Illuminating the evidence: A comprehensive review of light-assisted in-office tooth bleaching

To critically synthesize evidence on the role of light sources in-office tooth bleaching, including high-power lasers, LEDs of different wavelength profiles, photocatalytic bleaching strategies, and photobiomodulation (PBM), focusing on their mechanisms, efficacy, and safety.

A narrative review was conducted using a structured and comprehensive search strategy across PubMed, Scopus, Web of Science, and selected grey literature. After duplicate removal, title/abstract screening, and full-text evaluation, 242 studies were included (predominantly in vitro and randomized clinical trials - RCT). Only in-office bleaching protocols using lasers and LEDs were included, while studies based on at-home systems, halogen, xenon lamps, and plasma devices were excluded.

Evidence indicates that investigated visible-light sources did not consistently enhance bleaching efficacy of high-concentration hydrogen peroxide (HP). Wavelength-screening experiments show that meaningful photochemical enhancement occurs within the near-UV range, which is clinically undesirable. Violet LEDs (combined with low-concentration HP (6-15%) demonstrated improved efficacy and reduced sensitivity. When paired with photocatalysts, such as TiO₂, violet LED can further potentiate gel's efficacy while maintaining biocompatibility. Further RCT are necessary to confirm these findings. PBM (660-810 nm) does not activate peroxide but may modulate pulpal inflammation, although clinical analgesic effects remain inconsistent and protocol-dependent.

Current evidence does not confirm the clinical necessity of light activation for high-concentration gels. The most promising emerging approach is the violet LED-assisted activation of low-concentration peroxide or photocatalytic systems and PMB for modulating tooth sensitivity.