Redirecting mandibular growth through orthodontic dentoalveolar height development in growing patients with Class III malocclusion undergoing maxillary orthopedic protraction

Abstract

Introduction: To control mandibular growth could be the determining factor for any growing patients with Class III malocclusion undergoing maxillary orthopedics. It has been reported that orthodontic dentoalveolar height development (ODHD) through orthodontic total arch extrusion might redirect mandibular growth backward and downward in growing patients with Class III malocclusion. We hypothesized bimaxillary-ODHD (bimax-ODHD) should be equal to or exceed the mandibular condylar growth to redirect the mandible to grow downward and backward in growing patients with Class III malocclusion.

Methods: Twenty-seven consecutive growing patients with Class III malocclusion who underwent maxillary orthopedics (MO) were recruited in this study, including 13 control patients (aged 12.70 ± 2.09 years) who underwent treatment of MO with no ODHD and another 14 patients who underwent MO and ODHD (ODHD group; aged 12.75 ± 1.40 years). The pretreatment (T1) and posttreatment (T2) CBCT images were superimposed and measured for the amount of ODHD and maxillary downward growth (ODHD-Mx), ODHD in the mandible (ODHD-Mn), T2 - T1 changes on facial convexity, y-axis, maxillary and condylar growth, and mandibular posture. The data were analyzed statistically.

Results: The T2 - T1 treatment duration was 7.5 months, significantly (P = 0.028) shorter in the ODHD group. The maxillary and condylar growth were similar among the groups. The mandible grew forward and downward in the control group, the ODHD-Mx and ODHD-Mn were significantly (P = 0.011) more in the ODHD group, and the mandible significantly (P = 0.001) grew backward and downward. The mandible grew backward and downward when the bimax-ODHD (ODHD-Mx + ODHD-Mn) exceeded the condylar growth (r = 0.715; P <0.001).

Conclusions: The bimax-ODHD, including the downward growth of the maxilla, should be equal to or exceed the mandibular condylar growth to redirect the mandible to grow downward and backward and improve the skeletal facial convexity in growing patients with Class III malocclusion.