Nonsurgical Management of an Anterior Open Bite in a Young Adult

The patient had a Class II, division 1 malocclusion with Class II canine relationships, an end-on Class II molar relationship on the right, and a tendency toward a Class II molar relationship on the left, with moderate crowding in the lower arch. The overjet was excessive (4mm), the upper incisors were retroclined (U1-SN = 94°), and the lower incisors were normally inclined (IMPA = 87°). A 3mm anterior open bite was present from canine to canine, along with a 1mm posterior open bite from the upper right first premolar to first molar and at the upper left first premolar. A mild upper curve of Spee and moderate lower reverse curve of Spee were present. The transpalatal width was diminished (32mm), with a 1mm transverse discrepancy at the first molars.

Cephalometric analysis (Table 1) indicated a skeletal Class I relationship (ANB = 3.5°, Wits appraisal = +.6mm) with an orthognathic maxilla (SNA = 81°) and a slightly retrognathic mandible (SNB = 77°). The mandibular plane angle (FMA = 22°) and facial height (N-ANS = 55mm, ANSMe = 76mm) were normal.

The treatment objectives were to improve mastication and smile esthetics by correcting the anterior and posterior open bites, establishing Class I molar and canine relationships, resolving the lower crowding, and coordinating the arches. We planned a nonsurgical, nonextraction approach for the initial treatment. If necessary, selective extractions would be performed at a later stage. We planned to procline the upper incisors 10-15° and the lower incisors about 5°. In addition, the upper incisors would be extruded 1-2mm, and the lower incisors 2-3mm, to level the curves of Spee. The upper intermolar width would be expanded by about 1mm.

Treatment Progress

After the patient received a periodontal evaluation and his dentist’s approval for treatment, .018" full fixed appliances^* were placed. The upper and lower first molars were banded, and brackets were bonded from second premolar to second premolar in both arches.

Initial leveling and alignment were performed over three months with a sequence of .016" nickel titanium, .016" stainless steel, and .016" × .016" stainless steel archwires. During this phase, the patient wore bilateral ¼", 3.5oz anterior vertical elastics full-time from the upper to lower canines. The –3mm anterior open bite was corrected to a 2mm overbite while both arches were leveled (Fig. 2).

Three options for further treatment were then presented to the patient: extraction of the upper first premolars and lower second premolars; extraction of the lower left central incisor; or interproximal reduction at the lower incisors, leaving some residual crowding. After discussion of the advantages and limitations of each approach, the patient opted for extraction of the lower left central incisor.

Following the incisor extraction, space closure was conducted with power chains on .016" × .022" stainless steel archwires. Class II elastics (¼", 6oz) were worn for about four months to produce the Class II correction. The final phase of treatment involved finishing bends for detailing and arch coordination.

The total active treatment time was 25 months (Fig. 3). After debonding, two sets of upper and lower active clear retainers were delivered. The first set, worn full-time for two weeks, was designed to manage a small amount of residual lower incisor crowding and remaining spaces from the molar bands. The second set, designed for long-term retention, was worn full-time for six months, then at night indefinitely. The patient planned to address the impacted upper third molars with his general dentist.

Treatment Results

The anterior and posterior open bites were closed, resolving the patient’s chief complaint of difficulty chewing. Class I molar and canine relationships were established bilaterally. A positive overbite of about 2mm was achieved, although a 3-4mm overjet remained because of the lower incisor extraction and resulting Bolton discrepancy.

Cephalometric analysis showed minimal skeletal changes, with SNA decreasing 1°, SNB increasing 1°, and ANB decreasing 2° (Table 1). A 2° reduction in FMA was attributable to counterclockwise rotation of the mandible induced by a slight intrusion of the lower molars and the use of anterior vertical elastics. The upper incisors were proclined 20° (U1-SN = 114°) and protruded 5.2mm (U1-NA = 8mm), while the lower incisors were proclined 9° (L1-MP = 98.3°) and protruded 2.6mm (L1-NB = 5.2mm). The upper intermolar width increased 2mm, while the mandibular intercanine and intermolar widths remained unchanged. The reduction in profile convexity could be ascribed to incisor proclination, Class II correction, and a slight forward and upward rotation of the mandible. The upper lip was also slightly retruded (about 1mm) relative to the E-line, while the lower lip was protruded (about 2mm).

Mild gingival recession was noted on the lower right lateral incisor and canine, which is a well-documented side effect of incisor proclination.^10,11 The patient was referred to a periodontist for evaluation.

Discussion

In this case, the combination of full fixed appliances with the strategic use of vertical and Class II elastics effectively closed an anterior open bite through both incisor extrusion and counterclockwise mandibular rotation, as previously reported.^5,6,12 Anterior vertical elastics have been shown to successfully treat open-bite malocclusions through dentoalveolar rather than skeletal modifications¹²; the slight counterclockwise rotation of the mandible observed in this case also agrees with previous observations.⁶ Although recent studies have demonstrated acceptable stability for open-bite closure through incisor extrusion, there are still some concerns about long-term relapse.^1,12,13