|Year : 2015 | Volume
| Issue : 1 | Page : 3-9
Early orthopedic correction of skeletal Class III malocclusion using combined reverse twin block and face mask therapy
Vinay Kumar Chugh1, Pradeep Tandon2, Veerendra Prasad3, Ankita Chugh4
1 Department of Orthodontics, Vyas Dental College and Hospital, Jodhpur, India
2 Department of Faculty of Dental Sciences, KG Medical University, Lucknow, India
3 Department of Plastic Surgery, KG Medical University, Lucknow, India
4 Department of Dentistry, All India Institute of Medical Sciences, Jodhpur, Rajasthan, India
|Date of Web Publication||9-Jan-2015|
Dr. Vinay Kumar Chugh
Associate Professor, Vyas Dental College and Hospital, Pali Road, Kudi Haud, Jodhpur 342005, Rajasthan
Source of Support: None, Conflict of Interest: None
| Abstract|| |
A 6-year 8-month-old girl presented with a moderate Class III malocclusion characterized by mid-face deficiency and an anterior cross bite. In the first phase, the patient was treated with combination of reverse twin block and facemask therapy. In phase two, fixed appliances were placed in the permanent dentition. The post treatment results were good and a favorable growth tendency could be observed. The correction of the Class III malocclusion occurred by a combination of skeletal and dental improvements. This report shows successful correction of skeletal Class III malocclusion in the early transitional dentition using combination therapy.
Keywords: Class III malocclusion, early treatment, orthopedic correction
|How to cite this article:|
Chugh VK, Tandon P, Prasad V, Chugh A. Early orthopedic correction of skeletal Class III malocclusion using combined reverse twin block and face mask therapy. J Indian Soc Pedod Prev Dent 2015;33:3-9
|How to cite this URL:|
Chugh VK, Tandon P, Prasad V, Chugh A. Early orthopedic correction of skeletal Class III malocclusion using combined reverse twin block and face mask therapy. J Indian Soc Pedod Prev Dent [serial online] 2015 [cited 2020 Aug 11];33:3-9. Available from: http://www.jisppd.com/text.asp?2015/33/1/3/148960
| Introduction|| |
In the past, the orthodontic literature portrayed the Class III problem as one of mandibular prognathism. Many of the studies now increasingly suggest that the majority of Class III malocclusions have maxillary retrusion. ,,, Guyer et al.,  reported 63% Class III patients had maxillary skeletal retrusion with slightly prognathic or normal mandible. Sue et al., found that 62% of their Class III cases involved maxillary retrusion. Whenever maxillary deficiency is the cause of Class III malocclusion, decreased maxillary basal length and/or retruded position of the maxilla coupled with anterior cross bite are contributing factors.  Skeletal Class III malocclusion usually is a three-dimensional problem and patients often exhibits maxillary constriction that is manifested as an anterior and/or posterior cross bite. Sagittal discrepancy may worsen with age as the retarded maxillary growth is coupled with unimpeded growth of the mandible. Further, if the patients reports in late mixed or permanent dentition, the degree to which orthopedic alteration is possible is limited.
Typically, treatment approaches for young patients with Class III malocclusion have been directed at growth modification. Encouraging outcomes have been reported ,, with the use of reverse functional appliances including the Functional Regulator (FR III) and Reverse Twin-Block (RTB) appliances but the results are limited to dentoalveolar correction. Face mask/reverse head gear is an orthopedic appliance which when worn 10-14 hours a day for 9-12 months can skeletally advance the maxilla in the range of 2-4 mm in order to correct the Class III malocclusion. 
The results of Face mask therapy (FMT) as agreed by various investigators are essentially maxillary anterior displacement, improvement in facial profile, counter-clockwise rotation of the maxilla, mandibular backward and downward rotation, proclination of the maxillary incisors retroclination of the mandibular incisors, and increase in vertical dimension. ,,,,,, Maxillary protraction is generally considered to be stable and success rate of 66 to 75% has been reported. ,, However, there is a potential risk that some patients might require orthognathic surgery later in life because of unfavorable growth pattern usually due to horizontal mandibular growth.
Early interception with orthopedic appliances would advance the maxilla and at the same time restrict the mandibular growth. This enables a morphologic and functional condition that favours normal facial growth, in addition to establishing more acceptable esthetics in the early stages. We present a long-term followed case of a patient with a moderate Class III malocclusion treated successfully in early mixed dentition using combination of FMT and RTB.
