Objectives: Using such model, it was investigated herein whether the removal of a portion of the masseter would affect the structure and growth of the zygomatic flange.
Methods: The material consisted of 3 mini-pigs which had the dorso-caudal region of the masseter surgically removed, and 3 other age-matched mini-pigs which served as controls. The following parameters were analyzed: (1) the macro and microscopic shape of the zygomatic bone by morphometric methods; (2) the direction of bone growth by serial radiographs and implant markers; (3) weekly electromyographies of the muscles involved; (4) functional and quantitative mastication analysis by video imaging; and (5) volumetric density of the bony trabeculae and bone appositional growth rate using histologic evaluation on tetracyclin-labeled sections.
Results: The results showed that: (1) there was a significant reduction (9.88%) in the dorso-ventral length of the zygomatic flange in the experimental group (p<0.001); (2) the growth direction vector of the zygomatic bone was downwards and forward and was not altered by the removal of the dorso-caudal fibers of the masseter; (3) the muscular pattern was altered, since there was no activity in the muscular extirpation region; (4)differences were seen in gape between both groups, but with no conclusive information regarding muscular extirpation; and (5) the trabecular density and growth rate did not present significant differences.
Conclusions: These results indicate that there is a limited, albeit clear effect of the skeletal musculature on bone morphology.