1-stage versus 2-stage lateral maxillary sinus lift procedures: 4-month post-loading results of a multicenter randomised controlled trial.

To compare the efficacy of 1-stage versus 2-stage lateral maxillary sinus lift procedures. Sixty partially edentulous patients requiring 1 to 3 implants and having 1 to 3 mm of residual bone height and at least 5 mm of bone width below the maxillary sinus, as measured on CT scans, were randomised into two equal groups to receive either a 1-stage lateral window sinus lift with simultaneous implant placement or a 2-stage procedure with implant placement delayed by 4 months using a bone substitute in 3 different centres. Implants were submerged for 4 months and loaded with reinforced provisional prostheses, which were replaced, after 4 months, by definitive prostheses. Outcome measures were augmentation procedure failures, prosthesis failures, implant failures, complications and marginal peri-implant bone loss assessed by a blinded outcome assessor. Patients were followed up to 4 months after loading. Only data of implants placed in 1 to 3 mm of bone height were reported. Two patients dropped out from the 1-stage group and none from the 2-stage group. No sinus lift procedure failed in the 1-stage group but 1 failed in the 2-stage group, the difference was not statistically significant (P = 1.00). Two prostheses failed or could not be placed in the planned time in the 1-stage group and 1 in the 2-stage group, the difference was not statistically significant (P = 0.51). Three implants failed in 3 patients of the 1-stage group versus 1 implant in the 2-stage group, the difference was not statistically significant (P = 0.28). Two complications occurred in the 1-stage group and 1 in the 2-stage group, the difference was not statistically significant (P = 0.61). There were no statistically significant differences in bone loss between groups at loading (0.05 mm). Sites treated in 1 stage lost an average of 0.56 mm (SD: 0.36; 95% CI: -0.70 to -0.42; P < 0.001) of peri-implant bone and 2-stage sites approximately 0.61 mm (SD: 0.34; 95% CI: -0.74 to -0.48; P < 0.001). No statistically significant differences were observed between implants placed according to 1- or 2-stage sinus lift procedures. However, this study may suggest that in patients having a residual bone height between 1 and 3 mm below the maxillary sinus there might be a slightly higher risk for implant failures when performing a 1-stage lateral sinus lift procedure.