Several PSs are used to achieve the antimicrobial effect during the application of aPDT, but MB and TBO have been the most commonly tested option in in vivo and in situ studies.20,23–25 In this context, it is important to analyze the absorption spectrum of the PS and the emission spectra of the light source to have an efficient photodynamic action. Guglielmi et al.10 and Steiner-Oliveira et al.,14 in one of their experimental groups, used MB and red low power LASER light source with a wavelength of 660 nm that is coincident with the absorption band of MB (610 to 660 nm).26 Araújo et al.12 also used MB, however, a halogen curing light unit was used, which emits white light that has an emission spectrum ranging between 500 and 800 nm. Melo et al.13 and Borges et al.9 used TBO and LED sources that provided the emission spectrum within the characteristic absorption range for this PS (590 to 630 nm).26 Longo et al.,11 in turn, used AlClPc and a red laser of 660 nm, which is coincident with the electromagnetic spectrum, in which the phthalocyanine group absorbs light (660 to 700 nm).26 However, Steiner-Oliveira et al.14 tested two PS s, TBO with LED and MB with a low-power laser. This study demonstrated that all therapies, including the control group, reduced the number of all tested microorganisms except for S. sobrinus, and no statistical differences were observed among the protocols. In turn, there are no differences between the LED and low-power laser parameters. For these authors, the main goal of aPDT is to perform a conservative treatment of deep caries lesions to reduce the number of microorganisms in the remaining affected dentin to avoid the need for endodontic treatment.