Combined effects of photodynamic therapy and irrigants in disinfection of root canals

Root Canal Disinfection in Permanent Molars with Apical Lesion by Antimicrobial Photodynamic Therapy: Protocol for a Blind Randomized Clinical Trial

Objective: The proposed study aims to compare the effectiveness of conventional endodontic treatment (ET) with that of ET associated with antimicrobial photodynamic therapy (aPDT) in patients with apical lesion. Methods: Controlled, double-blind, randomized clinical trial (RCT); superiority study with three parallel arms. Randomization will be conducted in exchange blocks of six, with allocation 1:1:1. The control group will receive conventional ET, while experimental group 1 (EG1) will receive conventional ET + aPDT with laser at 660 nm, fluence of 600 J/cm2; EG2 will receive conventional ET + aPDT with laser at 660 nm, fluence of 1200 J/cm2. The primary outcome will be canal disinfection before treatment, measured by analysis of colony formation (CFU/mL) and the success rate measured after 6 months on the clinical and radiographic evaluations. The mean and standard deviation will be calculated for continuous outcomes, and the CFU/mL mean between groups will be evaluated by ANOVA test. The Chi-squared test will be calculated for binary outcomes. A logistic regression analysis will be performed to assess differences in the success rate between groups, adjusted for the covariates. The Stata 18 software will be used, with a significance threshold of 5%. Conclusions: Few RCTs have evaluated the effectiveness of aPDT in root canal disinfection in patients with permanent dentition presenting apical lesion. New RCTs with larger numbers of participants are needed to support using aPDT as an adjuvant to conventional ET in root canal disinfection for routine use in clinical practice. The trial was registered prospectively in ClinicalTrials.gov (NCT05916859).

Synergistic effect of TONS504-mediated photodynamic antimicrobial chemotherapy and additives widely contained in ophthalmic solutions: benzalkonium chloride and ethylenediaminetetraacetic acid

TONS504 (C₅₁H₅₈N₈O₅I₂), a chlorine derivative, effectively generates singlet oxygen by light activation and exhibits photodynamic antimicrobial effects (PAEs) on various pathogens. However, this photosensitizer has some limitations: a high tendency to self-aggregate and a relatively weak PAE for Gram-negative bacteria compared with Gram-positive bacteria. To overcome these limitations, the present study investigated the synergistic effects of the PAE of TONS504 and two additives commonly contained in ophthalmic solutions: benzalkonium chloride (BAC) or ethylenediaminetetraacetic acid (EDTA). Staphylococcus aureus and Pseudomonas aeruginosa were exposed to TONS504 and/or each additive. Photodynamic antimicrobial chemotherapy was performed with light irradiation centered at a wavelength of 665 nm with a total light energy of 30 J/cm². Following incubation, the number of colonies formed was counted. Additionally, we examined the inhibitory effects of the additives on TONS504 self-aggregation by observing its absorption spectrum. Consequently, the PAEs of TONS504 on S. aureus were enhanced by both additives, and BAC displayed stronger synergistic effects on the bacteria than EDTA. By contrast, only EDTA increased the PAE on P. aeruginosa. The peak of the TONS504 absorption spectrum shifted to a longer wave length and the absorbance increased in the presence of BAC, suggesting that BAC inhibited the self-aggregation of the photosensitizer. In conclusion, the combination of BAC or EDTA and TONS504-mediated photodynamic antimicrobial chemotherapy exhibits a synergistic antimicrobial effect on S. aureus and P. aeruginosa. The optimal additive to enhance the PAE may differ between bacterial strains.

Photodynamic therapy associated final irrigation in root canals of the primary teeth

The aim of this study was to analyze, in vitro, the reduction of Enterococcus faecalis in root canals of primary teeth after final irrigation and photodynamic therapy (PDT) use. Twenty primary molars were contaminated with Enterococcus faecalis. The teeth were randomly distributed into four groups according to the irrigation solutions and PDT use: G1 (Saline solution and no PDT use), G2 (17 % EDTA and no PDT use), G3 (Saline solution and PDT use) and G4 (17 % EDTA and PDT use). For PDT, 0.005 % toluidine blue was chosen as the photosensitizer, which was inserted in the canals with sterile paper cones. Bacterial counts were performed with a BHI test in blood agar plate, where bacteria were collected inside the canal for 30 s using sterile paper cones. The collection took place before and after the irrigation and PDT protocols. The samples were diluted, spread onto a blood agar plate and then incubated at 37 °C for 24 h. There was a reduction of the microbiota from the irrigation solutions before and after the final irrigation for all groups. It was observed a statistically significant reduction (p < 0,05) when PDT was used (97.6 % at the saline solution and 89.8 % at the 17 % EDTA) when compared to the groups with no PDT use. Our data demonstrated that PDT, according to the parameters used, increased the disinfection performance of the solutions tested in the root canals of primary teeth.

Effects of Rose Bengal- and Methylene Blue-Mediated Potassium Iodide-Potentiated Photodynamic Therapy on Enterococcus faecalis: A Comparative Study

BACKGROUND AND OBJECTIVES

This study was performed to compare the use of methylene blue (MB) and rose bengal (RB) in antimicrobial photodynamic therapy (PDT) targeting Enterococcus faecalis (E. faecalis) bacteria in planktonic and biofilm forms with potassium iodide (KI) potentiation.

