Predictors of Long-term Stability in Early Treatment of ClassIII Malocclusion

Objectives: The purposes of this study were to investigate the differences in the early craniofacial morphology of Class III malocclusions with good, fair and poor occlusal stability and to elucidate some cephalometric key determinants for discriminating the three groups. Methods: Lateral cephalograms of 45 subjects with Class ¥² malocclusion and anterior crossbite in the deciduous and mixed dentition were analyzed at the pretreatment, posttreatment, and long-term retention. Anterior crossbite had been corrected by a series of treatments. All subjects were reevaluated after a mean period of 8.8 years comprising active treatment plus retention. At this time, the sample was divided into three groups according to occlusal status and profile: good (Group 1), fair (Group 2), and poor (Group 3) occlusal stability group. Two-way analysis of variance and discriminant analysis for measurements of the initial stage were performed. Results: Although the variables for the size and anteroposterior position of mandible were almost similar in the 3 groups, the poor stability group had more obtuse mandible in the early stage. In the initial state, there was no significant difference in anteroposterior relationships among the 3 groups. Poor prognosis was expected in the group with hyperdivergent skeletal pattern. In the initial state, there was no significant difference in the steepness of occlusal plane among the 3 groups. The AB to mandibular plane angle and N-perpendicular to point A were selected as significant variables for discriminating the 3 groups, and the variable which had the most important contribution to discriminant function was AB to Mandibular plane angle. Especially the discriminant showed the highest accuracy in the prediction of poor prognosis. Conclusion: According to results, craniofacial features associated with long-term stability and discriminant function presented will be helpful to predict the prognosis of the early treatment of Class ¥² malocclusion.