The influence of masticatory hypofunction on developing rat craniofacial structure

C. Y. Tsai, L. Y. Yang, K. T. Chen, W. C. Chiu

Research output: Contribution to journalArticlepeer-review

34 Citations (Scopus)


The purpose of this study was to use botulinum neurotoxin type A (BoNT/A) selectively to evaluate the influence of localized masticatory atrophy and paresis on craniofacial growth and development. 60 growing rats, 4 weeks old, weighing approximately 120 g, were randomly divided according as follows (Long-Evans, N = 15 per group): I (Mb + Tns); II (Mns + Tb); III (Mb + Tb); IV (Mns + Tns), where Mb or Tb is the BoNT/A-injected masseter or temporalis muscles (1.0 U/muscle, 2.5 ml) and Mns or Tns is the saline-injected muscles (2.5 ml). After 7 weeks, the mature rats were killed, the muscles dissected and mean muscle mass recorded. Anthropometric cranial, maxillary and mandibular measurements were taken from the dried skulls. Changes in animal weight during the growth period were not statistically significant. The mean masticatory muscle mass was smaller for the BoNT/A-injected muscles of Mb and Tb. Anthropometric measurements of bony structures inserted by masseter and temporalis muscles revealed a significant treatment effect. The measurements showed a facial morphology typical of a dolichofacial profile: short upper face accompanied by a long lower face with an extended mandibular length and ramus height and constricted bicoronoidal and bigonial widths. The results suggest that induction of localized masticatory muscle atrophy with BoNT/A alters craniofacial growth and development.

Original languageEnglish
Pages (from-to)593-598
Number of pages6
JournalInternational Journal of Oral and Maxillofacial Surgery
Issue number6
Publication statusPublished - Jun 2010


  • botulinum neurotoxin
  • craniofacial growth and development
  • masseter muscle
  • masticatory muscle atrophy
  • temporalis muscle

ASJC Scopus subject areas

  • Surgery
  • Oral Surgery
  • Otorhinolaryngology


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