FRACTURE RESISTANCE OF ENDOCROWNS WITH DIFFERENT CAVITY DESIGN AND BASE MATERIALS IN MOLARS: AN IN VITRO STUDY

Objective: The present study tested the fracture strength and fracture mode of endocrowns of mandibular molars with
conventional and anatomical preparations using EverX Posterior, Smart Dentin Replacement® Plus Bulk Fill
Composite, and ceramic extension (central retainer).
Materials and Methods: Sixty intact recently extracted human mandibular third molars were en- dodontically treated
and were assigned to two main groups according to the preparation design: standard (conventional) and modified. The samples in each group were further divided into three subgroups (n=10) according to the material used as the base: fiber-reinforced composite (EverX Posterior), bulkfill flow-able composite (SDR), and ceramic extension.
Thermocycling (between 5°C and 55°C/1500 cycles) was performed on all specimens. Following which fracture load
was tested using a universal testing machine and the amount of maximum load on failure (Newton) was recorded.
Failure types were examined using a stereomicroscope and categorized. Data were subjected to one-way ANOVA
followed by Tukey’s post-hoc test for determination of statistically significant differences (p < 0.05).
Results: The significant test results showcased Conventional preparation methods having a higher mean than its
modified counterparts. Also, significantly between the material used Ever X poste- rior was the toughest with an
average fracture resistance of 2913N, followed by SDRbeing tougher than Ceramic. For the failure modes the most
common failure type was V. Between the two prep- aration methods, conventional samples had a significantly higher
chance of resulting in a Type I failure.
Conclusion: Conventional cavity preparation configuration produces a higher mean fracture re- sistance value it was,
however, significantly higher in comparison to the modified preparations. EverX Posterior was the most resistant base close to ceramic and resistant compared with SDR. Regarding the failure modes, conventional preparations presented a higher risk of Type I failures. These results demonstrate that preparation design and material selection are each of primary im- portance in maximizing fracture resistance and determining the characteristic of failure in restora- tions.