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

EFFECT OF LOW-LEVEL DIODE LASER ON DENTIN TOPOGRAPHY AND SYMPTOMATIC NONCARIOUS CERVICAL LESIONS PRIOR TO COMPOSITE RESTORATIONS: A SPLIT-MOUTH RANDOMIZED CONTROLLED TRIAL

OBJECTIVES

This study assessed alterations in sensitivity among symptomatic noncarious cervical lesions (NCCLs) following the application of 3 low-level diode laser wavelengths before composite restoration. It analyzed the changes in dentin topography using a scanning electron microscope (SEM).

MATERIALS AND METHODS

Nine patients with 36 NCCLs were randomly assigned intra-individually to 4 groups based on the laser wavelength: laser simulation, 445 nm, 660 nm, and 970 nm. Cavity preparation, irradiation, and composite restoration were performed for each lesion. Sensitivity to cold stimuli was recorded using a visual analog scale (VAS) before the intervention (baseline) and at 1 day, 14 days, 1-, 3-, and 6-month. Pulp sensibility was recorded using an electrical pulp tester (EPT) at baseline, before treatment, and at 3- and 6-month. Additionally, an in vitro examination was performed on 12 extracted human molars to yield 12 dentin discs. Each disc was randomly divided into 4 quadrants to receive the same laser wavelengths to determine the diameters of the tubules using SEM. Results were analyzed statistically for clinical studies by the Friedman test, while ANOVA (RM-ANOVA) was conducted in-vitro, followed by the Bonferroni test in the case of significance (P < .05).

RESULTS

VAS readings decreased across all groups, with a significant decrease observed for 660 nm and 970 nm from 14 days to 6-month, while at 445 nm there was a significant decrease at 6-month compared to the control (P < .05). EPT showed a significant decrease in pain threshold levels at 660 nm and 970 nm at 3- and 6-month, while 445 nm showed a significant decrease at 6-month compared to the control (P < .05). The mean tubular diameter at 445 nm decreased, with no significant difference from the control, whereas a significant decrease was found at 660 nm and 970 nm compared to the control (P < .05).

CONCLUSIONS

Prior to composite restoration in symptomatic NCCLs, diode lasers with a wavelength of 660 nm showed the highest reduction in sensitivity, followed by 970 nm, whereas 445 nm diode lasers showed the least reduction. Additionally, diode lasers with wavelengths of 660 and 970 nm reduced the width of the dentinal tubules (DT) without inducing melting, as viewed under SEM.

Effect of Laser Irradiation Modes and Photosensitizer Types on Antimicrobial Photodynamic Therapy (aPDT) for Streptococcus sobrinus in the Crown Dentin of Bovine Teeth: An Experimental In Vitro Study

This study aimed to assess the impact of different laser irradiation modes and photosensitizer types on the bactericidal efficacy of antimicrobial photodynamic therapy (aPDT). Dentin plates were prepared by sectioning the crown dentin of bovine teeth infected with Streptococcus sobrinus (n = 11). Nine aPDTs involving the combination of three 1% solutions of photosensitizers (brilliant blue, BB; acid red, AR; and methylene blue, MB) and three irradiation modes of semiconductor lasers (50 mW for 120 s, 100 mW for 60 s, and 200 mW for 30 s) were performed for each infected dentin plate, and the control consisted of the specimens not applied with aPDT. The bactericidal effects in 10 groups were evaluated using both assays of the colony count (colony-forming-unit: CFU) and adenosine triphosphate (ATP) (relative-light-unit: RLU). The data obtained were analyzed using the Kruskal-Wallis test (α = 0.05). The most aPDT groups exhibited significantly lower RLU and CFU values compared with the control (p < 0.05). The effect of irradiation modes on RLU and CFU values was significant in the aPDT group using BB (p < 0.05) but not in the aPDT group using AR or MB. The aPDT performed with AR or MB exerted a remarkable bactericidal effect.

