Tooth Whitening or Bleaching to Optimise the White Colour of the Teeth in Orthodontics?

The increasing demand for better dental aesthetics has driven the development of tooth-whitening techniques that are effective while reducing invasiveness. Hydrogen peroxide (HP) and carbamide peroxide (CP) continue to be the most common active ingredients in bleaching products. Various types of light and laser activation have been introduced to speed up the bleaching process and decrease clinical application time. However, published results regarding their effectiveness and biological safety are inconsistent and sometimes contradictory. Aim: The objective of this study was to identify irradiation conditions that optimise the whitening performance of peroxide-based bleaching agents while ensuring safety for dental hard tissues and ocular structures. This objective was achieved through a systematic synthesis and meta-analyses of both experimental and clinical evidence on bleaching techniques, light or laser activation, and related treatment outcomes. Additionally, the study aimed to provide an integrated overview of currently used irradiation technologies, bleaching agents, treatment protocols, and relevant safety considerations. Methods: A multi-stage analytical approach was employed. Evidence was collected from systematic reviews, randomised and non-randomised clinical trials, and laboratory-based in vitro investigations. The studies assessed differences in bleaching agents (HP and CP), their concentrations, and application protocols, as well as various activation systems, including halogen lamps, conventional LEDs, violet LEDs, metal–halide lamps, and laser wavelengths such as visible blue (~440 nm), red or near-infrared (~1.7 µm), and other spectral ranges. Extracted outcome measures included tooth colour improvement (ΔSGU, ΔE), incidence of tooth sensitivity, changes in enamel surface morphology, temperature increases in the pulp chamber, and the bond strength of restorative or orthodontic materials. When methodological compatibility permitted, quantitative synthesis and meta-analysis were conducted to estimate the effects of activation modalities and irradiation parameters. Results: Analysis of data from 28 systematic reviews and numerous clinical and laboratory studies showed that the degree of colour improvement did not consistently rely on peroxide concentration or on whether bleaching was performed in-office or through home-based protocols. In most studies, adding light activation did not produce a clearly superior whitening effect compared to chemically driven bleaching alone. However, certain laser-assisted methods—especially those using blue diode lasers around 440 nm or near-infrared diode lasers near 1.7 µm—were linked with faster whitening responses and, in several in vitro experiments, fewer enamel surface irregularities. Increases in pulp temperature remained below the generally accepted safety threshold of 5.5 °C in the reported experimental conditions. While laser activation reduced treatment time, some studies observed a temporary decrease in the bond strength of orthodontic brackets following bleaching. Photobiomodulation techniques seem promising for reducing post-treatment sensitivity, although more robust clinical evidence is still needed. Conclusions: Targeted activation with diode lasers, especially within the blue and near-infrared spectral ranges, may speed up the whitening process and potentially minimise structural changes to enamel when irradiation parameters are carefully managed. Despite these positive findings, current clinical evidence remains limited. Well-designed randomised controlled trials with standardised treatment protocols are essential to determine the best wavelengths, energy delivery settings, and safety limits for laser-assisted dental bleaching.