Effect of unintentional exposure of 2-stage implants upon subsequent osseointegration: Histologic findings 6 months postloading

The purpose of this study was to evaluate the effect of early spontaneous e xposure of 2-stage implants upon subsequent histologic bone contact followi ng occlusal loading. As part of a study comparing 2 types of metallic threa ded implants, 48 implants (24 CPTi and 24 Ti-13Nb-13Zr) were placed in maxi llary and mandibular posterior sites in 6 baboons. Implant exposure was eva luated at time of placement and at each weekly visit for the first 3 weeks, then at 1, 2, and 3 months, and also at 6 months for the maxilla. Block se ctions were removed 6 months after the implant restoration was placed into function. One third (33%) of the maxillary implants became exposed, while 6 6.5% of the mandibular implants became exposed, mostly at 1 to 3 weeks. For all maxillary implants, fibrous tissue contact in the unintentionally expo sed group (20.0%) was significantly greater than in the group that remained submerged (7.7%). Maxillary implants remaining submerged exhibited more si nus contact. For all mandibular implants, bone contact in the exposed group (38.9%) was significantly greater than in the submerged group (24.3%). Sim ilarly, exposed implants exhibited less fibrous tissue contact. All other p arameters in both maxillary and mandibular arches were statistically simila r when comparing unintentionally exposed implants to those that remained su bmerged. This study suggests that accidental exposure of 2-stage implants s hould result in overall similarities in postloading bone contact to 2-stage implants that remain submerged during the early postoperative healing peri od.