EFFECT OF IRRADIATION TIME ON TENSILE PROPERTIES OF STIFFNESS AND STRENGTH OF COMPOSITES

Purpose. We compared the effect of irradiation time on the diametral t ensile strength and stiffness of three visible light-cured composites. The sensitivity of the two mechanical properties to differentiate bet ween the materials was also investigated. Material and methods. Cylind rical specimens of three composites were cured for 20, 40, 80, and 120 seconds (n = 10) and loaded up to failure in a diametral tensile stre ngth test. Stiffness and diametral tensile strength values were record ed. Results. Irradiation time significantly influenced diametral tensi le strength (p = 0.0017) and stiffness (p = 0.0002). With the same irr adiation times the three tested materials demonstrated no significant difference when diametral tensile strength was studied (p = 0.31). How ever, stiffness values did show a significant difference (p = 0.0002). Conclusions. This study found that stiffness is more sensitive in dis closing differences in tensile properties between the materials than d iametral tensile strength.