Predictive variables for the outcome of early functional treatment of Class III malocclusion

The aim of this study was to select a model of cephalometric and occlusal predictive variables for the results of early treatment of Class III malocclusion, due to mandibular protrusion in the deciduous dentition. Lateral cephalograms and dental casts of 45 subjects (22 boys and 23 girls) with Class III malocclusion in the deciduous dentition were analyzed at the start of treatment (mean age 5.57 +/- 0.85 years). The patients were treated with a functional appliance (removable mandibular retractor). All subjects were reevaluated after a mean period of 9.54 +/- 2.28 years comprising active treatment plus retention. At this time, the sample was divided into two groups according to occlusal criteria: successful group (23 subjects) and unsuccessful group (22 subjects). Stepwise variable selection on the measurements at the time of first observation identified three predictive variables; the inclination of the condylar axis in relation to the stable basicranial line (CondAx-SBL), the inclination of the nasal line to the mandibular line (NL-ML), and the transverse width of the mandibular arch measured at the first deciduous molars. Discriminant analysis assigned a classificative power of 95.55% to the predictive model. On the basis of the equation generated by the multivariate statistical method, outcome of early treatment for each new case with Class III malocclusion in the deciduous dentition can be accordingly predicted. The important role of both vertical and transverse relationships in Class III prognosis was emphasized.