OBJECTIVEThe purpose of this study was to study the masticatory muscles affected by distraction osteogenesis of the mandible.

METHODSThe distraction osteogenesis (DO) was applied to distract the left mandible of 6 mongrel dogs that were divided into three experimental groups. After different distraction phase and consolidation phase, the masseter and the digastric muscle were taken out. The specimens were stained using hematoxylin/eosin and enzyme histochemistry. Afterwards, the specimens were observed with a light microscope to study the morphologic changes of the muscles. The contents of enzyme in the different groups were measured by VIDAS.

RESULTSThe masseter showed consequently atrophy, but the digastric muscle showed a progress of histomorphologic reconstruction, including atrophy and hypertrophy. The changes of the contents of enzyme and histomorphology were identical in the masticatory muscles.

CONCLUSIONThe digastric muscle parallel to the vector of mandibular distraction adapts the distraction by the way of atrophy, regeneration and hypertrophy. And the contents of enzyme appear to decrease at the beginning, increase afterwards, and return to the normal level finally. But the masseter perpendicular to the vector of mandibular distraction shows consequent atrophy, and the contents of enzyme consequently decrease, which means the metabolism decrease.