Destruction of cariogenic biofilms by antimicrobial photodynamic therapy mediated by phycocyanin and toluidine blue along with sodium fluoride varnish or titanium tetrafluoride

OBJECTIVE

Evaluation of the effect of phycocyanin (PC) and toluidine blue (TBO) along with sodium fluoride varnish (FV) or titanium tetrafluoride (TiF4) under the conditions of antimicrobial photodynamic therapy (PDT) on a dual-species cariogenic biofilm and on remineralization process.

DESIGN

After the development of Streptococcus mutansStreptococcus mutans and Lactobacillus acidophilus dual-species biofilms on the human enamel disks, they were divided into 11 groups (n = 9): Control (0.9 % saline), PC, TBO, FV, and TiF4 alone, PC and TBO in combination with a 635 nm diode laser (PDT treatment), PC-PDT+ (PC + FV or TiF4 + 635 nm diode laser), and TBO-PDT+ (TBO + FV or TiF4 + 635 nm diode laser). After the treatment, crystal violet assay was performed to determine the reduction of cariogenic biofilms. Enamel remineralization changes were analyzed using energy dispersive X-ray spectroscopy (EDX) and field emission scanning electron microscopy (FESEM) for the calcium and phosphorus (Ca/P) ratio.

RESULTS

Only TBO-PDT+ showed superior antibiofilm activity when TiF4 was applied. Furthermore, the highest Ca/P ratio was found after treatment of enamel surfaces with TiF4-TBO-PDT+. The FESEM images showed that the enamel disks treated with TiF4 plus TBO-mediated PDT exhibited surface coating. However, TiF4 plus PC-mediated PDT cannot repair demineralized enamel.

CONCLUSIONS

These data suggest that TBO-PDT along with TiF4 can effectively reduce cariogenic biofilms and significantly remineralize enamel disks, opening new avenues in caries prevention.

Comparative effects of the conventional, ultrasonic, and laser-activated irrigation on penetration depth of three photosensitizers in the root canal system

OBJECTIVES

This study compared the effects of conventional, ultrasonic, and laser-activated irrigation (LAI) on penetration depth of three photosensitizers (PSs) in the root canal system.

MATERIALS AND METHODS

In this in vitro, experimental study, 120 extracted anterior teeth were decoronated such that the remaining root length was standardized at 12 mm. After root canal instrumentation with the ProTaper rotary system and irrigation with 5.25% NaOCl, the roots were assigned to 12 groups for the application of toluidine blue (TB), curcumin, and phycocyanin PSs combined with the LAI using erbium laser with 0.4 mm and 0.6 mm tips, ultrasonic activation, and conventional irrigation. The specimens were sectioned apicocoronally, and the dye penetration depth was quantified in the coronal, middle, and apical thirds under a stereomicroscope at x20 magnification. Data were analyzed by the Kruskal-Wallis and Dunn test (alpha=0.05).

RESULTS

The effects of irrigation technique, PS type, and their interaction on dye penetration depth were significant at the apical, middle, and coronal thirds (P < 0.0001). TB + LAI with 0.4- and 0.6-mm laser tips showed the highest penetration depth while phycocyanin + LAI or conventional irrigation showed the lowest penetration depth at all areas. Dye penetration depth was the highest in the coronal, and the lowest in the apical third.

CONCLUSION

The LAI technique with erbium laser (0.4- and 0.6-mm tips) enhanced the penetration depth of TB. The tested irrigation techniques had no significant efficacy for enhancement of the penetration depth of curcumin and phycocyanin.

Antimicrobial Activity of Methylene Blue Associated with Photodynamic Therapy: In Vitro Study in Multi-Species Oral Biofilm

The control of infectious diseases caused by biofilms is a continuing challenge for researchers due to the complexity of their microbial structures and therapeutic implications. Photodynamic therapy as an adjunctive anti-infective treatment has been described as a possible valid approach but has not been tested in polymicrobial biofilm models. This study evaluated the effect of photodynamic therapy in vitro with methylene blue (MB) 0.01% and red LEDs (λ = 660 nm, power density ≈ 330 mW/cm2, 2 mm distance from culture) on the metabolic activity and composition of a multispecies subgingival biofilm. Test Groups LED and MB + LED showed a more significant reduction in metabolic activity than the non-LED application group (~50 and 55%, respectively). Groups LED and MB equally affected (more than 80%) the total bacterial count in biofilms. No differences were noted in the bacterial biofilm composition between the groups. In vitro LED alone or the MB + LED combination reduced the metabolic activity of bacteria in polymicrobial biofilms and the total subgingival biofilm count.

Application of Different Wavelengths of LED Lights in Antimicrobial Photodynamic Therapy for the Treatment of Periodontal Disease

Therapeutic light has been increasingly used in clinical dentistry for surgical ablation, disinfection, bio-stimulation, reduction in inflammation, and promotion of wound healing. Photodynamic therapy (PDT), a type of phototherapy, has been used to selectively destroy tumor cells. Antimicrobial PDT (a-PDT) is used to inactivate causative bacteria in infectious oral diseases, such as periodontitis. Several studies have reported that this minimally invasive technique has favorable therapeutic outcomes with a low probability of adverse effects. PDT is based on the photochemical reaction between light, a photosensitizer, and oxygen, which affects its efficacy. Low-power lasers have been predominantly used in phototherapy for periodontal treatments, while light-emitting diodes (LEDs) have received considerable attention as a novel light source in recent years. LEDs can emit broad wavelengths of light, from infrared to ultraviolet, and the lower directivity of LED light appears to be suitable for plaque control over large and complex surfaces. In addition, LED devices are small, lightweight, and less expensive than lasers. Although limited evidence exists on LED-based a-PDT for periodontitis, a-PDT using red or blue LED light could be effective in attenuating bacteria associated with periodontal diseases. LEDs have the potential to provide a new direction for light therapy in periodontics.

