Effect of Photodynamic Therapy on Microorganisms Responsible for Dental Caries: A Systematic Review and Meta-Analysis

Reduction of microorganisms in carious dentin by photodynamic therapy mediated by potassium iodide added to methylene blue and red laser

OBJECTIVE

To evaluate the effect of the association of potassium iodide to antimicrobial photodynamic therapy on human carious dentin produced with a microcosm biofilm model.

METHODS

A microcosm biofilm model was used to generate a caries lesion on human dentin. Pooled human saliva diluted with glycerol was used as an inoculum on specimens immersed on McBain artificial saliva enriched with 1 % sucrose (24 h at 37 °C in 5 % CO2). After refreshing culture media for 7 days, the dentin specimens were divided in 5 groups (3 specimens per group, in triplicate; n = 9): C (NaCl 0.9 %), CX (2 % chlorhexidine), PKI (0.01 % methylene blue photosensitizer+50 mM KI), L (laser at 15 J, 180 s, 22.7 J/cm2), and PKIL (methylene blue + KI + Laser). After the treatments, dentin was collected, and a 10-fold serial dilution was performed. The number of total microorganisms, total lactobacilli, total streptococci, and Streptococcus mutans was analyzed by microbial counts (CFU/mL). After normality and homoscedasticity analysis, the Welch's ANOVA and Dunnett's tests were used for CFU. All tests used a 5 % significance level.

RESULTS

CX and PKIL groups showed significant bacterial decontamination of dentin, compared to group C (p < 0.05) reaching reductions up to 3.8 log10 for CX for all microorganisms' groups and PKIL showed 0.93, 1.30, 1.45, and 1.22 log10 for total microorganisms, total lactobacilli, total streptococci, and S. mutans, respectively.

CONCLUSION

aPDT mediated by the association of KI and methylene blue with red laser reduced the viability of microorganisms from carious dentin and could be a promising option for cavity decontamination.

Bacterial resistance to antimicrobial photodynamic therapy: A critical update

Bacterial antibiotic resistance is one of the most significant challenges for public health. The increase in bacterial resistance, mainly due to microorganisms harmful to health, and the need to search for alternative treatments to contain infections that cannot be treated by conventional antibiotic therapy has been aroused. An alternative widely studied in recent decades is antimicrobial photodynamic therapy (aPDT), a treatment that can eliminate microorganisms through oxidative stress. Although this therapy has shown satisfactory results in infection control, it is still controversial in the scientific community whether bacteria manage to develop resistance after successive applications of aPDT. Thus, this work provides an overview of the articles that performed successive aPDT applications in models using bacteria published since 2010, focusing on sublethal dose cycles, highlighting the main PSs tested, and addressing the possible mechanisms for developing tolerance or resistance to aPDT, such as efflux pumps, biofilm formation, OxyR and SoxRS systems, catalase and superoxide dismutase enzymes and quorum sensing.

In vitro antibiofilm effect of different irradiation doses in infected root canal model

BACKGROUND

Eradication of endodontic biofilms from the infected root canal system is still the main concern in endodontics. In this study, the role of the power density parameter in the efficacy of antimicrobial photodynamic therapy (PDT) with toluidine blue O (TBO) and phycocyanin (PC) activated by a 635 nm diode laser (DL) against Enterococcus faecalis biofilm in the root canal model was investigated.

MATERIALS AND METHODS

The E. faecalis biofilm in the root canal was treated with TBO and PC with different power densities (636, 954, 1273, and 1592 W/cm2). The untreated biofilm represented the control group. After the treatments, the biofilms were analyzed based on the number of colonies per milliliter.

RESULTS

TBO and PC activated with 635 nm DL with a power density of 1592 W/cm2 were more efficient in removing E. faecalis biofilms within the root canals than those with a power density of 636 W/cm2 (p = 0.00).

CONCLUSION

The light power density optimized the bacterial reduction of E. faecalis biofilms in the root canal spaces. These results provide information on the decisive parameters for performing PDT on intracanal biofilms.

Comparative study of the effect of different exposure parameters of 635nm diode laser and toluidine blue O in eliminating Aggregatibacter actinomycetemcomitans biofilm from titanium implant surfaces

BACKGROUND

The aim of this study was to investigate the effects of antimicrobial photodynamic therapy (PDT) using 635 nm diode laser irradiation with an energy density of 6 to 30 J/cm2 and toluidine blue O (TBO) as a photosensitizer on the viability of Aggregatibacter actinomycetemcomitans attached to the surface of titanium implants.

MATERIALS AND METHODS

Titanium implants contaminated with A. actinomycetemcomitans were treated with TBO alone or in combination with different exposure parameters (light doses of 6 - 30 J/cm2 at 635 nm) and 0.2 % chlorhexidine (CHX). After treatment, colony forming units (CFUs)/ml were determined to assess PDT efficacy. The structure of the biofilm of A. actinomycetemcomitans was analyzed by field emission scanning electron microscopy (FESEM).

RESULTS

Under optimal conditions, the colony count was reduced by ∼90 %. Treatment with CHX was somewhat more effective (colony formation was reduced by ∼95 %), but this agent has adverse effects that can be avoided with PDT.

CONCLUSION

This study confirms the efficacy of PDT against A. actinomycetemcomitans depending on the light dose. Treatment with TBO + 635 nm diode laser has an effect that may be equivalent to that of CHX, but perhaps with fewer adverse effects.

Evaluation of antimicrobial photodynamic therapy and minimal intervention associated with deproteinisation in permanent teeth with molar incisor hypomineralisation: study protocol for a clinical, controlled, blinded trial

INTRODUCTION

Molar incisor hypomineralisation (MIH) is a qualitative defect of enamel development that occurs in the mineralisation phase. MIH affects one or more permanent molars and, occasionally, permanent incisors. The aim of the proposed study is to evaluate the clinical effect of antimicrobial photodynamic therapy (aPDT) on permanent teeth with MIH through decontamination and sensitivity control.

METHODS AND ANALYSIS

Patients from 8 to 12 years of age with permanent molars will be randomly allocated to three groups. Group 1: selective chemical-mechanical removal of carious dentinal tissue around the walls of the cavity with Papacárie Duo and a curette followed by the application of aPDT and deproteinisation with Papacárie Duo; group 2: selective removal of carious dentinal tissue around the walls of the cavity with a curette, followed by the application of aPDT and deproteinisation with a 5% sodium hypochlorite solution; group 3: selective removal of carious dentinal tissue using a curette. The selected teeth must have a carious lesion in the dentin and posteruptive enamel breakdown on one or more surfaces with an indication for clinical restorative treatment. The teeth will subsequently be restored using a mixed technique with resin-modified glass ionomer cement and bulk-fill composite resin. The data will be submitted to descriptive statistical analysis. Associations with age and sex will be tested using either the χ2 test or Fisher's exact test. Pearson's correlation coefficients will be calculated to determine the strength of correlations between variables. Comparisons of the microbiological results (colony-forming units) will be performed using analysis of variance and the Kruskal-Wallis test. Kaplan-Meier survival analysis will be performed to assess the performance of the restorations.

ETHICS AND DISSEMINATION

This protocol has been approved by the Human Research Ethics Committee of Nove de Julho University (certificate number: 61027522.0.0000.5511/approval date: 23 August 2022). The findings will be published in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

NCT05443035.

The effect of antibacterial photodynamic therapy with diode laser on chromogenic bacteria associated with dental black staining: An in-vitro study

BACKGROUND

Aggregatibacter actinomycetemcomitan (A.a) and Actinomyces naeslundii (A.n) are two gram-negative chromogenic bacteria involved in the formation of dental black stainings. Our study aimed to investigate the antibacterial effect of photodynamic therapy (aPDT) using two photosensitizers, Methylene Blue (MB) and Indocyanine Green (ICG).

