## 4 Discussion
evaluated endocrowns on anterior teeth rather than molars. [PERSON] et al. [33] found higher mean values (1368.77 \(\pm\) 237.34 N) but with more catastrophic failures (70% (than the present study (44%). [PERSON] et al. [65] found higher mean values (1618.3 N \(\pm\) 585 N) using zirconium lithium silicate blocks than those seen with lithium disilicate used in the current study. [65]. [PERSON] et al. [44] demonstrated the more favorable failure mode of composite endocrowns compared to lithium disilicates, even though the latter exhibited higher mean fracture resistance values (3320.35 \(\pm\) 961.21 N). This could be attributed to the composite material's bending under load and its elastic modulus resembling dentin. [PERSON] et al. concluded that CAD/CAM composite material exhibited higher fatigue resistance than lithium disilicate [66]. On the other hand, [PERSON] et al. [67] found lithium disilicate endocrowns to be more durable under lateral loading than composite. This could be explained by the results of stress concentration findings from a finite element analysis (FEA) study by [PERSON] et al. comparing endocrowns fabricated from different materials [68]. The statistical test used, in the current study, was the non-parametric Mann-Witney U-test, because it is like the independent sample t-test but for small sample size studies [69]. That test yielded a non-significant comparison, a _p_-value > 0.05. Another run using the _t_-test yielded a non-significant comparison between the independent variables, a _p_-value > 0.05. An independent sample T-test would have been used if the availability and number of tested specimens was large enough. The agreement between the evaluators to assess the specimens for the presence of fracture line involvement in endocrown/tooth structure after the fracture resistance test was minimal. However, even after the discussion, each evaluator could identify cracks the other evaluator did not notice at the first evaluation. Evaluating the fracture directly by visualizing the coronal and radicular portion of the tooth is essential and crucial. Although, it is sometimes difficult to apply that clinically without using other sophisticated diagnostic tools such as cone beam computed tomography radiographs (CBCT), transilluminators, microscopes, direct vision (exploratory flap/surgery), and staining dyes to trace. The agreement between the two evaluators regarding the number and the separation of pieces after fracture was moderate agreement. During the evaluation, two of the samples were separated after removing the root socket for the second evaluator to examine them visually, which might lead to the slight difference between the two evaluators' agreement with the reference observation. The agreement between the two evaluators regarding the fracture direction was weak agreement. This is probably due to visualizing the fracture using magnifying loupes and agreement on terminologies and classifications. The divergence between the evaluators, regarding the catastrophic or non-catastrophic rating, was mainly because the way each evaluator examined the failure mode initially and independently before reaching the consensus in the second stage. Therefore, the agreement was better before and after the consensus for evaluator two than the first evaluator, because evaluator two had another chance to examine the specimen in the same way he did before. Evaluator one had a first chance without full examination of the specimen, and a second chance with the direct examination of the specimen in question. Thus, the differences and divergences in the agreement originates. The study's results showed that the extension of the proximal box in the endocrown design did not influence fracture resistance. Furthermore, the fracture load was higher than the average maximum biting forces [70,71]. Previous studies utilized different methods for ensuring the seating of indirect restoration during cementation: finger pressure, control static loading using the universal testing machine, or not mentioned [15,21,23,32].