Open-bite. Am J Orthod 1971; 59:589-95.
19. Bowden BDA. A longitudinal study of the effects of digit- and dummy-sucking. Am J Orthod 1966;52:887-90.
20. Subtelny JD, Subtelny JD. Oral habits. Studies in form, function, and therapy. Angle Orthod 1973;43:343-83.
Journal of Orthodontics and Dentofacial Orthopedics
Spring-loaded bite-blocks for early correction of skeletal open bite associated with thumb sucking
Case report
Treatment progress