A Small Amount of Singlet Oxygen Generated via Excited Methylene Blue by Photodynamic Therapy Induces the Sterilization of Enterococcus faecalis

Concanavalin A Delivers a Photoactive Protein to the Bacterial Wall

Modular supramolecular complexes, where different proteins are assembled to gather targeting capability and photofunctional properties within the same structures, are of special interest for bacterial photodynamic inactivation, given their inherent biocompatibility and flexibility. We have recently proposed one such structure, exploiting the tetrameric bacterial protein streptavidin as the main building block, to target S. aureus protein A. To expand the palette of targets, we have linked biotinylated Concanavalin A, a sugar-binding protein, to a methylene blue-labelled streptavidin. By applying a combination of spectroscopy and microscopy, we demonstrate the binding of Concanavalin A to the walls of Gram-positive S. aureus and Gram-negative E. coli. Photoinactivation is observed for both bacterial strains in the low micromolar range, although the moderate affinity for the molecular targets and the low singlet oxygen yields limit the overall efficiency. Finally, we apply a maximum entropy method to the analysis of autocorrelation traces, which proves particularly useful when interpreting signals measured for diffusing systems heterogeneous in size, such as fluorescent species bound to bacteria.

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).

Evaluation of cytotoxicity impacts of combined methylene blue-mediated photodynamic therapy and intracanal antibiotic medicaments on dental stem cells

Root canal therapy is a predominant method for treatment of dental pulp and periapical diseases. Conventional methods such as mechanical instrumentations, chemical irrigation and intracanal medicaments pose a huge limitation to root canal disinfection as they kill bacteria and dental stem cells simultaneously. Therefore, much attention has been focused on finding more efficacious antibacterial methods that has no or negligible cytotoxicity for dental stem cells. Herein, we hypothesized that combining antibacterial medicaments with Antimicrobial photodynamic therapy (aPDT) and methylene blue (MB) as a photosensitizer would be effective in reducing death of dental pulp stem cells (DPSCs). To examine this, DPSCs were isolated from third molar teeth through enzymatic digestion. Isolated cells were cultured in αMEM and when reached adequate confluency, were used for further analysis. Cytotoxicity effect of different groups of MB, DAP, MB, LED and their combination on DPSCs was analyzed using MTT assay. DPSCs membrane integrity as a marker of live cells was assessed through measuring lipid peroxidation and lactate dehydrogenase (LDH) release into extracellular space. Results showed that the combination of LED, MB and TAP or aPDT, MB and DAP was more effective in reducing DPSCs death rate compared to TAP and DAP administration alone. Moreover, Malondialdehyde (MDA) and LDH levels were found to be decreased in cells exposed to combination treatment in comparison with single TAP or DAP therapy. Our study shows the promising perspectives of employing combined aPDT, MB and antibiotic medicaments for reduction of dental stem cell death.

Effect of different disinfection protocols in bacterial viability of an intraradicular biofilm formed in situ

The present study aimed to evaluate bacterial viability after the use of different disinfection protocols in root canals infected with a multispecies biofilm (MB) formed in situ. Palatal roots with a single canal were obtained from extracted maxillary molars and sterilized before being inserted into the mouth. The roots were contaminated with a MB in an intraoral appliance worn by ten volunteers. All volunteers wore six roots simultaneously in two intraoral devices for 21 days. One root from each volunteer was assigned to each group (n=10): PUI - passive ultrasonic irrigation; EC - Easy Clean; XPF - XP-endo Finisher; aPDT - antimicrobial photodynamic therapy; CI - conventional irrigation; and NC - negative control. The samples were evaluated under confocal laser scanning microscopy. The percentage of viable cells (VC) was calculated over the total percentage of MB biovolume. Data were statistically analyzed (α=5%). The cell viability in the entire root canal or for each third was compared between groups (Kruskal-Wallis test, Dunn post-hoc test) and for the same group (Friedman test, Dunn post-hoc test). Disinfection protocols were not significantly different from each other (P>.05). Samples in EC, PUI, and aPDT had lower cell viability than in NC (P<.05). In the coronal third of samples in the EC, XPF, PUI and aPDT, the percentage of VC biovolume was lower than in the NC (P<.05). The percentage of VC in EC samples was lower in the coronal and middle thirds than in the apical third (P<.05). EC, PUI and aPDT had significant effects on cell viability in intraradicular multispecies biofilm formed in situ when compared with untreated samples.

