# Effectiveness of Laser-Assisted Teeth Bleaching: A Systematic Review
###### Abstract
For instance, while natural teeth can exhibit significant color change, resin composites may experience limited or uneven color modification, which can lead to esthetic discrepancies between natural teeth and restorations. Resin composites, due to their organic matrix, are particularly susceptible to adverse effects from tooth whitening treatments. The oxidative hydrolysis induced by peroxides at the C-C bonds of the polymer matrix can lead to the degradation of the composite resin, causing discoloration, a loss of gloss, and structural weakening [4]. The integrity of the resin matrix can be compromised, leading to potential issues such as increased porosity and reduced bonding strength. Additionally, studies have found that repeated exposure to bleaching agents can exacerbate these issues, causing the progressive deterioration of the composite material over time. Some research also indicates that certain types of composite resins are more resistant to bleaching effects than others, suggesting that material composition and formulation play a significant role in the response to whitening treatments [8]. To address these concerns, it is essential to carefully select restorative materials that are compatible with whitening agents and to consider alternative or supplementary whitening strategies that minimize the impact on dental restorations. The mechanisms behind laser-assisted tooth bleaching can be divided into two basic methods: photothermal and photochemical reactions (Figure 1). In the photothermal method, the laser acts as an activator and enhancer for the bleaching agent, typically hydrogen peroxide (HP) or carbamide peroxide (CP). The laser's energy increases the rate of the chemical reactions involved in the bleaching process by heating the bleaching agent, which enhances its effectiveness. This method can lead to the more efficient breakdown of chromogenic compounds and accelerated whitening [2; 9]. In the photochemical method, laser light is absorbed by the bleached surfaces and directly induces the photooxidation of the chromogenic macromolecules. The energy from the laser light interacts with the pigment molecules, causing a chemical reaction that breaks down the color-producing compounds, resulting in a lighter shade of the tooth [10; 11]. This method leverages the laser's ability to generate reactive oxygen species that interact with and degrade chromogenic molecules. Each laser used in these procedures is characterized by several critical parameters: the wavelength of the emitted light (measured in nanometers, nm), the power density of the beam (measured in watts per square centimeter, W/cm\({}^{2}\)), and the type of energy emitted--whether pulsed or continuous [12; 13]. Additional features include the pulse rate and pulse duration, which influence the overall effectiveness and safety of the procedure [2; 9; 10; 11]. The choice of laser parameters can significantly affect the outcome of the bleaching treatment, as different wavelengths and power settings can result in varying levels of effectiveness and risk. The energy emitted by a laser must be meticulously controlled during in vivo tooth bleaching, as part of the beam is converted into heat. Excessive heat can increase the temperature of the tooth structure and the surrounding soft tissues, potentially leading to pulp damage, thermal injury, or discomfort [14; 15]. Effective cooling mechanisms and the precise calibration of laser settings are essential to mitigate these risks and ensure the safety of the procedure [16; 17]. The aim of this systematic review was to evaluate the role of laser-assisted teeth bleaching, considering its effectiveness on both dental restoration materials and natural teeth. After analyzing articles related to the use of laser irradiation to support the bleaching process, it was determined that a systematic review of this subject is justified. Currently, no systematic review on this topic has been published.