# Effectiveness of Laser-Assisted Teeth Bleaching: A Systematic Review
## 4 Discussion  
In this systematic review, we aimed to evaluate the efficacy of various laser wavelengths in bleaching procedures used for both natural teeth and restorative materials in comparison to traditional methods. Our findings suggest that laser-assisted bleaching can enhance the whitening effect for both natural teeth and dental restorative materials. A diode laser, with wavelengths ranging from 808 nm to 980 nm, was the most frequently utilized laser in these studies. [2; 33; 4; 5; 7; 9; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46; 47; 48; 49; 50; 51; 52; 53; 54]. Ten studies employing a diode laser concluded that its use enhances the whitening effect [53; 55; 38; 40; 42; 43; 48; 52; 53; 38]. Interestingly, it was observed that when using 35% hydrogen peroxide, the best whitening effects were achieved with a laser power of 1.5 W, regardless of whether the wavelength was 810 nm, 940 nm, or 980 nm [55; 56; 37]. For higher and lower power values, the results were not significant [55; 37]. Three papers focused on the laser-assisted bleaching of restorative materials. However, the differing methodologies and various variables assessed in these studies create difficulties in comparing the results. The use of the Nd:YAG laser for whitening non-vital teeth has proven to be as effective as 810 nm and 980 nm diode lasers [33]. Moreover, the results of two studies by [PERSON] et al. [10] and [PERSON] et al. [55] demonstrated the effectiveness of ErCr:YSGG laser whitening with the application of 35% hydrogen peroxide. Among the included papers, there were significant differences regarding the rationale for using laser-assisted activation in whitening procedures. [PERSON] et al. [3] reported that irradiation with an 808 nm diode laser combined with blue and violet LEDs increased whitening efficiency. In contrast, [PERSON] et al. [9], who added a violet LED to an 810 nm diode laser, found that the effect was no different from using 35% HP without activation [3; 9]. [PERSON] et al. [38], [PERSON] et al. [40], and [PERSON] et al. [5] agreed that diode lasers with wavelengths of 810 and 940 nm not only shortened the whitening time but also reduced post-treatment sensitivity. [PERSON] et al. [55] achieved a better whitening effect by activating 35% HP with an Er:YAG laser than with a 940 nm diode laser, but the difference in the \(\Delta\)E was less than 1, which means that it was not visually noticeable. However, according to [PERSON] et al. [55], it is still worth using the Er:YAG laser if the teeth require restoration after whitening, because they observed a better adhesion of materials to the whitened surfaces. However, the studies of [PERSON] et al. [67] show that the Er:YAG laser leads to damage of the enamel surface. [PERSON] et al. [64] used this laser for the intracoronoduticaly treated teeth. A better effect is visible here than in the walking bleaching technique using 20% HP. [PERSON] [68] wrote that heating 30% HP promotes the development of external cervical resorption; the question arises as to whether the use of 20% HP with an Er:YAG laser will result in a lower risk of this common complication. Other lasers discussed in this review include argon, Nd:YAG, and KTP lasers. The analysis of the compiled results indicates that the argon laser produced the least effective outcomes. Despite using bleaching agents such as 35% HP and 37% CP and a laser wavelength of 488 nm, its effect was not significantly visible. This may indicate insufficient laser power, meaning that it does not contribute to permanent enamel discoloration [62]. Other lasers, such as AsGaAL, Nd:YAG, or KTP lasers, did not show a better effect than the diode laser [1; 33; 48; 53; 59; 60; 61]. However, it is worth noting that, according to some studies, the KTP laser performs better on tea or fruit stains compared to the diode laser. This may indicate its superiority over the diode laser, as the spectrum of discolorations it affects appears to be somewhat broader [53]. Another important aspect is the irradiation time of the bleached surface.