MATERIALS AND METHODS

In this in-vitro study, two isolates of each selected bacterium were cultured and treated as follows; Negative control with no treatment; CHX as a positive control; ICG; MB; ICG with 808 nm laser activation; and MB with 660 nm laser activation. The number of colonies (CFU/mL) was determined to compare the groups. The qualitative evaluation of biofilm formation was done by scanning electron microscopy of treated enamel pieces. The logarithmic values of the colony counts were compared using One-way ANOVA and the Welch test Tukey HSD and Games-Howell tests were used for multiple comparisons. P-values of less than 0.05 were considered statistically significant.

RESULTS

The use of ICG alone or along with laser irradiation at the wavelength of 808 nm significantly reduced the number of colonies of A.a and A.n bacteria. Comparing the colony counts in the MB group with the positive control showed no significant decrease in bacterial load. On the contrary, activation of MB with 660 nm radiation of diode laser showed a significant antibacterial effect. The density of bacterial biofilm was significantly lower in the groups treated with MB and ICG without laser activation than in the control group; however, the reduction in bacteria biofilm density was more robust using photodynamic therapy with ICG.

CONCLUSION

aPDT using MB with 660 nm laser and ICG with 808 nm laser significantly reduced the number of chromogenic A.a and A.n bacteria, and photodynamic therapy with ICG was proven to be significantly more effective than MB with or without laser radiation.

The effect of photodynamic therapy in controlling the oral biofilm: A comprehensive overview

Several resistance mechanisms are involved in dental caries, including oral biofilms. An accumulation of bacteria on the surface of teeth is called plaque. Periodontitis and gingivitis are caused by dental plaque. In this review article, we aimed to review the studies associated with the application of photodynamic therapy (PDT) to prevent and treat various microbial biofilm-caused oral diseases in recent decades. There are several studies published in PubMed that have described antimicrobial photodynamic therapy (APDT) effects on microorganisms. Several in vitro and in vivo studies have demonstrated the potential of APDT for treating endodontic, periodontal, and mucosal infections caused by bacteria as biofilms. Reactive oxygen species (ROS) are activated in the presence of oxygen by integrating a nontoxic photosensitizer (PS) with appropriate wavelength visible light. By causing irreversible damage to microorganisms, ROS induces some biological and photochemical events. Testing several wavelengths has been conducted to identify potential PS for APDT. A standard protocol is not yet available, and the current review summarizes findings from dental studies on APDT.

Evaluation of photodynamic therapy on nanoparticles and films loaded-nanoparticles based on chitosan/alginate for curcumin delivery in oral biofilms

Nanoparticles and nanoparticle-loaded films based on chitosan/sodium alginate with curcumin (CUR) are promising strategies to improve the efficacy of antimicrobial photodynamic therapy (aPDT) for the treatment of oral biofilms. This work aimed to develop and evaluate the nanoparticles based on chitosan and sodium alginate encapsulated with CUR dispersed in polymeric films associated with aPDT in oral biofilms. The NPs were obtained by polyelectrolytic complexation, and the films were prepared by solvent evaporation. The photodynamic effect was evaluated by counting Colony Forming Units (CFU/mL). Both systems showed adequate characterization parameters for CUR release. Nanoparticles controlled the release of CUR for a longer period than the nanoparticle-loaded films in simulated saliva media. Control and CUR-loaded nanoparticles showed a significant reduction of 3 log10 CFU/mL against S. mutans biofilms, compared to treatment without light. However, biofilms of S. mutans showed no photoinactivation effect using films loaded with nanoparticles even in the presence of light. These results demonstrate the potential of chitosan/sodium alginate nanoparticles associated with aPDT as carriers for the oral delivery of CUR, offering new possibilities to improve the treatment of dental caries and infections. This work will contribute to advances in the search for innovative delivery systems in dentistry.

Evaluation of dual application of photodynamic therapy-PDT in Candida albicans

This study aimed to evaluate, in vitro, the efficacy of photodynamic therapy - PDT using dimethyl methylene blue zinc chloride double salt (DMMB) and red LED light on planktonic cultures of Candida albicans. The tests were performed using the ATCC 90,028 strain grown at 37 °C for 24 h, according to a growth curve of C. albicans. The colonies were resuspended in sterile saline adjusted to a concentration of 2 × 10⁸ cells / mL, with three experimental protocols being tested (Protocol 1, 2 and 3) with a fixed concentration of 750 ɳg/mL obtained through the IC₅₀, and energy density 20 J/cm². Protocol 1 was carried out using conventional PDT, Protocol 2 was applied double PDT in a single session, and Protocol 3 was applied double PDT in two sessions with a 24 h interval. The results showed logarithmic reductions of 3 (4.252575 ± 0.068526) and 4 logs (2.669533 ± 0.058592) of total fungal load in protocols 3 and 2 respectively in comparison to the Control (6.633547 ± 0.065384). Our results indicated that double application in a single session of PDT was the most effective approach for inhibiting the proliferation of Candida albicans (99.991% inhibition).

Potential Use of Brazilian Green Propolis Extracts as New Photosensitizers for Antimicrobial Photodynamic Therapy against Cariogenic Microorganisms

The synergic effect of Streptococcus mutans and Candida albicans increases dental caries severity. Antimicrobial photodynamic therapy (aPDT) is a non-invasive treatment for antimicrobial aspects. However, the current photosensitizers (PS) have many downsides for dental applications. This study aimed to evaluate the efficiency of two different Brazilian green propolis (BGP-AF and BGP-AG) as PS for aPDT against these microorganisms. A single-species biofilm was irradiated with crude extracts and their fractions and controls. Such extracts showed the best results and were evaluated in dual-species biofilms. Photodegradation, reactive oxygen species (ROS), cytotoxicity, and color stability assays were also investigated. Reductions higher than 3 log₁₀ CFU/mL (p < 0.0001) occurred for crude BGP in single- and dual-species biofilms. Singlet oxygen was produced in BGP (p < 0.0001). BGP-mediated aPDT delayed S. mutans and C. albicans regrowth after 24 h of treatment (p < 0.0001). Both BGP did not change the color of dental materials (p > 0.05). BGP-AF-mediated aPDT showed 72.41% of oral keratinocyte viability (p < 0.0001). BGP extracts may be used in aPDT against S. mutans and C. albicans. Specifically, BGP-AF may represent a promising PS for dental applications.

Fourier Transform Infrared Spectroscopy (FT-IR) of Pseudomonas aeruginosa post photodynamic therapy with Curcumin in vitro

Alternative therapies against pathogens are under intense investigation because of their increasing resistance to antibiotics. Photodynamic therapy (PDT) is one such alternative that has shown promising results. However, for the widespread use of PDT, it is essential to decipher underlying mechanisms, so as to improve PDT's therapeutic applications. Because of this, we have studied biochemical changes in pathogen Pseudomonas aeruginosa, a medically important bacteria that has developed antibiotic resistance, after PDT with curcumin photosensitizer. Results show a drastic decrease in α-helix protein and increased disordered and β-sheet secondary structure proteins in P. Aeruginosa post-PDT compared to control. Interestingly, these biochemical changes differ from PDT of pathogens Leishmania braziliensis and Leishmania major with photosensitizer methylene blue. This observation underlines the need for extensive studies on PDT of different pathogens to understand mechanisms of action and develop better PDT strategies.

Biofilm Lifestyle in Recurrent Urinary Tract Infections

Urinary tract infections (UTIs) represent one of the most common infections that are frequently encountered in health care facilities. One of the main mechanisms used by bacteria that allows them to survive hostile environments is biofilm formation. Biofilms are closed bacterial communities that offer protection and safe hiding, allowing bacteria to evade host defenses and hide from the reach of antibiotics. Inside biofilm communities, bacteria show an increased rate of horizontal gene transfer and exchange of resistance and virulence genes. Additionally, bacterial communication within the biofilm allows them to orchestrate the expression of virulence genes, which further cements the infestation and increases the invasiveness of the infection. These facts stress the necessity of continuously updating our information and understanding of the etiology, pathogenesis, and eradication methods of this growing public health concern. This review seeks to understand the role of biofilm formation in recurrent urinary tact infections by outlining the mechanisms underlying biofilm formation in different uropathogens, in addition to shedding light on some biofilm eradication strategies.

