A cone beam computer tomographic study of the cortical bone thickness in different class II facial patterns

PurposeThe purpose of this study was to determine the difference of cortical bone thickness in different Frankfort to Mandibular plane angle (FMA) and anatomical areas by cone beam CT.Materials and methodsTwenty skeletal class II adult females were included, and divided into three groups by the FMA: the high FMA group, average FMA group, and low FMA group. Their cone beam computer tomography data were used for measurements and statistics. The cortical bone thickness was measured in five anatomical areas: (a) the labial alveolar bone located 2.0 mm below the root apex of the mandibular central incisors, (b) the buccal shelf alveolar bone located between the mandibular first and second molars, (c) the labial alveolar bone located 2.0 mm above the root apex of the maxillary central incisors, (d) the buccal alveolar bone located 3.0 mm above the alveolar crest between the maxillary second premolar and the first molar, and (e) the infrazygomatic crest.ResultsThe right and left measurements of cortical bone thickness in five anatomical sites were not significantly different. This study also compared the cortical bone thickness with the patient's age, but no significant differences were observed.The results revealed no significant difference in cortical bone thickness with respect to FMA. The cortical bone thickness in the posterior area was higher than that in the anterior area. Both the anterior area and the posterior area of the mandible were thicker than those of the maxilla, but the bone thickness in the maxillary posterior area and infrazygomatic crest showed no significant difference.ConclusionAlthough the cortical bone thickness did not show a significant difference, such difference was present in different areas. Lower posterior > infrazygomatic crest, upper posterior > lower anterior > upper anterior. The upper posterior area and the infrazygomatic crest area showed no significant difference.