Purpose: To evaluate the efficacy of 10- to 16-mm-long implants inserted in maxillary sinuses augmented according to a lateral approach technique with 50% particulated autogenous bone harvested from the oral cavity and 50% Bio-Oss, versus 8-mm-long hydroxyapatite-coated implants placed in crestally augmented sinuses with autogenous bone according to the Cosci technique. All implants were early loaded at 45 days after placement.
Materials and methods: Forty partially or fully edentulous patients having 3 to 6 mm of residual crestal height and at least 4 mm thickness below the maxillary sinuses (measured on a CT scan) were randomised to receive one to three, 10- to 16-mm-long implants (20 patients) after lateral sinus lifting with 50% anorganic bovine (Bio-Oss) and 50% autogenous bone, or 8-mm-long implants (20 patients) after crestal sinus lifting with autogenous bone. Implants were submerged and left to heal for 45 days. Within 1 week of abutment connection, implants were loaded with screw-retained full acrylic provisional prostheses. Definitive metal-ceramic prostheses were provisionally cemented 45 days after abutment connection. Outcome measures were the number of prosthesis and implant failures, and any complications. In addition, the stability of individual implants was assessed with Osstell and Periotest at abutment connection (baseline) and after 1 year of loading by a blinded outcome assessor. All patients were followed up for 1 year after loading.
Results: No patient dropped out. In three patients of the 8-mm implant group, primary stability could not be initially obtained. However, after immediately replacing the unstable implants with implants with a larger diameter, sufficient primary stability was obtained. One implant failed in the short implant group and five implants failed in three patients of the longer implant group. The difference was not statistically significant. There were no differences in complications between groups. However, two major post-operative complications occurred in the longer implant group: one abscess and one sinusitis, which determined the complete failure of the treatment in two patients (4 implants lost). Osstell values increased, whereas Periotest valves decreased over time, and there were no differences between groups at any time point.
Conclusions: This study suggests that in atrophic maxillary sinuses with a residual height of 3 to 6 mm, it may not be necessary to perform lateral sinus lifting to place longer implants (10 to 16 mm); 8-mm short implants might be a preferable choice as the treatment appears to be associated with less morbidity. This study also suggests that it is possible to load early (at about 7 weeks) implants placed in lifted sinuses that achieved a sufficient primary stability at placement. These preliminary results must be confirmed by larger trials with follow-ups of 5 years or more to monitor the performance of short implants over time.