Long-term stability of rapid maxillary expansion combined with chincup protraction followed by fixed appliances

Abstract

Objective: To analyze the long-term stability of rapid maxillary expansion (RME) and protraction from chincup therapy in girls with Class III malocclusion.

Materials and methods: Twenty-two girls (mean age = 9.1 ± 0.6 years) with Class III malocclusion were treated with combined RME and protraction from a chincup, followed by fixed appliances. Lateral cephalograms were evaluated before treatment, at the end of a two-phase treatment protocol (mean age = 15.1 ± 1.1 years), and 10.9 ± 0.5 years after the end of treatment (mean age = 27.5 ± 0.5 years). The control group consisted of 22 matched girls with skeletal Class I malocclusion.

Results: After treatment, the Class III group showed significant improvement of the Class III malocclusion, mainly due to changes in the mandible (ie, SNB angle decreased 1.8 ± 1.6°) and significant improvement of the sagittal maxillomandibular relationship (Wits appraisal increased 2.6 ± 2.1 mm; ANB angle increased 1.0 ± 0.3 mm). These changes remained stable for an average of 10 years after the end of therapy. No tendency toward relapse was detected, and the mandibular position showed favorable outcomes.

Conclusions: RME and protraction from chincup therapy led to successful long-term outcomes in 18 of 22 patients (81.8%). This treatment approach can be considered an efficient therapy in growing girls with mild skeletal Class III malocclusion caused by maxillary retrusion and mandibular protrusion.