Diagnosis and treatment planning
A 6-year 8-month-old North Indian girl in the early transitional dentition was referred by her pediatrician to the Post Graduate Orthodontic Clinic for correction of malocclusion. She had no history of significant medical problems and no family history of hereditary disease. Her parents were concerned about her appearance and wondered whether something could be done at an early age. The patient's soft-tissue profile was concave with a relatively prominent lower lip, a retrusive midface, and a normal mandible. She had a mesial-step terminal plane relationship bilaterally, complete anterior cross bite with a negative overjet (−2.5 mm) and overbite of +5 mm at centric occlusion (CO). Her lower left primary mandibular second molar was carious [Figure 1] and [Figure 2]. On functional assessment, slight antero-posterior functional shift was present. At centric relation (CR), an edge-to-edge incisor relationship was observed. The cephalometric assessment showed a skeletal Class III malocclusion (A point-Nasion-B point (ANB) angle of −3° and Wits of −8 mm) mainly due to deficient maxilla (SNA 76°) with a tendency towards horizontal growth pattern (basal plane angle 20°), decreased lower anterior facial height (facial height ratio 52%), maxillary incisor retrusion (U1-PP: 100°) and mandibular incisor protrusion (L1-MP: 102°) [Table 1].
|Figure 2: (a-c) Pretreatment cephalometric tracing and panoramic radiograph|
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Cervical vertebrae maturation indicator (CVMI) assessment on lateral cephalogram indicated that patient was well before the initiation of the pubertal growth spurt. Inferior borders of body of the vertebrae C2, C3, and C4 were flat. At this stage, 80-100% of pubertal growth remains as it is known that development of concavity at lower borders of C2, C3, C4 indicates initiation of growth spurt.
Considering all these factors, the objective of phase I therapy (RTB and FMT) was to improve skeletal jaw deformity, to correct functional deviation, to achieve desirable anterior occlusion, and to normalize and enhance crainiofacial growth.
During Phase 1 left mandibular primary second molar was restored after which the bite was recorded in edge-to-edge position with 2 mm inter-incisal clearance. RTB appliance with hooks in maxillary primary first molar region for protraction therapy was fabricated [Figure 3]. After 2 months, patient got adjusted to the appliance and FMT was initiated [Figure 4]. Forces used for traction were in the range of 6-8 ounces per side in the beginning. After 4 months of combined RTB and FMT, there was improvement in facial profile with partial correction of anterior cross bite. The elastic force was subsequently increased to 14 ounces per side. Patient was instructed to wear the face mask for 10 hours per day. The facial mask was worn until a positive overjet of 2-4 mm was achieved inter-incisally [Figure 5] and [Figure 6]. The patient was seen at 6-week intervals for a total of 14 months. At the end of phase 1 (patient age; 7 years 10 months), slight posterior open bite was noted. In the retention phase, RTB appliance was continued up to 1 year for maintenance of the orthopedic correction gained by maxillary advancement. Upon completion of phase 1 treatment, the patient was kept under observation to monitor mandibular growth and eruption of the permanent dentition.
|Figure 6: (a and b) Cephalometric tracing just after phase 1 treatment. Anterior cross bite has been corrected|
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Second phase of fixed appliance therapy was initiated after the eruption of permanent teeth at the age of 12 years 6 months for final alignment of teeth. In phase 2 (fixed appliance), the molars and remaining teeth were bonded with a 0.022-in pre-adjusted edgewise appliance. The first arch wire, 0.016-in nickel-titanium, was followed by 0.017 × 0.025-in nickel-titanium, and 0.019 × 0.025-in stainless steel [Figure 7]. After 10 months of active treatment, the fixed appliances were removed. Hawley's retainer was placed in the maxillary arch and flexible spiral wire bonded retainer was placed in the mandibular arch.
Post treatment results revealed considerable improvement in soft tissue profile [Figure 8], with a positive incisor relationship. Maxilla had advanced sagittally by 2.5 mm, SNA angle had increased from 76° to 81° and there was an increase in vertical dimension (facial height ratio 55%) after active treatment [Figure 9]a and b, [Table 1]. Superimpositions of the cephalometric tracings showed that during the first phase the maxilla had moved substantially forward and slight downward and backward rotation of the mandible was seen. This adaptation presumably would not have occurred without treatment. The maxillary incisors erupted and became significantly protruded while the mandibular incisors became slightly retruded as an effect of face mask therapy [Figure 10].
|Figure 10: Overall superimposition registered on SN line at S; (A) Cephalometric superimpositions at ages 6 years 8 months (continuous) and 7 years 10 months (dotted): (B) Cephalometric superimposition at ages 6 years 8 months (continuous) and 13 years 4 months (dotted)|
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| Discussion|| |
Differential diagnosis of patients with true and pseudo Class III malocclusion should be based on family history, dental assessment of molar and incisor relationships and functional assessment to determine presence of CR-CO shift on mandibular closure.  CR-CO discrepancy generally indicates pseudo Class III malocclusion which can be treated by simple appliances. The objective is to eliminate interferences by labial tipping of upper incisors and lingual tipping of lower incisors. Simple appliances like tongue blade, inclined plane, 2 × 4 fixed appliances can be used. The functional appliances such as Frankel III, RTB, and reverse bionator are also indicated in patients presenting with functional shift on closure. When orthopedic correction in maxilla is desired, these appliances have no or little effects on changes in the position of maxilla. In the current case, patient had true Class III malocclusion due to mid-face deficiency along with anterior mandibular shift. Good potential of success of the treatment could be demonstrated due to the edge-to-edge relationship of the incisors. Patient presenting with some degree of anterior mandibular shift and moderate overbite have a more favorable prognosis with face mask therapy. 
