The Influence of Controlled Occlusal Overload on Peri-implant Tissue. Part 3: A Histologic Study in Monkeys

The influence of experimental occlusal overload on peri-implantitis in monkeys (Macaca fascicularis) has been examined to explain the pathology of the disease that develops in the tissue around osseointegrated implants. In the first article of this series, it was reported that bone resorption was not observed around implants when occlusal trauma was produced by a superstructure that was in supraocclusal contact with an excess occlusal height of approximately 100 µm, provided there was no inflammation in the peri-implant tissue. In the second part of the study, experimental inflammation was created in the peri-implant tissue, and occlusal overload was produced by a superstructure with an excess occlusal height of 100 µm. Notable bone resorption was observed around the implant with the passage of time. These results suggested that, in addition to the control of inflammation in peri-implant tissue, traumatic occlusion may play a role in bone breakdown around the implant. In the present study, while the peri-implant tissue was kept in an inflammation-free state, bone level changes around the implants were investigated when various levels of traumatic force were exerted. The supraoccluding prostheses were defined as excessively high by 100 µm, 180 µm, and 250 µm, respectively. The heights were determined with an image analysis device, and the bone responses around the implants induced by the traumatic forces were investigated. The results showed that bone resorption around implants tended to increase with 180 µm or more excessive height of the superstructure. This suggests that the threshold of excessive height of the superstructures at which peri-implant tissue breakdown may start is approximately 180 µm. It is also suggested that there is a possibility of bone resorption around the implants caused by excess occlusal trauma, even when there is no inflammation in peri-implant tissue. Keywords: animal study, bone resorption, comparative histology, endosseous dental implantation