The morphology of the attachment of skeletal muscles to the bones has been extensively documented. Three types of muscle-to-bone attachment have been described by Chong and Evans, namely periosteal attachment, endomysial insertion and tendinous insertion, and all three attachment types can be observed in one muscle3). Moss et al reported three types of muscle-to-bone attachment site, namely the periosteal attachment site, broad aponeurotic site, and tendinous site4). Yamada investigated the growth of the attachment site of the masseter muscle in rats and found that the attachment of this muscle greatly influences ossification5). However, detailed study on the relation between each type of muscle to bone attachment and the movement of mastication has not made. The masseter muscle, which is one of muscle of mastication, functions by attaching itself to the the mandible. Therefore, it seems that close relationship between the muscle and bone exists.

The masseter muscle functions by attaching itself to the mandible, and thus close correlation between the muscle and bone exists. Thus, it is important to study the relationship between the masseter muscle and mandible to clarify the complex movement of the jaw. In this study, the chronological changes in the attachment site of the masseter muscle to the mandible following injury were observed in rats.