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.

Keywords: Chincup; Class III; Long-term; Maxillary protraction; Stability.

Figure 1.

Class III group. Representative superimposition of T0 (before treatment, black lines) to T1 (end of the two-phase treatment, dark grey lines) to T2 (an average of 10 years after treatment, light grey lines).

Figure 2.

Control group. Representative superimposition of T0 (before treatment, black lines) to T1 (end of the 2-phase treatment, dark grey lines) to T2 (an average of 10 years after treatment, light grey lines).