Method: To strain gauge test, 10 MP were analyzed in sequential phases: S - sound, L0.5 - initial lesion (0.5 mm deep), L1 - intermediate lesion (1.0 mm), L1.5 -final lesion (1.5 mm), and LR - lesion restored. Two load applications were used: inner load (IL) and outer load (OL). The same groups were reproduced in experimental testing and a quantitative/qualitative finite element analysis was carried out to determine the maximum principal stress (σ1). The S, L1.5, and LR groups were tested for fracture resistance and fracture pattern analysis. The analysis statistics were performed using ANOVA, followed by Tukey’s test (P <0.05).
Result: The two-way ANOVA (2x5) showed that the factor loading and lesion showed significance (P<.05). The Tukey test (P<.05) demonstrated that specimens of the L1.5 group showed higher strain values and a statistically significant difference when compared with other groups for both types of loading. Regarding the load application, the OL showed a statistically significant difference for all groups when compared with the IL. The loading was critical in generating tension-stress, and the outer loading was responsible for higher strain values. The most concentrated damage increased stress at the depth of the lesion.
Conclusion: The restoration is able to restore a complex biomechanical stress distribution close to the sound tooth. The extent of damage and loading influenced the stress distribution, strain, and fracture resistance of samples. The L1.5 group exhibited higher strain values, the highest stress concentration, and more severe fractures. The outer loading seems to be more critical in the biomechanical behavior of MP.