In Vitro Evaluation of Photodynamic Activity of Plant Extracts from Senna Species against Microorganisms of Medical and Dental Interest

Background: Bacterial resistance requires new treatments for infections. In this context, antimicrobial photodynamic therapy (aPDT) is an effective and promising option. Objectives: Three plant extracts (Senna splendida, Senna alata, and Senna macranthera) were evaluated as photosensitizers for aPDT. Methods: Cutibacterium acnes (ATCC 6919), Streptococcus mutans (ATCC 35668), Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 25922), and Candida albicans (ATCC 90028) were evaluated. Reactive oxygen species production was also verified. Oral keratinocytes assessed cytotoxicity. LC-DAD-MS analysis identified the chemical components of the evaluated extracts. Results: Most species cultured in the planktonic phase showed total microbial reduction (>6 log10 CFU/mL/p < 0.0001) for all extracts. C. albicans cultured in biofilm showed total microbial reduction (7.68 log10 CFU/mL/p < 0.0001) for aPDT mediated by all extracts. Extracts from S. macranthera and S. alata produced the highest number of reactive oxygen species (p < 0.0001). The S. alata extract had the highest cell viability. The LC-DAD-MS analysis of active extracts showed one naphthopyrone and seven anthraquinones as potential candidates for photoactive compounds. Conclusion: This study showed that aPDT mediated by Senna spp. was efficient in microbial suspension and biofilm of microorganisms of medical and dental interest.

[Potentialities of photoactivated disinfection in dentistry]

Infection control is an essential part of dental practice. Oral antiseptics should be highly effective against the most common oral pathogens without causing microbial resistance, biocompatible with the human tissues with no interaction with fillings materials. Photoactivated disinfection (PAD) is based on activation of photosensitizers - specific substances releasing active oxygen forms after absorption of the light. The active oxygen forms destroy bacterial cell structures without affecting human cells. The overwhelming majority of Russian and international researchers have reported high effectiveness of PAD in periodontics, implantology and endodontics, whereas the use of PAD in caries treatment and prevention is not so fully understood yet. Earlier studies have demonstrated high sensitivity of cariogenic bacteria to PAD, suggesting it as an additional minimally invasive caries therapy improving treatment effectiveness. PAD spares dental tissues without reduction in the effectiveness of disinfection. It is particularly important in treatment of deep carious lesions and disinfection of thin dentine layer near the pulp. Effectiveness of PAD in caries treatment has been demonstrated for both permanent and deciduous dentition. PAD doesn't affect bond strength to fillings, improves plasticity of dental pulp and dental hard tissues mineralization in children. Effective control of a wide range of bacteria without causing resistance makes PAD a prospective method of treatment and prevention of caries.

Efficacy of antiseptics and chemomechanical methods for dentin caries lesions: A systematic review with GRADE approach

Objectives

Selective caries removal aims to remove carious tissue in deep dentin lesions. However, a discussion stands on the value of antiseptics and chemomechanical adjuvant methods to reduce the bacterial load on residual caries lesions. This systematic review has addressed two main clinical questions to compare the antimicrobial efficacy of available methods using (1) antiseptic or (2) chemomechanical agents before restoring dentin carious lesions.

Methods

We included randomized and non-randomized controlled trials (RCTs/ NRCTs). We searched eight databases from inception to October 2021. Paired reviewers independently screened studies, extracted data, and assessed the risk of bias. The primary outcome was the reduction in the number of total bacterial in dentin, whereas secondary outcomes were reduction in the number of Lactobacillus and Streptococcus. We used the ratio of ratio of post-treatment to baseline means between two interventions in the logarithmic scale as a proper effect measure. Certainty of evidence was assessed with the Grading of Recommendations, Assessment, Development and Evaluation approach.

Results

We included 14 RCTs and 9 NRCTs, with nine interventions. Regardless the method, the number of bacteria at baseline was similar or exceeded that after the intervention, particularly in NRCTs. The evidence was inconclusive for most comparisons. Among antiseptic agents, chlorhexidine (CHX) resulted in an average of 1.14 times [95% confidence interval (CI): 1.08-1.21] more total bacterial than photodynamic therapy in RCTs. Among NRCTS, the natural agents resulted in five times more total bacterial than CHX (95% CI: 2-11). For chemomechanical methods, the control resulted in eight times (95% CI: 4-17) more total bacterial than Carisolv (SHAA).

Conclusions

The certainty of the evidence was very low for all comparisons showing uncertainty whether one treatment could be more effective than another for dentin disinfection. So far, exclusively removing soft carious dentin would be enough to reduce the bacterial count.

Clinical efficacy of 5-aminolevulinic acid-mediated photodynamic therapy versus topical antifungal agent and surgical excision for the treatment of hyperplastic candidiasis

BACKGROUND

Hyperplastic candidiasis (HC) is a chronic infection of oral mucosa caused by Candida. Owing to its potential for malignant transformation, its intervention requires attention. Conventional surgical resection might lead to irreversible damage and impact the patient's quality of life. Hence, this study aimed to evaluate the clinical efficacy of 5-aminolevulinic acid (5-ALA)-mediated photodynamic therapy (PDT) alone and in combination with topical antifungal therapy (i.e., nystatin [combination therapy]) in comparison with nystatin and surgical resection for the treatment of HC.

METHODS

Forty subjects with clinical and histopathological diagnoses of HC were included in the study. Four study groups, with 10 participants each, were formed as follows: Group-I - receiving antifungal agent [nystatin]; Group-II - receiving surgical resection; Group-III - receiving PDT; and Group-IV - receiving 5-ALA-mediated PDT and nystatin [combination therapy]. Salivary and mucosal samples were collected for the quantification of Candida albicans and the treatment responses to different interventions were recorded at week-4, week-6, and week-8 after finishing therapies.

RESULTS

At the 3^rd follow-up (i.e., at end of the 8^th week after the interventions), complete improvement in 3 (30%), 2 (20%), 1 (10%), and 5 (50%) patients in group-I, group-II, group-III, and group-IV, respectively was observed. A statistically significant difference was obtained when the intervention responses were compared at week-4 (p<0.01), week-6 (p<0.01), and week-8 (p<0.0001) follow-ups in group-I, group-II, and group-IV subjects. At the 8-week follow-up regarding the salivary and mucosal samples, the lowest colony-forming units/milliliter score of C. albicans was observed in group-IV subjects.

CONCLUSION

The application of 5-ALA-mediated PDT in combination with nystatin gel possesses the potential as a well-tolerated and safe therapeutic modality for the treatment of patients with HC.

Caries-affected dentin disinfection using Triphala, Indocyanine green, and Potassium Titanyl Phosphate laser and their effect on adhesive bond strength

AIM

To assess the impact of new cavity sterilization types using ozone water (OW), Potassium Titanyl Phosphate laser (KTPL), Triphala, and indocyanine green photosensitizer (ICGP) on adhesive bond strength.

MATERIALS AND METHODS

Fifty human permanent molars were included based on the criteria of International Caries Detection and Assessment System (ICDAS) scores 4 and 5 visual examinations, surface hardness valuation, staining by a caries detector solution, and radiographs. Caries-affected dentin (CAD) samples were randomly distributed into groups based on methods of disinfection (n = 10). Group 1: chlorhexidine, group 2: ow, group 3: KTPL, group 4: Triphala, and group 5: ICGP. Following disinfection, specimens were applied with Adper prime and bond NT and then restored with resin composite. All specimens were positioned in a jig of the universal testing machine for shear bond strength (SBS). The debonded samples were analyzed under a stereomicroscope at 40x magnification to determine the type of failure. Analysis of variance (ANOVA) and Tukey HSD tests were used keeping the level of significance p < 0.05.

