3-D Evaluation of Treatment Outcomes following Class III Bone-Anchored Traction

Method: 25 consecutive skeletal Class III patients between the ages of 9 and13 (mean age 11.10 +/- 1.1years) were treated using Class III intermaxillary elastics and bilateral miniplates (2 in the infra-zygomatic crests of the maxilla and 2 in the anterior mandible). The patients had CBCTs taken before initial loading (T1), and one year out (T2). 3-D models were generated from the CBCTs, and registered on the anterior cranial base.  Treatment outcomes were analyzed and measured using SPHARM-PDM for quantitication of corresponding surface pointts.

Result: Corresponding color-coded difference maps  displayed the  surface distances  and  vectors between T1 and T2. Bone-Anchored traction produced sagittal and vertical skeletal changes in the mandible. The posterior ramus was displaced distally by 3.6mm (SD+/-1.4) while the chin was restrained 0.5mm (SD+/- 3.92).  The lower border of the mandible at menton was displaced inferiorly by 2.5mm (SD +/-1.4) while the lower border by gonion move downward by 3.6mm (SD+/-1.4) suggesting a closure of the mandibular plane angle.  The condyles were displaced distally and superiorly by 2.5mm (SD+/- 1.5mm) and 0.8mm (SD +/-2.4) respectively.  Vector SPHARM-PDM analysis showed a downward and backward displacement around gonion producing a closure of the gonial angle.

Conclusion: This new treatment approach induces a favorable control of mandibular growth for patients with components of mandibular prognathism.