The objective of this study was to investigate the effects of maxillary central incisor (U1) inclination changes on alveolar bone and root length in the 20 Class II division 1 and 20 Class II division 2 (CII div1, CII div2) Caucasian adolescents treated without extraction.

Forty U1s from each group were assessed for root length and alveolar variables at the crestal, mid-root, and apical levels using sagittal sections obtained from CBCT images pre- and post-treatment. Mixed MANOVAs, Repeated measures MANOVAs, Pearson correlations, and regression analyses were performed.

The facial bone height did not change significantly after an average of 15 degrees of proclination in the CII div2 group, whereas a statistically significant decrease in the palatal bone height was noted. However, in the CII div1 group, a statistically significant reduction in the facial and palatal bone height was observed with mild crown retroclination. Both groups had a significant decrease in total bone thickness at all levels, more decrease in the CII div2 group after treatment. No statistically significant difference in root length was observed between the groups during treatment.

The findings support that the flaring of retroclined U1s as a process for normalizing U1 inclination did not harm the facial alveolar bone height in the CII div2 non-extraction treatment. Crown proclination itself was not correlated to the amount of root resorption in Class II div1&2 non-extraction treatments in adolescents.