title: Bone changes in the mandible following botulinum neurotoxin injections.
abstract: In this study, botulinum neurotoxin type A (BoTx/A) was injected into the temporalis and masseter muscles of growing rats to induce masticatory hypoactivity. Sixty, 30-day-old, male Long-Evans rats were randomly divided into four groups. BoTx/A was bilaterally injected in the masseter muscles in group I, in the temporalis muscles in group II, and into both the masseter and the temporalis muscles in group III. Group IV served as the control in which saline was bilaterally injected into both muscles. Forty-five days after the injections, the rats were sacrificed. Observation of cortical bone thickness from bone biopsies of the right halves of the mandibles, evaluation of the volume of masseter and temporalis muscles with a plethysmometer, and scanning of bone mineral density (BMD) of the skull and mandibular bone structure with dual-energy X-ray absorptiometry were performed. One-way analysis of variance was employed to analyse measurements of muscle volume, BMD, and cortical bone thickness among the groups. The least square difference was then used to determine significance. Reduced cortical bone thickness and BMD of the skull and mandibular bone structure were observed. The volumes of the temporalis and masseter muscles injected with BoTx/A were smaller. Masticatory hypofunction affects bone structure during development.
authors.affiliation: Graduate Institute of Dentistry, Taipei Medical University and Hospital, Taiwan, Republic of China. cytsai@tmu.edu.tw
authors.forename: Chi-Yang
authors.initials: CY
authors.lastname: Tsai
authors.forename: Yi-Ming
authors.initials: YM
authors.lastname: Shyr
authors.forename: Wan-Chi
authors.initials: WC
authors.lastname: Chiu
authors.forename: Chi-Ming
authors.initials: CM
authors.lastname: Lee
mesh_terms: D015502:Absorptiometry, Photon; D000818:Animals; D001706:Biopsy; D001835:Body Weight; D015519:Bone Density / Q000187:drug effects; D019274:Botulinum Toxins, Type A / Q000494:pharmacology*; D002508:Cephalometry; D008297:Male; D008334:Mandible / Q000187:drug effects* / Q000473:pathology; D008406:Masseter Muscle / Q000187:drug effects / Q000473:pathology; D008409:Mastication / Q000187:drug effects; D009133:Muscular Atrophy / Q000139:chemically induced; D009498:Neurotoxins / Q000494:pharmacology*; D009929:Organ Size; D010991:Plethysmography; D011897:Random Allocation; D051381:Rats; D020318:Rats, Long-Evans; D012886:Skull / Q000187:drug effects / Q000473:pathology; D013703:Temporal Muscle / Q000187:drug effects / Q000473:pathology
chemical_list: D009498:Neurotoxins; D019274:Botulinum Toxins, Type A