Comparison of dentofacial effects of hybrid hyrax mentoplate combination and face mask applications used in skeletal class III treatments

The purpose of this prospective clinical study is to evaluate the effects of intermaxillary Class III elastics applied from the hybrid hyrax expander on the upper jaw, to mentoplate inserted in symphysis area in patients with skeletal Class III malocclusion in comparison with the effects of conventional face mask treatment. Forty patients in prepubertal or pubertal growth-development period, with skeletal Class III anomaly were divided into two groups of 20 individuals. In the first group (SA) intermaxillary elastics with 500 gr of force were applied from hybrid hyrax expander on the upper jaw to mentoplate on the lower jaw. In the second group (FM), 400-450 gr force was applied from the face mask to the bonded expansion appliance. The duration of treatment was 8.63 ± 3.98 months in the SA group and 7.41 ± 2.71 months in the FM group. Before and after treatment, lateral and posteroanterior cephalometric radiographs and plaster models were obtained from the individuals in both groups. To evaluate the cephalometric measurements, dependent sample t-test was used for intra-group changes and independent sample t-test was used for inter-group changes. Forward movement of maxilla was observed with maxillary anterior rotation in both groups. This movement was measured as 4.35 mm in the SA group and 1.6 mm in the FM group. In the SA group, there was no change in the sagittal and vertical movements of the mandible, but mandibular posterior rotation and increase in vertical values were seen in the FM group. In the FM group, protrusion of the upper incisors and retrusion of the lower incisors were seen as in the conventional facemask treatments. In SA group protrusion of the lower incisors and retrusion of the upper incisors were found. In our study, it was observed that the undesirable effects of conventional facemask treatment decreased in SA group. As an alternative to extra-oral devices commonly used in the treatment of skeletal Class III anomalies with maxillary retrognathia, successful effects can also be obtained with skeletal anchoring methods.