Introduction
In the Asian ethnic groups, the prevalence of Class III malocclusions is the greatest compared to other sagittal malocclusions. These patients along with the skeletal discrepancy show dentoalveolar, functional and also vertical, and transverse deviations which complicate the treatment planning.1 The main reason why these patients seek orthodontic treatment is compromised facial aesthetics and functions. Skeletal Class III malocclusions are the most difficult malocclusions to treat particularly because of the unfavorable growth pattern of the mandible and associated with the dental compensations.1 Many of these cases require orthopedic correction during the growing phase in children and for the non-growing patients orthognathic surgery is required for the best treatment outcome. The ideal treatment in adult patients is orthognathic surgery, which many patients refuse due to the invasive nature of the procedure.2, 3, 4
Expanding the conventional envelope of discrepancy, in some skeletal malocclusions, orthodontic camouflage may be considered to achieve appropriate occlusion, which would improve aesthetics and optimum function.5 The objective of the orthodontic camouflage involves the uprighting of the maxillary & mandibular anteriors on their respective jaw bases, sometimes needing selective extractions. Another alternative method for orthodontic camouflage in skeletal Cl III is by en-masse distalization of mandibular dentition.5
Before the advent of skeletal anchorage, distalization of the lower arch was difficult to achieve, time consuming and involved complicated appliances which were many times not accepted by the patient. Conventionally, individual molar distalization was done, followed by retraction of remaining teeth into gained space. However, with the advent of TAD’s and increasing use of extra alveolar TAD’s, it is now possible to distalize the lower arch en masse, without the use of complicate appliances or difficult biomechanics. This method is gaining rapid popularity as it is easy to perform, shortens the treatment time and is relatively more patient friendly.
Case Report
A 19 year old adult patient reported with a chief complaint of forwardly placed lower front teeth. He presented with a hypodivergent skeletal Cl III pattern with a prognathic mandible which was complicated by a negative overjet of 2 mm and asymmetric molar relation of full cusp angles Cl III molar relation on the right side and a half cusp Cl III molar relation on the left side. The general extra oral and intra oral features are summarised in Table 1 and Table 2.
The pre-treatment images (Figure 1, Figure 2, Figure 3, Figure 4).
Treatment Objectives
The treatment objectives of the case are summarised in the table 3.
Treatment plan
Keeping the mentioned treatment objectives in view, a treatment plan of orthodontic camouflage was devised. An asymmetric en masse distalization was planned to end in a Cl I molar relation bilaterally. The anchorage was gained using extra alveolar TAD’s placed in the buccal shelf area of the lower jaw bilaterally. An asymmetric molar relation dictated an asymmetric setback of the lower dentition. A posterior acrylic bite plate was used to facilitate no anterior tooth contact while en masse distalization in both the lower quadrants.
Alignment and levelling were done in the upper arch. Here a couple force was used with the help of a transpalatal arch to achieve the denotation of the second molar and to correct its overhanging palatal cusp. The upper and lower midlines were matched to the facial midline facilitated by asymmetric lower arch distalization (the third molars to be extracted and available space distal to the 2nd molars). The case finished with Class I molar and canine relationship bilaterally, dental midlines matching the facial midline, ideal overjet, ideal overbite, and correction of protrusive soft-tissue profile.
Treatment progress
The treatment sequence and biomechanics are summarized in Table 4. The bite plate is utilized for relieving the anterior crossbite, Figure 5 A.
Figure 5 B illustrates the mandibular arch distalization with the buccal shelf implants.
The mechanics for the correction of the rotations of the maxillary second molars are illustrated in Figure 6.
The post-completion of the treatment is seen in Figure 7, Figure 8, Figure 9.
Table 1
Table 2
Table 3
Table 4
Table 5
Table 6
Results
The case was finished with Angle’s Class I molar relationship along with Class I canine relation. The incisor relationship with normal overjet and overbite of 2 mm was achieved. The upper and lower dental midlines matched at the end of the treatment. All displacements and crossbites were corrected by the end of the treatment. No occlusal wear facets were noted with mutually protected occlusion and canine-guided excursive movements established. A consonant smile arc was achieved, and smile esthetics was significantly improved along with the facial profile.
