Methods: This retrospective cohort study consisted of patiens with periodontal disease treated and documented by graduate students as a part of their educational training at the Department of Periodontology and Fixed Prosthodontics, University of Bern, during the period 1978 to 2002. From the 392 original cases, 199 could be reexamined during 2005. Statistical analysis included Kaplan-Meyer failure and survival functions. Poisson regression compared the incidence rate between the four groups of crowns.
Results: 41 (64%) female and 23 (36%) male patients participated in the reexamination. At the time of seating the crowns, the mean patient age was 46.8 (range 24-66.3) years. 168 single unit crowns were seated. Their mean follow up time was 11.8 (range 0.8 – 26.4) years. During the time of observation, 22 biological and 12 technical complications occurred; 19 single crowns were lost. The chance for SC-v (56) to remain free of any complication or failure was 89.3% (95% CI 76.1 – 95.4) after ten years, for SC-e (34) 85.8% (95% CI 66.0 – 94.5), for SC-gc (39) 75.9% (95% CI 58.8 – 86.7), for SC-i (39) 66.2% (95% CI 45.1 – 80.7). SC-i had a survival rate of 95% at ten years, demonstrated a 34% rate of complications over ten years, were 3.5x more likely to have complications compared to SC-e. SC-gc failed three times more frequently than SC-e. SC-v had almost no complications and failures over ten years.
Conclusions: Risk evaluations provide important information on which to base decisions during treatment planning.