Purpose: This in-vitro study was conducted to assess the fracture resistance of resin-bonded ceramic endocrowns with different designs at varying intracoronal depths.
Materials and Methods: Forty-eight (n = 48) extracted mandibular first molar teeth were randomly divided into four groups (n = 12). In the control group, the specimens remained untreated. Whereas the specimens in the test groups A, B, and C were decapitated 2 mm above the cementoenamel junction (CEJ) and endodontically treated. The test groups were prepared with a butt-joint design in a standardised manner with varying intracoronal depths. Groups A, B, and C were prepared to receive lithium disilicate endocrown with intracoronal cores at 0 mm, 2 mm, and 4 mm, respectively. Crowns were fabricated as a non-anatomical design with a thickness of 3 mm. After ceramic bonding procedures, specimens underwent thermocyclic ageing prior to the fracture resistance test. Specimens were loaded at a 15-degree angle using the Universal Testing Machine and the failure modes were observed. One-way analysis of variance (ANOVA) and Chi-square were utilised for data statistical analyses.
Results: Significant statistical results in fracture resistance tests were found in all experimental groups. The highest load was found in group B, followed by group C, and lastly group A (P 0.05). Although endocrowns with no extension had the lowest fracture resistance, they showed a favourable cohesive failure with statistically no significant difference from the control group.
Conclusion: In bonded ceramic endocrowns, the fracture resistance is not newcessarily proportional to the intracanal depth. The intrcoronal cores of 4 mm did not show the highest fracture resistance, and their mode of failure was catastrophic compared to endocrowns with no intracoronal extensions.