Comportamento de três expansores maxilares em fissuras labiopalatinas: um estudo de elementos finitos

Abstract

Introduction: This study evaluated the stress distribution in the maxilla bone structure during rapid palatal expansion in a 17 years old male patient with bilateral non-syndromic cleft lip and palate (BCLP), using expanders with dental (HYRAX) and skeletal anchorage (MARPE). Material & Method: For the generation of the specific finite element models, cone beam computed tomography was used, and the DICOM files exported to the Mimics, 3-Matic (Materialise) and Patran (MSC Software) software. Three specific three-dimensional models were generated: A) HYRAX: Conventional hyrax screw(9mm) (four bands); B) MARPE-DS: Model with 3 miniscrews (1.8 mm diameter – 5.4mm length) and dental anchorage (four bands); and, C) MARPE-NoDS: Model with 3 mini screws without dental anchorage. The rapid maxillary expansion was simulated by activating the expanders transversely 1 mm on the X axis. Results: The HYRAX resulted in higher strain levels on the dentoalveolar region and also a null tensile stress at palatal bone structure. The MARPE-DS showed similar stress at dentoalveolar region than the HYRAX, and resulted in 4,000 µƐ at the center of palatal region. MARPE-NoDS only showed evident stress at the palatal region. High stress levels at root anchorage teeth were observed for HYRAX and MARPE-DS. On the contrary, the MARPE-NoDS resulted in no stress on the tooth structure. Conclusion: On the limits of the study design it is possible to conclude that the stress distribution from the expanders used in the BLCP showed an asymmetric expansive behavior. The Hyrax and MARPE-DS produced, during the initial activation phase of expansion, similar high strain at the dentoalveolar structures and the upper posterior teeth displacement. The MARPE-NoDS expander showed restricted strain on the palate.