Differentiation of Superoxide Radical Anion and Singlet Oxygen and Their Concurrent Quantifications by Nuclear Magnetic Resonance

While there have been various techniques, assays, and commercial kits developed to measure reactive oxygen species (ROS) with varying degrees of success, there is a lack of innovative methods to differentiate and quantify them simultaneously. In this work, we demonstrate a ¹⁹F nuclear magnetic resonance (NMR)-based method to differentiate two important types of ROS, superoxide radical anion and singlet oxygen, and to quantify them concurrently. By taking advantage of the unique chemical reactivity of two fluorine-containing molecules, 4-fluoro-3-methylphenyl boronic acid and 4-fluoro-3-methylphenol, serving as ¹⁹F NMR probes, we are able to differentiate and quantify, for the first time, superoxide radical anion and singlet oxygen generated by photosensitizers (PSs) concurrently. The results reveal that relative amounts of superoxide radical anion and singlet oxygen generated by a PS under light illumination are oftentimes sensitive to the environment, such as the presence or absence of electron donors. This method provides a means to identify the type of mechanism by which a PS functions under a given condition. We envision that this relatively simple, yet robust, method would be beneficial to a broad range of ROS-pertinent studies, such as photodynamic therapy and photoredox reactions.

The role of the light source in antimicrobial photodynamic therapy

Antimicrobial photodynamic therapy (APDT) is a promising approach to fight the growing problem of antimicrobial resistance that threatens health care, food security and agriculture. APDT uses light to excite a light-activated chemical (photosensitiser), leading to the generation of reactive oxygen species (ROS). Many APDT studies confirm its efficacy in vitro and in vivo against bacteria, fungi, viruses and parasites. However, the development of the field is focused on exploring potential targets and developing new photosensitisers. The role of light, a crucial element for ROS production, has been neglected. What are the main parameters essential for effective photosensitiser activation? Does an optimal light radiant exposure exist? And finally, which light source is best? Many reports have described the promising antibacterial effects of APDT in vitro, however, its application in vivo, especially in clinical settings remains very limited. The restricted availability may partially be due to a lack of standard conditions or protocols, arising from the diversity of selected photosensitising agents (PS), variable testing conditions including light sources used for PS activation and methods of measuring anti-bacterial activity and their effectiveness in treating bacterial infections. We thus sought to systematically review and examine the evidence from existing studies on APDT associated with the light source used. We show how the reduction of pathogens depends on the light source applied, radiant exposure and irradiance of light used, and type of pathogen, and so critically appraise the current state of development of APDT and areas to be addressed in future studies. We anticipate that further standardisation of the experimental conditions will help the field advance, and suggest key optical and biological parameters that should be reported in all APDT studies. More in vivo and clinical studies are needed and are expected to be facilitated by advances in light sources, leading to APDT becoming a sustainable, alternative therapeutic option for bacterial and other microbial infections in the future.

Application of Reactive Oxygen Species in Dental Treatment

Reactive oxygen species (ROS) and free radicals, which have been implicated in inflammation, pain, carcinogenesis, and aging, are actually used in dental treatments such as tooth bleaching and composite resin polymerization. Recently, numerous studies have investigated the application of ROS in the medical and dental fields. In previous studies, ROS were generated intentionally through pathways such as photolysis, photocatalytic methods, and photodynamic therapy, which are used in the medical field to target cancer. In the field of dentistry, generated ROS are applied mainly for periodontal treatment and sterilization of the root canal, and its effectiveness as an antibacterial photodynamic therapy has been widely reported.. Given this background, the present article aimed to review the basic effects of ROS in dental medicine, especially endodontic therapy, and to discuss future applications of ROS.

Effect of low-power diode laser on infected root canals

This study evaluated the effect of photodynamic therapy (PDT) on infected root canals. Twenty-one human teeth were selected, and 18 were infected by E. faecalis for 60 days. The antimicrobial strategies tested were: G1. Root canal preparation (RCP) using Niquel-Titanium (NiTi) rotary instruments, 2.5% NaOCl, and final irrigation with 17% EDTA, followed by PDT with methylene blue photosensitizer and laser diode low power; G2. RCP using stainless steel files and the same irrigation and PDT protocols as G1; G3. Same RCP protocol as G1 without PDT; G4. Only irrigation with 2.5% NaOCl; G5. Same PDT protocol as G1 without RCP; G6. Negative control; G7. Positive control. Samples for microbiological tests were collected initially (S1), after RCP (S2), and after PDT (S3). Subsequently, the roots were sectioned and prepared for Scanning Electron Microscopy (SEM) analysis. Bacterial growth was analyzed according to the turbidity of the culture medium, followed by spectrophotometric optical density (nm). The effect of PDT on the dentinal structure was evaluated at magnifications 1,600X and 5,000X and described qualitatively. The Wilcoxon test was used for the comparisons from the same specimens, and the Mann-Whitney test was used to compare groups ((=5%). Bacteria were found in all experimental groups' microbiological samples (S1, S2 and S3). The optical density of culture media was lower in S2 than in S1 of G1, 2, 3, and 4 (p> 0.05). After PDT (S3) in G1 and 2, there was an additional reduction in optical density of the culture medium, respectively (p>0.05). In Group 5, the analysis of culture media at S2 revealed an increase in optical density compared to S1(p>0.05). In SEM images of G1, 2, and 5, dentin with melting and recrystallization areas were evidenced. After preparation of the root canal with the rotary system or manually associated with 2.5% NaOCl, PDT was not able to completely eliminate E. faecalis present in the root canal.

