Dental Implant Thread Pitch and Its Influence on the Osseointegration Process: An In Vivo Comparison Study

Purpose: The design of an implant plays a fundamental role in the osseointegration process, particularly in low-density bone. It has been postulated that design features that maximize the surface area available for contact may improve mechanical anchorage and primary stability in cancellous bone. Two different implant profiles were compared to evaluate the influence of thread pitch on the osseointegration process in bone of low density and limited height. Materials and Methods: "Narrow-pitch" implants (NP) with a 0.5-mm pitch and "wide-pitch" implants (WP) with a 1.7-mm pitch were tested for osseointegration after 0 days and 4 and 8 weeks in a sheep iliac crest model. The two different implants were analyzed with biologic and biomechanical tests. Results: The present findings showed that initial mechanical anchorage and subsequent early endosseous integration in low-density bone could be improved by a reduction of thread pitch. The greater surface area gained by decreasing thread pitch increased bone-implant contact and primary stability from the time of implant placement. This better performance of the NP profile could be appreciated even at an early healing time when the subsequent biologic integration was enhanced not only in terms of a higher quantity of newly deposited bone but also more regular and mature geometric distribution of bone tissue at the interface. Conclusion: These results confirmed that, when primary stability is a concern, as in cancellous bone, increasing the implant surface area by using implants with smaller pitch might be beneficial. Keywords: dental implants, implant design, morphometry, osseointegration, thread pitch, torque tests