It is generally believed  that as a child grows it becomes increasingly difficult to protract the maxilla orthopedically. Treatment of Class III malocclusion was thus initiated in the early transitional dentition in order to have maximum skeletal effects. According to McNamara  , the best time to begin early Class III treatment is in the early mixed dentition coincident with eruption of the maxillary permanent central incisors. Class III subjects treated with rapid maxillary expansion and a FMT prior to the growth spurt (CVMI 1 stage) present with good long term results when compared to Class III subjects treated at a later stage that is at the peak in mandibular growth (CVMI 3 stage). Prepubertal orthopedic treatment of Class III malocclusion is more 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.  Numerous clinical reports have shown superior treatment outcomes in younger children with early mixed dentition. ,,, Clinically studies , have indicated that more anterior maxillary displacement can be found when treatment is initiated in deciduous or early mixed dentition. Another goal of early treatment is to eliminate CO and CR discrepancies.
The need to expand the maxilla before protraction is not entirely clear. Though most of the studies ,, utilize palatal expansion in conjunction with protraction to disarticulate the maxilla and initiate cellular response in circum-maxillary sutures, allowing a more positive reaction to protraction forces. The present case was however treated without maxillary expansion. Vaughn et al.,  demonstrated that facemask therapy with or without palatal expansion produced equivalent changes in the dentofacial complex that combined to improve the Class III malocclusion. Kim et al.,  in his meta-analysis of the effectiveness of protraction facemask concluded that there were no distinct differences between treatments with or without palatal expansion, except for maxillary incisal angulations.
Reverse twin block is designed to encourage maxillary development and at the same time to restrict forward mandibular development. Attachment hooks in the present case were incorporated in the maxillary appliance in primary first molar region.  This helped to apply the orthopedic forces simultaneously. In order to prevent dislodgement of the upper appliance due to heavy forces, the maxillary appliance was cemented before any orthopedic force was applied. Slight downward direction (20-30° to the occlusal plane) of the elastic traction between intraoral attachment was desirable as this would produce counterclockwise moment to act relative to the centers of resistance of the dentomaxillary complex and thus help in correction of deep bite.
Combination therapy  with RTB reinforced by reverse pull traction maximizes the forward component of force on maxilla, converting the technique into functional orthopedic system. Clark  states that reverse angulations of block harnesses occlusal forces to advance the maxilla and maxillary dentition while using the mandible as anchorage and restricting its development. The additional functional forces with the RTB would keep the maxilla protracted whenever the face mask is not worn. In contrast, the effects of the RTB appliance alone are primarily limited to the dentition, due to proclination of the upper incisors and retroclination of the lower incisors. Skeletal change is limited to slight downward and backward rotation of the mandible with an associated increase in vertical dimension. 
The end results of the combination therapy were good resulting in considerable improvement in facial esthetics. There was a significant sagittal advancement of maxilla with SNA angle showing a change of 5°. A wide variety of clinical results using this treatment can be found in the literature. ,, Recent investigators report an average SNA change of 2.35° with some patients showing 4° to 5° change and an average maxillary advancement of 3.3 mm to as high as 5 to 8 mm.  Incisor protrusion also increased after phase one therapy. The results of face mask therapy are combination of skeletal movement of maxilla (A point) and proclination of upper incisor as the twin block or maxillary splint is anchored to the dento-alveolar region. After active protraction of the maxilla, retention is vitally important in maintaining the treatment effects of the facemask. Overcorrection of the Class III malocclusion is recommended to counteract the post-protraction growth deficiency of the maxilla. Some clinicians recommend overcorrecting to a 2 to 4 mm positive overjet and then to use the facemask part-time for 3 to 6 months  depending on the patient's tendency to relapse. Frankel III regulator, RTB has also been advocated for 6-12 months post protraction.
Dentally, the buccal segment relationship was slightly towards Class II on right side which could not be corrected as the patient cooperation diminished toward the end due to prolonged treatment for 7 years. However, it is important to appreciate that the major treatment objective to achieve good facial balance was met and the teeth were properly positioned in the smile arc. Long-term stability of the treated cases relies on the presence of continued favorable growth. As the sagittal correction were maintained after phase two treatment routine retention appliances, removable Hawley's retainer in the maxillary arch and fixed bonded lingual retainer in the mandibular arch were used. CVMI assessment indicated that the pubertal growth spurt in which maximum mandibular growth is expected had already passed. According to Mitani et al.  Class III group show an incremental change similar to the Class I group and the skeletal framework would be maintained in post-pubertal period. Although any major growth changes in the mandible were not anticipated, nevertheless the patient was explained about the continued growth of the mandible till adulthood and night time wear of the chin cup appliance was advised.
| Conclusion|| |
Accurate diagnosis and understanding of the individual growth pattern is crucial in determining the proper timing of Class III treatment. The combination therapy of reverse twin block and facemask can be effective in the treatment of skeletal Class III malocclusion with retrusive maxilla and a hypodivergent growth pattern. Once a diagnosis is established, early interception of a Class III malocclusion promotes a more favorable environment for normal growth and results in improvement of the facial profile and self-esteem.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10]