Designing and application of a new medical instrument sterilization system using reactive oxygen species

The aim of this study is to design and test a new medical sterilization system as an alternative to the techniques used in the sterilization of medical instruments. The designed system, which uses a new oxygen molecule allotrope (NOMA) in the reactive oxygen species, is developed as an alternative to the sterilization systems using other gases. The test was conducted on 12 different materials, each having a surface of 2 cm², sterilized under 120 °C at 1 atm pressure for 20 min in the NUVE-OT 4060 sterilizer, and all surfaces were contaminated with a biological indicator Geobacillus stearothermophilus cultured in an incubator at 37 °C. Test samples in sterile Petri dishes were placed in a desiccator, and a sample was taken at 30-, 45-, and 60-min test periods and were placed on an agar medium and put in a Memmert incubator IN75 at 37 °C; in the controls conducted following 16-18 h of incubation period, no bacterial growth was observed in the newly designed system tested with gram positive bacilli; moreover, it was observed that the new system was 100% effective in sterilizing the microbes as no growth was observed on the samples. Within the scope of this study, a faster, low-cost, low-temperature, residue-free, and human and environmental friendly system was developed and tested for sterilization of medical devices compared to existing sterilization methods using NOMA.

Radiation mode and tissue thickness impact on singlet oxygen dosimetry methods for antimicrobial photodynamic therapy

The target of the presented study is to evaluate the performances of illumination modes on Photodynamic therapy (PDT) for different tissue depths. For this purpose, radiation-based super pulse and pulse illumination modes were investigated for antimicrobial PDT (AmPDT). Singlet oxygen luminescence level was measured from two different points. The first one was to appraise the light penetration depth effect on singlet oxygen luminescence level for various radiation modes. The second one explored the singlet oxygen luminescence dosimetry (SOLD) method from deeper photosensitizer accumulated tissue levels. Two main experiments were performed in this study. The singlet oxygen concentration was calculated with singlet oxygen explicit dosimetry (SOED) and SOLD methods for various tissue depths in these experiments. According to the results of the experiments, super pulse mode (SPM) provided relatively high Staphylococcus Aureus (S. aureus) cell death by 5-12%. The penetration depth was increased between 0.2 mm and 0.7 mm during the experiments. SOLD-based singlet oxygen detection system was utilized to detect singlet oxygen production levels from various tissue thicknesses to evaluate the system's usefulness for deeper infected tissues. It was observed that SPM was more effective than pulse mode radiation after a certain tissue depth (≤ 2 mm).

Investigation of the Dual-Stage Method of Active Er:YLF Laser Drug Delivery Through the Nail and Laser-Induced Transformations of the Drug Extinction Spectrum

BACKGROUND AND OBJECTIVE

A novel dual-stage method for active laser drug delivery (DSLADD) in the treatment of nail diseases is being presented. This method includes sequentially performed microporation of the nail with submillisecond pulses of Er:YLF laser radiation through a layer of an aqueous solution of drug deposited on the nail surface (Stage 1) and exposure this layer to the same laser radiation to deliver drug under the nail plate (Stage 2). The delivery of methylene blue (MB) as one of the possible drugs in the treatment of nail diseases is investigated. The influence of the thickness of the MB layer, as well as the energy and number of applied laser pulses, on the rate of active laser delivery is discussed. To illustrate the possible effect of delivery on the drug delivered, special attention is paid to the deformation of the extinction spectrum of MB solution after laser irradiation.

STUDY DESIGN/MATERIALS AND METHODS

Diode-pumped Er:YLF laser was used for DSLADD. The process of DSLADD under the nail plate was investigated using digital video microscopy. For different values of the thickness of MB solution layer applied to the nail plate and the energy of laser pulses, the number of laser pulses required to create a single through a microchannel in the nail plate and the number of laser pulses required to deliver the solution to the ventral side of the nail plate after its microporation were registered. The mass and the dose of MB solution penetrated under the nail plate, and the rate of MB solution delivery through a single microchannel was determined. Investigation of the influence of Er:YLF laser radiation parameters on the extinction spectrum of the drug was performed using a fiber spectrometer. The extinction spectra of the 0.001% aqueous solution of MB were recorded before and after exposure to a different number of Er:YLF laser pulses with the energy of 1-4 mJ.

RESULTS

It was found that the minimum number of laser pulses required for active Er:YLF laser drug delivery under the nail corresponds to the MB layer thickness of 100 μm and the laser pulse energy of 4 mJ. It is shown that in this case, the rate of active laser delivery of MB solution reaches 0.26 ± 0.03 mg/pulse. The radiation of the Er:YLF laser affects the shape of the extinction spectrum of the aqueous solution of MВ, which is associated with the transition of the dye from the monomeric to dimeric state. Depending on the laser pulse energy, the fraction of a certain conformational state in the aqueous MB solution can decrease or increase, stimulating a possible change in its photodynamic and antiseptic activity.

