title: Botulinum neurotoxin type A in the masseter muscle: effects on incisor eruption in rabbits.
abstract: BACKGROUND
  Botulinum neurotoxins are responsible for the paralytic food poisoning, botulism. Commercial formulations such as botulinum neurotoxin type A are increasingly used for various conditions, including cosmetic recontouring of the lower face by injection of the large masseter muscles. The paralysis of a major muscle of mastication lowers occlusal force and thus might affect tooth eruption. The purpose of this study was to investigate the effects of unilateral masseter muscle injection of botulinum neurotoxin type A on the rate of eruption of incisors in a rabbit model. We hypothesized that the teeth would overerupt in an underloaded environment.
  
  
  METHODS
  Forty rabbits were injected with either botulinum neurotoxin type A or saline solution in 1 masseter muscle. Mastication and muscle force production were monitored, and incisor eruption rate was assessed by caliper measurement of grooved teeth.
  
  
  RESULTS
  The injection of saline solution had no effect. The masseter muscle injected with botulinum neurotoxin type A showed a dramatic loss of force 3 weeks after injection despite apparently normal mastication. Incisor eruption rate was significantly decreased for the botulinum neurotoxin type A group, an effect attributed to decreased attrition.
  
  
  CONCLUSIONS
  This study has implications for orthodontics. Although findings from ever-growing rabbit incisors cannot be extrapolated to human teeth, it is clear that botulinum neurotoxin type A caused a decrease in bite force that could influence dental eruption.
authors.affiliation: Dept. of Orthodontics, University of Washington, Seattle, WA, USA. Navarrete.dds@gmail.com.
authors.forename: Alfonso L
authors.initials: AL
authors.lastname: Navarrete
authors.forename: Katherine L
authors.initials: KL
authors.lastname: Rafferty
authors.forename: Zi Jun
authors.initials: ZJ
authors.lastname: Liu
authors.forename: Wenmin
authors.initials: W
authors.lastname: Ye
authors.forename: Geoffrey M
authors.initials: GM
authors.lastname: Greenlee
authors.forename: Susan W
authors.initials: SW
authors.lastname: Herring
mesh_terms: D000818:Animals; D001732:Bite Force; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage* / Q000494:pharmacology; D004576:Electromyography; D005260:Female; D007180:Incisor / Q000187:drug effects / Q000502:physiology*; D007273:Injections, Intramuscular; D008406:Masseter Muscle / Q000187:drug effects*; D008409:Mastication / Q000502:physiology; D023421:Models, Animal; D053580:Muscle Strength / Q000502:physiology; D009465:Neuromuscular Agents / Q000008:administration & dosage* / Q000494:pharmacology; D011817:Rabbits; D011897:Random Allocation; D014078:Tooth Eruption / Q000187:drug effects / Q000502:physiology*; D014741:Video Recording
chemical_list: D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A
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