Efficacy of methylene blue and curcumin mediated antimicrobial photodynamic therapy in the treatment of indirect pulp capping in permanent molar teeth

PURPOSE

This study aimed to evaluate the adhesive bond strength and antibacterial efficacy of methylene blue (MB)-mediated antimicrobial photodynamic therapy (aPDT) and curcumin (CUR)-mediated aPDT versus the conventional disinfectants, such as chlorhexidine gluconate (CHX) gel and sodium hypochlorite (NaOCl), for indirect pulp capping (IPC) treatment of permanent molars.

METHODS

One Hundred grossly carious human permanent molars were collected through non-traumatic extraction. All specimens were embedded in polyvinyl cross-sections to the cemento-enamel junction. The cavity preparation was conducted by grinding the samples using silicon carbide discs. After culturing Streptococcus mutans (S. mutans), a 10 µL of S. mutans suspension (10⁶ colony forming units/mL) was transferred in each tooth cavity and anaerobically incubated for 48 hours at 37°C. All specimens were randomly divided into 5 groups: Group-I: samples treated IPC; Group-II: samples treated with 2% CHX gel; Group-III: samples treated with 6% NaOCl; Group-IV: irradiation of prepared cavity with MB-mediated aPDT; and Group-V: irradiation of prepared cavity with CUR-mediated aPDT. After disinfection methods, the universal adhesive was used, and all specimens were restored using giomer. Eventually, confocal laser scanning microscopy, shear bond strength (SBS), micro-tensile bond strength (μTBS), four-point bending strength (4P-BS) analyses were performed, and the data were analyzed statistically.

RESULTS

At baseline, the highest SBS (48.8 ± 6.5 MPa), μTBS (54.3 ± 3.9 MPa), and 4P-BS (123 ± 32 MPa) scores were demonstrated by the samples treated with MB-mediated aPDT. However, after 12 months of storage, the highest SBS (42.3 ± 3.9 MPa) and μTBS (45.2 ± 6.6 MPa) scores were shown by samples treated with MB-mediated aPDT, while CUR-mediated aPDT treated samples demonstrated the highest 4P-BS scores (70 ± 18 MPa). Moreover, the highest antibacterial activity against S. mutans was shown by the samples treated with MB-mediated aPDT.

CONCLUSIONS

The application of aPDT, especially MB-mediated, demonstrated superior SBS, μTBS, and 4P-BS values as well as antibacterial activity against S. mutans as compared to 2% CHX gel and 6% NaOCl as cavity disinfectants for IPC treatment of permanent molars.

Does potassium iodide help in the microbial reduction of oral microcosm biofilms after photodynamic therapy with methylene blue and red laser?

OBJECTIVE

To evaluate the efficacy of methylene blue (MB)-mediated antimicrobial photodynamic therapy (aPDT) doped with potassium iodide (KI) against oral microcosms biofilms cultured in dentin.

METHODS

A saliva-glycerol stock formed from pooled human saliva was diluted in McBain artificial saliva with 1% sucrose (1:1), inoculated on bovine dentin blocks, and refreshed daily for 5 days. The biofilms were divided (n = 9/group) and treated with 0.9% NaCl (C), 0.2% chlorhexidine (CX), 0.01% MB + low-power laser 15 J, 88 mW, 180 s (PL), and 0.01% MB + 50 mM KI + laser (PKIL). Serial dilution was performed, and cellular viability (CFU/mL) was evaluated for total microorganisms, total lactobacilli, total streptococci, and S. mutans. Additional biofilms were cultured and treated (n = 4) for biomass determination (%BMR). The microscopic structure of the biofilms was observed by SEM. One-way ANOVA and Tukey tests were conducted (α=5%).

RESULTS

Total microorganisms and total streptococci significantly reduced in biofilms treated with CX and PKIL when compared to C, but the CX, PKIL, and PL treatments did not differ from each other. Total lactobacilli and S. mutans showed a significant reduction in the CX, PL, and PKIL groups when compared to C, but with no difference between them. Biomass analysis showed a significantly reduction for CX and PKIL compared to C. SEM micrographs showed noticeable changes in bacterial membrane integrity for the PKIL and CX groups.

CONCLUSION

The addition of KI to methylene blue-mediated aPDT in microcosm biofilms was effective in reducing oral microorganisms, but the effect was group dependent.

Antibacterial activity of curcumin and its essential nanoformulations against some clinically important bacterial pathogens: A comprehensive review

Multidrug-resistant bacterial infections can kill 700,000 individuals globally each year and is considered among the top 10 global health threats faced by humanity as the arsenal of antibiotics is becoming dry and alternate antibacterial molecule is in demand. Nanoparticles of curcumin exhibit appreciable broad-spectrum antibacterial activity using unique and novel mechanisms and thus the process deserves to be reviewed and further researched to clearly understand the mechanisms. Based on the antibiotic resistance, infection, and virulence potential, a list of clinically important bacteria was prepared after extensive literature survey and all recent reports on the antibacterial activity of curcumin and its nanoformulations as well as their mechanism of antibacterial action have been reviewed. Curcumin, nanocurcumin, and its nanocomposites with improved aqueous solubility and bioavailability are very potential, reliable, safe, and sustainable antibacterial molecule against clinically important bacterial species that uses multitarget mechanism such as inactivation of antioxidant enzyme, reactive oxygen species-mediated cellular damage, and inhibition of acyl-homoserine-lactone synthase necessary for quorum sensing and biofilm formation, thereby bypassing the mechanisms of bacterial antibiotic resistance. Nanoformulations of curcumin can thus be considered as a potential and sustainable antibacterial drug candidate to address the issue of antibiotic resistance.

Influence of antimicrobial photodynamic therapy with different pre-irradiation times on children's dental biofilm: randomized clinical trial

PURPOSE

Photodynamic therapy (PDT) is effective in reducing pathogenic microorganisms in the oral cavity and in preventing dental diseases. This study evaluated the pre-irradiation time using PDT (diode laser associated with 0.01% methylene blue) to decrease the number of microorganisms in the visible plaque in permanent teeth.

METHODS

This randomized clinical trial included 108 homologous lower permanent first molars (36 and 46) with biofilm from 54 children aged six to 12 years. PDT was performed (0.01% methylene blue photosensitizer/therapeutic laser-InGaAIP), according to the following protocols: Group 1, biofilm collection of the distal area of the lingual surface of 36 µm before PDT; group 2, mesial area of the lingual surface of 36 µm 1 min after PDT; group 3, area of the lingual surface of 46 µm before PDT; and group 4, mesial area of the lingual surface of 46 µm 5 min after PDT.

RESULTS

After statistical analysis, significant differences were observed between the groups (p = 0.000). In groups 2 and 4, the number of bacteria tended to decrease, with a more evident bacterial reduction in group 4.

CONCLUSIONS

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.

CLINICAL TRIAL REGISTRATION

ReBEC Identifier: RBR-6bqfp3; Date of Register: March 2nd, 2020. Retrospectively Registered.

New Trends in Photodynamic Inactivation (PDI) Combating Biofilms in the Food Industry-A Review

Biofilms cause problems in the food industry due to their persistence and incompetent hygiene processing technologies. Interest in photodynamic inactivation (PDI) for combating biofilms has increased in recent years. This technique can induce microbial cell death, reduce cell attachment, ruin biofilm biomolecules and eradicate structured biofilms without inducing microbial resistance. This review addresses microbial challenges posed by biofilms in food environments and highlights the advantages of PDI in preventing and eradicating microbial biofilm communities. Current findings of the antibiofilm efficiencies of this technique are summarized. Additionally, emphasis is given to its potential mechanisms and factors capable of influencing biofilm communities, as well as promising hurdle strategies.

Photodynamic potential of curcumin in bioadhesive formulations: Optical characteristics and antimicrobial effect against biofilms

BACKGROUND

Although Curcumin (CUR) has great potential as a photosensitizer, the low solubility in water impairs its clinical performance in photodynamic inactivation (PDI). This study sought to establish an effective antimicrobial protocol for PDI using CUR in three different bioadhesive formulations.

METHODS

A CUR-loaded chitosan hydrogel with a poloxamer (CUR-CHIH), a CUR-loaded liquid crystal precursor system (CUR-LCP), a CUR-loaded microemulsion (CUR-ME), and CUR in dimethylsulfoxide (DMSO) solution (CUR-S; control formulation) were tested against in vitro and in situ oral biofilms. The optical properties of each formulation were evaluated.

RESULTS

All of the formulations exhibited lower absorbance than CUR-S; however, the CUR-LCP curve bore the highest resemblance. The CUR present in all formulations was completely degraded after 15 min of illumination. In vitro experiments showed that CUR-S was the only formulation able to significantly reduce biofilm viability of Candida albicans and Lactobacillus casei when compared to the negative control (no PDI); the amount of reduction obtained was 1.8 and 3.7 log (CFU/mL) for C. albicans and L. casei, respectively. There was a significant reduction on the viability of Streptococcus mutans biofilms when CUR-S and CUR-LCP were applied (approximately 3.5 and 1.6 log [CFU/mL], respectively). In situ testing showed antimicrobial efficacy against S. mutans and general microorganisms.

CONCLUSIONS

Although the evaluated protocols has not been effective to all of the evaluated microorganisms, PDI showed potential against dental biofilms and evidence that the phototoxic effects of CUR have a high relation with the type of formulation in which it is loaded.

Antimicrobial photodynamic therapy mediated by methylene blue coupled to β-cyclodextrin reduces early colonizing microorganisms from the oral biofilm

OBJECTIVE

To test the effect of antimicrobial photodynamic therapy (A-PDT) on the oral biofilm formed with early colonizing microorganisms, using the photosensitizer methylene blue coupled with β-cyclodextrin nanoparticles and red light sources laser or LED (λ =660 nm).

METHODS

The groups were divided into (n = 3, in triplicate): C (negative control, 0.9 % NaCl), CX (positive control, 0.2 % chlorhexidine), P (Photosensitizer/Nanoparticle), L (Laser), LED (light-emitting diode), LP (Laser + Photosensitizer/Nanoparticle) and LEDP (LED + Photosensitizer/Nanoparticle). A multispecies biofilm composed ofS. gordonii, S. oralis, S. mitis, and S. sanguinis was grown in microplates containing BHI supplemented with 1% sucrose (w/v) for 24 h. Light irradiations were applied with a laser at 9 J for 90 s (320 J/cm²), or with LED, at 8.1 J for 90 s (8.1 J/cm²). The microbial reduction was assessed by counting viable biofilm microorganisms in selective culture media, before and after the treatments. Data normality was assessed by the Shapiro-Wilk test, and the results were submitted to Kruskal-Wallis analysis, followed by Dunn's test, with a significance level of 5%.

RESULTS

The groups LP and LEDP were able to significantly reduce the biofilm microorganism counts by as much as 4 log₁₀ times compared to the negative control group (p < 0.05) and did not statistically differ from the positive control group (CX) (p > 0.05).

CONCLUSION

The A-PDT mediated by encapsulated β-cyclodextrin methylene blue irradiated by Laser or LED was effective in the microbial reduction of multispecies biofilm composed of early colonizing microorganisms.

Comparative Effect of Two Red Lights on Streptococcus mutans Biofilms and Assessment of Temperature Variances in Human Teeth During In Vitro Photodynamic Antimicrobial Chemotherapy

Objective: The goals of this investigation were to compare the effect of photodynamic antimicrobial chemotherapy (PACT) with two different red lights on in vitro Streptococcus mutans biofilms, as well as to assess the temperature variances caused by PACT on human teeth. Methods: S. mutans biofilms (n = 3) were grown on hydroxyapatite disks, and the antimicrobial effect of PACT was evaluated using toluidine blue O (100 μg/mL) associated with Laserbeam^® (LB 56.6 J/cm²) and LumaCare™ (LC -56.6, 158.5, 317.0, and 475.6 J/cm²). Pulpal temperature variances were analyzed using a digital thermocouple placed into the pulp chamber and positioned at the cement-enamel junction level of five teeth samples during irradiation times of 300, 600, and 900 sec for LB, and 22, 60, 120, and 180 sec for LC. The mean average temperature variance was calculated for each group. All data were analyzed through analysis of variance. Results: LB (900 sec) and LC (22 sec) induced similar reductions in the viability of microorganisms. LB did not cause statistically significant increase of temperature, regardless of experimental time, and LC caused temperature increase within the safe spectrum up to 60 sec. Conclusions: PACT seems to be a minimal invasive approach for reducing the viability of cariogenic bacteria. Thus, when applied in vitro for times equal or inferior to 900 and 60 sec for LB and LC, respectively, these light sources might be considered harmless to tooth structures.

Gelatin nanoparticles loaded methylene blue as a candidate for photodynamic antimicrobial chemotherapy applications in Candida albicans growth

Gelatin nanoparticles (GN) with an intrinsic antimicrobial activity maybe a good choice to improve the effectiveness of photodynamic antimicrobial chemotherapy (PACT). The aim of this study was to development gelatin nanoparticles loaded methylene blue (GN-MB) and investigate the effect of GN-MB in the Candida albicans growth by PACT protocols. The GN and GN-MB were prepared by two-step desolvation. The nanoparticulate systems were studied by scanning electron microscopy and steady-state techniques, the in vitro drug release was investigated, and we studied the effect of PACT on C. albicans growth. Satisfactory yields and encapsulation efficiency of GN-MB were obtained (yield = 76.0% ± 2.1 and EE = 84.0% ± 1.3). All the spectroscopic results presented here showed excellent photophysical parameters of the studied drug. Entrapment of MB in GN significantly prolongs it's in vitro release. The results of PACT experiments clearly demonstrated that the photosensitivity of C. albicans was higher when GN-MB was used. Gelatin nanoparticles loaded methylene blue-mediated photodynamic antimicrobial chemotherapy may be used against Candida albicans growth.

Blue photosensitizers for aPDT eliminate Aggregatibacter actinomycetemcomitans in the absence of light: An in vitro study

The main treatment of periodontal disease is the mechanical removal of supra and subgingival biofilm. Adjuvant therapies as antimicrobial photodynamic therapy (aPDT) may offer improved clinical and microbiological results. The aim of this in vitro study was to evaluate the effect of toluidine and methylene blue dyes, associated with red laser and LED, on elimination of a suspension of Aggregatibacter actinomycetemcomitans (A.a). Experimental groups (n = 29) consisted of positive (broth) and negative (gentamicin) controls, three different dyes concentrations (0.05; 0.1; 10 mg/ml) alone or associated with laser (660 nm) at two power settings (70 and 100 mW) and LED (627 ± 10 nm). Bacterial suspension received all treatments, and after serial dilutions they were cultured for 24 h in petri dishes for colony forming unit counts. Data were analyzed by ANOVA complemented by Tukey's test (p < 0.05). The results showed that both dyes, at a concentration of 10 mg/ml, alone or associated with laser and LED, caused 100% of death similar to the negative control (p > 0.05). It can be concluded that blue dyes for aPDT, at high concentration (10 mg/ml), are capable of eliminating A.a without adjuvant use of light sources.

Rose Bengal incorporated to α-cyclodextrin microparticles for photodynamic therapy against the cariogenic microorganism Streptococcus mutans

Rose Bengal@α-cyclodextrin (RB@α-CD) microparticles (μPs) were prepared and the RB inclusion in α-CD was experimentally demonstrated through infrared, UV-VIS absorption spectroscopy and cyclic voltammetry. The RB inclusion in α-CD was theoretically investigated using classical molecular mechanics calculations, the simulation results showing that RB can be included in both the narrow and wide apertures of the α-cyclodextrin ring with configurations exhibiting average binding energies of about 27 kcal mol^-1. The prepared RB@α-CD microparticles were characterized through Scanning Electron Microscopy (SEM) and it was demonstrated that they are highly efficient in the photodynamic therapy against a Streptococcus mutans (the main bacteria of cariogenic dental plaque) suspension, as a concentration of RB@α-CD μPs 10 times smaller than the usual concentration of pure RB is still capable to produce significant antibacterial activity.

Evaluation of photosensitizer penetration into sound and decayed dentin: A photoacoustic spectroscopy study

BACKGROUND

Photodynamic therapy (PDT) may have topical indications. In those cases it is important for a topical photosensitizer to penetrate into the tissue to which it has been applied. This study aimed to compare the penetration of two different concentrations of erythrosine into intact and in vitro decayed dentin samples.

METHODS

This in vitro study evaluated erythrosine (0.3 and 5%) penetration into sound (intact) and decayed dentin. A total of 11 dentin discs were prepared and divided into two equal halves, in order to keep one half sound while the other half was submitted to sterilization and an in vitro demineralization model for 5 days. Before erythrosine application, the organic and inorganic composition of all samples was evaluated by Fourier Transform Raman spectroscopy, and after erythrosine application for 30 min, the penetration depth was determined by Photoacoustic spectroscopy technique.

RESULTS

The results indicated that 0.3% erythrosine showed a higher penetration depth into sound dentin (p = 0.002); and 5% erythrosine higher penetration into decayed dentin (p < 0.001). However considering clinical parameters, no statistically significant difference was found between any of the conditions tested.

CONCLUSIONS

Erythrosine demonstrated ability to penetrate into dentin, irrespective of sound or decayed condition. Photoacoustic spectroscopy can be considered a method for estimating the penetration into hard tissues, and in conjunction with Raman spectroscopy, these are effective methods for evaluating the spectral response of dentin. Considering that erythrosine is capable of penetrating into decayed dentin, clinical trials are needed to test the effectiveness of this photosensitizer in Photodynamic therapy and Antimicrobial Photodynamic therapy.

Effect of antimicrobial photodynamic therapy (aPDT) on the sterilization of infected dentin in vitro

The aim of this study was to evaluate the bactericidal effect of antimicrobial photodynamic therapy (aPDT) on an infected dentin model. Dentin plates were prepared from extracted human molars and infected through immersion in a solution of Streptococcus mutans. The nine experimental groups consisted of two laser irradiation groups (650 nm laser: 650 laser and 940 nm laser: 940 laser), two photosensitizer groups (methylene blue: MB, and azulenocyanine: Azc), four aPDT groups (650 nm laser irradiation of MB: 650 laser-MB, 650 nm laser irradiation of Azc: 650 laser-Azc, 940 nm laser irradiation of MB: 940 laser-MB and 940 nm laser irradiation of Azc: 940 laser-Azc) and a control. The bactericidal effects on each group were evaluated by colony count and adenosine triphosphate (ATP) assays. Based on the results of the colony count assay, the 650 laser-MB and 940 laser-MB groups formed significantly fewer colonies than the other experimental groups. Significantly fewer colonies were observed in the 940 laser-Azc group than in the control, but significant differences in the numbers of colonies were not observed between the 650 laser-Azc and control groups. The 940 laser group formed slightly fewer colonies than the 650 laser group, but the difference was not significant. In addition, the number of colonies in the MB group was significantly less than the number in the Azc group. The results of the ATP assay were similar to those of the colony count assay. aPDT with MB showed a significant bactericidal effect on dentin plates infected with S. mutans.

Enhancement of photodynamic inactivation of Staphylococcus aureus biofilms by disruptive strategies

Photodynamic inactivation (PDI) has been used to inactivate microorganisms through the use of photosensitizers and visible light. On the one hand, near-infrared treatment (NIRT) has also bactericidal and dispersal effects on biofilms. In addition, dispersal biological tools such as enzymes have also been employed in antibiotic combination treatments. The aim of this work was to use alternative approaches to increase the PDI efficacy, employing combination therapies aimed at the partial disruption of the biofilms, thus potentially increasing photosensitizer or oxygen penetration and interaction with bacteria. To that end, we applied toluidine blue (TB)-PDI treatment to Staphylococcus aureus biofilms previously treated with NIRT or enzymes and investigated the outcome of the combined therapies. TB employed at 0.5 mM induced per se 2-log drop in S. aureus RN6390 biofilm viability. Each NIRT (980-nm laser) and PDI (635-nm laser) treatment induced a further reduction of 1-log of viable counts. The combination of successive 980- and 635-nm laser treatments on TB-treated biofilms induced additive effects, leading to a 4.5-log viable count decrease. Proteinase K treatment applied to S. aureus of the Newman strain induced an additive effect on PDI mortality, leading to an overall 4-log decrease in S. aureus viability. Confocal scanning laser microscopy after biofilm staining with a fluorescent viability test and scanning electron microscopy observations were correlated with colony counts. The NIRT dose employed (227 J/cm²) led to an increase from 21 to 47 °C in the buffer temperature of the biofilm system, and this NIRT dose also induced 100% keratinocyte death. Further work is needed to establish conditions under which biofilm dispersal occurs at lower NIRT doses.

Effect of Photodynamic Antimicrobial Chemotherapy on Mono- and Multi-Species Cariogenic Biofilms: A Literature Review

OBJECTIVE

The aim of this literature review is to study the effect of photodynamic antimicrobial chemotherapy (PACT) on mono- and multi-species cariogenic biofilms.

METHODS

To this purpose, the database, PubMed, was searched using the descriptors, photodynamic therapy, antimicrobial photodynamic chemotherapy, and photoinactivation, associated with the mandatory presence of the word biofilm. A total of 98 references published from 2003 to 2016 were selected. Moreover, literature reviews (15), investigations that did not have biofilms related to dental caries (65), and those that did not have Streptococcus mutans count as an outcome (7) were excluded, yielding a final amount of 11 publications.

RESULTS

The results revealed that Toluidine Blue O was the most used photosensitizer. Among the sources of light, light-emitting diode was the choice, and the biofilm models varied between in vitro and in situ. Multi-species biofilms were more resistant to the antimicrobial effects of PACT due to the thickness and complexity they have, which impede the penetration of the photosensitizer. This fact may also be associated with the type of photosensitizer used as well as with the light exposure time since the antimicrobial effect seems to be dose dependent. Despite this, in all the included publications, the therapy was effective in reducing S. mutans count.

CONCLUSIONS

This review demonstrated that under different conditions, PACT is effective in reducing S. mutans count in monospecies biofilms. Multi-species biofilms were more resistant to the antimicrobial action of the therapy, possibly due to their thickness and complexity.

Effect of fiber insertion depth on antibacterial efficacy of photodynamic therapy against Enterococcus faecalis in rootcanals

OBJECTIVES

This in vitro study evaluated the effect of fiber insertion depth on antimicrobial efficacy of antimicrobial photodynamic therapy (aPDT) using a photosensitizer (PS; toluidine blue) and a red light-emitting diode (LED) in root canals infected with Enterococcus faecalis.

MATERIALS AND METHODS

Single-rooted extracted teeth were prepared with nickel-titanium-instruments, sterilized, contaminated with E. faecalis, and incubated for 72 h. Roots were randomly divided into four experimental groups: PS only, LED only, aPDT with LED in the apical third, aPDT with LED in the coronal third, as well as into infection and sterile controls (each n = 10). Samples were taken by collecting standardized dentine shavings from the root canal walls. After serial dilution and culturing on blood agar, colony-forming units (CFU) were counted.

RESULTS

Both aPDT groups showed a CFU reduction of 1-2 log₁₀ steps compared with the infection control, whereas the effect of fiber insertion depth was negligible (<0.5 log₁₀ steps). CFU reduction of approximately 0.5 log₁₀ steps for PS alone was detected compared with the infection control, but PS alone was less effective than both aPDT groups. No antibacterial effect was detected for LED alone.

CONCLUSIONS

aPDT reduced E. faecalis within the root canal, whereas fiber insertion depth had a negligible influence on antimicrobial effectiveness of aPDT.

CLINICAL RELEVANCE

The insertion depth of the light-emitting diode may not influence the antibacterial efficacy of photodynamic therapy against E. faecalis in straight root canals.

Effect of the antimicrobial photodynamic therapy on microorganism reduction in deep caries lesions: a systematic review and meta-analysis

This study aimed to perform a systematic review to assess the effectiveness of antimicrobial photodynamic therapy (aPDT) in the reduction of microorganisms in deep carious lesions. An electronic search was conducted in Pubmed, Web of Science, Scopus, Lilacs, and Cochrane Library, followed by a manual search. The MeSH terms, MeSH synonyms, related terms, and free terms were used in the search. As eligibility criteria, only clinical studies were included. Initially, 227 articles were identified in the electronic search, and 152 studies remained after analysis and exclusion of the duplicated studies; 6 remained after application of the eligibility criteria; and 3 additional studies were found in the manual search. After access to the full articles, three were excluded, leaving six for evaluation by the criteria of the Cochrane Collaboration’s tool for assessing risk of bias. Of these, five had some risk of punctuated bias. All results from the selected studies showed a significant reduction of microorganisms in deep carious lesions for both primary and permanent teeth. The meta-analysis demonstrated a significant reduction in microorganism counts in all analyses (p<0.00001). Based on these findings, there is scientific evidence emphasizing the effectiveness of aPDT in reducing microorganisms in deep carious lesions.

Devices for In situ Development of Non-disturbed Oral Biofilm. A Systematic Review

Objective: The aim of this review was to assess the types of devices used for in situ development of oral biofilm analyzed microbiologically.

Materials and Methods: A systematic search of the literature was conducted to identify all in situ studies of oral biofilm which used an oral device; the Ovid MEDLINE and EMBASE databases complemented with manual search were used. Specific devices used to microbiologically analyze oral biofilm in adults were included. After reading of the selected full texts, devices were identified and classified according to the oral cavity zone and manufacturing material. The “ideal” characteristics were analyzed in every group.

Results: The search provided 787 abstracts, of which 111 papers were included. The devices used in these studies were classified as palatal, lingual or buccal. The last group was sub-classified in six groups based on the material of the device. Considering the analyzed characteristics, the thermoplastic devices and the Intraoral Device of Overlaid Disk-holding Splints (IDODS) presented more advantages than limitations.

Conclusions: Buccal devices were the most commonly used for the study of in situ biofilm. The majority of buccal devices seemed to slightly affect the volunteer's comfort, the IDODS being the closest to the “ideal” model.

Clinical Relevance: New devices for in situ oral biofilm microbiological studies should take into account the possible effect of their design on the volunteer's comfort and biofilm formation.

Randomized in vivo evaluation of photodynamic antimicrobial chemotherapy on deciduous carious dentin

The aim of this randomized in vivo study was to compare antimicrobial chemotherapies in primary carious dentin. Thirty-two participants ages 5 to 7 years underwent partial caries removal from deep carious dentin lesions in primary molars and were subsequently divided into three groups: control [chlorhexidine and resin-modified glass ionomer cement (RMGIC)], LEDTB [photodynamic antimicrobial chemotherapy (PACT) with light-emitting diode associated with toluidine blue solution and RMGIC], and LMB [PACT with laser associated with methylene blue solution and RMGIC]. The participants were submitted to initial clinical and radiographic examinations. Demographic features and biofilm, gingival, and DMFT/DMFS indexes were evaluated, in addition to clinical and radiographic followups at 6 and 12 months after treatments. Carious dentin was collected before and after each treatment, and the number of Streptococcus mutans, Streptococcus sobrinus, Lactobacillus casei, Fusobacterium nucleatum, Atopobium rimae, and total bacteria was established by quantitative polymerase chain reaction. No signs of pain or restoration failure were observed. All therapies were effective in reducing the number of microorganisms, except for S. sobrinus. No statistical differences were observed among the protocols used. All therapies may be considered as effective modern approaches to minimal intervention for the management of deep primary caries treatment.

Photodynamic antimicrobial chemotherapy and ultraconservative caries removal linked for management of deep caries lesions

BACKGROUND

Ultraconservative removal of carious tissue is becoming increasingly highlighted for management of deep caries lesions, and combined with an antimicrobial photochemistry-based treatment modality (PACT), this approach can be enhanced favoring dental tissue repair and preservation. The aim was to investigate the effectiveness of PACT using a light emitting diode (LED) associated with a photosensitizer toluidine blue ortho (TBO) on deep caries lesions.

METHODS

For that, a single blind, randomized, controlled, split-mouth clinical trial where 45 patients with at least two deep carious lesions on permanent posterior teeth was performed. The primary intervention was deep caries lesion management with disinfection of remaining dentin tissue using PACT. Bacterial counts were measured following treatments as the main outcome. The remaining dentinal samples of each lesion were treated with either non-PACT-control or PACT. The PACT procedure were characterized by 100 μg mL(-1) TBO followed by 94J cm(-2) LED irradiation. Samples of dentin were collected before and immediately after treatments for microbiological analysis of total viable bacteria, mutans streptococci and Lactobacillus spp. counts. Microbial reduction was data were submitted to unpaired t test (α=5%).

RESULTS

PACT led to statistically significant reductions in mutans streptococci (1.08 ± 1.20 log), Lactobacillus spp. (1.69 ± 1.37 log), and total viable bacteria (1.07 ± 1.01 log) compared to the control, which showed log reductions respectively of 0.05 ± 0.49, 0.52 ± 0.89, and 0.47 ± 0.77 for the same microorganisms.

CONCLUSION

Dentin from deep carious lesions treated with PACT showed a decrease in cariogenic microbial load.

Effect of Twice-Daily Blue Light Treatment on Matrix-Rich Biofilm Development

Background

The use of blue light has been proposed as a direct means of affecting local bacterial infections, however the use of blue light without a photosensitizer to prevent the biofilm development has not yet been explored. The aim of this study was to determine how the twice-daily treatment with blue light affects the development and composition of a matrix-rich biofilm.

Methodology/Principal Findings

Biofilms of Streptococcus mutans UA159 were formed on saliva-coated hydroxyapatite discs for 5 days. The biofilms were exposed twice-daily to non-coherent blue light (LumaCare; 420 nm) without a photosensitizer. The distance between the light and the sample was 1.0 cm; energy density of 72 J cm^-2; and exposure time of 12 min 56 s. Positive and negative controls were twice-daily 0.12% chlorhexidine (CHX) and 0.89% NaCl, respectively. Biofilms were analyzed for bacterial viability, dry-weight, and extra (EPS-insoluble and soluble) and intracellular (IPS) polysaccharides. Variable pressure scanning electron microscopy and confocal scanning laser microscopy were used to check biofilm morphology and bacterial viability, respectively. When biofilms were exposed to twice-daily blue light, EPS-insoluble was reduced significantly more than in either control group (CHX and 0.89% NaCl). Bacterial viability and dry weight were also reduced relative to the negative control (0.89% NaCl) when the biofilms were treated with twice-daily blue light. Different morphology was also visible when the biofilms were treated with blue light.

Conclusions

Twice-daily treatment with blue light without a photosensitizer is a promising mechanism for the inhibition of matrix-rich biofilm development.

Longitudinal effect of curcumin-photodynamic antimicrobial chemotherapy in adolescents during fixed orthodontic treatment: a single-blind randomized clinical trial study

White spot lesions are one of the concerns during the fixed orthodontic treatment. Thus, the aim of the present study was to evaluate the antimicrobial/anti-inflammatory effect of curcumin-photodynamic antimicrobial chemotherapy (c-PACT) and chlorhexidine varnish on the plaque accumulation and gingival bleeding in adolescents under fixed orthodontic treatment. A randomized clinical trial was performed with an initial number of 45 patients being distributed into three groups: group I-chlorhexidine varnish 2%, group II-placebo varnish, and group III-c-PACT (curcumin at 1.5 mg.mL(-1)) exposed to blue Light-emitting diode (LED) light at 450 nm (power density = 165 mW.cm(-2), fluency = 96 J.cm(-2), total dose = 150.7 J). The treatments were performed for four consecutive times with an interval of 1 week each. After the interventions, two calibrated examiners (Kappa value = 0.75) analyzed the dental plaque accumulation by plaque index (PI) and gingivitis condition by gingival bleeding index (GBI) with 1 and 3 months of follow-up after the treatments comprised a final sample of 35 patients. No significant difference was found to PI between the groups during baseline and 1-month period. Group III (1.52 ± 0.51) presented significance difference from group I (0.91 ± 0.75) and group II (1.03 ± 0.51) at 3 months of follow-up. In this same period, there was more plaque accumulation with significant statistical difference (P ≤ 0.05) in comparison to the other periods to all studied groups. There was a GBI reduction statistically significant to groups I and III at 1-month follow-up in comparison to other periods. No effect was verified to dental plaque accumulation after the photodynamic application mediated with curcumin activated with a blue LED light.

Comparative evaluation of photodynamic therapy using LASER or light emitting diode on cariogenic bacteria: An in vitro study

OBJECTIVE

The aim of this study was to evaluate in vitro the effect of photodynamic therapy (PDT) using LASER or light emitting diode (LED) on cariogenic bacteria (Streptococcus mutans [SM] and Lactobacillus casei [LC]) in bovine dentin.

MATERIALS AND METHODS

Twenty five fragments of dentin were contaminated with SM and LC strands and divided into five experimental groups according to the therapy they received (n = 5): C - control (no treatment), SCLED - no dye/LED application (94 J/cm(2)), SCLASER - no dye/LASER application (94 J/cm(2)), CCLED - dye/LED application (94 J/cm(2)) and CCLASER - dye/LASER application (94 J/cm(2)). The dye used was methylene blue at 10 mM. Dentin scrapes were harvested from each fragment and prepared for counts of colony forming units (CFU)/mL. The data were analyzed using Kruskal-Wallis, followed by Student-Newman-Keuls (α =0.05).

RESULTS

Regarding SM, groups CCLASER and CCLED showed a significant reduction in CFU/mL, which was statistically superior to the SCLASER, SCLED and C groups. Regarding LC, the groups CCLASER and CCLED caused a significant reduction in CFU/mL when compared with SCLASER, which showed intermediate values. SCLED and C had a lesser effect on reducing CFU/mL, where the former showed values similar to those of SCLASER.

CONCLUSIONS

In conclusion, PDT combined with LASER or LED and methylene blue had a significant antimicrobial effect on cariogenic bacteria in the dentin.

Antimicrobial photodynamic therapy and dental plaque: a systematic review of the literature

Background. The aim of this study was to perform a systematic review of the literature on the efficacy of antimicrobial photodynamic therapy (PDTa) on cariogenic dental biofilm. Types of Studies Reviewed. Studies in vivo, in vitro, and in situ were included. Articles that did not address PDTa, those that did not involve cariogenic biofilm, those that used microorganisms in the plankton phase, and reviews were excluded. Data extraction and quality assessments were performed independently by two raters using a scale. Results. Two hundred forty articles were retrieved; only seventeen of them met the eligibility criteria and were analyzed in the present review. Considerable variability was found regarding the methodologies and application protocols for antimicrobial PDTa. Two articles reported unfavorable results. Practical Implications. The present systematic review does not allow drawing any concrete conclusions regarding the efficacy of antimicrobial PDTa, although this method seems to be a promising option.

Antimicrobial photodynamic therapy for inactivation of biofilms formed by oral key pathogens

With increasing numbers of antibiotic-resistant pathogens all over the world there is a pressing need for strategies that are capable of inactivating biofilm-state pathogens with less potential of developing resistances in pathogens. Antimicrobial strategies of that kind are especially needed in dentistry in order to avoid the usage of antibiotics for treatment of periodontal, endodontic or mucosal topical infections caused by bacterial or yeast biofilms. One possible option could be the antimicrobial photodynamic therapy (aPDT), whereby the lethal effect of aPDT is based on the principle that visible light activates a photosensitizer (PS), leading to the formation of reactive oxygen species, e.g., singlet oxygen, which induce phototoxicity immediately during illumination. Many compounds have been described as potential PS for aPDT against bacterial and yeast biofilms so far, but conflicting results have been reported. Therefore, the aim of the present review is to outline the actual state of the art regarding the potential of aPDT for inactivation of biofilms formed in vitro with a main focus on those formed by oral key pathogens and structured regarding the distinct types of PS.