CONCLUSION

For the first time, a novel DSLADD through the nail has been described and investigated in vitro. It was demonstrated that at Er:YLF laser pulse repetition rate of f = 30 Hz, microporation of the nail plate and drug delivery through a single microchannel will be about 1.5 s. Lasers Surg. Med. © 2021 Wiley Periodicals LLC.

Cytotoxic, Migration, and Angiogenic Effects of Photodynamic Therapy and Photobiomodulation Associated with a Revascularization Protocol

INTRODUCTION

This study evaluated photodynamic therapy (PDT) and photobiomodulation therapy (PBM) as adjuncts to pulp revascularization using cultures of apical papilla cells (APCs) and endothelial cells (HUVECs).

METHODS

The root canal and apical foramen of 2 mandibular first premolars were enlarged to simulate immature teeth. The canal of 1 tooth was filled with 1 mL 0.005% methylene blue (MB). After that, the canals of both teeth were irrigated with 20 mL 1.5% sodium hypochlorite (NaOCl) and 20 mL 17% EDTA. The resulting solutions were diluted in cell culture media at a concentration of 0.5% (0.5% MB + NaOCl + EDTA and 0.5% NaOCl + EDTA). After PDT (0.5% MB + NaOCl + EDTA + PDT) and PBM (0.5% NaOCl + EDTA + PBM) applications, the effects were evaluated to determine cytotoxicity, polarity index, APC migration, and HUVEC sprouting, and results were compared with those of their controls (solutions without laser application). Cell culture media (CT) was also used as a control. Data were analyzed using 1-way analysis of variance and the Tukey post hoc test (P ≤ .05).

RESULTS

PDT and PBM promoted greater APC viability than their controls, and PDT had greater cell viability than CT (P < .05). All protocols reduced APC migration when compared with CT (P < .05). HUVEC sprouts grown out of spheroids in PBM had a greater ratio area than their control (P ≤ .01), and the PDT ratio of the spheroid area was similar to that of its control (P > .05).

CONCLUSIONS

PBM and PDT seem to be potentially effective adjuncts to revascularization in nonvital immature teeth.

Insight into hydroxyl radical-mediated cleavage of caged methylene blue: the role of Fenton's catalyst for antimalarial hybrid drug activation

Methylene blue with a 10-N carbamoyl linkage was reported to be a hydroxyl radical triggered cleavable ligand. Probed by this platform, hemoproteins were demonstrated to be a much more efficient Fenton's catalyst than commonly used inorganic Fe(ii) salts. The applicability of this ligand was demonstrated through the capability of being triggered by elevated reactive oxygen species levels at diseased tissue, with malaria-parasitized erythrocytes as an in vitro model.

Methylene blue as a far-red light-mediated photocleavable multifunctional ligand

Methylene blue (MB) was discovered as a multifunctional far-red photocleavable ligand capable of rendering a series of MB conjugated compounds with off-to-on fluorescence switch, photodynamic therapy and triggered release of conjugated molecule.

Potassium iodide enhances the photobactericidal effect of methylene blue on Enterococcus faecalis as planktonic cells and as biofilm infection in teeth

OBJECTIVE

To explore the effectiveness, biosafety, photobleaching and mechanism of antimicrobial photodynamic therapy (aPDT) using methylene blue (MB) plus potassium iodide (KI), for root canal infections.

METHODS

Different combinations and concentrations of MB, KI and 660 nm LED light were used against E. faecalis in planktonic and in biofilm states by colony-forming unit (CFU), confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM). Human gingival fibroblasts (HGF) were used for safety testing by Cell Counting Kit-8 (CCK8) and fluorescence microscopy (FLM). The photobleaching effect and mechanisms were analyzed.

RESULTS

KI could not only enhance MB aPDT on E. faecalis in both planktonic and biofilm states even in a hypoxic environment, but also produced a long-lasting bactericidal effect after end of the illumination. KI could accelerate photobleaching to reduce tooth staining by MB, and the mixture was harmless for HGFs. Mechanistic studies showed the generation of hydrogen peroxide and free iodine, and iodine radicals may be formed in hypoxia.

CONCLUSION

aPDT with MB plus KI could be used for root canal disinfection and clinical studies are worth pursuing.

The Effect of Different Implant Surfaces and Photodynamic Therapy on Periodontopathic Bacteria Using TaqMan PCR Assay following Peri-Implantitis Treatment in Dog Model

Introduction

Peri-implantitis is one of the late complications that leads to implant failure and is associated with specific microorganisms identified as periodontopathic bacteria. The objective of this study was to evaluate the relationship between the different implant surfaces and number of Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola using TaqMan PCR assay after peri-implantitis treatment using photodynamic therapy.

