Activation-deactivation rapid palatal expansion and reverse headgear in Class III cases.

The aim of this study was to evaluate and compare the dentofacial effects of 1 week rapid palatal expansion (RPE) and activation-deactivation (A/D) RPE protocols with reverse headgear (RH). Two groups, each containing 15 subjects, were included in this study. In the RPE group (seven males and eight females, 11.94 ± 1.62 years), Hyrax screws were activated every 12 hours for 1 week. At the end of this period, RPE was stopped and the patients were instructed to wear the RH. In the A/D-RPE group (seven males and eight females, 11.34 ± 1.81 years), the screws were activated every 12 hours for 1 week. Subsequently, the screws were deactivated every 12 hours for 1 week followed by activation and deactivation for the following 2 weeks. After this protocol, the patients were instructed to use the RH. A total force of 700 g was applied to both groups for 16-18 hours/day for the first 3 months, for 12 hours/day for the second 3 months, and for 6 hours/day for the second 6 months. Lateral cephalometric films were taken before treatment (T1) and at the end of the first (T2) and second (T3) 6 months to evaluate the dentofacial changes. Intragroup differences of each landmark at T2-T1, T3-T2, and T3-T1 were analysed with a paired t-test (P < 0.016), and intergroup differences were compared with an independent t-test (P < 0.05). Anterior movement of point A (4.13 mm) for the A/D-RPE group was approximately twice of the RPE group (2.33 mm; P < 0.001). Backward movement of the mandible showed no significant difference between the groups. Anterior face height increases did not demonstrate significant differences between the groups. The pronounced anterior movement of point A demonstrates that the A/D-RPE procedure positively affects maxillary protraction.