Growth effects of botulinum toxin type A injected into masseter muscle on a developing rat mandible

Oral Dis. 2008 Oct;14(7):626-32. doi: 10.1111/j.1601-0825.2007.01435.x. Epub 2008 Mar 6.


Objectives: Botulinum toxin type A (BTX-A) reduces the muscular contractions by temporarily inhibiting the release of acetylcholine at the neuromuscular junction. The purpose of this study was to investigate the effects of the BTX-A injected into the masseter muscle of a developing rat mandible.

Materials and methods: Four-week-old male (no. 80) Sprague-Dawley rats were divided into four groups: control group, saline group, BTX-A group and baseline control group. Rats of baseline group were sacrificed at 0 day to provide baseline values of the mandibular measurements. The masseter muscle of rats in the saline and the BTX-A group were administered with saline and BTX-A solutions respectively. Experimental animals were sacrificed after 4 weeks.

Results: The BTX-A group demonstrated smaller mandibular dimension compared with the other groups (P < 0.05). Their condylar cartilages showed increased apoptosis at the proliferation stage of the reserve zone and masseter muscle fibers demonstrated atrophic changes.

Conclusions: The result demonstrated BTX-A influence on inhibitory action of the developing mandible because of apoptosis at the proliferation stage of the reserve zone of the condylar cartilage in developing rat mandible.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis
  • Botulinum Toxins, Type A / administration & dosage
  • Botulinum Toxins, Type A / pharmacology*
  • Cartilage, Articular / drug effects
  • Injections, Intramuscular
  • Male
  • Mandible / drug effects*
  • Mandible / growth & development
  • Mandibular Condyle / drug effects
  • Masseter Muscle / drug effects
  • Maxillofacial Development / drug effects*
  • Rats
  • Rats, Sprague-Dawley


  • Botulinum Toxins, Type A