Efeitos na posição mandibular decorrentes da expansão rápida da maxila, em tomografia computadorizada Cone Beam

Abstract

Introduction: The aim of this study was to evaluate and compare the effects on the sagittal and vertical position of the jaw resulting from rapid maxillary expansion (RME), with Haas- type and Hyrax- type expanders by using cone beam computed tomography. Methodology: The sample consisted of 33 subjects with transverse maxillary deficiency (mean age 10.7 years) randomly divided into 2 groups: Haas (n = 18) and Hyrax (n = 15). All patients underwent the same activation protocol, a total of 8 mm expansion reached to the end of the ERM. The evaluation was performed on CBCT scans of the face using the Efilm software in the times: T1 (initial), T2 (after the active phase of the ERM) and T3 (after 6 months stabilized the screw expander). Dentoskeletal measures undertaken in the maxilla and mandible were analyzed and compared by analysis of variance with repeated measures with mixed model, considering the significance level of 5%. Results: Immediately after RME (T2), mandibular displacement back (SNB; p= 0,024) and down (SN.PM; p= 0,007), an increasing in lower anterior face height (ENA-ME; p= 0,001) and a tendency to open bite occurred in both groups. These changes tended to return to values similar to the initial retention period (T3). The verticalization of the lower molars was verified, in T3, and extrusion in relation to the mandibular plane in T2. Conclusion: The ERM caused mandible displacement backward and downward, increasing in lower anterior face height and a tendency to bite opening immediately after RME. However, these effects were temporary. The lower molars showed a tendency to verticalize after 6-months retention period. The Haas-type and Hyrax-type expanders showed similar results.