3.1. Caries
Early and severe childhood caries is a public health problem which requires great effort from health professionals who care for children [
52]. Minimal intervention combined with knowledge about the development of dental caries has led to major transformations in the paradigm of restorative treatment, with a marked shift involving the maximum preservation of healthy dental tissue capable of remineralization [
53].
Studies evaluating PDT in eliminating bacteria related to endodontic infections have increased in recent years. PDT has decontamination rates that reach 97-100%, matching those achieved with high-power lasers. The antimicrobial effect of PDT on endodontic pathogens (P. gingivalis, P. intermedia, F. nucleatum, P. micros, P. endodontalis) has been observed both in vitro and in vivo [
39,
54,
55,
56]. PDT has shown to be effective also in reducing E. faecalis present in canals contaminated in vitro (39,57). This is a very important result since this bacterium is related to persistent and refractory endodontic infections.
PDT has shown to be a promising alternative for antimicrobial treatment, and, in this study, a technique was used to evaluate its effectiveness in the treatment of total viable bacteria, Streptococci Mutans, and Lactobacillus Spp. Molar caries lesions were treated with 0.01% MB dye and irradiated with a low-power laser (λ=660 nm; 100 mW; 320 Jcm²; 90 s; 9J). Dentin samples from the pulpal wall region were collected using micropuncture before and immediately after treatment. The results found showed statistically significant reductions in Streptococcus Mutans (1.38 log), Lactobacillus Spp. (0.93 log), and total viable bacteria (0.91 log) [
52]. However, in another study, a decrease in the bacterial cultures tested was observed, but without statistically significant differences. The authors attributed the probability of this fact to the difference in dosimetry applied in comparison with other studies, and the type of dentin substrate, which contributed to the differences between the findings of the study carried out with permanent teeth and this study, which used carious lesions in deciduous teeth (58).
S. mutans are bacteria present in the mouth and comprise 70% of the bacteria in dental plaque. Although dental caries is a multifactorial complication, S. mutans biofilms are the main cause of cavitated carious lesions. Considering the importance of this fact, Azizi et al. [
59] evaluated several intervention possibilities using chlorhexidine (gold standard) and variations in the use of light and photosensitizers. After the intervention, the number of Streptococcus was reassessed and, as a result, it proved to be an effective treatment.
Continuing the evaluation of the bactericidal effects of S. mutans, Nagai et al. [
18] formed nine experimental groups, namely, 1. 650 nm laser irradiation, 2. 940 nm laser irradiation, 3. The application of MB, 4. the application of neocyanine blue, 5. 650 nm laser irradiation with MB, 6. 650 nm laser irradiation with Azc, 7. 940 nm laser irradiation with MB, 8. 940 nm with Azc, and 9. the untreated control group. The bactericidal efficacy of each treatment examined in this study was different. The combination of PDT with MB and a 650 or 940 nm laser, as well as the combination of Azc with a 940 nm laser and MB, significantly reduced the number of S. mutans in infected dentin plaques [
18].
Twenty children between 6 and 8 years old with active caries and dentin cavitation, located on the occlusal surface of homologous deciduous molars, showed that aPTDT can be used as an additional treatment against cariogenic microorganisms, after selective caries removal, without compromising composite resin restorations. PDT was performed on selected teeth (n = 20), after selective caries removal, using an InGaAlP laser (TF Premier mm Optics) with the following specifications: wavelength 660 nm, light spectrum region red, power 100 mW, energy density 640 J/cm2, for 180 s, associated with a 0.005% methylene blue photosensitizer. The pre-irradiation time was 5 min. Then, the teeth were rinsed abundantly with water for 1 min. After treatment, there was a significant reduction in the number of microorganisms after selective caries removal (p = 0.04) and after the application of PDT (p = 0.01). The reduction in the CFU of S. mutans was 76.4% after caries removal, but when associated with PDT, it was 92.6%. After 6 months of clinical evaluation, no differences between the groups were found for retention, marginal adaptation, color, marginal discoloration, and secondary caries [
60].
Aiming to investigate the amount of bacterial destruction by riboflavin-mediated PDT around fixed orthodontic appliances using the two bacterial strains Streptococcus mutans and Streptococcus sanguinis, a total of 80 metallic brackets were divided into 4 groups consisting of 20 brackets each. Group I: riboflavin + LED irradiation; Group II: riboflavin alone; Group III: immersion in 0.2 % chlorhexidine gluconate solution; and Group IV: not subjected to any treatment. All metallic brackets were immersed in the standard bacterial solutions and incubated for 48 h. All samples were subjected to an MTT assay for microbial cell viability testing after treatment. After 24 h of incubation, biofilms which adhered on the mesh of metallic brackets after treatment were assessed using confocal laser microscopy. This laboratory investigation revealed that riboflavin-mediated PDT significantly reduced the amount of S. mutans and S. sanguinis around the orthodontic brackets [
61].
In this in vitro study, the researchers carried out the bacterial inoculation of E. faecalis in a 1% Pioktanin blue solution; in the control group, distilled water was added to the microtube. For laser irradiation, a diode laser was used (OPELASER Filio; Yoshida TradeDental Distribution Co., Ltd., Tokyo, Japan) at a wavelength of 808 nm, as well as a flexible fiber delivery system (Φ=0, 2 mm). Laser irradiation was performed with an output power of 3 W with continuous waves at 6 mm from the bottom of the 1.5 ml microtube for 10, 20, 40, 50, and 60 seconds. Controls were performed without laser irradiation and with laser irradiation for 60 seconds without Pioktanin. After irradiation, bacterial counts were performed, and greater reductions in the number of E. faecalis colonies were observed with a longer laser irradiation time compared to the control (without laser and Pioktanin). The greatest reductions were seen in the non-laser Pioktanin group compared with laser irradiation for the 10 and 20 seconds group. Diode laser irradiation in combination with PB as a PS is effective for killing E. faecalis without inducing toxicity to HDFa cells. This treatment can be useful for root canal irrigants [
17].
Lactobacillus acidophilus bacteria present in infected dentin were evaluated in this study to measure the bactericidal effects of the PDT technique with two PS: acid red (AR) and brilliant blue (BB) associated with two wavelengths of light: red and infrared. The groups were divided into two laser irradiation groups (650 nm and 940 nm), two PS groups (BB and AR), and four PDT groups (650 nm laser irradiation with BB; 650 nm laser irradiation with AR; 940 nm laser irradiation with BB; and 940 nm laser irradiation with AR and a control). The irradiation mode was set to continuous wave, the irradiation distance was fixed at 10 mm using a flexible arm, the irradiation time was 60 s, the light delivery was the actual measurement value when using the chip, the 940 laser was 0.6 W, and the 650 laser was 0.009 W. The PDT with the 650 nm laser combined with BB solution was most effective in sterilizing dentin plaques infected with L. acidophilus [
14].
Fekrazad et al. [
62] conducted a clinical trial to evaluate the effects of PDT in reducing Streptococcus mutans in children with severe early childhood caries. Twenty-two children aged 3-6 years were selected. TBO powder dissolved in sterile distilled water was used to obtain a final concentration of 0.1%, which was then kept in dark glass. The patients were treated with 10 ml of TBO (0.1mg/ml) for 1 minute and were irradiated by a light-emitting diode (LED), which emitted light at 2000 mW/cm2, with a predominant wavelength of 630 nm per 150 seconds after 10 minutes considered the pre-irradiation time. Exposure sites involved the buccal, lingual, and palatal surfaces of all teeth and the dorsal surface of the tongue, which was exposed for 30 seconds using the blunt head of the LED unit. The total energy density was 300 J/Cm2. After treatment, the S. mutans count in saliva decreased significantly after 1 hour. However, the difference in the reduction in the S. mutans counts in saliva was not significant between the baseline and 7 days after treatment.
