title: Observation of the bone surrounding an overloaded implant in a novel rat model.
abstract: OBJECTIVE
  Although the recent success rates of dental implants are quite high, it is still true that loading during the bone healing period may be more likely to discourage osseointegration and that occlusal overloading might result in implant failure, even after osseointegration is established. The purposes of this study were to establish an appropriate experimental animal model and to histologically assess degenerative changes in established osseointegration under early and excessive occlusal loading.
  
  
  METHODS
  Forty rats were divided into control and experimental groups. The maxillary first and second molars on both sides were extracted, and machined-surface titanium implants were placed. In the experimental group, 2 or 4 weeks after implant placement, abutments that were designed to overload the implants were attached. Control group implants did not receive abutments and remained in situ 2 or 4 weeks. Sections were prepared and observed histologically.
  
  
  RESULTS
  Attrition of occluding opposite teeth and shiny spots on the abutments indicated that this model was useful for histologic investigation of the remodeling and bone changes around implants. Specimens showed remarkable bone loss and deterioration of osseointegration when overloading began at 2 weeks. Overloading applied after 4 weeks of healing induced active bone resorption in remote areas of the implants after 15 days of occlusion, while bone resorption at the interface was limited.
  
  
  CONCLUSIONS
  The authors successfully established an implant occlusion model using rats. This model revealed degenerative changes in osseointegration and/or in the bone around implants upon excessive occlusal loading. These results emphasize the risks associated with immediate loading and overloading. This is the first study to reveal the possibility of bone loss around overloaded implants in the absence of infection using a small animal model.
authors: Division of Bioprosthodontics, Department of Oral Science, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
authors: Masako
authors: M
authors: Nagasawa
authors: Ryohei
authors: R
authors: Takano
authors: Takeyasu
authors: T
authors: Maeda
authors: Katsumi
authors: K
authors: Uoshima
mesh_terms: D016301:Alveolar Bone Loss / Q000209:etiology / Q000473:pathology*; D000818:Animals; D001732:Bite Force; D059605:Dental Implant-Abutment Design; D015921:Dental Implants; D003766:Dental Occlusion; D057893:Immediate Dental Implant Loading / Q000009:adverse effects* / Q000379:methods; D008297:Male; D008334:Mandible; D008437:Maxilla; D023421:Models, Animal; D008963:Molar; D016348:Osseointegration; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D014025:Titanium; D019217:Tooth Attrition / Q000209:etiology; D014075:Tooth Discoloration / Q000209:etiology
chemical_list: D015921:Dental Implants; D014025:Titanium