Comparison of stepwise vs single-step advancement with the Functional Mandibular Advancer in Class II division 1 treatment

Abstract

Objective: To compare two groups of subjects at the peak of the pubertal growth period treated with the Functional Mandibular Advancer (FMA; Forestadent, Pforzheim, Germany) appliance using either single-step or stepwise mandibular advancement.

Materials and methods: This study was conducted on 34 Class II division 1 malocclusion subjects at or just before the peak phase of pubertal growth as assessed by hand-wrist radiographs. Subjects were assigned to two groups of mandibular advancement, using matched randomization. Both groups were treated with the FMA. While the mandible was advanced to a super Class I molar relation in the single-step advancement group (SSG), patients in the stepwise mandibular advancement group (SWG) had a 4-mm initial bite advancement and subsequent 2-mm advancements at bimonthly intervals. The material consisted of lateral cephalograms taken before treatment and after 10 months of FMA treatment. Data were analyzed by means paired t-tests and an independent t-test.

Results: There were statistically significant changes in SNB, Pg horizontal, ANB, Co-Gn, and Co-Go measurements in both groups (P < .001); these changes were greater in the SWG with the exception of Co-Go (P < .05). While significant differences were found in U1-SN, IMPA, L6 horizontal, overjet, and overbite appraisals in each group (P < .001), these changes were comparable (P > .05).

Conclusion: Because of the higher rates of sagittal mandibular skeletal changes, FMA using stepwise advancement of the mandible might be the appliance of choice for treating Class II division 1 malocclusions.

Keywords: Angle Class II; Functional orthodontic appliance.

Figure 1.

Application of Functional Mandibular Advancer.

Figure 2.

Skeletal and dental cephalometric measurements: (1) SNA angle; (2) SNB angle; (3) ANB angle; (4) N-ANS on FH (ANS horizontal); (5) N-Pg on FH (Pg horizontal); (6) Co-Gn; (7) Co-Go; (8) SN-GoGn angle; (9) Ar-Go-Me angle; (10) U1-SN angle; (11) IMPA; (12) U6-vertical; (13) U6-horizontal; (14) L6-vertical; (15) L6-horizontal.