title: Histomorphometric evaluation of delayed changes in masseter muscle after lengthening the rabbit mandible by distraction osteogenesis.
abstract: OBJECTIVE
  The aim of the study was to evaluate the delayed responses and changes of gradually lengthened masseter muscles of rabbit mandibles.
  
  
  METHODS
  Unilateral lengthening of rabbit mandibles was performed in 18 New Zealand rabbits for 7 days at the rate of 1 mm day(-1). Mandibles of animals were removed at months 3, 4, and 6 after distraction. Biopsy samples of distracted and contralateral side masseter muscles were histopathologically evaluated and mean area of muscle fibers (MAF) was evaluated with histomorphometric methods. Results were statistically analyzed.
  
  
  RESULTS
  Mild to moderate atrophy of the fibers, and necrosis and myophagocytosis in some areas were the leading features at month 3 and which were decreased at month 4 in distracted side-muscle specimens, with no statistically significant differences when compared with non-distracted side muscles at the same periods. Almost completely, normal fibers were detected in distracted muscle specimens at month 6. Evidence of myopathic changes was found to disappear at month 6 and no significant difference was found in the MAF of distracted side muscles.
  
  
  CONCLUSIONS
  This study showed that the masseter muscle could adapt to gradual lengthening of the mandible within 6 months. Regenerative features and some degree of atrophic changes that could be observed at months 3 and 4 disappeared at month 6, with adaptation of the fibers.
authors.affiliation: Faculty of Dentistry, Department of Oral and Maxillofacial Surgery, Kirikkale University, Kirikkale, Türkiye.
authors.forename: H H
authors.initials: HH
authors.lastname: Tüz
authors.forename: D
authors.initials: D
authors.lastname: Dolanmaz
authors.forename: A Alper
authors.initials: AA
authors.lastname: Pampu
authors.forename: R S
authors.initials: RS
authors.lastname: Kişnişci
authors.forename: O
authors.initials: O
authors.lastname: Günhan
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D008137:Longitudinal Studies; D008297:Male; D008334:Mandible / Q000601:surgery*; D019186:Mandibular Advancement / Q000379:methods*; D008406:Masseter Muscle / Q000033:anatomy & histology* / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000502:physiology; D019857:Osteogenesis, Distraction / Q000379:methods*; D011817:Rabbits; D012038:Regeneration