Effect of unintentional exposure of 2-stage implants upon subsequent osseointegration: histologic findings 6 months...

The purpose of this study was to evaluate the effect of early spontaneous exposure of 2-stage implants upon subsequent histologic bone contact following occlusal loading. As part of a study comparing 2 types of metallic threaded implants, 48 implants (24 CPTi and 24 Ti-13Nb-13Zr) were placed in maxillary and mandibular posterior sites in 6 baboons. Implant exposure was evaluated 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 sections were removed 6 months after the implant restoration was placed into function. One third (33%) of the maxillary implants became exposed, while 66.5% of the mandibular implants became exposed, mostly at 1 to 3 weeks. For all maxillary implants, fibrous tissue contact in the unintentionally exposed group (20.0%) was significantly greater than in the group that remained submerged (7.7%). Maxillary implants remaining submerged exhibited more sinus contact. For all mandibular implants, bone contact in the exposed group (38.9%) was significantly greater than in the submerged group (24.3%). Similarly, exposed implants exhibited less fibrous tissue contact. All other parameters in both maxillary and mandibular arches were statistically similar when comparing unintentionally exposed implants to those that remained submerged. This study suggests that accidental exposure of 2-stage implants should result in overall similarities in postloading bone contact to 2-stage implants that remain submerged during the early postoperative healing period.