CBCT comparison of dentoskeletal effects of haas-type and hyrax-type expanders using deciduous teeth as anchorage: A randomized clinical trial

The aim of this study was to compare the three-dimensional dentoskeletal effects of Haas-type and Hyrax-type expanders using primary teeth as anchorage for rapid palatal expansion (RPE). Thirty-four subjects in mixed dentition were divided according to their expander’s type: Hyrax (n= 16; 6F, 10M; mean age 8 ± 3 yrs) or Haas (n= 18; 14F, 4M; mean age 8 ± 2 yrs). Each patient underwent CBCTs before (T0) and after RPE (T1). Dentoskeletal changes were collected. A paired sample t-test and independent t-test were used to compare each variable within the same group and between groups, respectively, with a 5% significance. The Hyrax group showed an increase in all dentoskel-etal parameters; skeletal expansion was significantly increased anteriorly (1.76 mm) and posteriorly (1.93 mm). The greatest dental expansion was observed in the anchorage unit (6.47 mm), about twice as much as permanent molars (3.42 mm). The same statistical significance of Haas group measure-ments was observed; anteriorly skeletal expansion (2.97 mm) was greater than posteriorly (1.93 mm) and dental expansion was greater on anchored teeth (6.80 mm) than non-anchored teeth (4.57 mm). No statistical significance was observed between Hyrax and Hass groups. CBCT analysis showed that, in RPE, the dental expansion was greater than skeletal expansion. No significant or clinical changes were observed between Hyrax and Haas appliances anchored to primary teeth.