Comparison of changes in skeletal, dentoalveolar, periodontal, and nasal structures after tooth-borne or bone-borne rapid maxillary expansion: a parallel cohort study

Introduction: This parallel cohort study aimed to assess the dentoalveolar, skeletal, periodontal, and airway effects of tooth-borne (hyrax) and computer-guided miniscrew-supported rapid palatal expansion appliances. Methods: Thirty-six subjects were randomly allocated into 2 groups. Eighteen subjects (mean age, 12.2 years; male-to-female ratio, 10:8) were assigned to receive treatment with the hyrax appliance (group A), and 18 subjects were treated with the computer-guided miniscrew-supported appliance (group B). The same type of expansion screw and expansion protocol was used in both groups. Linear and angular measurements of skeletal, dentoalveolar, periodontal, and nasal floor changes were performed on the pretreatment and posttreatment cone-beam computed tomography images (6-month follow-up). Descriptive statistics and the independent Student t test were used for the statistical analysis. Intraoperator reliability was evaluated using a 2 sample t test. The level of significance was P ≤0.05. Results: Ten subjects were censured because posttreatment cone-beam computed tomography imaging was not performed because of the coronavirus disease 2019 pandemic. In the remaining 26 subjects, increases in linear measurements were observed in both groups. The transversal skeletal increase was greater and statistically significant in the group treated with the bone-borne expander (P ≤0.05). The dentoalveolar transverse diameters were greater in the tooth-supported expander group, with no statistically significant difference between the groups. The buccal inclination of the maxillary first molar was observed in the group with the tooth-borne expander, with a statistically significant difference between the 2 groups. A slight reduction of buccal and palatal thicknesses at the level of the maxillary first molars was observed in both groups, smaller in the skeletal expander group, with a statistically significant difference between the 2 groups only on the right buccal cortical plate. The width of the nasal floor increased more in the group with skeletal expander with a statistically significant difference of 2 mm. Conclusions: Computer-guided miniscrew-supported maxillary expanders allowed a greater transversal increase of the nasal-maxillary skeletal structures by reducing the dentoalveolar side effects of the tooth-supported devices.