Depths of cure and effect of shade using pulse-delay and continuous exposure photo-curing techniques

This study investigated the extent of cure (monomer conversion into polymer) of a variety of photo-initiated resin composites and different shades. Cure values were measured at the top surface and at simulated lighting conditions 0.5, 1.0 and 2.0 mm below the top. The exposure methods used were continuous output at 600 mW/cm2 (10, 20 or 40 seconds), initial component of the pulse-delay technique (pulse) (3 seconds at 200 mW/cm2) and the entire pulse-delay technique (pulse, 3-minute delay, 10 seconds at 600 mW/cm2). The results showed very little difference in conversion values between A2 and D2 shades of the same composite with respect to depth. Conversion values using only the pulse method were remarkably low at the top surface and diminished rapidly at depths. Conversion using the pulse-delay technique produced similar values as that of the continuous 10-second exposure at similar depths but still decreased remarkably at depth. Conversion values using the pulse-delay technique and a 20-second continuous exposure were significantly lower than those obtained using continuous 40-second exposure.