Objective This study aims to measure the cortical bone thickness of adults and adolescents at different sites of infrazygomatic crest and to compare the specific differences between the two groups by cone beam computed tomography(CBCT). Methods The oral and maxillofacial CBCT data of 30 patients, including 15 adults and 15 adolescents, were collected. Multiple measurements were performed at different slices of infrazygomatic crest at 13, 15, and 17 mm apical from the reference line(the horizontal line where the mesio-buccal cusp of the upper first molar lies). The data were analyzed statistically. Results The cortical bone thickness of the infrazygomatic crest in adults ranged from (1.91±0.54) mm to (2.62±0.74) mm. The cortical bone was thickest at the interradicular space of the maxillary first and second molars and thinnest at the mesial-buccal root of the maxillary first molar. The cortical bone thickness of the infrazygomatic crest in adolescents ranged from (1.30±0.51) mm to (3.08±1.01) mm. The cortical bone was thickest at the interradicular space of the maxillary second premolar and first molar and thinnest at the distal-buccal root of the maxillary first molar or the mesial-buccal root of the maxillary second molar. Conclusion The cortical bone thickness of all the measured sites of the infrazygomatic crest in both adults and adolescents guaranteed the stability of micro-implant anchorage. The best micro-implant anchorage placement sites of the infrazygomatic crest for adults and adolescents lie in the interradicular space of the maxillary first and second molars and the interradicular space of the maxillary second premolar and first molar, respectively.
