Orthopedic outcomes of hybrid and conventional Hyrax expanders: Secondary data analysis from a randomized clinical trial

Objectives: To compare the effects of a hybrid miniscrew-supported expander versus a conventional Hyrax (CH) expander in growing patients. Materials and Methods: Forty patients were randomized into two groups: a hybrid Hyrax (HH) expander group using a Hyrax expander with two miniscrews and a CH expander group. The final sample had 18 subjects (8 female, 10 male; initial age of 10.8 years) in the HH group and 14 subjects (6 female, 8 male; initial age of 11.4 years) in the CH group. Cone-beam computed tomography examinations and digital dental models were obtained before expansion and 11 months postexpansion. The primary outcomes included the orthopedic transverse effects of expansion. Intergroup comparison was performed using analysis of covariance (P < .05). Results: Significantly greater increases in the nasal cavity width, maxillary width, and buccal alveolar crest width were found for the HH group. No intergroup differences were observed for dental arch width or shape changes. Conclusions: The HH group showed greater increases in the nasal cavity width, maxillary width, and buccal alveolar crest width. No differences were observed for intermolar, interpremolar, or intercanine widths; arch length; or arch perimeter. Arch size and shape showed similar changes in both groups.