Relapse of mandibular incisor alignment is not associated with the total posttreatment mandibular rotation.

Introduction: Our objective was to determine whether total posttreatment mandibular rotation is associated with mandibular incisor crowding after retention.

Methods: Mandibular incisor irregularity (II) at least 10 years out of retention (T3) measured on dental casts from the postretention database at the University of Washington in Seattle was used to define subjects (II ≥6 mm, relapse group) and controls (II ≤3.5 mm, stable group). After matching patients and controls for the pretreatment II, the relapse group consisted of 33 subjects (17 boys, 16 girls; age at the end of treatment [T2], 15.0 years; follow-up, 16.8 years), and the stable group comprised 36 subjects (11 boys, 25 girls; age at T2, 16.0 years; follow-up, 15.1 years). On cephalograms taken at T2 and T3, facial morphology was evaluated, and total posttreatment mandibular rotation was measured with a structural method. Logistic regression analyses were used to determine the association between relapse and amount of total mandibular rotation. The models were adjusted for potentially confounding variables (age at T2, sex, length of follow-up, and intercanine width change during treatment).

Results: No association between total posttreatment mandibular rotation and relapse was found (P = 0.515). Total mandibular rotations were comparable in the relapse and stable groups (P = 0.386). Age at T2 was found to be correlated with long-term incisor stability (P = 0.030). Sex and intercanine width change during treatment were not related to relapse (P = 0.225 and P = 0.264, respectively).

Conclusions: Total mandibular rotation is not associated with relapse of the mandibular incisors. Posttreatment skeletal and dental growth changes were comparable in the relapse and stable groups.