Fracture load of nonvital premolars with crowns and different posts

Objectives: The aim of the study was to evaluate the influence of different posts and types of cementation on the fracture load of crowned endodontically treated premolars with class II cavities in an in-vitro setting. Methods: 56 single-rooted human premolars were selected. 48 teeth were endodontically treated and prepared with standardized MO cavities and a circular ferrule preparation. Subgroups of 8 teeth each either received no posts or were restored with screws (BKS), glass fiber posts (DentinPost) or quartz fiber posts (DT Light SL). 16 teeth were restored with zirconia posts (CeraPost). The BKS-screws and 8 zirconia posts were conventionally cemented with a glass ionomer cement, all others with Panavia F. The specimens were restored with composite cores and crowns cast from a nonprecious metal. 8 sound premolars served as control. After thermomechanical fatigue testing the samples were loaded until fracture at an angle of 45°. Results: The sound teeth showed a significant higher fracture load (792,50 N ± 210,01 N) in comparison to all groups. Conventionally cemented zirconia posts showed the lowest fracture load (327,00 N ± 45,84 N). The highest fracture load was found with DT Light SL (421,75 N ± 90,19 N). Only the difference between these two groups was statistically significant. Post fractures only occurred in the two groups with zirconia posts. In comparison to the adhesively luted zirconia posts twice as many conventionally cemented posts fractured. Conclusions: Concerning the fracture load there was statistically no difference between the restoration of less decayed nonvital premolars with crowns and posts or crowns alone. Fiber posts showed better results compared to zirconia posts.