Does excessive occlusal load affect osseointegration? An experimental study in the dog.

Abstract

The purpose of this study was to evaluate the effect of excessive occlusal load following placement of titanium implants in the presence of healthy peri-implant mucosal tissues. Mandibular bilateral recipient sites in six Labrador dogs were established by extracting premolars and molars. After 3 months, two TPS (titanium plasma sprayed) implants and two SLA (sandblasted, large grit, acid etched) implants were placed on each side of the mandible in each dog. Three implants were lost in the initial healing phase, leaving 45 implants for evaluation. Following 6 months of healing, gold crowns were placed on implants on the test side of the mandible. The crowns were in supra-occlusal contact with the opposing teeth in order to create excessive occlusal load. Implants on the control side were not loaded. Plaque control was performed throughout the experimental period. Clinical measurements and standardised radiographs were obtained at baseline and 1, 3 and 8 months after loading. At 8 months, the dogs were killed and histologic analyses were performed. At 8 months, all implants were osseointegrated. The mean probing depth was 2.5+/-0.3 and 2.6+/-0.3 mm at unloaded and loaded implants, respectively. Radiographically, the mean distance from the implant shoulder to the marginal bone level was 3.6+/-0.4 mm in the control group and 3.7+/-0.2 mm in the test group. Control and test groups were compared using paired non-parametric analyses. There were no statistically significant changes for any of the parameters from baseline to 8 months in the loaded and unloaded implants. Histologic evaluation showed a mean mineralised bone-to-implant contact of 73% in the control implants and 74% in the test implants, with no statistically significant difference between test and control implants. In the presence of peri-implant mucosal health, a period of 8 months of excessive occlusal load on titanium implants did not result in loss of osseointegration or marginal bone loss when compared with non-loaded implants.