Standard morphology of the oral commissure and changes resulting from reconstruction for defects involving the commissure

The aim of this study was to characterize the standard morphology of the oral commissure and to describe the changes after reconstruction in patients with through-and-through cheek defects involving the oral commissure. Indices for the morphological analyses of the commissure were derived from examinations of 50 normal Japanese volunteers. Ten patients with full-thickness cheek defects involving the commissure were then evaluated. All of these patients underwent free flap reconstruction with vermilion advancement flaps from the remaining vermilion. The morphology of the commissure with the mouth closed was classified based on the point of entrance of the vermilion into the oral cavity. In normal volunteers, the commissure pattern consisting of the entrance of the upper vermilion into the oral cavity before the lower vermilion and just prior to forming the oral commissure was considered to be the standard. However, in the reconstructed cases, there was an increase in the pattern in which the lower vermilion enters the oral cavity before the upper vermilion for the remaining commissure postoperatively, especially when the lower lip defects were greater than those of the upper lip. It is important to refer not only to the standard morphology of the commissure, but also to the changes according to the extent of resection and the method of reconstruction.