RESULTS

The highest bond of adhesive resin was displayed by group 2 specimens cleaned using OW (16.71 ± 0.19 MPa). Whereas, the lowest bond integrity was observed by group 5 specimens disinfected using ICGP (11.21 ± 0.16 MPa). It was observed samples disinfected with OW (16.71 ± 0.19 MPa) in group 2 and samples in group 4 (16.09 ± 0.26 MPa) treated with Triphala displayed comparable outcomes of bond strength (p > 0.05). It was observed that group 2 (70%) and 4 (80%) treated specimens accounted mostly for cohesive failure. However, groups 1 (80%), 3 (60%), and 5 (70%) displayed an adhesive failure pattern.

CONCLUSION

OW and Triphala displayed better bond integrity of adhesive resin to CAD and therefore have the potential to be used as a cavity disinfectant in clinical settings. However, ICGP and KTPL displayed weak bonds of adhesive to CAD. More work is needed to extrapolate the findings of the present study.

The effect of 400 nm femtosecond laser and Zn(II)chlorin e6 methyl ester (Zn(II)e6Me) photosensitizer on disinfection of radicular dentin bonded to glass fiber post

AIM

To assess and compare push-out bond strength (PBS) when canal disinfected with 5.25% NaOCl, 400 nm femtosecond laser, and natural PS activated by PDT (CP and Zn (II) Ce6 methyl ester) on bond efficacy of radicular dentin bonded to glass fiber post.

MATERIAL AND METHODS

A sum of 40 non-traumatic, cautiously extracted with closed apex human mandibular premolars were collected and decoronated up to the cement-o-enamel junction. Canals of all specimens were cleaned and shaped using a Protaper universal NiTi system via a crown-down approach, then finally dried out and obturated with gutta-percha. Post alignment space was formed with peso reamers and sanitized. Then samples were randomly allocated into four groups as per the radicular dentin designated disinfection protocols. Group 1 disinfected with curcumin photosensitizer + EDTA, group 2: 5.25% NaOCl and EDTA, group 3: Zn (II) Ce6 methyl ester and EDTA and group 4 sanitized with 400 nm fs-laser + EDTA. GFP was cemented into the radicular canal space and specimens were placed in a thermocycler. Segmentation of the root was done at three levels (coronal, middle, and apical) and positioned in a universal testing machine for PBS analysis. Failure mode analysis was performed using a stereomicroscope and statistical analysis was executed by one-way ANOVA and Tukey multiple comparison tests at a statistically significant level of p < 0.05.

RESULTS

The highest PBS was revealed by group 2 canal disinfected with 5.25% NaOCl +17% EDTA (control) at coronal (9.49 ± 1.42 MPa) and middle (7.545 ± 0.15 MPa) root levels. Whereas, the lowest PBS was displayed by group 3: Zn (II) Ce6 methyl ester +17% EDTA at coronal (6.31 ± 0.54 MPa) middle (4.85 ± 0.11 MPa) root levels respectively. Intergroup comparison presented that radicular dentin disinfected with 400 nm femtosecond laser + 17% EDTA substantiated comparable PBS result to group 2 (control) at all three root levels (p > 0.05). Likewise, root surface disinfection with Curcumin activated by PDT+17% EDTA unveiled no statistically significant result for specimens disinfected with Zn(II) Ce6 methyl ester +17% EDTA(p > 0.05). Furthermore, apical root segments in all groups showed a substantial decrease in PBS value and were comparable (p > 0.05).

CONCLUSION

The bond efficacy of glass fiber post to radicular dentin disinfected with 400 nm femtosecond laser has the potential to be used as an alternative to conventional sodium hypochlorite.

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.

Photodynamic therapy for treating infected skin wounds: A systematic review and meta-analysis from randomized clinical trials

BACKGROUND

Infected skin wounds represent a public health problem that effects 20 million people worldwide. Photodynamic therapy (PDT) is a treatment option with excellent results against several infections.

OBJECTIVE

This study aimed to perform a systematic review and meta-analysis on PDT efficacy for treating infected wounds based on randomized clinical trials (RCTs).

METHODS

PubMed, Scopus, Web of Science, SciELO, and the Cochrane library were searched. The Delphi List criteria and the Revised Cochrane risk-of-bias (Rob 2) were used for evaluating the quality of clinical trials. Meta-analyses were performed with the random-effect model. The odds ratio was the effect measure for binary outcomes, while the standard mean difference was used for continuous outcomes. The trim-and-fill method was used to detect small-study effects. The quality of evidence was verified for each outcome.

RESULTS

Only four out of 573 articles were selected for the qualitative and quantitative analyses. The most frequent cause of infected wounds was impaired venous circulation (75%). All studies used red LED light. PDT reduced healing time and improved the healing process and wound oxygenation. Patients treated with PDT showed 15% to 17% (p = 0.0003/ I²=0%) lower microbial cell viability in the wound and a significantly smaller wound size (0.72 cm²/p = 0.0187/I²=0%) than patients treated with placebo or red-light exposure. There was a high level of evidence for each meta-analysis outcome.

CONCLUSION

PDT can be an excellent alternative treatment for infected skin wounds, though larger trials are needed.

Antimicrobial photodynamic therapy as an adjunctive treatment to ultrasound for the dentin caries-like lesion removal

OBJECTIVE

To evaluate in vitro the efficacy of ultrasound device to remove caries-like dentin and the curcumin-mediated antimicrobial photodynamic therapy (aPDT) to decontaminate the affected dentin.

METHODS

Bovine dentin specimens (n = 173) of 4 × 4 × 2 mm were first submitted to Knoop surface microhardness to standardize the specimens (29 ± 3 KHN). Artificial caries lesion was induced by Streptococcus mutans strain by biological model for 7 days. Infected dentin was removed (1 min) with the following techniques: dentin excavator, bur at low-speed rotation and ultrasound device. After that, aPDT application was performed using blue LED under 460 nm. Polarized light microscopy (PLM), removal rate (n = 10), cross-sectional microhardness (n = 10), colony forming units per milliliter (CFU) (n = 9) and confocal laser microscopy (CM) (n = 2) were performed. ANOVA with Welch correction, post-hoc Games-Howell and two-way ANOVA followed by Tukey's post-hoc tests were used.

RESULTS

PLM confirmed the caries lesion formation with a depth of ∼147.9 µm. Groups treated with ultrasound showed lower removal rate (p = 0.001). Regardless of the treatment, the microhardness values increased as function of depth (p ≤ 0.05). Carbide bur showed the highest microhardness value, followed by ultrasound and excavator. CFU and CM showed a significant reduction in S. mutans after aPDT application.

CONCLUSION

Ultrasound was efficient, since it removed infected dentin, preserving the affected dentin and aPDT can be used as a complementary therapy to decontaminate the affected dentin.

CLINICAL SIGNIFICANCE

Ultrasound device may help the clinician to remove dentin caries-like lesions since it is a conservative technique and provided the removal of infected dentin, preserving the affected dentin. aPDT application may be used as a complimentary technique to promote antibacterial effect and possibly minimize the risk of secondary caries.

Efficacy of Antimicrobial Photodynamic Therapy Mediated by Photosensitizers Conjugated with Inorganic Nanoparticles: Systematic Review and Meta-Analysis

Antimicrobial photodynamic therapy (aPDT) is a method that does not seem to promote antimicrobial resistance. Photosensitizers (PS) conjugated with inorganic nanoparticles for the drug-delivery system have the purpose of enhancing the efficacy of aPDT. The present study was to perform a systematic review and meta-analysis of the efficacy of aPDT mediated by PS conjugated with inorganic nanoparticles. The PubMed, Scopus, Web of Science, Science Direct, Cochrane Library, SciELO, and Lilacs databases were searched. OHAT Rob toll was used to assess the risk of bias. A random effect model with an odds ratio (OR) and effect measure was used. Fourteen articles were able to be included in the present review. The most frequent microorganisms evaluated were Staphylococcus aureus and Escherichia coli, and metallic and silica nanoparticles were the most common drug-delivery systems associated with PS. Articles showed biases related to blinding. Significant results were found in aPDT mediated by PS conjugated with inorganic nanoparticles for overall reduction of microorganism cultured in suspension (OR = 0.19 [0.07; 0.67]/p-value = 0.0019), E. coli (OR = 0.08 [0.01; 0.52]/p-value = 0.0081), and for Gram-negative bacteria (OR = 0.12 [0.02; 0.56/p-value = 0.0071). This association approach significantly improved the efficacy in the reduction of microbial cells. However, additional blinding studies evaluating the efficacy of this therapy over microorganisms cultured in biofilm are required.

Application of lasers in dentistry: a bibliometric study of the top 100 most-cited papers

This bibliometric study analyzed the 100 most-cited papers about the use of lasers and their modalities in dentistry. A search strategy was created using specific keywords related to the topic. A comprehensive search was then conducted in the Web of Science Core Collection (WoS-CC) database up to July 2021. Papers that addressed the application of any type of laser and its modalities in dentistry were included. Each paper was cross-matched with the number of citations on Scopus and Google Scholar. The following data were extracted from papers: title, number of citations, authorship, country, year of publication, journal, study design, subject, laser type, and oral health outcomes. The VOSviewer software was used to generate bibliometric networks. The total number of citations ranged from 120 to 4,124 and 23 papers received more than 200 citations. Papers were published from 1964 to 2015. Most papers were from Europe (42%) and Anglo-Saxon America (27%). The USA was the country with more top 100 papers (25%). Papers were published mainly in Lasers in Surgery and Medicine (15%) and Lasers in Medical Science (7%). VOSviewer maps demonstrated the existence of national and international research collaborations among institutions and authors. Most studies had a laboratory design (57%) and were about restorative dentistry (32%) and periodontics (21%). This bibliometric study of the top 100 most-cited papers on lasers in dentistry allowed a quantitative and qualitative analysis of this very promising research field, revealing a net of collaboration and the importance of this topic in dentistry.

Topographical changes and bactericidal efficacy of antimicrobial photodynamic therapy on titanium implant surface

BACKGROUND

A lot of research has been done on various disinfection modalities used to achieve an aseptic implant surface. However, the bacterial efficacy and the topographical alterations resulting from the use of these techniques have never been compared.

OBJECTIVE

This study aimed to evaluate and compare the disinfection efficacy and surface changes on a bacteria contaminated titanium block following application of various disinfectants.

METHOD

Ultrasonically cleaned titanium blocks were contaminated with Porphyromonas gingivalis and Tannerella forsythia. The infected titanium implants were randomly divided into four experimental groups and decontaminated using antimicrobial photodynamic therapy (aPDT), laser therapy, chlorhexidine and hydrogen peroxide. Bacterial viability and surface changes following decontamination were analyzed.

RESULT

Bacterial viability decreased in all the groups with aPDT having the highest reduction. Surface roughness remained unchanged whereas the contact angle lessened in the aPDT group.

CONCLUSION

aPDT could possibly be a suitable alternative to other disinfection regimen to treat periimplantitis.

EFFICACY OF CURCUMIN-MEDIATED ANTIBACTERIAL PHOTODYNAMIC THERAPY FOR ORAL ANTISEPSIS: A SYSTEMATIC REVIEW AND NETWORK META-ANALYSIS OF RANDOMIZED CLINICAL TRIALS

BACKGROUND

currently, the presence of oral microorganisms resistant to traditional treatment is increasing, thus search for new modalities of therapies is needed. In this context, antimicrobial photodynamic therapy (aPDT) is an alternative approach for the treatment of resistant or not resistant microorganisms. Therefore, the aim of the present study was to conduct a systematic review and meta-analysis of randomized clinical trials of aPDT for oral antisepsis against oral polymicrobial biofilms.

METHODS

PubMed, Science Direct, Scopus, SciELO, Lilacs, Cochrane Library and Embase databases were searched. In total, five articles were included for qualitative analysis and four articles were used for quantitative analyses. Bias assessment of the eligible articles was made using the RoB 2 criteria. Network meta-analysis was performed using the random-effect model. Subgroup's analysis was also conducted. The groups evaluated were aPDT, exposure to light only and no treatment at all (control group). The quality of evidence was accessed by CINeMA approach.

RESULTS

aPDT mediated by curcumin had significant results in the reducing bacterial load (0.31-0.49 log₁₀ UFC/ I²=0%) when compared with the control group. The included articles were classified as low risk of bias, despite biases detected by allocation and blinding. Moreover, quantitative analysis between aPDT and control group and between light and control group were classified with low risk of confidence rating, while the results from aPDT versus light were classified as moderate risk of confidence rating.

CONCLUSION

aPDT has significant efficacy for oral antisepsis, however more randomized clinical trials will be needed to validate the present results.

Antibacterial Effect of Red Laser Therapy on Enterococcus faecalis Using Different Photosensitizers: An In Vitro Study

Objective

To assess the antibacterial effect of red laser using different photosensitizers such as methylene blue and malachite green on monoradicular premolars contaminated with E. faecalis ATCC 29212.

Methods

This was an in vitro experimental study. Monoradicular premolars (44, 45, 34, and 35) were used, which were treated with ProTaper Next. After instrument change, irrigation, disinfection, and aspiration were performed with 2 ml of 4% NaOCl with a NaviTip 30°G needle (Ultradent, South Jordan, UT, USA). Group 1: RL + MB (red laser associated with methylene blue photosensitizer), group 2: RL + MG (red laser associated with malachite green photosensitizer), and group 3: control (no treatment). The E. faecalis strain was cultured on trypticase soy agar (TSB) (Difco, Detroit, MI, USA) and incubated at 37°C for 24 h. After the incubation period, colony-forming units (CFU/ml) of each group were counted using the plate count method. The ANOVA test was used with a significance level of p < 0.05.

Results

Group 1 had the lowest antibacterial contamination as it averaged only 530 ± 581.3 CFU/ml, while group 2 had the highest contamination with an average of 1990 ± 542.5 CFU/ml. Comparison revealed that there were statistically significant differences between the RL + MB and RL + MG groups (p < 0.001).

Conclusions

Group 1 had the best antimicrobial potential because it presented the lowest contamination in CFU/ml of E. faecalis compared to group 2 and group 3.

Exploring the use of a Ruthenium complex incorporated into a methacrylate-based dental material for antimicrobial photodynamic therapy

OBJECTIVES

To evaluate the effects of a blue light photosensitizer (PS), Ruthenium II complex (Ru), on the chemical, physical, mechanical, and antimicrobial properties of experimental dental resin blends.

METHODS

The experimental resin (BisEMA, TEEGDMA, HPMA, ethanol, and photoinitiator) was loaded with Ru at 0.00%, 0.07%, 0.14%, 0.28%, 0.56%, 1.12%, 1.2%, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% w/w. Samples were evaluated for the degree of conversion (DC) after 30 and 60 s curing-time (n = 6). Selected formulations (0.00%, 0.28%, 0.56%, 1.12%) were further tested for shear bond strength (SBS) (n = 15); flexural strength (FS) (n = 12); and antimicrobial properties (CFUs), in dark and light conditions. These latter tests were performed on specimens stored for 24-h or 2-month in 37°C water. Water sorption (WS) and solubility (SL) tests were also performed (n = 12). Data were analyzed either by a one- or two-factor general linear model (α = 0.05).

RESULTS

Overall, Ru concentration above 1.2% resulted in reduced DC. In SBS results, only the 1.12%Ru resin blend samples had statistically lower values compared to the 0.00%Ru resin blend at 24-h storage (p = 0.004). In addition, no differences in SBS were detected among the experimental groups after 2-month storage in water. Meanwhile, FS increased for all experimental groups under similar aging conditions (p < 0.001). Antimicrobial properties were improved upon inclusion of Ru and application of light (p < 0.001 for both) at 24-h and 2-month storage. Lastly, no detectable changes in WS or SL were observed for the Ru-added resins compared to the 0.00%Ru resin blend. However, the 0.28% Ru blend presented significantly higher WS compared to the 0.56% Ru blend (p = 0.007).

CONCLUSIONS

Stable SBS, improved FS, and sustained antimicrobial properties after aging gives significant credence to our approach of adding the Ruthenium II complex into dental adhesive resin blends intended for an aPDT approach.

Dental-Plaque Decontamination around Dental Brackets Using Antimicrobial Photodynamic Therapy: An In Vitro Study

Background: In orthodontic therapy, the enamel around brackets is very susceptible to bacterial-plaque retention, which represents a risk factor for dental tissues. The aim of this study was to evaluate the effect of methylene blue and a chlorophyllin–phycocyanin mixture, used with and without light activation, in contrast with a 2% chlorhexidine solution, on Streptococcus mutans colonies. Methods: Twenty caries-free human extracted teeth were randomized into five groups. A Streptococcus mutans suspension was inoculated on teeth in groups B, C, D, and E (A was the positive-control group). Bacterial colonies from groups C, D, and E (B was the negative-control group) were subjected to photosensitizers and 2% chlorhexidine solution. For groups C and D, a combined therapy consisting of photosensitizer and light activation was performed. The Streptococcus mutans colonies were counted, and smears were examined with an optical microscope. Two methods of statistical analysis, unidirectional analysis of variance and the Tukey–Kramer test, were used to evaluate the results. Results: A statistically significant reduction in bacterial colonies was detected after the combined therapy was applied for groups C and D, but the most marked bacterial reduction was observed for group D, where a laser-activated chlorophyll–phycocyanin mixture was used. Conclusions: Photodynamic therapy in combination with methylene blue or chlorophyllin–phycocyanin mixture sensitizers induces a statistically significant decrease in the number of bacterial colonies.

Efficacy of antimicrobial photodynamic therapy compared to nystatin therapy in reducing Candida colony count in patients with Candida-associated denture stomatitis: a systematic review and meta-analysis

Purpose This meta-analysis assessed the efficacy of antimicrobial photodynamic therapy (aPDT) compared to conventional nystatin therapy (NYT) in reducing Candida colony count in patients with Candida-associated denture stomatitis (CADS) and critically appraised the available literature.Methods This meta-analysis was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) updated guidelines. A literature search was performed in four electronic databases to identify relevant articles up to 15 August 2021. Randomised controlled trials (RCTs) that assessed the efficacy of aPDT compared to NYT in reducing Candida colony count in patients with CADS were investigated. The weighted mean difference (MD) and 95% confidence interval were calculated. The I2 statistic was used to determine heterogeneity at the level of α = 0.10. The Cochrane risk of bias (RoB 2) tool was used to assess the risk of bias. Certainty of the evidence was determined using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) ranking system.Results Only three eligible RCTs with 141 participants were included in this systematic review and meta-analysis. Based on the pooled results, NYT compared to aPDT generally performed better in reducing Candida colony count (Log10 CFU/mL) in patients' palate and patients' denture. The included studies had a moderate risk of bias and the certainty of the evidence was low.Conclusion Although still inconclusive, based on the current evidence, aPDT may be effective in reducing Candida colony count and treating CADS. Nonetheless, it does not appear to be more effective than conventional NYT in this regard. According to the limited number of included studies, more well-designed RCTs with larger sample sizes and standardised methodology should be conducted to validate this conclusion.

Adjunctive use of antimicrobial photodynamic therapy in the surgical treatment of periapical lesions: a case series

BACKGROUND

Antimicrobial photodynamic therapy (aPDT) is being used in endodontics to improve orthograde root canal disinfection as an adjunct to standard treatments. Conversely, evidence concerning the application of aPDT in retrograde endodontic surgery is limited. Thus, the aim of the present study was to provide additional data regarding the use of aPDT in the surgical endodontic treatment of periapical lesions.

METHODS

A total of 25 consecutive patients presenting teeth with periapical radiolucency eventually associated with clinical signs and symptoms of apical periodontitis were included. Following access flap completion, osteotomy, mechanical debridement, root apical third resection, and preparation of the root-end cavity, aPDT was applied to decontaminate the surgical site using phenothiazine chloride dye at a concentration of 10 mg/mL and irradiation with a hand-held 100-mW diode laser with a wavelength of 660 ± 10 nm. At the latest follow-up visit, healing was evaluated as successful, uncertain, or failure according to well-established clinical and radiological criteria.

RESULTS

Overall, 31 periapical lesions were treated with aPDT. Healing proceeded uneventfully. The mean follow-up time was 36.19 months, with times ranging from 12 to 85 months. A total of 25 (80.65%) cases were classified as successful, 5 (16.13%) as uncertain, and only one (3.22%) as failure. Irrespective of the treatment outcome, all treated teeth were still functional, with no symptoms reported by the patients.

CONCLUSION

aPDT as an adjunctive treatment modality in the surgical endodontic treatment of periapical lesions showed promising medium-term results associated with preservation of all diseased teeth.

Antimicrobial action of photodynamic therapy on Enterococcus faecalis biofilm using curing light, curcumin and riboflavin

The aim of this study was to assess the effect of antimicrobial photodynamic therapy (aPDT) with curcumin and riboflavin on three-week Enterococcus faecalis biofilm. At first the 15-mm root canals of 65 single rooted extracted human teeth (including maxillary incisors, mandibular and maxillary canines and mandibular premolars) were separated from the crown and were prepared with ProTaper instruments. After autoclave sterilisation, samples were inoculated with E. faecalis suspension, and incubated for three weeks. After ensuring biofilm formation by scanning electron microscopy (SEM) in two teeth, the remaining 63 teeth were randomly divided into seven groups (n = 9): aPDT + curcumin, aPDT + riboflavin, LED, curcumin, riboflavin, 5.25% NaOCl (positive control) and no intervention (negative control). For light source a LED unit with 390-480 nm wavelength (peak of 460 nm), power density of 1000 ± 100 mW cm^-2 and mean energy density of 60 J cm^-2 was used. The roots were horizontally sectioned into coronal, middle and apical thirds each with 5 mm thicknesses. Dentin chips with equal weight (1 ± 0.005 g) were collected from the root canal walls with Gates Glidden drills and were transferred into microtubes containing 1 mL of sterile saline and vortexed for 30 s. Next, 10 µL of the contents of each tube was serially diluted and eventually, 10 µL of each solution was cultured on BHI agar. The number of colony-forming units was determined. Data were analysed using the Kruskal-Wallis and Friedman tests. The colony reduction was not significantly different between NaOCl and either riboflavin + LED or Curcumin + LED. The 5.25% NaOCl group showed maximum reduction in colony count, compared with the negative control (P = 0.00). Groups with aPDT with Curcumin + LED (P = 0.005), and with riboflavin + LED (P = 0.011) showed significant reduction in colony count in all three canal thirds (P < 0.05) without any difference with one another. With significant reduction of E. faecalis colony count, aPDT with Curcumin and riboflavin can serve as an adjunct to routine root canal disinfection method.

