Evaluation of cuspal deflection and fracture resistance of endodontically treated teeth restored with different restorative material combinations.

Objective: This study evaluated the effects of restorations using varied materials and their combinations on cuspal deflection and fracture resistance of endodontically treated MOD cavitated maxillary premolars.

Materials and methods: 168 premolar teeth were used in the study. The teeth were divided into 14 groups (12 teeth in each group) as Positive control (Group 1), Negative control (Group 2) and Test groups (Group 3-14). MOD cavities were prepared, and then endodontic treatments were performed on teeth in all groups except the positive control group. Group 1 was the Positive control (intact teeth), and Group 2 was the Negative control (only MOD cavity and endodontic treatment). In Groups 3-7 and Groups 9-13, EverX Posterior, SDR Plus Bulk Fill Flowable, G-aenial Universal Injectable, Biodentine, and Fuji II LC were used as the lower layer, respectively. In Groups 3-7, Filtek One Bulk Fill Restorative was used as the upper layer, while in Groups 9-13, Tetric N-Ceram was used. Group 8 was entirely restored with Filtek One Bulk Fill Restorative and Group 14 with Tetric N-Ceram. Cusp deflection was measured. Fracture resistance testing was performed.

Results: Within each group, there was a statistically significant decrease in cusp deflection change values at all measured time points (p < 0.05 In the comparison between the groups, cusp deflection change values ​​were found to be significantly higher at all times in the groups where EverX Posterior was applied as the lower layer and Tetric N-Ceram was the upper layer (p < 0.05). In the groups where Filtek One Bulk Fill Restorative was used, differences were seen between the groups at all times (p < 0.05).Groups 4 and 5 exhibited fracture resistance similar to the positive control group (p > 0.05). In the comparison between the groups, a significant increase in fracture resistance was observed in the groups in which only EverX Posterior and SDR Plus Bulk Fill Flowable were applied as the lower layer and the upper layer was Filtek One Bulk Fill Restorative (p < 0.05).

Conclusions: Endodontically treated teeth may exhibit different cuspal deflections and fracture resistance when restored with different materials and combinations of these materials.

Clinical relevance: When performing coronal restoration of an endodontically treated premolar teeth, it is recommended to select and use the appropriate restorative material, taking into account the position of the tooth in the mouth, cavity dimensions and the amount of material loss.