抄録
In our previous study which examined cases of skeletal mandibular protrusion without asymmetry, deformation of cranial vaults was seen in many cases, ranging from moderate to severe degree, in a three-dimensional manner. The findings demonstrated that asymmetric cranial vaults having unilaterally longer sagittal length are associated with posteriorly located mandibular fossae on the same side. Interestingly, the mandibular body length compensated the bilateral difference in the sagittal position of the mandibular fossae to prevent lateral deviation of the mandible.
In contrast to symmetric cases, the asymmetric mandibular appearance is associated with excess growth in the unilateral mandibular body and/or ramus, rolling of the occlusal plane and mandible, and deformation of various mandibular internal structures. In asymmetric mandibular cases, the three-dimensional position of the mandibular fossae is unclear. To clarify this point and to consider the pathogenesis of lateral deviation of the mandible, 30 female cases with mandibular protrusion with more than 3mm laterally deviated Pog were examined using computed tomography.
As reported previously in cases without asymmetry, deformation of cranial vaults was also seen in many mandibular asymmetric cases, ranging from moderate to severe degree, in a three-dimensional manner. A significant correlation was seen between the bilateral difference in the sagittal length of cranial vaults and the bilateral difference in the sagittal position of mandibular fossae. Moreover, a significant correlation was seen between the bilateral difference in the transverse length of cranial vaults and the bilateral difference in the transverse position of mandibular fossae. These findings indicate that the unilateral mandibular fossae were located more posteriorly and laterally in association with the posteriorly and laterally deformed cranial vaults. All 30 cases had shorter mandibular bodies on the Pog-deviated side than on the non-deviated side. Twenty-four out of 30 cases exhibited more posteriorly located mandibular fossae on the Pog-deviated side than on the non-deviated side, which can worsen the mandibular asymmetry.
These findings indicate that the shape of the cranial vaults is related to the anterior-posterior and transverse position of mandibular fossae in cases of skeletal asymmetric mandibular protrusion. In contrast to our previous study which examined cases of skeletal mandibular protrusion without asymmetry, the bilateral difference of mandibular body lengths in asymmetric cases could not compensate the bilateral unbalance in the A-P position of mandibular fossae.
