Effect of irradiation time on tensile properties of stiffness and strength of composites

Purpose. We compared the effect of irradiation time on the diametral tensile strength and stiffness of three visible light-cured composites. The sensitivity of the two mechanical properties to differentiate between the materials was also investigated. Material and methods. Cylindrical specimens of three composites were cured for 20, 40, 80, and 120 seconds (n = 10) and loaded up to failure in a diametral tensile strength test. Stiffness and diametral tensile strength values were recorded. Results. Irradiation time significantly influenced diametral tensile strength ( p = 0.0017) and stiffness ( p = 0.0002). With the same irradiation times the three tested materials demonstrated no significant difference when diametral tensile strength was studied ( p = 0.31). However, stiffness values did show a significant difference ( p = 0.0002). Conclusions. This study found that stiffness is more sensitive in disclosing differences in tensile properties between the materials than diametral tensile strength. (J Prosthet Dent 1997;77:471-4.).