The short-term treatment effects of face mask therapy in Class III patients based on the anchorage device Miniplates vs rapid maxillary expansion

Objective: To compare the short-term treatment effects of face mask therapy with miniplates (FM-MP) and face mask therapy with rapid maxillary expansion appliance (FM-RME) in growing Class III malocclusion patients with maxillary hypoplasia. Materials and Methods: Twenty patients were allocated into two groups according to the anchorage device: FM-MP group (n = 10; mean age = 11.2 +/- 1.2 years; miniplates in the zygomatic buttress area) and FM-RME group (n = 10; mean age = 10.7 +/- 1.3 years; bonded or banded RME). The face mask was applied for 12 to 14 hours/day in both groups with a force of 400 g/side directed 30 degrees downward and forward from the occlusal plane. Lateral cephalograms were taken before (T1) and after FM-MP or FM-RME therapy (T2). Skeletodental and soft-tissue variables were measured. Paired and independent t-tests were performed for statistical analysis. Results: Both groups exhibited significant forward movement of point A and posterior repositioning and opening rotation of the mandible from T2 to T1. The FM-MP group showed significant protraction of orbitale (Delta SNO), and the FM-RME group showed a decrease in overbite and an increase in Bjork sum. Comparing the amount of changes between the two groups, the FM-MP group displayed greater forward movement of the maxilla than the FM-RME group (Delta SNA, Delta A to N perp, all P < .05). However, the FM-RME group exhibited a greater opening rotation of the mandible (Delta SNB, Bjork sum, all P < .01; Delta Pog to N-perp, P < .05) and labioversion of the maxillary incisors (Delta U1-FH, P < .05). Conclusion: FM-MP therapy induces a greater advancement of the maxilla, less posterior repositioning and opening rotation of the mandible, and less proclination of the maxillary incisors than FM-RME therapy. (Angle Orthod. 2012;82:846-852.)