Cephalometric changes – The Cephalometric changes along with the pre-treatment cephalometric values (Table 5) and post-treatment cephalometric values (Table 6) are mentioned in the.
Discussion
In the treatment of orthodontic camouflage in skeletal Cl III malocclusions, counter clockwise rotation of the jaws is undesirable. 6, 7, 8 This can be facilitated planning biomechanics where the vectors of force is as parallel to the lower occlusal plane as possible. Here in this case report, the correction is achieved by minimal clockwise rotation of the mandibular plane with the fixed appliance along with the buccal shelf bone screw in a Class III adult patient. The severity of the skeletal discrepancy, degree of the incisor compensations, facial growth pattern, periodontal status, anterior facial proportions, and aesthetic appearance of the patient are the important factors to be considered during planning the biomechanics of a skeletal Cl III case where orthodontic camouflage is desired. 9, 10, 11, 12, 13
There have been various studies that determine which cases of skeletal Class III malocclusion can be treated by orthodontic camouflage by enlarging the envelope of discrepancy. 14, 15, 16, 17, 18, 19 In general it is hypothesized that surgery is ideally indicated when the ANB angle is more than -5 degrees, and the Wits appraisal shows mandibular prognathism more than 5mm. In the present case report, the ANB angle was – 5 degrees, IMPA was 94 degrees, and the Wits appraisal was -5mm. This made the present case a borderline case and as the patient did not agree to a surgical treatment plan, orthodontic camouflage was planned by asymmetric en masse distalization of the lower arch.
The patient also showed some functional forward shift of the mandible, which can be observed in many cases of Cl III with an anterior cross bite due to occlusal interferences. Orthodontic camouflage in many Class III cases addresses the sagittal problems, but seldom on the improvement of vertical deficiency. 20, 21, 22, 23, 24 The extrusion of the maxillary anteriors was planned to improve the incisor visibility and smile arc as reported in a few can reports published. 24 The clockwise rotation of the occlusal plane was advantageous in improving smile arc as proposed by Eric Liou et al. 9 Posterior bite plate was used on the upper posteriors to open the bite while the reverse overjet was corrected. After achieving a positive overjet, the posterior bite plate was discontinued. Two buccal shelf bone screws (2x12mm) were placed in the third and fourth quadrants. A parallel force vector was used. Asymmetric mandibular dentition distalization was desired which was more on the right side to correct a full cusp Cl III molar relation to a Cl I molar relation. On the left side the amount of distalization was limited to correct a half cusp Cl III to a Cl I molar relation. The distalization force was stopped after achieving Cl I molar relation bilaterally. The goal of achieving a functional mutually protected occlusion with cuspid rise was achieved.
Critical appraisal
Although the results from an orthodontic point of view look satisfactory, as a new modality of treatment, a long-term follow-up will determine the success achieved. All the aesthetic and functional goals were achieved and a stable posterior occlusion with symmetric cusp to fossa relation was established bilaterally. The case selection, the biomechanics, and the appreciation of the anatomic limitations would remain as some of the important perspectives for achieving the final objective.
Conclusion
The primary objective of any new clinical protocol is to enhance treatment quality by incorporating precision, expanding treatment horizons, and to make the treatment more acceptable to the patient.
By employing extra radicular bone screws in distalization techniques, with careful biomechanical consideration, we can effectively address emerging challenges and surpass limitations, ultimately striving for the pinnacle of the ever eluding clinical excellence.
Patient Consent Declaration
The author affirms that all appropriate patient consent forms have been obtained. The patients have willingly given their consent for the usage of their images and other clinical information in the journal. The patients are aware that their names and initials will not be disclosed, and utmost efforts will be taken to protect their identity. However, complete anonymity cannot be guaranteed.
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