###### Abstract  
Laser-activated tooth bleaching is discussed as a means to optimize results, while minimizing adverse side effects, but it lacks consensus in the scientific literature. Therefore, this systematic review aims to evaluate the protocols and outcomes of laser-activated vs. non-activated bleaching methods for safe and effective approaches. The PubMed, Cochrane, Scopus, ScienceDirect, and Google Scholar search engines, with the following MeSH terms and keywords: (bleaching OR whitening) AND laser AND (tooth OR dental OR enamel OR dentine), were used to identify human clinical trials and in vitro studies regarding laser-activated dental bleaching. After applying the keywords and additional filters, and inclusion and exclusion criteria, the final number of included articles was 19 clinical and 20 in vitro studies. Laser activation yielded no significant color improvement, but reduced gel contact time (10 min). Laser-activated bleaching required 24% less hydrogen peroxide (HP) concentration to achieve similar results. Additionally, there were no significant differences in terms of sensitivity and hard tissue alterations between the laser-activated and conventional groups. The benefits associated with laser-activated bleaching render it a compelling option. Nevertheless, a comprehensive evaluation of bleaching gels and activation protocols is imperative. Ultimately, this analysis provides clinical guidance pertaining to the facilitatory employment of laser irradiation. bleaching; dentistry; laser; light; parameters; sensitivity; systematic review; tooth color; tooth whitening +
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the oxidation of the organic enamel matrix can contribute to the treated teeth acquiring a more \"opaque\" appearance [10]. The whitening effects outlined above may be accelerated through the implementation of various methods, including the use of higher concentrations of HP, an extended bleaching duration, the application of heat, and activation through light or laser systems [11]. By employing these techniques, it becomes possible to achieve higher levels of HP penetration into the dental tissue, a process consequently leading to an improved bleaching outcome [11]. In particular, the application of light or lasers during bleaching episodes has been described in the literature as a means to decrease patients' chair time, and, more importantly, to minimize the contact time of these potentially toxic agents with dental tissues [1]. The main distinction between broad-band light and laser applications lies in the fact that ordinary light sources emit a broad spectrum, multi-wavelength photonic energy, compared to the monochromatic light characteristic of lasers [4,12]. However, this difference may constitute a higher risk of potential thermal damage with ordinary light sources [12]. In view of the transparency of HP to visible and near-infrared laser light commonly used in clinical practices, coloring agents are incorporated as absorbers within the bleaching gel to induce specific photothermal effects, resulting in increased ROS generation and improved color outcome [4]. This approach also mitigates heat-related risks to dental pulp [4,11,13]. Notably, a 10 \({}^{\circ}\mathbb{C}\) temperature increase within the bleaching agent approximately doubles the rate of chemical reactions, leading to faster ROS reactions, and hence more rapid interaction with pigmented molecules within the teeth [1,4,6]. Furthermore, in terms of the photochemical effects (photodissociation), an activation of HP through direct excitation is exclusively achievable through irradiation with high-energy photons, since its dissociation energy is determined to be 2.02 eV [4,14]. Photonic energy and emission wavelength are inversely related, and therefore laser systems in wavelength ranges below 614 nm are capable of inducing this reaction [4,14,15].