Method

Forty-eight dental implants with four different surface treatments (M: machined; SA: sandblasted acid-etched; S: 1 µm sputter HA-coated; and P: plasma spraying HA-coated) were inserted in six beagle dogs. After nine months of peri-implantitis induction, a split mouth design was used; on control side decontamination was performed using open flap mechanical debridement OFD with plastic curette, while photodynamic therapy PDT using diode laser (Ga Al As 830-nm) was used in the test side. For the following 2 weeks low-level laser therapy LLLT (10mW) was applied for the test side on alternative days for 6 sec on each implant side. Peri-implant microbial samples were collected using paper points and analyzed using TaqMan PCR before peri-implantitis treatment, immediately after treatment and 5 months posttreatment.

Results

Both treatment modalities showed significant decrease in all bacterial count from baseline to immediately after treatment (P< 0.0001). The count increased between immediately after treatment to 5 months after treatment (P< 0.0001); however, the count after 5 months was significantly lower than at baseline. PDT had a stronger effect on reducing P. gingivalis count than T. denticola and T. forsythia compared to OFD. For T. forsythia, implant surface treatment had the greatest effect which was also statistically significant (P= 0.02) with considerably lower effect of PDT or their interaction.

Conclusion

The results suggest that PDT and OFD have significant benefits in peri-implantitis treatment by reducing bacterial count. The presence of bacterial complex with different response to therapeutic modality suggests the use of combined decontamination methods for peri-implantitis treatment.

Laser Assisted Treatment of Extra Oral Cutaneous Sinus Tract of Endodontic Origin: A Case Report

Introduction: Sinus tract (or fistula) is a common manifestation of pulpal necrosis with periapical pathosis that requires conventional or rarely surgical- endodontic treatment in order to heal. It is mainly identified intraorally and in rare cases manifestation is extra orally, which may frequently be misdiagnosed with cutaneous lesion and incorrectly treated. New technologies such as lasers have been developed as adjuncts to standard endodontic antimicrobial procedures in order to increase the success rate of endodontic therapy while complying with the desire of saving a natural tooth. Case Presentation: Herein, we present a clinical case of extra oral sinus tract with periodic pus drainage that was successfully treated by combining conventional endodontic therapy, intra canal photodynamic therapy (PDT), extra oral low level laser therapy (LLLT) and laser treatment for extra oral fistula. Conclusion: Treatment of the odontogenic lesion among with the extra oral lesion was an ingenious and successful technique which was achieved via laser technology and winded up to patient's consent and satisfactory results.

Effect of high voltage atmospheric cold plasma on white grape juice quality

BACKGROUND

This study focuses on the effects of novel, non-thermal high voltage atmospheric cold plasma (HVACP) processing on the quality of grape juice. A quality-based comparison of cold plasma treatment with thermal pasteurization treatment of white grape juice was done.

RESULTS

HVACP treatment of grape juice at 80 kV for 4 min resulted in a 7.4 log₁₀ CFU mL^-1 reduction in Saccharomyces cerevisiae without any significant (P > 0.05) change in pH, acidity and electrical conductivity of the juice. An increase in non-enzymatic browning was observed, but total color difference was very low and within acceptable limits. Spectrophotometric measurements showed a decrease in total phenolics, total flavonoids, DPPH free radical scavenging and antioxidant capacity, but they were found to be comparable to those resulting from thermal pasteurization. An increase in total flavonols was observed after HVACP treatments.

CONCLUSION

HVACP treatment of white grape juice at 80 kV for 2 min was found to be comparable to thermal pasteurization in all analyzed quality attributes. HVACP has shown the potential to be used as an alternative to thermal treatment of white grape juice. © 2017 Society of Chemical Industry.

The Antibacterial Effect of Additional Photodynamic Therapy in Failed Endodontically Treated Teeth: A Pilot Study

Introduction: Root canal therapy as a routine dental procedure has resulted in retention of millions of teeth that would otherwise be lost. Unfortunately, successful outcomes are not always achievable within initial endodontic treatments, and that necessitates further treatment. Nonsurgical retreatment is the first choice in most clinical situations. The aim of this clinical pilot study was to assess the effect of additional photodynamic therapy (PDT) on intraradicular bacterial load following retreatment of failed previously root treated teeth. Methods: Thirty single-rooted/canalled endodontically treated matured teeth (in 27 healthy patients) accompanied by apical periodontitis (AP) were selected for this study. Standard protocol was followed for nonsurgical retreatment of each tooth. Microbiological samples were taken after establishment of apical patency, finished cleaning/shaping procedure, and PDT (665 nm, 1 W, 240 seconds). All samples were cultured for 72 hours and colony-forming unit (CFU) was counted. McNemar test was used for statistical analysis of the data. The level of significance was set at 0.001. Results: Routine cleaning and shaping resulted in twenty four negative (80%) out of 30 cultures. Four additional negative results were obtained after additional PDT (93.3%). The addition of PDT to routine procedures significantly enhanced the number of bacteria-free samples (P < 0.001). Conclusion: Regarding elimination of intraradicular microbiota, additional PDT may increase the effectiveness of conventional chemomechanical preparation in previously root filled teeth accompanied by AP. Well controlled randomized clinical trials should be planned for future.

A two-photon fluorescent probe for nitroreductase imaging in living cells, tissues and zebrafish under hypoxia conditions

A two-photon fluorescent probe FNTR, constructed for nitroreductase by using a fluorine derivative as a TP fluorophore and a p-nitrobenzyl carbamate group as a recognition domain, was successfully applied to detect endogenous NTR in living cells, tissues and zebrafish.

Nitroreductase-triggered activation of a novel caged fluorescent probe obtained from methylene blue

A near-infrared fluorescent probe based on methylene blue (p-NBMB) was developed for the detection of nitroreductase. Conjugating methylene blue with a p-nitrobenzyl moiety enables it to be activated by nitroreductase-catalyzed 1,6-elimination, resulting in the release of an active methylene blue fluorophore.

The Antibacterial Efficacy of Photo-Activated Disinfection, Chlorhexidine and Sodium Hypochlorite in Infected Root Canals: An in Vitro Study

INTRODUCTION

This study compared the efficacy of light-activated low-power laser, 2% chlorhexidine (CHX) and 2.5% NaOCl in eliminating Enterococcus faecalis (E. faecalis) from the root canal system.

METHODS AND MATERIALS

The root canals of 60 maxillary central incisors were contaminated with E. faecalis and then the bacteria were incubated for 24 h. All the root canals were instrumented in a crown-down manner with #4 and 3 Gates-Glidden drills, followed by RaCe rotary files (40/0.10, 35/0.08, and 30/0.06). The samples were randomly assigned to three experimental groups and one control group (n=15). In the control group no intervention was made. In the photo-activated disinfection (PAD) group, laser therapy was undertaken with diode laser beams (with an output power of 100 mW/cm(2)) for 120 sec. For the other two experimental groups, root canals were irrigated either with 5 mL of 2% CHX or 2.5% NaOCl solutions, respectively. The Kruskal-Wallis test was used to compare the CFU values of the bacteria and post-hoc Bonferroni test was used for pairwise comparisons. The level of significance was set at 0.05.

RESULTS

The inhibition of bacterial growth in all the experimental groups was significantly superior to the control group (P<0.05). There was no significant difference between the effect of PAD and 2% CHX (P=0.05). The effect of 2.5% NaOCl was significantly better than that of the PAD technique (P<0.001). In addition, 2.5% NaOCl was significantly better than 2% CHX (P=0.007).

CONCLUSION

Photodynamic therapy was effective in reducing the E. faecalis counts in comparison with the control group, but 2.5% NaOCl solution was the most effective protocol.

Evolution of the role of phototherapy during endodontic decontamination

A microbe free root canal space before obturation leads to higher success rate and conventional chemo-mechanical debridement might not achieve this goal completely. First trials of laser in dentistry started from surgical intervention on caries and bones of oral cavity and extended to prepare cavities and even shaping root canals. Afterward lasers were implicated soon into direct debridement of root canal space. Anyhow failure of laser to remove debris totally from root canal space is demonstrated recently, additionally it might lead to damages to surrounding tissues or inorganic material of root canal if be used without precaution. Nowadays the theory of light assisted protocols became another start point for laser in endodontics. Laser has been introduced as an adjuvant to conventional debridement of root canals. We used Medline search engine to collect scientific publications to edit this review article in purpose of revealing the evolution of laser position from an ultimate cleaning methodology to an adjuvant to conventional root canal disinfection protocols.

Post-Treatment Apical Periodontitis Successfully Treated with Antimicrobial Photodynamic Therapy Via Sinus Tract and Laser Phototherapy: Report of Two Cases

OBJECTIVE

The purpose of this study was to report the application of antimicrobial photodynamic therapy (aPDT) via sinus tract associated with laser phototherapy (LPT) in conservative treatment of a late failure of endodontic retreatment in two clinical cases of post-treatment apical periodontitis.

BACKGROUND DATA

Post-treatment apical periodontitis is a microbiological matter, because infection is present in almost all cases associated with this condition, even in teeth with apparently adequate root canal treatments. Infection is usually located within the root canal system, but in a few cases it may spread to the periradicular tissues. Many biofilms are susceptible to aPDT, particularly in dental disease. In the present two cases reports, aPDT was applied via sinus tract.