Photodynamic therapy combined with itraconazole against a case of cutaneous blastomycosis

Cutaneous blastomycosis is endemic to North America and is often caused by dimorphic fungi with spores that are inhaled, inoculated spores, or hyphae that infect immunosuppressed and healthy people. It is sporadic and described as a universal imitator with morphological manifestations as erythema, nodules, and ulcers. Our case demonstrated a 69-year-old female bitten by her pet dog who was then diagnosed with cutaneous blastomycosis through social history and detailed laboratory examinations. She experienced a prolonged failure with antibacterial treatment, negative stool and tissue culture, and chronic inflammatory cell infiltrates on tissue pathology. High-throughput sequencing was performed and showed evidence of Blastomyces dermatitidis aetiology. Photodynamic therapy combined with oral itraconazole was administered, and the patient recovered in a short time. Our case presents inoculated cutaneous blastomycosis and a treatment approach in which photodynamic therapy combined with oral itraconazole significantly reduced the duration of disease treatment and affords a promising choice for the treatment of cutaneous blastomycosis.

Coordination Complexes as a New Generation Photosensitizer for Photodynamic Anticancer Therapy

Photodynamic therapy (PDT) has become an alternative to standard cancer treatment methods such as surgery, chemotherapy and radiotherapy. The uniqueness of this method relies on the possibility of using various photosensitizers (PS) that absorb and convert light emission in radical oxygen-derived species (ROS). They can be present alone or in the presence of other compounds such as metal organic frameworks (MOFs), non-tubules or polymers. The interaction between DNA and metal-based complexes plays a key role in the development of new anti-cancer drugs. The use of coordination compounds in PDT has a significant impact on the amount ROS generated, quantum emission efficiency (Φem) and phototoxic index (PI). In this review, we will attempt to systematically review the recent literature and analyze the coordination complexes used as PS in PDT. Finally, we compared the anticancer activities of individual coordination complexes and discuss future perspectives. So far, only a few articles link so many transition metal ion coordination complexes of varying degrees of oxidation, which is why this review is needed by the scientific community to further expand this field worldwide. Additionally, it serves as a convenient collection of important, up-to-date information.

Bacterial Biofilm Inhibition: A Focused Review on Recent Therapeutic Strategies for Combating the Biofilm Mediated Infections

Biofilm formation is a major concern in various sectors and cause severe problems to public health, medicine, and industry. Bacterial biofilm formation is a major persistent threat, as it increases morbidity and mortality, thereby imposing heavy economic pressure on the healthcare sector. Bacterial biofilms also strengthen biofouling, affecting shipping functions, and the offshore industries in their natural environment. Besides, they accomplish harsh roles in the corrosion of pipelines in industries. At biofilm state, bacterial pathogens are significantly resistant to external attack like antibiotics, chemicals, disinfectants, etc. Within a cell, they are insensitive to drugs and host immune responses. The development of intact biofilms is very critical for the spreading and persistence of bacterial infections in the host. Further, bacteria form biofilms on every probable substratum, and their infections have been found in plants, livestock, and humans. The advent of novel strategies for treating and preventing biofilm formation has gained a great deal of attention. To prevent the development of resistant mutants, a feasible technique that may target adhesive properties without affecting the bacterial vitality is needed. This stimulated research is a rapidly growing field for applicable control measures to prevent biofilm formation. Therefore, this review discusses the current understanding of antibiotic resistance mechanisms in bacterial biofilm and intensely emphasized the novel therapeutic strategies for combating biofilm mediated infections. The forthcoming experimental studies will focus on these recent therapeutic strategies that may lead to the development of effective biofilm inhibitors than conventional treatments.

Antimicrobial effects of photodynamic therapy with Fotoenticine on Streptococcus mutans isolated from dental caries

Photodynamic therapy (PDT) is a promising strategy to control cariogenic pathogens, such as Streptococcus mutans. Seeking to reach the total bacterial elimination from dental surfaces, novel photosensitizers have been investigated, such as Fotoenticine (FTC) derived from chlorin e6. The objective of this study was to investigate the photodynamic effects of FTC against several clinical strains of S. mutans. Clinical isolates were obtained from patients with active carious lesions, identified by molecular analysis and subjected to PDT using laser irradiation (660 nm and 39.5 J/cm²) in planktonic and biofilm stages. We identified 11 S. mutans strains from cervical, occlusal and proximal caries. PDT mediated by FTC has totally eliminated the S. mutans cells in planktonic growth for all analyzed strains. In biofilms, PDT with FTC reached statistically significant reductions compared with the non-treated control group, at 5.4, 5.5 and 6.5 Log₁₀ (CFU/mL), respectively, for the strains from proximal, occlusal and cervical caries. The scanning electron microscopy evaluations confirmed that PDT mediated by FTC was able to disaggregate and kill the S. mutans cells adhered to enamel surface, suggesting its potential to disinfect the dental tissues.

Curcumin-loaded Pluronic® F-127 Micelles as a Drug Delivery System for Curcumin-mediated Photodynamic Therapy for Oral Application

Antimicrobial photodynamic therapy (aPDT) is promising for oral decontamination. Curcumin has been used as photosensitizer; however, the hydrophobic properties can negatively affect aPDT. This study evaluated the aPDT efficacy using Cur-loaded Pluronic^® F-127 micelles against Streptococcus mutans and Candida albicans biofilms. Micelles characterization was performed by zeta potential, dynamic light scattering, transmission electron microscopy, absorption and fluorescence spectroscopy. Cur concentrations, cell viability by CFU mL^-1 and confocal microscopy were determined. Data were analyzed by parametric and nonparametric tests under 5%. Cur-loaded Pluronic^® F-127 exhibited spherical shape, suitable particle size (≤100 nm), adequate polydispersity index, best stability, lower photodegradation and autoaggregation compared to unloaded-Cur. Both microorganisms were sensitive to Cur-loaded Pluronic^® F-127 micelles aPDT, with minimum inhibitory concentration (MIC) of 270 μm and 2.1093 μm for S. mutans and C. albicans suspended culture, respectively. Cur-loaded Pluronic^® F-127 aPDT exhibited antibacterial/antifungal effect against the biofilms (~3 log₁₀ reduction; P ≤ 0.05); however, similar to unloaded (P ≥ 0.05). Confocal images confirmed these results. Cur-loaded Pluronic^® F-127 micelles exhibited good photo-chemical properties and may be a viable alternative to deliver Cur and to improve aPDT effect during the treatment of dental caries. Moreover, Pluronic^® micelles can enhance the solubility, stability, permeability and control the release of Cur.

Phenothiazine Dyes Induce NADH Photooxidation through Electron Transfer: Kinetics and the Effect of Copper Ions

Phenothiazine dyes, methylene blue, new methylene blue, azure A, and azure B, photosensitized the oxidation of nicotinamide adenine dinucleotide (NADH), an important coenzyme in the living cells, through electron transfer. The reduced forms of these phenothiazine dyes, which were produced through electron extraction from NADH, underwent reoxidation to the original cationic forms, leading to the construction of a photoredox cycle. This reoxidation process was the rate-determining step in the photoredox cycle. The electron extraction from NADH using phenothiazine dyes can trigger the chain reaction of the NADH oxidation. Copper ions enhanced the photoredox cycle through reoxidation of the reduced forms of phenothiazine dyes. New methylene blue demonstrated the highest photooxidative activity in this experiment due to the fast reoxidation process. Electron-transfer-mediated oxidation and the role of endogenous metal ions may be important elements in the photosterilization mechanism.

Effects of Antimicrobial Photodynamic Therapy on Organic Solution and Root Surface In Vitro

Antimicrobial photodynamic therapy (a-PDT) is attracting attention as a new form of dental treatment. While it is primarily applied to produce an antibacterial effect, it decreases lipopolysaccharide (LPS) and protease activity. Here, we evaluated differences in the antibacterial activity of a-PDT on three types of bacteria and the effects on the organic substances (i.e., albumin and LPS). Furthermore, we investigated the effects of a-PDT on root surfaces. A FotoSan630® and toluidine blue were used to perform a-PDT in this study. We measured its antimicrobial activity against Porphyromonas gingivalis, Streptococcus mutans, and Enterococcus faecalis. Antimicrobial testing revealed strong antimicrobial action and P. gingivalis, E. faecalis, and S. mutans were almost undetectable after 50, 120, and 100 s, respectively. In organic resolution tests, albumin was significantly decreased from 1 min after a-PDT application onward, while LPS significantly decreased at 5 min after the application. The root surfaces after a-PDT were confirmed to be cleaner than the controls without suffering any damage. Depending on the bacterial species, a-PDT exhibited antimicrobial activity against various types of bacteria and sensitivity differed. Moreover, we reported that a-PDT resolves protein and LPS, enabling the formation of a healthy root surface without any damage.

