title: Bone metabolic activity around dental implants under loading observed using bone scintigraphy.
abstract: OBJECTIVE
  The purpose of this study was to determine dynamic changes in bone metabolism around osseointegrated titanium implants under mechanical stress.
  
  
  METHODS
  Two titanium implants were inserted parallel to each other in the tibiae of rats and perpendicular to the bone surface with the superior aspect of the implant exposed. Eight weeks after insertion, closed coil springs with 0.5, 1.0, 2.0, and 4.0 N were applied to the exposed superior portion of the implant for 7 weeks to apply a continuous mechanical stress. Bone scintigrams were performed using a gamma camera with a modified high-resolution pinhole collimator. Images were made at 1, 4, 7, 10, 14, 21, 28, 49, and 56 days after insertion and at 3 days and at weekly intervals until 7 weeks after load application. The ratio of the metabolic activity around the implants to that around a reference site (uptake ratio) was established. The Friedman, Steel, and Tukey tests (P < .05) were used to assess statistical significance.
  
  
  RESULTS
  In the process of osseointegration, the uptake ratio increased during the first week after implant insertion and then gradually decreased. During the initial 3 weeks the uptake ratio was significantly higher than at 1 day after insertion. In the process of load application, the uptake ratio increased with 2.0- and 4.0-N loads; it was significantly higher until 6 weeks than it had been before load application.
  
  
  CONCLUSIONS
  Bone metabolism around the implants increases with loading and depends on the magnitude and period of the loading.
authors.affiliation: Division of Advanced Prosthetic Dentistry, Tohoku University Graduate School of Dentistry, Sendai, Japan.
authors.forename: Hiroto
authors.initials: H
authors.lastname: Sasaki
authors.forename: Shigeto
authors.initials: S
authors.lastname: Koyama
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Yokoyama
authors.forename: Keiichiro
authors.initials: K
authors.lastname: Yamaguchi
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Itoh
authors.forename: Keiichi
authors.initials: K
authors.lastname: Sasaki
mesh_terms: D000818:Animals; D001842:Bone and Bones / Q000378:metabolism*; D003758:Dental Implantation, Endosseous; D015921:Dental Implants; D020007:Implants, Experimental; D008297:Male; D016348:Osseointegration / Q000502:physiology*; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D051381:Rats; D017208:Rats, Wistar; D013314:Stress, Mechanical; D013669:Technetium Tc 99m Medronate; D013977:Tibia / Q000000981:diagnostic imaging
chemical_list: D015921:Dental Implants; D019275:Radiopharmaceuticals; D013669:Technetium Tc 99m Medronate