Influence of static overload on the bony interface around implants in dogs

Purpose: The am of this study was to investigate bony changes around selectively overloaded implants in dogs. Materials and Methods: Twelve adult male beagles were used: 4 animals each for control, 4-week-load, and 12-week-load groups, Three implants were placed on the right side of each of the 12 animals and the time point designated as the study's baseline. Superstructures were then fabricated and attached only in the 2 implant-loaded groups 12 and 20 weeks following implant placement. Each lower distal implant was then fit with a cantilever-type superstructure extending in a mesial direction so as to be able to generate a controlled overload. The mesial and central implants were attached via superstructures equipped with a stainless steel screw, which could be tightened to create a controlled overload force. The force was induced by a controlled static 250-mu m submerging of the cantilever of the distal implant. After 24 weeks, tissue specimens including implants were evaluated histologically and histomorphometrically. Results: Numerous fluorescence-labeled bone areas were noted in the 4-week-load group, showing a high remodeling activity. Marginal bone loss was significantly greater in the 12-week-load group than in the 4-week-load group. The ratio of fluorescence-labeled bone area in the inner thread region was significantly higher in the 4-week-load group than in the 12-week-load group. Conclusions: These findings demonstrate that static overload-induced forces can elicit changes in peri-implant bone in experimental animals.