Anatomic research on the perioral muscles, functional matrix of the maxillary and mandibular bones.

The aim of this research was to study, on the basis of anatomic specimen, the insertion of and the existing correlation between the orbicularis oris, the perioral and the buccinator muscles. Dissections were performed on 40 embalmed caucasian specimens. The skin and the subcutaneous stratum were removed from the perioral zone starting from the base of the nose and the zygomatic arch down to the hyoid bone. The orbicularis oris and the facial muscles were isolated in the successive planes. In the more superficial layer, the following muscles were displayed: the orbicularis oris around the oral opening, the mentalis in the lower part, the transversus menti, the depressor anguli oris and the depressor labii inferioris, the risorius, and the zygomaticus major and minor positioned on the area of the labial commissure. The buccinator muscle was situated under this superficial stratum. In 85% of the specimens we found a fourth inferior band of the buccinator muscle that runs continuously from one side to the other of the mandible. This bundle always ran cranially to the foramen mentale. The findings have been compared with magnetic resonance images obtained from ten patients. One of the main findings was that the majority of these muscles were so densely interrelated that they could be considered parts of two functional units. A deep unit is composed of the buccinator muscle and the inner ring of the orbicularis oris and a superficial unit is built up by the depressor anguli oris, the zygomaticus, the risorius and the outer ring of the orbicularis oris. MR imaging confirmed these findings.