Prognosis of multi-unit implant supported and combined tooth-implant supported fixed dental prostheses: a retrospective cohort study with a mean observation period of 4.27 years.

OBJECTIVES

The objective of this retrospective cohort study was to evaluate survival of multi-unit FDPs in comparison to 3-unit fixed dental prostheses (FDPs).

MATERIALS AND METHODS

434 FDPs placed in 326 patients were selected from a prospective clinical long-term study. 213 FDPs were solely implant-supported, 154 FDPs tooth-implant supported, and 67 FDPs were cantilever FDPs. The most FDPs had 3-units (n = 315), 95 FDPs had 4-units, and 24 FDPs had more than 4 units. The most FDPs had a unit/abutment relation of ≤ 1.5 (n = 336), and 98 FDPs had a relation of > 1.5. Kaplan-Meier curves were used to estimate the survival probability of the FDPs for the variables type of FDP support, number of units and loading factor. Univariate log-rank tests were used to test for differences between groups within variables.

RESULTS

The mean observation period was 4.27 years. In the observation period of up to 12.6 years 17 FDPs failed mainly through technical complications. The underlying causes were implant loss (n = 6), abutment tooth loss (n = 5), loosening of the abutment screw (n = 1), and extensive chipping (n = 5). Survival probability of all FDPs was ≥ 89,6% after 10 years. Log-rank tests revealed no significant differences between groups for all variables (support, number of units, and loading factor (p ≥ .339).

CONCLUSIONS

Because of their promising prognosis 4-unit FDPs placed on implants or a combination of tooth and implant can be recommended as an alternative to 3-unit FDPs. A higher number of implants in relation to FDP units does not improve the prognosis of FDPs.

CLINICAL RELEVANCE

Support, number of units and the loading factor do not influence the survival of FDPs. Therefore, 4-unit FDPs placed on implants or a combination of tooth and implant are a valuable treatment alternative to 3-unit FDPs.