Efficacy of tooth bleaching with and without light activation and its effect on the pulp temperature: an in vitro study.

The aim of this in vitro study was to evaluate the colour stability of bleaching after light activation with halogen unit, laser, LED unit or chemical activation up to 3 months after treatment. Four groups of teeth (n = 20) were bleached with Opalescence Xtra Boost (38% hydrogen peroxide) using four different methods: activation with halogen, LED, laser or chemical activation only. All teeth were bleached in one session for four times (4 × 15 min) and the colour was evaluated using a spectrophotometer at the following time points: before bleaching, immediately after bleaching, 1 day, and 1 and 3 months after the end of bleaching. Between the tested time points, the teeth were stored in 0.9% NaCl solution. Additionally, the temperature increase in the pulp chamber was measured using a measuring sensor connected to a computer. Bleaching with the halogen unit showed the highest colour change. Halogen unit, laser and chemical activation resulted in whiter teeth after 1 and 3 months compared to the colour after the end of the bleaching procedure (p ≤ 0.05). Three months after the end of bleaching, the shade changes observed were-halogen: 7.1 > chemical activation: 6.2 > LED: 5.4 > laser: 5.2. Halogen showed the highest temperature increase (17.39°C ± 1.96) followed by laser (14.06°C ± 2.55) and LED (0.41°C ± 0.66) (p < 0.0001). Chemical activation did not affect the temperature in the pulp chamber. The use of light activation did not show any advantages compared to chemical bleaching. Although halogen unit showed the higher shade's change, its use resulted also in the higher pulp temperature. According to the present findings, light activation of the bleaching agent seems not to be beneficial compared to bleaching without light activation, concerning the colour stability up to 3 months after bleaching and the pulp temperature caused during the bleaching procedure.