Early implant loading in the atrophic posterior maxilla: 1-stage lateral versus crestal sinus lift and 8 mm hydroxyapatite-coated implants. A 5-year randomised controlled trial.

Purpose: To evaluate the efficacy of long implants (10-16 mm) inserted in maxillary sinuses augmented according to a lateral approach versus short (8 mm) implants placed in crestally augmented sinuses, early loaded after 45 days. Materials and methods: Forty partially or fully edentulous patients having 3 to 6mm of residual crestal height and at least 4mm in thickness below the maxillary sinuses were randomised according to a parallel group design to receive either one to three 10 to 16 mm-long hydroxyapatite-coated implants (20 patients) after lateral sinus lifting with 50% anorganic bovine (Bio-Oss) and 50% autogenous bone, or 8mm implants (20 patients) after crestal sinus lifting with autogenous bone. Implants were submerged and left healing for 45 days before loading the implants. Within 1 week after 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 prosthesis and implant failures, any complications, and radiographic peri-implant marginal bone level changes. In addition, the stability of individual implants was assessed with Osstell and Periotest at abutment connection (baseline), and at 1 and 5 years after loading by blinded outcome assessors. All patients were followed up to 5 years after loading. Results: One patient dropped out (death) from the longer implant group. One implant failed in the short implant group versus 5 implants in 3 patients of the longer implant group. The difference was not statistically significant. Four complications occurred in 4 patients of the short implant group versus 8 complications in 7 patients of the long implant group, the difference being not statistically significantly different. However, the 2 major postoperative complications occurred in the longer implant group: 1 abscess, and 1 sinusitis that led to the complete failure of the treatment in 2 patients (4 implants lost). A total of 0.72 mm of peri-implant marginal bone was lost after 5 years at long implants and 0.41 mm at short implants, the difference between the two groups was statistically significant (P = 0.028). Osstell values increased and Periotest decreased over time and there were no differences between groups at any time points. Conclusions: In atrophic maxillary sinuses with a residual bone height of 3 to 6mm, 8 mm short implants placed in a simultaneously crestally lifted sinus might be a preferable choice than a 1-stage lateral sinus lift for placing longer implants since they appear to be associated with less morbidity. If these implants are placed with an insertion torque >35 Ncm and are joined together under the same prosthesis, they can be early loaded at 6 weeks.