PSI - Issue 79

Mays H. Udah et al. / Procedia Structural Integrity 79 (2026) 53–64

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Fig. 7. Stress distributions and the expected initial crack's location for filling Filtek Z250: (a) square filing shape; (b) round filling shape

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Fig. 8. Stress distributions and the expected initial crack's location for filling IPS-Empress: (a) square filing shape; (b) round filling shape

The results indicate that fracture formation in the square-shaped cavity occurred at a stress level of 5324.8 MPa, whereas in the round-shaped cavity, the fracture stress was 7215.2 MPa. Despite the difference in stress values, the fractures formed at nearly the same location in both cases. This suggests that the shape of the tooth hole has a significant impact, with the round shape providing better performance compared to the square shape. In contrast, when the optimal filling, Filtek Z250, was used (as shown in Fig. 7), no fractures were observed in either the round or square cavities. These findings confirm that the ANSYS results strongly support the arrangement of fillings based on their performance. The results further demonstrated that Filtek Z250 experienced stress levels far below the fracture threshold. In contrast, the square cavity showed signs of stress concentration at one of the sharp corners, reinforcing the conclusion that the round shape performs significantly better than the square shape. 3.2. Load effect In the second analysis, crack initiation and propagation in dentin under different loading conditions were simulated. The force was applied at three different levels to study the effect of force variation on crack growth. The analysis revealed that both crack length and growth increase with increasing force (Table 3). When a normal biting force of 400 N was applied to the tooth, the crack length measured 0.518 mm. Increasing the force by 53% resulted in a 100% increase in crack length, while a 25% reduction in the applied force led to an 11.8% decrease in crack length. Loading at a 45-degree angle produced crack growth results that more accurately reflect real-life conditions compared to distributed vertical loading, see Fig. 9.