Split-line patterns of the mandible following masseterectomy in adult and growing monkeys.

Architectural changes of the mandibular ramus following masseterectomy were analyzed by means of the split-line technique in both adult and growing monkeys. The right masseter muscle was resected in ten tufted capuchin monkeys (Cebus apella) and they were sacrificed following a 12-month period. Along with modifications in the shape of the mandible, the masseterectomy induced structural changes as revealed by alterations in the split-line patterns. These changes were much more evident in the adult animals. In growing monkeys, intrinsic forces determine an architecture of mandibular growth, represented by the direction of the splits. This is not influenced by the lack of mechanical factors like muscle action. Conversely, the final fibrous architecture of the bone in the adult monkey may be modified by extrinsic mechanical factors.