Oliveira et al. [
63] reported a case in which they evaluated the effect of PDT on the viability of specific groups of microorganisms from the biofilms of dental microcosms on the occlusal surfaces of erupted first permanent molars. Biofilms were irradiated once with visible red-light wavelength (625 ± 30 nm) and a power density of 40 mW/cm2, using fluences of 18.75 J/cm2, 37.5 J/cm2, or 75 J/cm2, which correspond to 1.88 J, 3.75 J, and 7.50 J of total light energy. These irradiation parameters were achieved by varying the time of exposure to light (468 s, 935 s, and 1870 s). Then, the biofilms were immediately washed in CPW medium and kept in the dark until sonication. In this study, PDT promoted a significant reduction in microorganisms, with a trend towards a dose-dependent effect.
Carvalho et al. [
64] presented a case report of a 9-year-old female patient with deep caries in the lower right first molar who was treated with PDT to neutralize the remaining bacteria. Papacarie Duo® (PD) and PDT were combined. After the application of Papacarie Duo®, the carious tissue was carefully removed as the cavity was stained for 1 min with rose Bengal solution, irradiated with high-intensity LED constituting the PDT technique, and definitively restored with composite resin. At the 6-month follow-up, there were no signs of caries, showing the success of the applied techniques. Although it achieved excellent clinical and bacterial reduction results, the approach took an excessive amount of time to manage the carious lesion.
With the aim of evaluating the use of PDT as an adjuvant in the minimally invasive treatment (partial removal) of primary carious tissue, Ornellas et al. [
65] recruited 18 children aged 4 to 5 years with primary molars with active lesions of deep caries. The treatment was performed with 100 μg mL-1 of MB solution for 5 minutes, and then irradiation took place with a low-power laser emitting red light (InGaAIP-gallium–indium aluminum phosphide; with a wavelength of 660 nm; 100 mW; 300 J cm of 2; and 9J of energy). After treatment, there was a microbial reduction that varied from 69.88% to 86.29% and was significantly observed for total microorganisms, streptococci mutans, Streptococcus spp., and Lactobacillus spp. The authors concluded that PDT presents a promising future for clinical use as an adjuvant for the reduction in microorganisms in all types of dentins.
A randomized clinical trial included 108 homologous permanent mandibular first molars [
36,
46] with biofilm from 54 children aged 6 to 12 years. PDT was performed (0.01% PS MB/therapeutic laser-InGaAIP), according to the following protocols: group 1: the collection of biofilm from the distal area of the lingual surface 36 µm before PDT; group 2: the mesial area of the lingual surface of 36 µm 1 min after PDT; group 3: the lingual surface area of 46 µm before PDT; and group 4: the mesial area of the lingual surface of 46 µm 5 min after PDT. The authors concluded that pre-irradiation reduced the number of colony-forming units of mature bacterial biofilms in vivo. A time of 5 min resulted in a greater reduction in the number of colony-forming units (70).
Faria et al. (66) carried out a clinical study to evaluate the clinical performance of composite resin restorations in deciduous molars submitted to selective caries removal associated with PDT. The primary molars of patients aged 6 to 15 years with deep carious lesions, without signs and symptoms of pulpal involvement, were included in the study. After treatment, the authors concluded that the marginal adaptation of resin restorations in deciduous molars was positively affected by PDT after 12 months of follow-up.
Nassaj et al. [75] evaluated the effect of PDT with a different PS on the microleakage of composite resin restorations. Seventy-two deciduous teeth with sound labial/buccal and lingual surfaces were collected for this study. The teeth were randomly divided into four control groups: PDT with indocyanine green, PDT with MB, PDT with TBO, and the control group. No significant difference was observed in the microleakage between the groups on the occlusal wall. However, there was a significant difference in the cervical wall between the control and TBO groups and the control and MB groups. There was a significant difference in the microleakage between the occlusal and cervical walls within each group. The authors conclude that PDT can be used in cavities with enamel margins to decrease the microbial load and prevent secondary caries, but PDT is not recommended for cavities with cementum margins. Alternatively, it can be performed with indocyanine green as a photosensitizer in these cases.
