EFFECT OF EXCITATION-ENERGY ON DENTIN BOND STRENGTH AND COMPOSITE PROPERTIES

A number of available dentine adhesives and dental composites require light activation for polymerization. There are many variables which af fect the light absorbing properties (e.g. bond strength) of these mate rials. The purpose of this study was to determine the influence of exc itation energy (EE) on the dentine shear bond strength (SBS) of two le ngths (2.1 mm and 3.25 mm) of light-cured (or dual-cured) dentine adhe sives/dental composites. Diametral tensile (DTS) and compressive (CS) strengths of the same composites were also studied as a function of EE . Three resin composites with their respective adhesives (Marathon One /Tenure, Z100/Scotchbond Multi-Purpose and Herculite XRV/Optibond) wer e used. Five commercial curing lights were used to produce spectra of 100-650 mW cm-2. The data were analysed using ANOVA and the Tukey LSD test. No significant correlation was observed at the P > 0.05 level be tween EE and SBS in the shorter specimens. The SBS of Optibond is inde pendent of EE and composite length. The SBS data were also analysed wi th Weibull statistics. The characteristic strengths calculated varied between 14 and 27 MPa. For the composites tested, mean values of DTS v aried between 33 and 54 MPa and CS varied between 167 and 414 MPa. The DTS and CS of Z100 were significantly greater than those of the other materials. Intensities greater-than-or-equal-to 250 mW cm-2 produced equivalent mechanical properties within all composite materials and eq uivalent bond strengths in systems which included dentine, adhesive an d composite resin.