Similarity of stress distribution in bone for various implant surface roughness heights of similar form.

Surface roughness effects on osseointegration can be considered from two viewpoints: purely mechanical effects of stresses attributable to roughness and cell and molecular response to surface roughness.The goal of this study is to provide a theoretical basis to understand the effects of surface roughness size on the osseointegration of implants. The emphasis is primarily on the purely mechanical effects.Mathematical proofs of some similarity principles are provided.The main result is that if the geometric form of the roughness or thread cross-section is held constant, then the peak elastic stress depends on the form but not on the size of the roughness or thread height.The purely mechanical effects of surface roughness are well understood on a theoretical basis. The interpretation for clinical procedures, however, needs careful attention. Considering the present state of knowledge and clinical experience, no change in the roughness height of current practice is recommended.