Nonsurgical Treatment of a Surgically Prepared Skeletal Class III Patient Using Skeletal Anchorage

A skeletal Class III is one of the most complex malocclusions to treat.^1,2 According to Ellis and McNamara, it is most commonly characterized by a retrusive maxilla, protrusive maxillary incisors, retrusive mandibular incisors, a protrusive mandible, and excessive lower facial height.³ Adult skeletal Class III patients can be treated by either orthodontic camouflage or orthognathic surgery, depending on the degree of skeletal discrepancy, the skeletal pattern, and the age of the patient.⁴ Orthodontic camouflage treatment generally involves retroclination of the mandibular incisors and proclination of the maxillary incisors to achieve a positive overjet and correct the canine relationship. Options include extraoral traction or the use of Class III elastics (alone or in combination with sliding jigs), with space provided by interproximal stripping or extractions.⁵ Recently, the introduction of skeletal anchorage has made orthodontic camouflage a more viable option in mild to moderate skeletal Class III cases.

The situation becomes more complicated if orthognathic surgery is planned, but the patient refuses surgery while presurgical orthodontic treatment is already in progress—especially if the patient has a vertical growth pattern. In such a case, as described in this report, skeletal anchorage can allow distalization of the entire mandibular dentition as an alternative to premolar extractions.⁶

Diagnosis and Treatment Plan

A 21-year-old male presented with the chief complaints of an unesthetic facial appearance, irregular teeth, and speech difficulties. He reported a history of trauma to his upper front teeth. The patient had a dolichocephalic skull, a leptoprosopic face, acceptable facial symmetry, and a concave profile with lip incompetence (Fig. 1). There was a 4mm anterior open bite, and the upper midline was shifted 2mm to the right. The maxillary arch displayed 6mm of crowding, with a palatally positioned upper right lateral incisor and an amalgam restoration on the upper right first molar. The mandibular arch had 4mm of crowding, with amalgam restorations in the posterior regions. The lower right first molar restoration was fractured, and the lower premolars were supraerupted.

After six months of en-masse distalization, when 3mm of positive overjet had been created, retraction of the maxillary dentition was initiated using loop mechanics (Fig. 4). An open U-loop made of .016" × .022" beta titanium wire was applied on the left side for anterior space closure, while power chains were added to expedite canine retraction. The right extraction space had already been closed by distal canine movement during the leveling and alignment phase, since the lateral incisor was palatally positioned.

When the patient moved overseas, four months after placement of the elastomeric chain, we could not complete the treatment as planned. Two years later, the patient reported to the clinic requesting that the appliances be debonded; they were removed without occlusal settling or the establishment of proper interdigitation.

The patient was advised to continue his tongue exercises. A fixed lower 3-3 retainer was bonded.

Treatment Results

Nearly all of the initial treatment objectives were achieved (Fig. 5A). The upper and lower crowding and anterior open bite were resolved in the presurgical orthodontic phase. After the subsequent compromise treatment, the smile esthetics improved considerably, and the lip incompetence and negative lip step were corrected. The patient was satisfied with his profile. The dental midlines were coincident with the facial midline; acceptable overbite and overjet were achieved, along with Class I canine and Class II molar relationships. The patient did not report any TMJ pain or discomfort during or after orthodontic treatment. A panoramic radiograph showed no signs of significant root or bone resorption, with acceptable root parallelism.

Sugawara and colleagues found that while many types of mechanics could be used to distalize the mandibular molars to some extent, the amount of distal translation that could be achieved was quite limited.¹⁰ They concluded that the use of skeletal anchorage could provide three-dimensional control of tooth movement, even if the amount of required movement was greater than the mesiodistal width of the premolars. When distalization of more than 3-4mm is performed with anchorage from interradicular miniscrews, however, the force required may cause frequent screw failures.^11,12 Miniplates can withstand more force and are more stable because they are anchored to the bone with multiple screws.^12-15 A systematic review by Schätzle and colleagues reported a 7.3% failure rate for miniplates, compared with 16.4% for miniscrews.¹⁴ Since 7mm of molar distalization was required in our case, we chose to use miniplates instead of miniscrews.

A minor 2° opening of the mandibular plane angle was an expected compromise due to our change in treatment plan, but neither the profile nor the TMJ function of the patient was affected. Retraction mechanics using skeletal anchorage helped to correct the deviated occlusal plane in the lower arch. The upper arch showed slight proclination and the lower showed retroclination, as is common in camouflage treatment of skeletal Class III patients. In the end, we were able to manage this surgically prepared skeletal Class III patient through a nonsurgical approach with skeletal anchorage. Treatment resulted in a pleasing profile, proper occlusion, and normal overjet and overbite, although the occlusion was less than ideal because of unforeseen circumstances.

Stability of treatment is a major concern of every orthodontist. Angle attributed relapse of orthodontic treatment to unfavorable environmental factors. Proffit, in his “equilibrium theory revisited,” maintained that intrinsic forces from the tongue can affect the equilibrium of tooth positions.¹⁶ Particularly in an open-bite Class III case, the posture, size, and position of the tongue are critical during retention; a neuromuscular adaptation to an altered tongue position can be expected. Our patient was advised to continue his tongue exercises, and a fixed lower retainer was bonded for long-term stability.