A METAANALYSIS OF MANDIBULAR INTERCANINE WIDTH IN TREATMENT AND POSTRETENTION

The meta-analysis technique of literature review was applied to a tota l of 26 previous studies to assess the longitudinal stability of postr etention mandibular intercanine width. Weighted averages and standard deviations for the means of 1,233 subjects were compared for linear ch anges in intercanine transverse dimensions during treatment (T1), imme diately after treatment (T2), and after removal of all retention (T3). Net change was defined as the difference between means at T3 and T1. Dimensional changes were also evaluated on the basis of patient pretre atment Angle classification, extraction, and nonextraction treatment m odalities of each group. Paired two-tail t-tests were performed betwee n T3 and T1 means on all groups at the a priori level of significance set at a less than or equal to 0.05. Statistically significant differe nces were observed for the following groups: all patients; nonextracti on; extraction; Class I; Class I extraction; Class II extraction; and, Class I Division 1 nonextraction. The findings of this study indicate that regardless of patient diagnostic and treatment modalities, mandi bular intercanine width tends to expand during treatment on the order of one to two millimeters, and to contract postretention to approximat ely the original dimension. While statistically significant difference s could be demonstrated within various groups, the magnitudes of the d ifferences were not considered clinically important.