In vitro bone strain analysis of implant following occlusal overload

ObjectivesTo enumerate peri-implant bone strain pattern under quantified occlusal load and verify the bone response through comparison with the critical strain thresholds defined by Frost's bone mechanostat theory. Material and MethodsMandibular unilateral recipient sites in two greyhound dogs were established with posterior teeth extractions. After 6weeks, four titanium implants were placed in each dog mandible. Following 12weeks of healing, successfully osseointegrated implants were placed in supra-occlusal contact via screw-retained non-splinted metal crowns. Plaque control and a dental health enhancing diet were prescribed. A bite force detection device was used to quantify in vivo occlusal load as the dogs functioned with supra-occlusal contact. After 8weeks, the dogs were sacrificed. In vitro peri-implant bone strain under quantified occlusal load was measured using bonded stacked rosette strain gauges. ResultsThe average and peak in vivo occlusal load measured were 434 and 795 newton (N). When individually and simultaneously loaded in vitro (476N), absolute bone strains up to 1133 and 753microstrains (epsilon) were measured at implant apices, respectively. Bone strain reaching 229 epsilon was recorded at distant sites. For bone strain to reach the pathological overload threshold defined by Frost's bone mechanostat theory (3000 epsilon), an occlusal load of 1344N (greater than peak measured in vivo) is required based on the simple linear regression model. ConclusionUnder the in vivo and in vitro conditions investigated in this study, peri-implant bone was not found to be under pathological overload following supra-occlusal contact function. Strain dissipation to distant sites appeared to be an effective mechanism by which implant overload was avoided.