title: Growth effects of botulinum toxin type A injected unilaterally into the masseter muscle of developing rats.
abstract: OBJECTIVE
  To evaluate the effects of botulinum toxin type A (BTX-A) on mandible skeletal development by inducing muscle hypofunction.
  
  
  METHODS
  Four-week-old Sprague-Dawley rats (n=60) were divided into three groups: Group 1 animals served as controls and were injected with saline; Group 2 animals were injected unilaterally with BTX-A (the contralateral side was injected with saline); and Group 3 animals were injected bilaterally with BTX-A. In Group 2, the saline-injected side was designated the control side (Group 2-1), whereas the BTX-A-injected side was designated the experimental side (Group 2-2). After four weeks, the animals were sacrificed, dry skulls were prepared, and mandibles were measured.
  
  
  RESULTS
  In the unilateral group, the experimental side (Group 2-2) had reduced dimensions for all mandible measurements compared with the control side (Group 2-1), suggesting a local effect of BTX-A on mandible growth, likely due to muscle reduction.
  
  
  CONCLUSIONS
  Localized BTX-A injection induced a change in craniofacial growth, and the skeletal effect was unilateral despite both sides of the mandible functioning as one unit.
authors.affiliation: Department of Pediatric Dentistry, Institute of Oral Health Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul 135-710, Korea; Department of Pediatric Dentistry, School of Dentistry, Dental Research Institute, Pusan National University, Yangsan 626-870, Korea.
authors.forename: Chanyoung
authors.initials: C
authors.lastname: Park
authors.forename: Kitae
authors.initials: K
authors.lastname: Park
authors.forename: Jiyeon
authors.initials: J
authors.lastname: Kim
mesh_terms: D000818:Animals; D001835:Body Weight; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage / Q000737:chemistry*; D007273:Injections, Intramuscular; D008297:Male; D008334:Mandible / Q000503:physiopathology; D008406:Masseter Muscle / Q000187:drug effects* / Q000378:metabolism; D009119:Muscle Contraction / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D019274:Botulinum Toxins, Type A
keywords: Botulinum toxin; Craniofacial growth; Mandible