METHODS

In the two clinical cases, endodontic retreatment was unsuccessful, with the presence of a persistent swelling sinus tract, despite the standard quality of the endodontic retreatment. Before any surgical intervention, a noninvasive aPDT via sinus tract was performed. The photosensitizer methylene blue (0.01%) was inserted through the entrance of the sinus tract. Laser irradiation was performed perpendicularly (660 nm, 40 mW, 90 J/cm(2), 63 sec/point) directly over the entrance of the sinus tract. LPT (808 nm, 100 mW, 210 J/cm(2), 59 sec/ point) was applied after each aPDT session. Seven (case 1) and 10 (case 2) successive aPDT applications were performed followed by LPT.

RESULTS

The 18 month follow-up after treatment revealed control of the swelling sinus tract and diminishing of persistent apical periodontitis. The treatment succeeded, avoiding both surgical interventions and antimicrobial prescription.

CONCLUSIONS

The protocol of aPDT associated with LPT applied via sinus tract was revealed to be efficient for clinical infection control, and was found to be safe and conservative.

Repeated exposures to blue light-activated eosin Y enhance inactivation of E. faecalis biofilms, in vitro

BACKGROUND

In dentistry, antibacterial photodynamic therapy (a-PDT) has shown promising results for inactivating bacterial biofilms causing carious, endodontic and periodontal diseases. In the current study, we assessed the ability of eosin Y exposed to 3 irradiation protocols at inactivating Enterococcus faecalis biofilms, in vitro.

METHODS

E. faecalis biofilms formed on hydroxyapatite disks were incubated with eosin Y (10-80μM), then activated with blue light using different irradiation protocols. Biofilms exposed to continuous exposure were incubated for 40min before being light-activated for 960 s. For the intermittent exposure, biofilms were exposed 4 times to the light/photosensitizer combination (960 s total) without renewing the photosensitizer. For repeated a-PDT, the same light dose was delivered in a series of 4 irradiation periods separated by dark periods; fresh photosensitizer was added between each light irradiation. After treatment, bacteria were immediately labeled with LIVE/DEAD BacLight Bacterial Viability kit and viability was assessed by flow cytometry (FCM). Results were statistically analyzed using one-way ANOVA and Tukey multiple comparison intervals (α=0.05).

RESULTS

The viability of E. faecalis biofilms exposed to 10μM eosin Y, was significantly reduced compared to controls (light only-eosin Y only). After a second exposure to blue light-activated eosin Y, viability significantly decreased from 58% to 12% whereas 6.5% of the bacterial biofilm remained live after a third exposure (p<0.05). Only 3.5% of the bacterial population survived after the fourth exposure.

CONCLUSIONS

The results of this study indicate that blue light-activated eosin Y can photoinactivate E. faecalis biofilms grown on hydroxyapatite disks. Also, repeated exposures to blue light-activated eosin Y were shown to significantly improve efficacy. Further studies seem warranted to optimize the antibacterial activity of blue light-activated eosin Y on major oral pathogens.

A novel set of symmetric methylene blue derivatives exhibits effective bacteria photokilling – a structure–response study

This study focuses on the structure–response relationship of symmetrically substituted phenothiazinium dyes.

Photodynamic therapy: An adjunct to conventional root canal disinfection strategies

Although chemical-based root canal disinfectants are important to reduce microbial loads and remove infected smear layer from root dentin, they have only a limited ability to eliminate biofilm bacteria, especially from root complexities. This paper explores the novel photodynamic therapy (PDT) for antimicrobial disinfection of root canals. The combination of an effective photosensitizer, the appropriate wavelength of light and ambient oxygen is the key factor in PDT. PDT uses a specific wavelength of light to activate a non-toxic dye (photosensitizer), leading to the formation of reactive oxygen species. These reactive oxygen molecules can damage bacterial proteins, membrane lipids and nucleic acids, which promote bacterial cell death. In, addition PDT may enhance cross-linking of collagen fibrils in the dentin matrix and thereby improving dentin stability. The concept of PDT is plausible and could foster new therapy concepts for endodontics. The available knowledge should enable and encourage steps forward into more clinical-oriented research and development. This article discusses PDT as related to root canal disinfection, including its components, mechanism of action, reviews the current endodontic literature and also highlights the shortcomings and advancements in PDT techniques.

Photodynamic therapy in combating the causative microorganisms from endodontic infections

Photodynamic therapy (PDT) is presented as a promising antimicrobial therapy that can eliminate microorganisms present in endodontic infections. This treatment is based on the use of a nontoxic photosensitizing agent followed by irradiation of a resonant light source being capable of generating highly reactive species that are harmful to microorganisms. The purpose of this paper is to review the dental literature about the main factors that encompass the use of PDT combined with endodontic treatment for decontamination of the root canal system. A literature search was performed using the following index databases: PubMed, ISI Web of Knowledge and MedLine, between 2000 and 2014, looking for studies regarding antimicrobial action of PDT and its application to endodontic therapy. It was observed that despite numerous promising results, it is still necessary to establish different parameters so that PDT can be used with maximum effectiveness in eliminating microorganisms that cause endodontic infections.