STUDY DESIGN/MATERIALS AND METHODS

E. faecalis bacteria in planktonic form were exposed to antimicrobial PDT protocols activating MB and RB, with or without KI potentiation, following laser irradiation with different exposure times, 60 mW/cm² laser power, and different photosensitizer agent (PS)/potentiator concentrations to observe relationships among the variables. Two continuous-wave diode lasers were used for irradiation (red light: λ = 660 nm and green light: λ = 565 nm). The pre-irradiation time was 10 minutes. The vitality of E. faecalis biofilm was assessed by confocal laser scanning microscopy, and the morphology was determined by scanning electron microscopy. The effects on the proliferation of stem cells from the apical papilla (SCAPs) were analyzed by cell counting kit-8 assay. The staining effect of antimicrobial PDT on dentin slices was investigated. Statistical analysis using a one-way analysis of variance was done.

RESULTS

KI-potentiated RB and MB antimicrobial PDT both effectively eradicated E. faecalis bacteria in planktonic and biofilm forms. The minimum bactericidal concentrations of PSs (±100 mM KI) were obtained through PDT on planktonic E. faecalis, and the optimal light parameters were 60 mW/cm² , 6 J/cm² for 100 seconds. KI-potentiated PDT effectively strengthened the ability to inhibit E. faecalis biofilm with 86.50 ± 5.78% for MB (P = 0.0015 < 0.01) and 91.50 ± 1.75% for RB (P = 0.0418 < 0.05) of bactericidal rate, with less toxicity for SCAPs (P < 0.001) and less staining. KI could reduce the staining induced by antimicrobial PDT on dentin slices.

CONCLUSION

A combination of KI and antimicrobial PDT may be a useful alternative to conventional disinfection methods in endodontic treatment. MB and RB antimicrobial PDT at much lower concentrations with KI could hopefully achieve disinfection effects comparable with those of 1.5% NaClO while causing few adverse effects on SCAPs. KI helps to avoid staining problems associated with high concentrations of photosensitizer agents. Lasers Surg. Med. © 2020 Wiley Periodicals, LLC.

Evaluation of Photodynamic Therapy Using a Diode Laser 635 nm as an Adjunct to Conventional Chemo-Mechanical Endodontic Procedures against Enterococcus faecalis Biofilm: Ex-Vivo Study

The study aimed to evaluate the antimicrobial effect of photodynamic therapy (PDT) with the use of Toluidine Blue (TB) on extracted teeth infected with biofilms of Enterococcus faecalis. Fifty-four extracted teeth with single-roots and single canals were mechanically shaped, autoclaved, and contaminated with E. faecalis. They were randomly divided into six groups: two groups were negative and positive control groups, two groups were subjected to mechanical instrumentation and PDT with different pre-irradiation times and irradiation times, and two groups were subjected to chemo-mechanical endodontic treatment and PDT with different pre-irradiation times and irradiation times. In PDT groups, after the application of TB, the canals were irradiated with a diode laser of wavelength 635 nm, with a fiber diameter of 200 μm and 100 mW of power in continuous mode. The bacterial load was evaluated using a BioTimer Assay protocol. The greatest reduction of bacterial load was observed in groups of combined PDT with chemo-mechanical treatment. The reductions of bacterial load in groups of combined PDT with chemo-mechanical treatment, and in the positive control group, were significant (p < 0.01) when compared to that of the negative control group. Photodynamic therapy as an adjunctive modality may improve the disinfection capacity of conventional endodontic treatment against E. faecalis.

Evaluation of the outcome of various laser therapy applications in root canal disinfection: A systematic review

BACKGROUND

Any successful endodontic therapy requires elimination of the endodontic biofilms through meticulous root canal disinfection methods. Sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA) are the most common effective irrigants, in removing smear-layer from the coronal and middle thirds of the dental canals but reduced considerably towards the apical one third. In recent years, newly alternative treatment modalities have been proposed, including high-power lasers and antimicrobial photodynamic therapy (aPDT). Our work was conducted to evalaute the outcome of root canal disinfection in relation to the efficacy of various treatment modalities. Furthermore, every effort was made to present an overview of the aPDT outcomes, as a model for this application, and to propose laser parameters protocol with positive results.

METHODS

The electronic databases PubMed was searched from January 2013- January 2019. Our inclusive criteria based on laser therapy applications, as a model for root canal disinfection. The search terms utilised various combinations as follows: photodynamic therapy or antimicrobial photodynamic therapy or photoactivated disinfection or light activated disinfection or laser activated disinfection or laser therapy, and endodontic.

RESULTS

The results of this systematic review concluded that the effectiveness of aPDT and various laser wavelengths protocols, in removing endodontic biofilms from infected root canals, remains unattainable.

CONCLUSIONS

Study concluded that the combination of aPDT with antimicrobial irrigants could provide a synergetic effect. However, due to the heterogeneity of the selected studies and their limitations, in terms of lack of standardised protocol or discrepancy in the methodology, authors suggest further validated approaches to achieve optimal outcomes.

Photodynamic therapy in endodontics

Photodynamic therapy (PDT) is a treatment modality that was initiated in 1900; however, it was not until the last decade that PDT regained attention for its several favourable features during the treatment of microbial infections in endodontics. Recently, several papers advocated its use for root canal treatment. The concept of photodynamic inactivation requires microbial exposure to either exogenous or endogenous photosensitizer molecules, followed by visible light energy, typically wavelengths in the red/near-infrared region that cause the excitation of the photosensitizers resulting in the production of singlet oxygen and other reactive oxygen species that react with intracellular components and consequently produce cell inactivation and death. Recently, PDT has been suggested as a promising effective adjunct to standard antimicrobial intracanal cleaning and shaping for the treatment of periapical lesions. Current publications tested PDT in terms of bacterial load reduction in vivo, in vitro and ex vivo, showing promising results. The purpose of this article was to review the existing literature on PDT in the endodontic field regarding its mechanism of action, photosensitizers and light sources, limitations and clinical procedures. Although positive results have been demonstrated in vitro, there are considerably fewer in vivo investigations. In conclusion, more in vivo studies are needed on the use of antimicrobial PDT in root canal treatment.