Effect of Light Activation of Bleaching Agent on Whitening Efficacy and Intra-Pulpal Temperature Rise

Objectives: To evaluate the effects of laser and LED lights, used for bleaching, on intra-pulpal temperature rise and shade enhancement.
Methods: Fifty extracted human premolars, cleaned and sectioned from mid-root area, were divided into 5 groups (n=10): group 1 (No light activation), group 2 (continuous 3 mins LED light activation), group 3 (intermittent LED light activation), group 4 (980 laser activation), and group 5 (980 laser activation). The intra-pulpal temperature rise was measured with a thermocouple. The mean temperature was recorded before and after bleaching. Improvement in the shade (ΔE) was recorded before and after 24 hours of bleaching.
Results: Increased intra-pulpal temperatures were seen after treatment with the laser 810 (p<0.001). The remaining four groups exhibited comparable increases in intra-pulpal temperature. The time to reach highest intra-pulpal temperature (Tmax) was shortest for the laser 810 group (p<0.03) and was comparable among the remaining groups. The ΔE in all samples was more than the perceptibility ΔE threshold difference of 1-2. ΔE was highest for the laser 980 and laser 810 groups (4.5 and 5 respectively).
Conclusions: The heat generating light units (LEDs and lasers) resulted in shade improvement. However, a sharp rise in the intra-pulpal temperature was observed with both the LED and laser 810. The laser 980 provided maximum shade enhancement with a slower and less pronounced intrapulpal temperature rise. The use of light potentiating heat in tooth whitening procedures may result in shade improvement with caution of intra-pulpal temperature elevation that can be harmful to the dental pulp.