The Effect of Novel Laser-Activated Bleaching Protocols on the Color Change of Non-Vital Anterior Teeth: An In Vitro Study.

Objective:  This study compares the color change of non-vital anterior teeth after laser-activated bleaching and conventional walking bleaching technique.

Materials and methods:  Sixty extracted teeth were endodontically treated, stained in a black tea solution, and the baseline shade was measured using a spectrophotometer (Easyshade, VITA). Bleaching was done using either: internal bleaching with 35% H₂O₂ (Opalescence Endo) and then tooth sealed for 5 days (Gr1), 35% H₂O₂ (JW Next) for 7 minutes (Gr2), internal and external bleaching for 7 minutes (Gr3), diode laser-activated internal bleaching for 30 seconds (940 nm, continuous wave, 2 W, noncontact mode, 300 um, non-initiated tip), wait for 7 minutes, second laser application for 30 seconds, tooth sealed for 5 days (Gr4), diode laser-activated internal bleaching for 24 hours (Gr5), or diode laser-activated internal and external bleaching for 24 hours (Gr6) (n = 10). The color change (ΔE₀₀) was measured and data were analyzed using one-way analysis of variance followed by Tukey post hoc test (a = 0.05). The inner dentin of the samples was inspected using scanning electron microscopy.

Results:  All the tested bleaching techniques were able to change the color. All the laser-activated bleaching protocols, namely, Gr4, Gr5, and Gr6, showed higher mean ΔE₀₀ values than the non-laser-activated bleaching Gr2 and Gr3 (p < 0.05) and were statistically similar (p > 0.05) to the control group Gr1. Laser-activated bleaching caused surface modification and dentinal tubule opening.

Conclusion:  All the tested laser-activated bleaching protocols showed faster and more efficient color change, comparable to the conventional 5-day walking bleaching protocol.