[Effect of botulinum toxin type A injection into the masseter muscle on mandibular development in rats].

OBJECTIVE

To investigate the effect of Botulinum toxin type A (Botox) injection into the masseter muscle on mandibular development in rats.

METHODS

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.

RESULTS

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).

CONCLUSIONS

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.