Effect of rapid maxillary expansion and transpalatal arch treatment associated with deciduous canine extraction on the eruption of palatally displaced canines: A 2-center prospective study.

INTRODUCTION Our aim was to investigate the effect of rapid maxillary expansion and transpalatal arch therapy combined with deciduous canine extraction on the eruption rate of palatally displaced canines (PDCs) in patients in the late mixed dentition in a 2-center prospective study. METHODS Seventy subjects were enrolled based on PDCs diagnosed on panoramic radiographs. The treatment group (TG, 40 subjects) underwent RME followed by TPA therapy and extraction of the deciduous canines. The control group (CG, 30 subjects) received no orthodontic treatment. At the start of the trial, panoramic radiographs and dental casts were compared between the TG and the CG with the Mann-Whitney U test (P <0.05). At the second observation (cervical vertebral maturation stage 5 or 6), all subjects were reevaluated, and the eruption of the maxillary permanent canines was assessed. The rates of success in the TG were compared with those in the CG by means of chi-square tests (P <0.05). The association of PDCs with other dental anomalies was reported. RESULTS No statistically significant difference was found for any measurement at the start of the trial between the 2 groups. The prevalence rates of eruption of the maxillary canines were 80% for the TG and 28% in the CG, a statistically significant difference (chi-square =16.26, P <0.001). The prevalence rate at the start for the pubertal stages of cervical vertebral maturation (63%) was significantly greater in the unsuccessfully treated subjects than in the successfully treated ones (16%). In the CG, all successful subjects had PDCs that overlapped the corresponding deciduous canine or the distal aspect of the lateral incisor. Eruption of PDCs in both groups was associated significantly with an open root apex. CONCLUSIONS Rapid maxillary expansion therapy followed by a transpalatal arch combined with extraction of the deciduous canine is effective in treating patients in the late mixed dentition with PDCs. Pretreatment variables indicating success of treatment on the eruption of PDCs were less severe sectors of displacement, prepubertal stages of skeletal maturity, and open root apices of PDCs. Several dental anomalies were associated significantly with PDCs, thus confirming the genetic etiology of this eruption disturbance.