Analysis of performance of root-form endosseous implants placed in the maxillary sinus

To evaluate the long-term effect on metal-bone interface of the perforation of the maxillary antral floor by root-form titanium implants, a study was undertaken in five mature Macaca fascicularis monkeys. One root-form titanium implant was placed bilaterally in the maxillary sinus perforating the sinus 5 mm and a second implant was placed completely in bone tissue. The protruding implant in the right antrum was grafted with autogenous cancellous bone and porous bone mineral (Bio-Oss) and the contralateral antral implant protruding in the antrum was left without grafting. The bilateral implants were used to support "free-standing" fixed prostheses, which were in full function for 14 months, during which time there was excellent clinical function and no mobility of the implants. Histomorphometric analysis of specimens revealed that there was no difference in the trabecular pattern or the amount of calcified matrix vs. marrow vascular spaces along the titanium implant interface. New reparative bone partially restored the osseous surface along the implant on the ungrafted side. Implants in the grafted antrum demonstrated bone regeneration over the implant surface ranging from 2 cm to complete regeneration. Histomorphometric analysis revealed the peri-implant bone to contain some particles of the Bio-Oss, although most of the implant bone interface exhibited only vital bone and marrow vascular spaces. The study indicates that the protrusion of implants maximally into the sinus floor does not necessarily require a bone graft to produce functional abutments for fixed prostheses and that implants can function well with 5 mm of protrusion into the antrum with excellent bone-metal interface.