title: Effects of occlusion on mandibular morphology and architecture in rats.
abstract: BACKGROUND
  A rodent occlusal hypofunction model has been widely established in jawbone-related studies. However, the effects of occlusal stimuli, with total elimination of molar contacts, and its rehabilitation on mandibular remodeling remain unclear.
  
  
  METHODS
  Forty-eight 5-wk-old Sprague-Dawley male rats were used. Twenty-four experimental rats underwent occlusal hypofunction by insertion of a bite-raising appliance. Twenty-four rats received no treatment (control group). Two weeks later, half the experimental rats (occlusal hypofunction group) were killed; the appliance was removed from the remaining experimental rats (recovery group) for two additional weeks before killing. Control animals were killed biweekly. Body weight and masseter muscle weight were measured, and the mandibles were subjected to micro-computed tomography to evaluate the mandibular morphology and cortical bone characteristics. The expressions of osteoblast- and osteoclast-related genes were evaluated with quantitative polymerase chain reaction.
  
  
  RESULTS
  No significant body weight differences were observed between the experimental and control rats. However, lighter masseter muscle, shorter mandibular incisor crown, mandibular body and ramus, and higher mandibular alveolar process and first molar fossae were observed in the occlusal hypofunction group. Moreover, the cortical bone characteristics associated with the expression of osteoblast- and osteoclast-related genes were remarkably different in the central and posterior mandible in the occlusal hypofunction group. At the 2-wk recovery time point after occlusal stimuli, the altered parameters in the masseter and mandible returned to normal levels.
  
  
  CONCLUSIONS
  Mandibular remodeling via bone turnover is region specific for altered occlusal stimuli. Normal occlusion is an important determinant of the mandibular morphology and architecture.
authors.affiliation: State Key Laboratory of Military Stomatology, Department of Orthodontics, School of Stomatology, Fourth Military Medical University, Xi'an, People's Republic of China.
authors.forename: Jia
authors.initials: J
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Military Stomatology, Center for Tissue Engineering, School of Stomatology, Fourth Military Medical University, Xi'an, People's Republic of China.
authors.forename: Shi-Yu
authors.initials: SY
authors.lastname: Liu
authors.affiliation: Department of Stomatology, Hospital Attached to Aeromedicine Institute of PLA, Beijing, People's Republic of China.
authors.forename: Ya-Juan
authors.initials: YJ
authors.lastname: Zhao
authors.affiliation: Department of Stomatology, The 461 Hospital of PLA, Changchun, People's Republic of China.
authors.forename: Xu
authors.initials: X
authors.lastname: Gu
authors.affiliation: State Key Laboratory of Military Stomatology, Department of General Dentistry & Emergency, School of Stomatology, Fourth Military Medical University, Xi'an, People's Republic of China. Electronic address: lqaq726@163.com.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Li
authors.affiliation: State Key Laboratory of Military Stomatology, Department of Orthodontics, School of Stomatology, Fourth Military Medical University, Xi'an, People's Republic of China. Electronic address: zuolinj@fmmu.edu.cn.
authors.forename: Zuo-Lin
authors.initials: ZL
authors.lastname: Jin
authors.affiliation: State Key Laboratory of Military Stomatology, Department of General Dentistry & Emergency, School of Stomatology, Fourth Military Medical University, Xi'an, People's Republic of China. Electronic address: cyj1229@fmmu.edu.cn.
authors.forename: Yong-Jin
authors.initials: YJ
authors.lastname: Chen
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D001835:Body Weight; D015519:Bone Density / Q000502:physiology; D008297:Male; D008310:Malocclusion / Q000000981:diagnostic imaging / Q000473:pathology* / Q000534:rehabilitation; D008334:Mandible / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology*; D008406:Masseter Muscle / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D055114:X-Ray Microtomography
chemical_list: D015415:Biomarkers
keywords: Bone marker; Bone mineral density; Mandible; Micro-CT; Occlusal hypofunction; Rat