title: Prolonging the duration of masseter muscle reduction by adjusting the masticatory movements after the treatment of masseter muscle hypertrophy with botulinum toxin type a injection.
abstract: BACKGROUND
  Botulinum toxin type A (BTX-A) is widely used for the clinical treatment of masseteric hypertrophy. Until now, few reports have discussed how to prolong the duration of its effectiveness.
  
  
  OBJECTIVE
  This study evaluated that purposely adjusting the masticatory movements is possible of postponing the masseter muscle rehypertrophy.
  
  
  METHODS
  Ninety-eight patients were randomly and equally divided into 2 groups, and 35 U BTX-A per side was injected into the masseters. The thickness and volume of the masticatory muscles were measured by ultrasound and computerized tomography, respectively. Patients in Group 1 were instructed to strengthen their masticatory effort during the denervated atrophic stage of the masseter (the interval was evaluated by real-time ultrasound monitoring), whereas patients in Group 2 were not given this instruction. When the masseter muscle began to recover, patients in both groups were instructed to reduce their chewing.
  
  
  RESULTS
  The duration of the masseter muscle rehypertrophy was significantly prolonged in Group 1 patients. The thickness and the volume of the other masticatory muscles were significantly increased in Group 1 but were either slightly decreased or insignificantly different in Group 2.
  
  
  CONCLUSIONS
  Purposely strengthening masticatory muscle movement during the denervated atrophic stage of the masseter can prolong the duration of masseter rehypertrophy.
authors.affiliation: *All the authors are affiliated with the Department of Plastic & Reconstructive Surgery, Ninth Hospital of Shanghai, Jiaotong University School of Medicine, Shanghai, China.
authors.forename: Jiao
authors.initials: J
authors.lastname: Wei
authors.forename: Hua
authors.initials: H
authors.lastname: Xu
authors.forename: Jiasheng
authors.initials: J
authors.lastname: Dong
authors.forename: Qingfeng
authors.initials: Q
authors.lastname: Li
authors.forename: Chuanchang
authors.initials: C
authors.lastname: Dai
mesh_terms: D000293:Adolescent; D000328:Adult; D019274:Botulinum Toxins, Type A / Q000627:therapeutic use*; D005081:Exercise Therapy; D005260:Female; D006801:Humans; D006984:Hypertrophy / Q000473:pathology* / Q000628:therapy*; D008297:Male; D008406:Masseter Muscle / Q000002:abnormalities* / Q000000981:diagnostic imaging / Q000473:pathology; D008409:Mastication; D008875:Middle Aged; D009465:Neuromuscular Agents / Q000627:therapeutic use*; D009929:Organ Size; D011859:Radiography; D012008:Recurrence; D013997:Time Factors; D014463:Ultrasonography; D055815:Young Adult
chemical_list: D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A