Targeting immunogenic cancer cell death by photodynamic therapy: past, present and future

The past decade has witnessed major breakthroughs in cancer immunotherapy. This development has been largely motivated by cancer cell evasion of immunological control and consequent tumor resistance to conventional therapies. Immunogenic cell death (ICD) is considered one of the most promising ways to achieve total tumor cell elimination. It activates the T-cell adaptive immune response and results in the formation of long-term immunological memory. ICD can be triggered by many anticancer treatment modalities, including photodynamic therapy (PDT). In this review, we first discuss the role of PDT based on several classes of photosensitizers, including porphyrins and non-porphyrins, and critically evaluate their potential role in ICD induction. We emphasize the emerging trend of ICD induction by PDT in combination with nanotechnology, which represents third-generation photosensitizers and involves targeted induction of ICD by PDT. However, PDT also has some limitations, including the reduced efficiency of ICD induction in the hypoxic tumor microenvironment. Therefore, we critically evaluate strategies for overcoming this limitation, which is essential for increasing PDT efficiency. In the final part, we suggest several areas for future research for personalized cancer immunotherapy, including strategies based on oxygen-boosted PDT and nanoparticles. In conclusion, the insights from the last several years increasingly support the idea that PDT is a powerful strategy for inducing ICD in experimental cancer therapy. However, most studies have focused on mouse models, but it is necessary to validate this strategy in clinical settings, which will be a challenging research area in the future.

Efficacy of antimicrobial photodynamic therapy with Rose Bengal and blue light against cariogenic bacteria

OBJECTIVE

We evaluated the effect of antimicrobial photodynamic therapy (a-PDT) with Rose Bengal and blue light LED on bacteria that initiate and promote dental caries.

DESIGN

Colony forming units of Streptococcus mutans, Streptococcus sobrinus, Streptococcus sanguinis, and Lactobacillus salivarius under planktonic and biofilm conditions were counted after a-PDT treatment using Rose Bengal and blue light LED. In addition, cariogenic bacteria from saliva and dental plaques from ten volunteers were used for evaluation of a-PDT treatment.

RESULTS

We found that a-PDT using Rose Bengal at > 10 μg/mL had antimicrobial effects on oral Gram-positive S. mutans, S. sobrinus, S. sanguinis, and L. salivarius under both planktonic and biofilm conditions. The effect was also observed for cariogenic bacteria that formed biofilms containing water-insoluble glucans, through which the bacteria are firmly attached to the tooth surface. Moreover, a-PDT led to a marked reduction in cariogenic bacteria in saliva and dental plaques.

CONCLUSION

a-PDT could be a useful approach for controlling dental caries in dental surgery.

Polyacrylic Acid with Methylene Blue Dye as a Sensitizing Agent for Photodynamic Therapy to Reduce Streptococcus mutans in Dentinal Caries

Objective: To evaluate 11.5% polyacrylic acid (PA) containing 0.3% methylene blue (MB) dye as a photosensitizer for photodynamic therapy (PDT) of carious dentin. Methods: One hundred twenty molars were selected and the dentin was exposed for cariogenic challenge, where the molars were placed in brain heart infusion medium containing a standard strain of Streptococcus mutans (ATCC). Samples were randomly divided into eight groups (n = 15): S: saline, PA, MB: MB 0.3%, PA+MB: PA containing 0.3% MB + LLL: irradiation with low-level laser, PDT (MB): MB 0.3% + laser, PDT (PA): PA + laser, and PDT (PA+MB): PA containing 0.3% MB + laser. Carious dentin was collected before and after exposure to S. mutans. All samples of carious dentin were homogenized, diluted, and seeded in mitis salivarius bacitracin medium, and the cultures were incubated at 37°C for 15 days in anaerobic jars. The Wilcoxon test was used for analysis. Results: The percent microbial reduction achieved with each treatment was as follows: PDT (MB), 53.62%; PDT (PA+MB), 50.47%; PDT (PA), 46.73%; PA, 38.51%; MB, 19.75%; PA+MB, 17.18%; LLL, 12.83%; S, 5.99%. The greatest reductions in S. mutans growth occurred with PDT (MB), PDT (PA+MB), and PDT (PA) when compared to the S group (p = 0.0002, 0.0023, and 0.0232, respectively). Conclusions: PA containing 0.3% MB can be used as a photosensitizer for PDT to reduce S. mutans burden in carious dentin.

Light Energy Dose and Photosensitizer Concentration Are Determinants of Effective Photo-Killing against Caries-Related Biofilms

Caries-related biofilms and associated complications are significant threats in dentistry, especially when biofilms grow over dental restorations. The inhibition of cariogenic biofilm associated with the onset of carious lesions is crucial for preventing disease recurrence after treatment. This in vitro study defined optimized parameters for using a photosensitizer, toluidine blue O (TBO), activated via a red light-emitting diode (LED)-based wireless device to control the growth of cariogenic biofilms. The effect of TBO concentrations (50, 100, 150, and 200 μg/mL) exposed to light or incubated in the dark was investigated in successive cytotoxicity assays. Then, a mature Streptococcus mutans biofilm model under sucrose challenge was treated with different TBO concentrations (50, 100, and 150 μg/mL), different light energy doses (36, 108, and 180 J/cm²), and different incubation times before irradiation (1, 3, and 5 min). The untreated biofilm, irradiation with no TBO, and TBO incubation with no activation represented the controls. After treatments, biofilms were analyzed via S. mutans colony-forming units (CFUs) and live/dead assay. The percentage of cell viability was within the normal range compared to the control when 50 and 100 μg/mL of TBO were used. Increasing the TBO concentration and energy dose was associated with biofilm inhibition (p < 0.001), while increasing incubation time did not contribute to bacterial elimination (p > 0.05). Irradiating the S. mutans biofilm via 100 μg/mL of TBO and ≈180 J/cm² energy dose resulted in ≈3-log reduction and a higher amount of dead/compromised S. mutans colonies in live/dead assay compared to the control (p < 0.001). The light energy dose and TBO concentration optimized the bacterial elimination of S. mutans biofilms. These results provide a perspective on the determining parameters for highly effective photo-killing of caries-related biofilms and display the limitations imposed by the toxicity of the antibacterial photodynamic therapy’s chemical components. Future studies should support investigations on new approaches to improve or overcome the constraints of opportunities offered by photodynamic inactivation of caries-related biofilms.

Antimicrobial Photoinactivation Approach Based on Natural Agents for Control of Bacteria Biofilms in Spacecraft

A spacecraft is a confined system that is inhabited by a changing microbial consortium, mostly originating from life-supporting devices, equipment collected in pre-flight conditions, and crewmembers. Continuous monitoring of the spacecraft’s bioburden employing culture-based and molecular methods has shown the prevalence of various taxa, with human skin-associated microorganisms making a substantial contribution to the spacecraft microbiome. Microorganisms in spacecraft can prosper not only in planktonic growth mode but can also form more resilient biofilms that pose a higher risk to crewmembers’ health and the material integrity of the spacecraft’s equipment. Moreover, bacterial biofilms in space conditions are characterized by faster formation and acquisition of resistance to chemical and physical effects than under the same conditions on Earth, making most decontamination methods unsafe. There is currently no reported method available to combat biofilm formation in space effectively and safely. However, antibacterial photodynamic inactivation based on natural photosensitizers, which is reviewed in this work, seems to be a promising method.