Comparative antibacterial efficacy of photodynamic therapy and ultrasonic irrigation against Enterococcus faecalis in vitro

Enterococcus faecalis poses a challenge to the efficacy of traditional root canal disinfection methods. This study was aimed to establish a synergistic root canal disinfection strategy combining ultrasonic irrigation with photodynamic therapy (PDT) together and to test its antibacterial efficacy against E. faecalis. Twenty-seven bovine root canals infected with E. faecalis were randomly divided into three groups and treated with different disinfection methods as follows: ultrasonic irrigation with 2.5% NaOCl, methylene blue (MB)-mediated PDT, or combined ultrasonic irrigation and PDT as described above. Quantification of E. faecalis was performed on the root canals before and immediately after the disinfection treatment. Residual bacteria were determined by counting colony-forming units. Samples were randomly selected from the three groups, and the morphology of residual bacteria inside the dentinal tubules was studied by scanning electron microscopy. The number of surviving E. faecalis in the group treated with the combination method was significantly lower (P < 0.05) than those in the ultrasonic irrigation-treated or PDT-treated groups. Similar results were found in the morphological studies of the three groups. The results of our study highlighted the importance of combination of ultrasonic irrigation and PDT to produce significant antibacterial efficacy against E. faecalis during root canal disinfection.

Inactivation of Candida albicans following exposure to 624-nanometer light from a supraluminous diode array

OBJECTIVE

To determine the potential for visible light (405 or 624 nm) to produce an inhibitory effect on Candida albicans. In addition, the study sought to evaluate a series of doses in terms of their respective inhibiting capabilities.

BACKGROUND DATA

The authors have studied the effect of blue light on Staphylococcus aureus and found that a bactericidal outcome can be obtained with low doses of blue light.

METHODS

Candida albicans was tested because of its common appearance in human skin and mucous membrane infections. The organism was treated in vitro with 405-nm (blue) and with 624-nm (red) light emitted from a supraluminous diode array. Doses of 3, 9, 15, 30, and 60 J/cm(2) were used. Colony counts were performed and compared with untreated controls using Student t tests and 1-way analysis of variance with Tukey post hoc analysis.

RESULTS

The results revealed no inhibition produced by 405 nm on C albicans (F4,20 = 0.901; P = .482). However, 624 nm did inhibit growth of C albicans at 3, 9, and 30 J/cm(2) (F4,20 = 6.064; P = .002).

CONCLUSIONS

Appropriate doses of 624-nm light from a supraluminous diode array can inhibit the growth of C albicans in vitro. Three, 9, and 30 J/cm(2) are all effective dose levels.

Microgel-encapsulated methylene blue for the treatment of breast cancer cells by photodynamic therapy

Purpose

Photodynamic therapy (PDT) is gaining increasing recognition for breast cancer treatment because it offers local selectivity and reduced toxic side effects compared to radiotherapy and chemotherapy. In PDT, photosensitizer drugs are loaded in different nanomaterials and used in combination with light exposure. However, the most representative issue with PDT is the difficulty of nanomaterials to encapsulate anticancer drugs at high doses, which results in low efficacy of the PDT treatment. Here, we proposed the development of the poly(N-isopropylacrylamide) (PNIPAM) microgel for the encapsulation of methylene blue, an anticancer drug, for its use as breast cancer treatment in MCF-7 cell line.

Methods

We developed biocompatible microgels based on nonfunctionalized PNIPAM and its corresponding anionically functionalized PNIPAM and polyacrylic acid (PNIPAM-co-PAA) microgel. Methylene blue was used as the photosensitizer drug because of its ability to generate toxic reactive oxygen species upon exposure to light at 664 nm. Core PNIPAM and core/shell PNIPAM-co-PAA microgels were synthesized and characterized using ultraviolet-visible spectroscopy and dynamic light scattering. The effect of methylene blue was evaluated using the MCF-7 cell line.

Results

Loading of methylene blue in core PNIPAM microgel was higher than that in the core/shell PNIPAM-co-PAA microgel, indicating that electrostatic interactions did not play an important role in loading a cationic drug. This behavior is probably due to the skin layer inhibiting the high uptake of drugs in the PNIPAM-co-PAA microgel. Core PNIPAM microgel effectively retained the cationic drug (i.e., methylene blue) for several hours compared to core/shell PNIPAM-co-PAA and enhanced its photodynamic efficacy in vitro more than that of free methylene blue.

Conclusion

Our results showed that the employment of core PNIPAM and core/shell PNIPAM-co-PAA microgels enhanced the encapsulation of methylene blue. Core PNIPAM microgel released the drug more slowly than did core/shell PNIPAM-co-PAA, and it effectively inhibited the growth of MCF-7 cells.