|Year : 2017 | Volume
| Issue : 1 | Page : 86-89
Reverse twin block for interceptive management of developing class III malocclusion
Meenu Mittal1, Harpreet Singh2, Ashok Kumar1, Poonam Sharma2
1 Department of Pediatric and Preventive Dentistry, ESIC Dental College, New Delhi, India
2 Department of Orthodontics, ESIC Dental College, New Delhi, India
|Date of Web Publication||31-Jan-2017|
A-29, Ground Floor, Hauz Khas, New Delhi - 110 016
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Early correction of developing class III malocclusions remains a complex challenge. Treatment approaches for these young patients have been directed at growth modification. Encouraging outcomes have been reported with the use of Class III functional appliances including reverse twin block (RTB) appliance. The present paper tries to provide an insight into RTB appliance used for successful interceptive management of developing class III malocclusion in two children. RTBs were fabricated with bite registered in the position of maximum possible retrusion of mandible with interincisal clearance of 2 mm and vertical clearance of 5 mm in the buccal segments. Anterior crossbite was corrected, and there was a marked improvement in facial appearance of the children. RTB can be a viable and effective functional appliance treatment modality for early management of developing class III malocclusion.
Keywords: Developing class III, interceptive management, reverse twin block
|How to cite this article:|
Mittal M, Singh H, Kumar A, Sharma P. Reverse twin block for interceptive management of developing class III malocclusion. J Indian Soc Pedod Prev Dent 2017;35:86-9
|How to cite this URL:|
Mittal M, Singh H, Kumar A, Sharma P. Reverse twin block for interceptive management of developing class III malocclusion. J Indian Soc Pedod Prev Dent [serial online] 2017 [cited 2017 May 26];35:86-9. Available from: http://www.jisppd.com/text.asp?2017/35/1/86/199221
| Introduction|| |
One of the most difficult and challenging problems to treat in the mixed dentition is the class III malocclusion as it tends to deteriorate with age. Children with developing class III malocclusion may have a combination of skeletal and dentoalveolar deformities. The skeletal components could be maxillary skeletal retrusion, mandibular skeletal protrusion, or a combination of the two. Posterior or anterior cross-bite may also be present in addition to these sagittal problems.
Early treatment of class III malocclusion provides a more favorable environment for normal growth and hence improves the orofacial, nutritional, esthetic, and psychosocial development of the child. Myriad interceptive approaches include fixed appliances, removable appliances, removable functional appliances, chin cup, protraction head gear, and skeletal anchorage systems.
The traditional twin block appliance by Clark is widely accepted and commonly used for the treatment of class II malocclusions. Another variation of twin block, called as reverse twin block (RTB) appliance, may be used for rapid correction of developing class III malocclusions., In RTB, the occlusal inclined planes are reversed so as to apply a forward component of force to the upper arch and a downward and distal force to the mandible in the lower molar region. The inclined planes are set at 70° angle to the occlusal plane with bite blocks covering lower molars and upper deciduous molars or premolars with sagittal screws to advance the upper incisors.
This article describes interceptive management of developing class III malocclusion in two children using RTB appliance.
| Case Reports|| |
Case report 1
An 11-year-old boy presented with the chief complaint of low self-esteem and bullying by peers due to unaesthetic appearance of front teeth. The family history was not suggestive of any genetic predisposition. Medical and dental history was noncontributory. A concave profile was noticed with an appearance of maxillary growth restriction on extraoral examination [Figure 1]a and [Figure 1]b.
|Figure 1: Case 1 Pretreatment (a-d), With RTB appliance (e), and Post treatment (e-i) photographs|
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Intraoral examination revealed a mixed dentition stage with erupted lower permanent canines and erupting upper permanent canines. Bilateral developing class III molar relation with reverse overjet of 4mm and overbite of 4mm was noticed alongwith anterior mandibular displacement on closure [Figure 1]c and [Figure 1]d. Lateral cephalometric analysis revealed a class III skeletal pattern (orthognathic maxilla and mild mandibular prognathism) with slightly proclined maxillary incisors (U1 to SN, 107°) and normal mandibular incisor inclinations (IMPA, 89°) [Figure 2]a.
|Figure 2: Lateral cephalogram: Case 1 pretreatment (a), Case 1 posttreatment (b), Case 2 pretreatment (c) and Case 2 posttreatment follow up (d)|
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Treatment plan involved elimination of anterior displacement, correction of anterior crossbite, and temporary restriction of mandibular growth. RTB was fabricated with bite registered in the position of maximum possible retrusion of mandible with interincisal clearance of 2 mm and vertical clearance of 5 mm in the buccal segments [Figure 1]e.
With RTB, anterior crossbite was corrected in 6 months, which was maintained at 3-year follow-up [Figure 1]f,[Figure 1]i and [Figure 2]b. Posttreatment and follow-up skeletal and dental changes are mentioned in [Table 1]. The patient and his parents were delighted with the remarkable esthetic changes in profile and appearance of teeth. The patient is continuing with the same appliance at night time to retain the achieved correction.
Case report 2
An 8-year-old boy presented with a concave profile and complaints about his facial appearance and irregularly placed upper and lower front teeth [Figure 3]a and [Figure 3]b. Anterior displacement of mandible on closure was detected.
|Figure 3: Case 2 pretreatment (a-d), posttreatment (e-h), and with reverse bionator appliance (i) photographsh|
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Intraoral examination revealed an early mixed dentition stage with erupted upper and lower permanent incisors and first molars. Mild mandibular and maxillary anterior crowding with developing class III molar relation on both sides and a reverse overjet of 4 mm and overbite of 3 mm was seen [Figure 3]c and [Figure 3]d.
