Prediction of lower incisor proclination during Xbow treatment based on initial cephalometric variables.

Objective: To predict lower incisor proclination from initial cephalometric values in Class II division 1 patients treated in phase I with the Xbow appliance.
Materials and Methods: Two hundred forty-nine mild to moderate Class II division 1 patients treated with the Xbow appliance as a phase I treatment were considered. Patients were in late mixed dentition or early permanent dentition. Commonly used cephalometric variables at T1 (before treatment) were used to predict lower incisor proclination after Xbow treatment (T2). A principal component analysis (PCA) was performed. The four extracted PCA components were skeletal component, incisal distance, anterior facial projection, and maxillo-mandibular relation. Thereafter, a multiple linear regression analysis (MLRA) was performed using the four extracted PCA components at T1 as predictor variables, and lower incisor inclination relative to the mandibular plane (L1-MP) at T2 as the dependent variable.
Results: The mean L1-MP at T1 was 95.46 degrees and the mean L1-MP at T2 was 98.51 degrees, resulting in a mean difference of 3.04 degrees. Only incisal distance and maxillo-mandibular relation PCA components had significance (P < .05) according to the MLRA. The overall model gave an adjusted R2 value (coefficient of determination) of 0.091.
Conclusion: The best prediction model could account for only 9% of the total variability. Using common cephalometric variables at T1, average lower incisor proclination from Xbow treatment cannot be predicted in a clinically meaningful way.