Resistance of Resin-Bonded Ceramic Endocrowns of Different Intracoronal Depths

This in-vitro study was conducted to assess the fracture resistance of resin-bonded ceramic endocrowns with different designs at varying intracoronal depths.

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.

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.

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.