Cephalometric evaluation revealed class III jaw-base relationship (ANB, −4°; Wits appraisal, −8 mm) with slightly proclined maxillary incisors (U1 to SN, 108°) and relatively normal inclinations of mandibular incisors (IMPA, 89°) [Figure 2]c.
Anterior crossbite was corrected and the patient developed a habitual closure of mandible in a backward position after 10 months of wearing the appliance. There was a marked improvement in facial appearance of the child. Pre- and post-treatment skeletal and dental changes are shown in [Table 2].
The child is wearing reverse bionator as retention appliance at night [Figure 3]i. A normal overjet and overbite relation is maintained at 2-year follow-up [Figure 3]e,[Figure 3]f,[Figure 3]g,[Figure 3]h and [Figure 2]d.
| Discussion|| |
Class III patients commonly report for early treatment as occurrence of an end–to-end incisor relationship, or a frank anterior crossbite is easily perceived by the family practitioner or the parent as an abnormal occlusal relationship.
Treatment in all developing class III cases should be undertaken as soon as the abnormality is detected to prevent it from becoming permanent and full-blown class III malocclusion. Provision of early treatment is aimed at (i) prevention of progressive damaging soft tissue or bony changes, i.e., abnormal wear and dental compensation of mandibular incisors leading to labial alveolar plate thinning and gingival recession; (ii) redirecting future growth of jaws in more favorable direction; (iii) occlusal function improvement; (iv) simplification of phase II comprehensive orthodontic/surgical treatment; (v) prevention of temporomandibular joint symptoms; and (vi) restoration of facial esthetics. The optimal time for beginning treatment is in early mixed dentition, which may be coincident with the loss of maxillary deciduous incisors and eruption of the upper permanent central incisors. Favorable treatment results in developing class III malocclusions in younger children with early mixed dentition have been shown in various clinical reports., Prepubertal orthopedic treatment of class III malocclusion is effective both in the maxilla (which shows a supplementary growth of about 2 mm over class III untreated controls) and in the mandible where it shows restriction in growth of about 3.5 mm over controls., Even with early intervention, stability will depend on several factors, such as maxillary and/or mandibular skeletal involvement, growth potential, age, family history, genetic influence, and patient compliance.
Various methods for interception of developing class III malocclusion are (i) appliances to restrain growth of the mandible-like chin cup with headgear; (ii) appliances primarily directed for orthopedic effect on maxilla such as protraction face mask; (iii) appliances which affect both the jaws by altering growth - such as functional appliances like RTB, Frankel appliance FR III, class III bionator.
When orthopedic correction in maxilla is desired in patients with class III malocclusion due to mid-face deficiency, favorable growth with face mask can be achieved. It may be difficult to gain compliance with this appliance. FR-III Frankel appliance has been used effectively to treat class III malocclusion in the mixed dentition and is easiest to manage clinically of all Frankel appliances. It is relatively inconspicuous, especially compared with the orthopedic facial mask. However, longer treatment duration of 12–24 months with FR-3 appliance to produce a similar response is a major deterrent in ensuring better patient compliance as compared to 6 months with face mask therapy.
Oldest of the orthopedic approaches in treating class III malocclusion is the chin cup, which is indicated for use in patients with mild to moderate mandibular prognathism. The overall results are unpredictable with chin cup as they generally depend on the amount of force applied and duration of daily wear.
Mild class III skeletal pattern (mild mandibular prognathism with a normal or mild maxillary retrognathism) with an average or below average maxillary-mandibular plane angle and lower facial height are the ideal skeletal indicators for the use of RTB. Dental indicators are reverse overjet with anterior crossbite, excessive overbite, minimal incisor compensation, forward mandibular displacement on closure, and edge-to-edge incisor relationships in centric relation. Reverse angulation of blocks in an RTB harnesses occlusal forces to advance the maxilla and maxillary dentition while using the mandible as an anchorage and restricting its development.,, The effects of the RTB appliance are primarily limited to the dentition, due to proclination of the upper incisors and retroclination of the lower incisors. Skeletal changes are limited to slight downward and backward rotation of the mandible with an associated increase in vertical dimension.
With RTB, no damaging force is exerted on the condyles because the bite is hinged open with the condyles down and forward in the fossae, and the inclined planes are directed downward and backward on the mandibular teeth. From the lower molar, the force vector in the mandible passes toward the gonial angle which best absorbs occlusal forces., Other advantages of RTB include ease of fabrication, tolerability by patient, durability, and cost effectiveness.,
Tendency for class III was reduced in our patients as maxillary growth was facilitated by correction of reverse overjet while mandibular growth was restricted. It was decided to wait till pubertal growth spurt for further evaluation and treatment which could vary from no treatment to fixed orthodontic treatment or surgical correction. Early treatment reduces the need of treatment in the permanent dentition and gives more favorable and stable changes. However, early class III correction may be lost during teenage years as mandibular growth exceeds maxillary growth during adolescence. Hence, patients who receive early treatment may still require surgical treatment at the end of growth period, which might be frustrating to the patient or the dentist.
The outcome of any individual class III patient is very often difficult to estimate and possibility of surgical correction should be explained to the patient and parents at the beginning of interceptive management. Because of unpredictability of growth of mandible, the patients were advised to continue with the retentive appliances at night time till cessation of active growth.,
| Conclusions|| |
Early diagnosis and interception of developing class III malocclusion is indispensable for redirecting future growth of jaws in a more favorable direction. RTB is a viable and effective functional appliance treatment modality for early management of developing class III malocclusion.
As growth pattern of class III malocclusion is established early, which tends to deteriorate with age, pediatric dentists have a vital role to play in its diagnosis and interceptive management. By promotion of unhindered favorable growth of maxilla and transient restriction of mandibular growth, RTB can be a viable and effective treatment modality for early management of developing class III malocclusion.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2]