Fracture load of nonvital premolars with fillings and different posts

Objectives: Aim of the in-vitro study was to evaluate the influence of different posts and types of cementation on the fracture load of endodontically treated premolars with class II cavities. Methods: 56 single-rooted human premolars were selected. 48 teeth were endodontically treated and prepared with standardized MO cavities. 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). All fiber posts and 8 zirconia posts were adhesively luted with Panavia F, the BKS-screws and another 8 zirconia posts were conventionally cemented with a glass ionomer cement. The specimens were restored with composite fillings. 6 experimental groups and one control group of sound premolars came to thermomechanical fatigue testing and loading until fracture at an angle of 45° to the long axis of the tooth. Results: The sound teeth showed a significant higher fracture load (792,50 N ± 210,01 N) in comparison to all groups except the group DT Light SL (555,63 N ± 206,72 N). Both groups with fiber posts showed significant higher fracture load values in comparison to the groups with zirconia posts or without posts. Regarding the fracture load of the adhesively luted and conventionally cemented zirconia posts, no significant difference could be found. Fracture modes were defined as favourable (above simulated bone level) and unfavourable (below simulated bone level). No post fractures were observed. The groups with fiber posts did not show a more favourable fracture mode than the other groups. Conclusions: This investigation showed that compared to a restoration without posts the use of intraradicular posts can significantly increase the fracture resistance of nonvital premolars with class II cavities and composite fillings.