Aim: The aim of this study was to evaluate and compare the diametral tensile strength (DTS) of 4 types of composite materials including bulk fill type (tetric evo ceram) cured with two different curing intensities.
Materials and methods: Four types of light-activated composite materials of A3 shade were selected for this study: Tetric Evo Ceram-Ivoclar Vivadent; Ceram X.mono- Dentsply; Nano Ceram-Bright-DMP; Estelite Sigma Quick-Tokuyama. Twenty specimens of each composite material were prepared: ten specimens were cured with high intensity 1200 mW/cm2 (n = 10) (high-intensity group) for 20 seconds and ten specimens were cured with low intensity 650 mW/cm2 (n = 10) (low intensity group) for 20 seconds. Specimens were prepared following the ISO 4049 and ADA/ANSI 27 Specifications in which cylindrical specimens (n = 20 of each material) of 4 mm in depth and 6 mm in diameter were prepared and stored in distilled water for 24 hours at 37°C. The DTS test was performed using the universal testing machine (Testometric/UK) with a crosshead speed of 1.0 mm/minute. The specimens were placed with their long axes perpendicular to the surface of the applied compressive load until failure. Values of the DTS in MPa were calculated and statistically analyzed by one way analysis of variance (ANOVA) and Tukey tests at 95% level of significance.
Results: The mean of DTS in the high-intensity group ranged from 38.49 to 48.79 MPa, whereas the mean of DTS in the lowintensity group ranged from 24.58 to 38.15 MPa. The p values of statistical tests were all less than 0.05. One-way analysis of variance (ANOVA) tests for DTS values of all the four composite groups cured with high intensity at 1200 mW/cm2 and for DTS values of all the four composite groups cured with low intensity at 650 mW/cm2 revealed that there were statistically significant differences (p. 0.05).
Conclusion: Within the limitations of the study we can conclude that high-intensity curing significantly resulted in higher DTS values in all the composites being tested in this study due to a better degree of conversion and composite composition also significantly influences its DTS values.
Clinical significance: Diametral tensile strength (DTS) of any restorative material is an essential test that simulates the tensile behavior of the restorative material during function in the oral cavity which is an indicator for the general strength and durability of the restoration in oral service.
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