Similar findings were reported by Kozlovsky et al., who performed a split-mouth design on Beagle dogs, placing prosthetic abutments on implants, either in supra-occlusion or infraocclusion. They found no loss of osseointegration or marginal bone loss with non-inflamed, occlusally overloaded prostheses on dental implants. In fact, the authors demonstrated, in the absence of inflammation, there was an increase in the bone to implant contact when overloading the implants.

As is apparent, there are conflicting data in these experimental studies which can be attributed to confounding variables such as differences in experimental design, occlusal overload, and bone quality. Lateral forces applied on the implant prostheses in dogs could only be simulated by artificially created cusp inclines of different types as dogs are unable to perform lateral movements. Some researchers created a lateral displacement on the supra-occluding cusp where others created premature contact in centric occlusion. Finally, different regimens of oral hygiene were used and certainly could not preclude the presence of peri-implant inflammation.

Despite the conflicting evidence, two conclusions have been drawn. Precipitous bone loss from overloading has been shown in a few investigations, but the majority of the more recent animal studies has not replicated these findings. Total loss of osseointegration of an integrated implant appears possible when the applied force exceeds the biological threshold, but this limit is currently unknown, and contingent on the bone quality and possibly the level of inflammation. While it is difficult to quantify the magnitude and direction of naturally occurring occlusal forces, a number of clinical studies may offer clues to appropriate implant/prosthetic treatment planning to minimize peri-implant disease and point to future research.

Bruxism

Twenty percent to 35.9% of patients may generate forces of such magnitude to cause microfracture of the bone around dental implants with concomitant bone loss and implant failure due to bruxism.