Abstract: PURPOSE: To measure the density of the cortex in the zygomatic alveolar ridge region of adults by 3D reconstruction, and to analyze the differences of cortical bone density between different vertical facial types in the zygomatic alveolar ridge in different vertical facial types. METHODS: Spiral CT scanning data of 48 patients (24 males and 24 females) were chosen for 3D reconstruction and divided into 3 groups(low-angle group, average-angle group and high-angle group) according to the size of the mandibular plane angle (FH-MP), 18 points at which the six planes of the zygomatic alveolar ridge on the left of the upper jaw intersected at 13, 15 and 17 mm above the baseline(the horizontal line of mesial buccal tip of the first maxillary molar) were measured. SPSS 17.0 software package was used for statistical analysis. RESULTS: There was no significant difference between genders, there was significant difference among different vertical bone facial types (P<0.05）, among which the low-angle group [(1331.65±185.70) HU] was the highest and the high-angle group [(1245.62±207.63) HU] was the lowest. There was significant difference in BMD between different sites in different vertical facial types and the sites with the highest BMD in each group were located at 17 mm above on the occlusion plane. Cross-sectional evaluation showed that the high-angle group was located at the level of the proximal and middle buccal root of the first molar, and the mean-angle group was located between the proximal and distal buccal root, and the low-angle group was located at the level of the distal buccal root of the first molar. CONCLUSIONS: There was significant difference in density and distribution of bone cortex in zygomatic alveolar ridge between different vertical facial types in adults, which provides a reference basis for adults to select appropriate site of micro-implant anchorage and to ensure the stability of anchorage in orthodontic treatment.

Key words: Zygomatic alveolar ridge, Vertical facial type, Density of cortical bone, Micro-implantation anchorage, 3D reconstruction