Long-Term Prognosis of Implant-Supported Long-Span FDPs?

Objectives: The objective of this clinical study was to evaluate long-term survival of long-span FDPs in comparison to 3-unit FDPs.
Methods: 434 FDPs placed in 326 patients (mean age: 60.77 years; 140 male) were evaluated after up to 13 years. Eighty FDPs were located in anterior regions, 308 FDPs in posterior regions, and 46 FDPs covered anterior and posterior quadrants. The sample included 3-unit FDPs (n=317), 4-unit FDPs (n=92) and FDPs with more than 4 units (n=25). Conventional FDPs were exclusively implant-supported (n=213) or combined tooth implant-supported (n=154). Cantilever FDPs were almost exclusively implant-supported (n=66) with only one exception. In contrast to 3-unit FDPs, the relation between number of units per abutment was higher than 1.5 in 98 FDPs. Kaplan-Meier curves were used to calculate survival curves. Differences between curves were assessed with log-rank tests. Cox regression analysis was performed to consider possible risk factors (location, number of units, support, relation unit per abutment) for FDP survival simultaneously.
Results: Seventeen FDPs failed predominantly because of biological complications, as implant failure (n=6) or abutment tooth loss (n=5). Extended veneer fractures accounted for five failures and abutment screw loosening for one failure. Kaplan-Meier analysis revealed a probability of survival for the complete sample of 91% after 10 years. The number of units (p=.905) and the type of support (implant-implant, tooth-implant, cantilever) had no effect on FDP survival (p=.339). A higher unit per abutment relation (>1.5) resulted in a 10-year survival rate of 96% compared to 90% for FDPs with lower unit per abutment relations, without significant difference (p=.539). Cox regression analysis revealed posterior location as a significant risk factor (Hazard ratio:4.6; p=.041).
Conclusions: Because of their promising long-term prognosis 4-unit FDPs placed on two implants or a combination of tooth and implant can be recommended as an alternative to 3-unit FDPs.