Immediate loading of fixed partial prostheses reconstructed using either tapered or straight implants in the posterior area: A randomized clinical trial

Background: In immediately loaded implants within 72 h after the implant placement in the unilaterally and partially edentulous ridge, primary stability is considered critical, which can be influenced by the design of the implant fixture. Purpose: To determine the outcomes at 1 year after the immediate loading of multiunit fixed partial prostheses over either tapered implants (TIs) or straight implants (SIs) in the posterior region. Materials and methods: Forty-eight patients (24 patients, 52 implants in TI group; 24 patients, 50 implants in SI group) were included for the study. Except for the one SI group patient whose two implants showed the insertion torque less than 30 Ncm, provisional prostheses designed and fabricated from intraoral scan data obtained immediately after implant surgery were delivered to rest of the 47 subjects at 3–7 days. After a year, the survival rate was estimated by intention-to-treat (ITT) and per-protocol (PP) analyses, and marginal bone loss (MBL) and implant stability were also analyzed statistically (p < 0.05). Results: Survival rate at implant level in TI group was 96.2%, and that of SI group in the ITT analysis was 86.0%. Intergroup difference, however, was not statistically significant (p > 0.05). Insertion torque was significantly higher in TI group than SI group (47.12 ± 6.37 Ncm vs. 41.60 ± 9.77 Ncm; p < 0.05). MBLs of both groups were less than 0.1 mm at 1-year follow-up and was similar between two groups (p > 0.05). Conclusions: Immediate loading of fixed partial prostheses after TI and SI placement showed reliable outcomes in the partially edentulous posterior ridge. In terms of the initial mechanical stability, the performance was superior for TIs than for SIs.