Multivariate Influence of Prosthetic Superstructures on Immediately Loaded Implant Success

Objectives: To examine the influence of immediate implant placement and loading on the treatment outcome in restorative dental therapy. Methods: A total of 195 patients (age 16.5–80.4 years) consecutively admitted between May 2003 and June 2010 were included in the study. The specimens examined were 310 prosthetic restorations supported by 896 immediately loaded implants. The mean follow-up time was 27.5 months. 45.8% of the implants were placed immediately into fresh extraction socket. The study distinguished between removable (strictly implant-supported) and fixed types of restorations (single crowns, implant-supported bridges, combination bridges). Results: The overall implant success rate was 96.7%. Statistically significant results of multivariate analysis (p < 0.05) were found for the following factors: time in function (p < 0.001), type of prosthetic design (p < 0.001), type of connection between implant and restoration (p < 0.001) and which jaw was restored (p = 0.026). Neither the patient's age or sex nor the implant's position in the jaw, its design or height had a significant influence on clinical outcomes. One-piece implants exhibited the best results; this finding was statistically significant. Implants inserted in fresh extraction sockets had reduced hazard ratio of 0.483 compared to implants placed in healed bone. This influence was significant in univariate analysis (p = 0.040), but not in multivariate analysis (p = 0.085). Conclusions: With adjusted hazard ratios of up to 51, the prosthetic design and its realization significantly influence the success rate of implant-supported restorations. Immediate stabilization by the prosthetic superstructure significantly improves treatment success. The only statistically significant patient-intrinsic factor was the parameter “maxilla versus mandible” with an adjusted hazard ratio of 2.75. This risk can be successfully lowered by increasing the number of implants placed in the maxilla. The decreasing risk of implant loss proved significant after the first six months of functional loading.