A protocol for an overview of systematic reviews to map photodynamic inactivation evidence in different dental specialties

This is a protocol for an overview to summarize the findings of Systematic Reviews (SR) dealing with Photodynamic Inactivation (PDI) for control of oral diseases. Specific variables of oral infectious will be considered as outcomes, according to dental specialty. Cochrane Database of Systematic Reviews (CDSR), MEDLINE, LILACS, Embase, and Epistemonikos will be searched, as well as reference lists. A search strategy was developed for each database using only terms related to the intervention (PDI) aiming to maximize sensitivity. After checking for duplicate entries, selection of reviews will be performed in a two-stage technique: two authors will independently screening titles and abstracts, and then full texts will be assessed for inclusion/exclusion criteria. Any disagreement will be resolved through discussion and/or consultation with a third reviewer. Data will be extracted following the recommendations in Chapter V of Cochrane Handbook and using an electronic pre-specified form. The evaluation of the methodological quality and risk of bias (RoB) of the SR included will be carried out using the AMSTAR 2 and ROBIS. Narrative summaries of relevant results from the individual SR will be carried out and displayed in tables and figures. A specific summary will focus on PDI parameters and study designs, such as the type and concentration of photosensitizer, pre-irradiation time, irradiation dosimetry, and infection or microbiological models, to identify the PDI protocols with clinical potential. We will summarize the quantitative results of the SRs narratively.

The Effects of Antimicrobial Photodynamic Therapy Used to Sterilize Carious Dentin on Rat Dental Pulp Tissue

Antimicrobial photodynamic therapy (aPDT) used to sterilize carious dentin may irritate pulp tissues because of tissue-penetrating laser and singlet oxygen generation. This study aimed to assess the effects of aPDT on rat pulp tissues. A cavity formed in a rat maxillary first molar was treated with aPDT. The combined photosensitizer and laser irradiation conditions in the aPDT groups were as follows: methylene blue and 100 mW for 60 s, brilliant blue (BB) and 100 mW for 60 s, BB and 50 mW for 120 s, and BB and 200 mW for 30 s. Each cavity was treated with an all-in-one adhesive and filled with flowable resin. aPDT was not applied for the control. In each group, the rats were sacrificed on postoperative days 1 and 14, and thin sections of the treated teeth were prepared. Pulp tissue disorganization (PTD), inflammatory cell infiltration (ICI), and tertiary dentin formation (TDF) were evaluated. At 1-day evaluation, there were significant differences between the aPDT group and controls with respect to PTD and ICI (p < 0.01); 14 days later, almost all specimens showed tertiary dentin formation. The application of aPDT caused reversible damage to the rat pulp, while in the long term, healing occurred with the formation of tertiary dentin.

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.

Application of Photodynamic Therapy in Pediatric Dentistry: Literature Review

Microbiological control of dental pathologies presents a significant clinical challenge for dental surgeons, particularly considering drug-resistant microorganisms. To address this issue, Antimicrobial Photodynamic Therapy (PDT) has emerged as an effective and complementary technique for microbial reduction. This therapy involves the application of a photosensitizer dye (PS) either topically or systemically, followed by exposure to low-power lasers with appropriate visible light wavelengths. PDT has found a valuable place in dentistry across various specialties, including surgery, periodontics, endodontics, dentistry, implantology, orthodontics, and pediatrics. In the realm of pediatric dentistry, managing microorganisms during dental treatments has become a major challenge. Considering its promising results and ease of application, Photodynamic Therapy presents an interesting alternative for clinical practice. However, it is important to note that specific protocols must be followed for each application, encompassing the type of photosensitizer, concentration, pre-irradiation time, light type, wavelength, energy, power, and mode of light delivery. Researchers have been steadily refining these protocols to facilitate PDT's integration into clinical practice. The objective of this review is to describe in which procedures and oral health problems in children PDT can be applied. In this sense, we list what the literature brings about the possibilities of applying PDT in a pediatric dentistry clinic.

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.

Guaiazulene and related compounds: A review of current perspective on biomedical applications

BACKGROUND

Thousands of people worldwide pass away yearly due to neurological disorders, cardiovascular illnesses, cancer, metabolic disorders, and microbial infections. Additionally, a sizable population has also been impacted by hepatotoxicity, ulcers, gastroesophageal reflux disease, and breast fissure. These ailments are likewise steadily increasing along with the increase in life expectancy. Finding innovative therapies to cure and consequently lessen the impact of these ailments is, therefore, a global concern.

METHODS AND MATERIALS

All provided literature on Guaiazulene (GA) and its related compounds were searched using various electronic databases such as PubMed, Google Scholar, Web of Science, Elsevier, Springer, ACS, CNKI, and books via the keywords Guaiazulene, Matricaria chamomilla, GA-related compounds, and Guaiazulene analogous.

RESULTS

The FDA has approved the bicyclic sesquiterpene GA, commonly referred to as azulon or 1,4-dimethyl-7-isopropylazulene, as a component in cosmetic colorants. The pleiotropic health advantages of GA and related substances, especially their antioxidant and anti-inflammatory effects, attracted a lot of research. