Changes of masseter muscle following curved osteotomy of mandibular angle in goats

Abstract

Objective To investigate the changes of the masseter muscle following osteotomy of the prominent mandibular angle and to provide guidance for the resection of mandibular angle. Methods Ten goats were equally divided into two groups. In group A we performed unilateral curved osteotomy of the mandibular angle, and in group B we performed unilateral dissection of the masseter muscle. The cross section area (CSA) and the sarcomere length of masseter muscle were measured beore and after operation. Results (1) Cross section area (CSA) of masseter muscle fiber in curved ostectomy group decreased at 1,2, 3 and 6 months after operation in different extent. Comparing with the control group, the difference was statistically significant (P 0.01). (2) Sarcomere length of masseter muscle in curved ostectomy group decreased in 1 week, 1 and 2 months after operation, which had significantly statistic difference with control group (P<0.01). At 3 months after operation, sarcomere length recovered to normal. In dissection group, sarcomere length decreased in 1 week and 1 month after operation, which had significantly statistic difference with control group (P<0.01). At 2 month after operation, it recovered to normal. Conclusion Certain extent of atrophy does happen to masseter muscle after mandibular angle ostectomy. Meanwhile, these changes do not significantly impair the function of masseter muscle. According to this, we suggest a simple mandibular angle ostectomy without partial resection of masseter muscle in case of mild to morderate mandibular angle hypertrophy. Doing so, we can not only achieve the cosmetic effect but also reduce the implications. Key words: Prominent mandibular angle; Masseter muscle; Cured osteotomy