Narrow- (3.0 mm) versus standard-diameter (4.0 and 4.5 mm) implants for splinted partial fixed restoration of posterior mandibular and maxillary jaws: A 5-year retrospective cohort study

Background: Evidence concerning predictability of narrowdiameter implants (NDIs) (<3.3 mm) to restore partially edentulous posterior maxillary and mandibular areas is limited. The aim of this study is to compare the 5-year outcomes of NDIs (3.0 mm) and standard-diameter implants (SDIs) (4.0 to 4.5 mm) supporting fixed partial dentures (FPDs) in posterior mandibular and maxillary jaws. Methods: All patients treated with at least two adjacent NDIs or SDIs according to available bone thickness and with a minimum follow-up of 5 years after placement were invited to undergo a clinical and radiologic examination. Outcome measures were implant and FPD failures, biologic and prosthetic complications, and marginal bone loss. Results: A total of 107 out of 127 patients attended the examination: 49 (113 implants) of the NDI group, and 58 (126 implants) of the SDI group. Two NDIs failed in one patient versus four SDIs in four patients (P = 0.37). One FPD failed in the NDI group versus two FPDs in the SDI group (P >0.99). Nine biologic complications occurred in the NDI group and twelve in the SDI group (P = 0.81). Twelve prosthetic complications occurred in the NDI group and only two in the SDI group (P = 0.001). Peri-implant marginal bone loss at 5 years was 0.95 ± 0.84 mm for the NDI group and 1.2 ± 0.86 mm for the SDI group (P = 0.06). Conclusion: Five-year data indicate that FPD treatment in posterior mandibular and maxillary jaws with NDIs was as reliable as with SDIs, although NDIs showed a higher risk of prosthetic complications.