To investigate the cortical bone density in the posterior maxillary and maxillary region of adults with different vertical facial types, and to provide a reference for the successful clinical implantation of MSI.

The cluster sampling method was used to select 57 scanned patients from 20-40 years old in Huadu District Maternal and Child Health Hospital (Hu Zhong Hospital) from January 2015 to December 2018. There were 20 patients in high-angle group, 22 patients in mean-angle group and 15 patients in low-angle group respectively. Three dimensional model was reconstructed by Ez3D-i software, and the cortical bone density (HU value) was measured in 12 interradicular sites of maxilla and mandible (4 mm from the top of alveolar ridge) . One-Way analysis of variance (ANOVA) was applied to compare the difference of mean cortical bone mineral density (BMD) and mean cortical bone density of the three groups.

There was statistical difference of the cortical bone density in the buccal posterior area of maxilla and mandible in three groups (P<0.001) , with the smallest cortical bone density of the high-angle group. There was no significant difference of the cortical bone density in the palatal posterior area of maxilla. Significant difference of the cortical bone density was found among maxillary buccal posterior area, maxillary palatal posterior area and mandibular buccal posterior area in each group (P<0.001) , with the smallest cortical bone density at maxilla palatal side and the largest cortical bone density at the mandibular buccal side.

Cortical bone density in the buccal posterior area of maxilla and mandible was affected by different vertical facial types which indicated that it must be cautious for high-angle adults to implant MSI in the buccal posterior area of maxilla. Cortical bone density in the palatal posterior area of maxilla was hardly affected by different vertical facial types, but with low density, which also showed that it should be cautious to implant MSI in the palatal posterior area of maxilla.