Effect of botulinum toxin type A injection into the masseter muscle on mandibular development in rats / 中华整形外科杂志

ABSTRACT

<p><b>OBJECTIVE</b>To investigate the effect of Botulinum toxin type A (Botox) injection into the masseter muscle on mandibular development in rats.</p><p><b>METHODS</b>12 28-day-old Wistar rats were divided into two groups as Botox group (n= 6) and control group (n = 6) which received anesthesia only. In Botox group, Botox was injected into the right masseter muscle, while only sterile saline into the left muscle. When the rats were 75-day-old, CT scan and 3D reconstruction were performed for cephalometry. The masseter muscles at both sides were weighed. Histologic study of masseter muscle and mandible was also performed.</p><p><b>RESULTS</b>The weight of right masseter muscle was (0.4575 +/- 0.0940) g in Botox group, and (0.8899 +/- 0.1030) g in control group (< 0.05). The mandibular height II and III was (10.8 +/- 0.8) mm and (9.5 +/- 0.6) mm in Botox group and (12.5 +/- 0.6) mm and (10.7 +/- 0.4) mm in control group, respectively (P < 0.05). The intergonial distance was (11.6 +/- 0.6) mm and (12.4 +/- 0. 6) mm in Botox and control group, respectively (P > 0.05).</p><p><b>CONCLUSIONS</b>When the rats receive Botox injection into the masseter muscle at young age, the grown-up rats have a decreased mandibular height, but the mandibular length and intergonial distance are not affected.</p>