3.5. Endodontic Treatments
Based on previous studies, Okamoto et al. [
69] performed a comparative study of endodontic treatments in deciduous teeth for two groups that were randomly allocated: group I involved patients undergoing conventional endodontic therapy (n = 15), and group II included patients submitted to conventional endodontic therapy combined with PDT (n = 15). The chosen photosensitizing agent was MB (concentration of 0.005%), which was applied inside the canal with a sterile paper cone for 3 min, followed by irradiation of laser light for 40 seconds (wavelength: 660 nm, density energy: 4 J/cm², power: 100 mW), delivered in direct contact at the root canal entrance. Clinical follow-up investigating fistulas and mobility was performed at 1 and 3 months after endodontic treatment. The reduction in the bacterial load was 93% in group I and 99% in group II, with no statistically significant difference. Conventional treatment combined with antimicrobial PDT with the parameters used in this study proved to be effective, but it showed an equal efficacy to conventional endodontic treatments alone.
Okamoto et al. [
66] performed a series of cases with the aim of testing the combination of conventional endodontic therapy in primary teeth with PDT. Five deciduous anterior teeth were evaluated in healthy children aged 3 to 6 years, regardless of their race or ethnicity, with a diagnosis of pulpal necrosis due to caries, in conditions to be restored, and with at least 2/3 of the root remaining. The 0.005% MB solution was inserted into the root canal for three minutes. After three minutes, the paper tips were removed, and the laser was applied with radiant exposure of 4J/cm2, an output power of 100mW, and a low-power laser emitting ʎ = 660 nm for 40 seconds, leaving the laser tip active in contact with the canal. In this study, no optical fibers were used. The results obtained in this series of cases showed a bacterial reduction from 37.57% to 100%. The authors concluded that PDT can be considered an easy-to-apply alternative that does not generate microbial resistance, to act as a support in the decontamination of root canals.
Another case report described the impact on the quality of life and oral health, after endodontic treatment associated with PDT, in the traumatized deciduous teeth of a 4-year-old female patient who was assisted in a Dental Trauma Care Program considering a period of 12 months of follow-up. The 4-year-old child had discolored teeth, as he had fallen from his own height. The channel was filled with 0.01% MB dye as a photosensitizer for 5 minutes. Then, a laser fiber, with a wavelength of 660 nm, 100 mW, and 120 J/cm 2 4 J, was introduced into the apical portion of the root canal, moving from apical to cervical to ensure the equal diffusion of light into the lumen of the root canal channel for 90 seconds. The child was very pleased with the result. The clinical and radiographic findings during the 12-month evaluation period showed the absence of a radiolucent area in the periapical region with new bone formation, and the restorations were perfectly adapted. The association of PDT with a conventional endodontic treatment was effective in this case. It allowed the regression of the sinus tract and the formation of new bone. Furthermore, this case report emphasizes the need for and importance of monitoring cases of dental trauma in pediatric dentistry clinics [
70].
Silva et al. [
71] investigated the action of PDT in controlling pain after endodontic treatment in asymptomatic teeth with a primary infection in a single visit. Sixty single-rooted teeth with pulp necrosis and periapical lesions were selected and randomly divided into two groups (n=30) according to the protocol: a control group and a group undergoing PDT. The PDT consisted of 0.005% MB as a photosensitizer, using a AsGaAl diode laser, with a wavelength of 660 nm, 100 mW of power, and 9 J of energy, and optical fibers which were 365 μm in diameter. There was a statistically significant difference in the periods of 8, 12, 24, 48, and 72 hours between the control group and the PDT group. It is concluded that PDT had a significant effect on decreasing post-endodontic treatment pain in teeth with pulp necrosis and asymptomatic periapical lesions.