Timing of loading and effect of micromotion on bone-dental implant interface: Review of experimental literature

A significant no-load healing period is the generally accepted prerequisite for osseointegration in dental implantology. The aim of this article was to examine whether this no-load healing period is validated by the experimental literature. In vivo histological data was scrutinized to identify the effect of early loading protocols on the bone-implant interface. Several loading modes were identified. They were categorized into groups according to implant design and the type of prosthetic reconstruction, and by their ability to introduce a distinct magnitude of motion at the interface. Specific histologic responses of early loaded implants (i.e., fibrous repair or osseointegration) were suggested to be directly related to the specific combinations of the above parameters. Early loading per se was not found to be detrimental to osseointegration. Specifically, only excessive micromotion was directly implicated in the formation of fibrous encapsulation. The literature suggests that there is a critical threshold of micromotion above which fibrous encapsulation prevails over osseointegration. This critical level, however, was not zero micromotion as generally interpreted. Instead, the tolerated micromotion threshold was found to lie somewhere between 50 and 150 microns. Suggestions are made for the earliest loading time that achieves osseointegration.