Palatal Bone Thickness of MSE Implantation area in Adult Patients with Skeletal Class Ⅲ Malocclusion: A Cone-beam Computed Tomographic Study

Background: Analyze the palatal bone thickness of maxillary skeletal expander (MSE) implantation area in adult patients with skeletal class Ⅲ malocclusion based on Cone-beam computed tomography (CBCT) data, and to provide a reference for the implantation of the miniscrew.Methods: A total of 80 adult patients (40 M, 40 F) with an normal angle before treatment were divided into two groups; skeletal class Ⅲ malocclusion group and skeletal Ⅰ malocclusion group according to sagittal facial type, with 40 patients in each group, with a male to female ratio of 1: 1. CBCT scanner was used to obtain DICOM data from all patients.The palatal bone thickness was measured at 45 sites with MIMICS 21.0 and SPSS 22.0 was employed for statistical analysis. The bone thickness of different regions of the palate in the same group was analyzed by one-way analysis of variance (ANOVA) method; Fisher’s least significant difference (LSD)-t method was used for comparison in pairs, and an independent sample t-test was employed to test the difference of bone thickness in the same area between the two groups.Results: (1) There was no significant difference among the anterior, middle, and posterior regions of the midline area in patients with skeletal class Ⅲ malocclusion (P > 0.05). Palatal bone thickness decreased gradually from front to back in the middle and lateral areas in both groups (P < 0.001). (2) The bone thickness of the anterior, middle, and posterior regions of the two groups gradually decreased from the middle area to the parapalatine region. (3) The palatal bone were significant thinner in the area 9.0 mm before the transverse palatine suture in midline area, 9.0 mm before and after the transverse palatine suture in the middle area, and 9.0 mm after the transverse palatine suture in the lateral area.Conclusion: (1) The palatal bone of patients with class Ⅲ malocclusion was thinner in some areas, so the MSE implant anchorage position could be moved forward appropriately. (2) The thin palatal bone increased the risk of MSE anchorage screw penetrating nasal mucosa and even inferior turbinate. Patients should be given a more precise and personalized implantation scheme based on factors such as palatine bone thickness and palatal morphology.