Comparison of the effectiveness of skeletal and tooth-borne protraction methods with or without alternate rapid maxillary expansion and constriction protocol in patients with Class III malocclusion

This study aimed to compare the efficiency of maxillary protraction achieved through facemask treatment with either a hybrid-hyrax (HH) or an acrylic cap splint (ACS) appliance when used in conjunction with alternate rapid maxillary expansion and constriction (Alt-RAMEC) or conventional rapid maxillary expansion (RME) protocols.

This study analyzed a total of 60 patients in 4 groups of 15 patients each and treated with HH-Alt-RAMEC protocol (HH-Alt, aged 10.38 ± 1.19 years), ACS-Alt protocol (aged 10.43 ± 0.99 years), HH-RME protocol (aged 9.74 ± 1.05 years) and ACS-RME protocol (aged 10.70 ± 0.98 years). Lateral cephalograms were taken before and after the facemask were compared. A 1-way analysis of variance with a Tukey honest significant difference post-hoc test was used for intergroup comparisons, whereas a paired sample t test was employed for intragroup comparisons.

Correction of Class III skeletal malocclusion was achieved in all groups. HH-Alt showed significantly more maxillary protraction with an increase in AVRP of 4.02 mm compared with 2.65 mm in ACS-Alt and 2.3 mm in ACS-RME (P <0.001). HH-RME also showed a significantly more maxillary protraction in AVRP of 3.58 mm compared with 2.3 mm in ACS-RME (P <0.001). The rate of protraction was higher in HH-Alt (0.61 ± 0.16) and HH-RME (0.56 ± 0.29) than in ACS-RME (0.31 ± 0.12). The maxilla showed significantly more rotation in ACS-Alt (-1.66° ± 1.13°) and ACS-RME (-1.97 ± 1.75°) than in HH-Alt (-0.49° ± 1.18°) and HH-RME (-0.35° ± 1.86°), whereas the mandible showed significantly more clockwise rotation in ACS-RME (2.08 ± 1.71) than in HH-Alt (0.80 ± 0.94) and HH-RME (0.63 ± 1.82). The maxillary skeletal effect in the overjet correction was greater in HH-Alt (71.0%).

All treatment options achieved maxillary protraction. In the short term, hybrid groups (HH-Alt and HH-RME) provide more effective maxillary skeletal protraction than ACS-RME and demonstrate superior control in the vertical dimension than in tooth-borne groups. The Alt-RAMEC protocol improved the amount of maxillary protraction of the tooth-borne appliance group. The choice of anchorage of the appliance (skeletal or tooth-borne) is found to be more critical than the expansion method (RME or Alt-RAMEC).