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The relationship between the shape of the cranial vault and the position of the mandibular fossa is not clear. To clarify the relationship, three-dimensional analysis was performed using cases with mandibular protrusion but without facial asymmetry. Nineteen female patients with skeletal mandibular protrusion who had visited Meikai University Hospital were used in this study. The lateral

BackgroundThe precise characteristics of posterior cranial vault deformation are difficult to identify using a two-dimensional analysis. Recently, three-dimensional analysis using computed tomography (CT) data and software analysis has enabled us to examine the craniofacial structure precisely. To identify the deformation in the cranial vaults by a three-dimensional analysis and examine its effects on other structures, CT data of skeletal mandibular protrusion cases without lateral deviation of pogonion (Pog) were examined.MethodsThirty-two adult female patients with skeletal mandibular protrusion who visited Meikai University Hospital were included in this study. CT images were taken before orthognathic surgeries, and the craniofacial structures were examined threedimensionally.The lateral deviation of Pog was less than 3 mm in all cases.Genetic/congenital anomaly cases, endocrine disorders, or cases with severe trauma or temporomandibular disorder were excluded.ResultsMany cases had three-dimensional deformations in the cranial vaults. The cranial vaults with unilateral posterior deformation had posteriorly positioned mandibular fossae on the same sides. Mandibular body lengths were related to the position of the mandibular fossae, and the posterior mandibular fossae tended to have longer mandibular body lengths on the same sides. Masseter muscles with larger volumes were related to longer mandibular body lengths.ConclusionsMandibular body lengths can compensate for the bilateral difference in the position of the mandibular fossae to avoid lateral deviation of the Pog. The masseter muscles are likely one of the factors related to the bilateral differences in the mandibular body length.

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