Effect of Platform Switching on Collagen Fiber Orientation and Bone Resorption Around Dental Implants: A Preliminary Histologic Animal Study

Purpose: To show the presence and direction of the collagen fiber orientation around platform-switched (PS) and non-platform switched (NPS) implants at the crestal bone level. Materials and Methods: Twelve implants (six PS and six NPS implants) were placed with single-stage surgery in three dogs. The implant abutments were disconnected and reconnected after 8, 10, 12, and 14 weeks. The animals were sacrificed in the 18 week. The specimens were stained with hematoxylin and eosin and examined using polarized light microscopy. Results: The PS implant specimens showed circular fiber orientation at the implant platform level and the NPS implants showed similar fiber orientation at the bone level of the first implant thread. All specimens demonstrated a circular fiber orientation of the collagen fibers at the crestal bone level. Conclusions: The discrepancy in implantabutment diameter involving a change from a wider implant platform to a smaller abutment diameter, described as platform switching, seems to provoke a circular fiber orientation at the implant platform level. Similar circular fiber orientation was found at the first implant thread bone level for regular implants without platform switching. The histologic results support the hypothesis that platform switching can reduce crestal bone loss and can serve as a "mechanical retention factor" for periodontal fiber orientation. More clinical and histologic studies are needed to corroborate this preliminary finding. Keywords: bone preservation, circular fibers, collagen fibers, implants, platform switching, soft tissue stabilization, transversal fibers