Quantitative evaluation of palatal bone thickness for the placement of orthodontic miniscrews in adults with different facial types.

To quantitatively evaluate palatal bone thickness in adults with different facial types using cone beam computed tomography (CBCT).  Methods: The CBCT volumetric data of 123 adults (mean age, 26.8 years) collected between August  2014 and August 2016 was retrospectively studied. The subjects were divided into a low-angle group (39 subjects), a normal-angle group (48 subjects) and a high-angle group (36 subjects) based on facial types assigned by cephalometric radiography. The thickness of the palatal bone was assessed at designated points. A repeated-measure analysis of variance (rm-ANOVA) test was used to test the relationship between facial types and palatal bone thickness. Results: Compared to the low-angle group, the high-angle group had significantly thinner palatal bones (p less than 0.05), except for the anterior-midline, anterior-medial and middle-midline areas.  Conclusion: The safest zone for the placement of microimplants is the anterior part of the paramedian palate. Clinicians should pay special attention to the probability of thinner bone plates and the risk of perforation in high-angle patients.