title: Stability of loaded and unloaded implants with different surfaces.
abstract: OBJECTIVE
  To compare the torsional strengths and the effects of functional loading on five different implant surface structures.
  
  
  METHODS
  This in vivo longitudinal study of 9 months' duration examined osseointegration in 180 stepped cylindric implants placed into the mandibles of 18 healthy sheepdogs. Implants with five different surface structures were placed (n = 36 in each group): (1) smooth surface; (2) deep profile structure (DPS); (3) titanium plasma sprayed (TPS); (4) hydroxyapatite coated; and (5) sol-gel hydroxyapatite coated (SGHA). All implants were investigated under standardized conditions. At uncovering (3 months), half the implants were loaded with prefabricated crowns for 6 months, and the other half remained unloaded. Removal torque values were evaluated at 3, 6, and 9 months after implant placement. The data were analyzed using analysis of variance and Scheffé correction (alpha < .05).
  
  
  RESULTS
  All smooth-surface and SGHA implants failed in succession during the fourth and ninth months of the study. After 3 months the removal torque resistance of DPS, TPS, and hydroxyapatite-coated implants was significantly higher (P < .001) than that seen in the other two groups. Initially, the removal torque resistance of unloaded hydroxyapatite-coated implants was superior, and the decrease during the observation period was not significant. The increase in removal torque resistance under functional loading was not significant for the DPS implants. A significant increase was found in removal torque resistance for the loaded TPS implants (P < .05). The unloaded DPS and TPS implants showed no change in removal torque levels after the closed healing period of 3 months.
  
  
  CONCLUSIONS
  Successful osseointegration was achieved with DPS, TPS, and hydroxyapatite-coated implants, and smooth-surface and SGHA implants failed. Removal torque resistance was enhanced with controlled functional loading.
authors.affiliation: Clinic of Operative Dentistry and Preventive Dentistry, Center for Dental and Oral Medicine, University of Hamburg, Germany.
authors.forename: Ibrahim
authors.initials: I
authors.lastname: Nergiz
authors.forename: Nejat
authors.initials: N
authors.lastname: Arpak
authors.forename: Hamid
authors.initials: H
authors.lastname: Bostanci
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Scorziello
authors.forename: Petra
authors.initials: P
authors.lastname: Schmage
mesh_terms: D000818:Animals; D020099:Coated Materials, Biocompatible; D003758:Dental Implantation, Endosseous / Q000295:instrumentation* / Q000379:methods; D015921:Dental Implants; D017267:Dental Prosthesis Design; D003799:Dental Stress Analysis; D020878:Device Removal; D004285:Dogs; D008137:Longitudinal Studies; D008334:Mandible; D016348:Osseointegration / Q000502:physiology*; D013499:Surface Properties; D019415:Torque; D016474:Weight-Bearing
chemical_list: D020099:Coated Materials, Biocompatible; D015921:Dental Implants