Interceptive treatment of palatal impaction of maxillary canines with rapid maxillary expansion: a randomized clinical trial.

INTRODUCTION: Our aim in this prospective randomized clinical study was to assess the prevalence rate of eruption of palatally displaced canines, diagnosed at an early developmental stage with posteroanterior radiographs and consequently treated by rapid maxillary expansion. METHODS: A sample of 60 subjects in the early mixed dentition with palatally displaced canines diagnosed on posteroanterior radiographs was enrolled in the trial. Their age range at the first observation (T1) was 7.6 to 9.6 years, with a prepubertal stage of skeletal maturity (CS1 or CS2). The 60 subjects were randomly allocated to the treatment group (TG, 35 subjects) or the no-treatment group (NTG, 25 subjects). The TG was treated with a banded rapid maxillary expander; after expansion, all patients were retained with the expander in place for 6 months. Thereafter, the expander was removed, and the patients wore a retention plate at night for a year. The NTG received no treatment. All subjects were reevaluated in the early permanent dentition (T2) (postpubertal CS4). The number of dropouts was recorded. The main outcome recorded at T2 was successful or unsuccessful eruption of the maxillary permanent canines. The starting forms at T1 for measurements on posteroanterior and panoramic films were compared in the 2 groups with the Mann-Whitney U test (P <0.05). The prevalence rates of successful and unsuccessful treatments in the TG were compared with those in NTG with chi-square tests (P <0.05). From T1 to T2, there were 3 dropouts in each group. RESULTS: The final sample comprised 32 subjects in the TG and 22 subjects in the NTG. No statistically significant differences were found for any variable at T1. The prevalence rates of successful eruption of the maxillary canines were 65.7% (21 subjects) in the TG and 13.6% (3 subjects) in the NTG. The comparison was statistically significant (chi-square = 12.4; P <0.001). Subjects with palatally displaced canines in the early mixed dentition do not have transverse deficiency of the maxillary arch. CONCLUSIONS: The use of a rapid maxillary expander as an early interceptive approach is effective for increasing the rate of eruption of palatally displaced canines