Upper canine response to rapid maxillary expander anchored to deciduous vs. permanent molars

Purpose: To understand whether two different designs of Haas-type rapid maxillary expander (H‑RME) might have a different influence on canine eruption. Patients and methods: In all, 108 subjects seeking orthodontic treatment were selected and divided into two groups—H‑RME with bands on the upper second deciduous molars (GrE), H‑RME with bands on the upper first permanent molars (Gr6)—and were also compared to an historical untreated control group (CG) of 29 subjects. Panoramic x‑rays (OPG) were performed before and after RME (T0–T1: 16 ± 7 months) and the upper canine angulation to the midline (“α” angle) was measured on both pre- and posttreatment OPG. Results: A significant improvement of the canine position (decrease of the α angle) following RME in subjects with mixed dentition was reported in both treated groups, although the different design of the RME did not significantly affect canine angulation. Canine angulation in untreated subjects with transversal discrepancy did not improve significantly. Conclusion: Using RME in the early mixed dentition appears to be an effective procedure to increase the rate of eruption of maxillary canines, but the position of the bands on the upper second deciduous molars or on the upper first permanent molars and the significant different expansion of the upper dental arch at the canine level does not significantly influence the canine angulation following early treatment therapy.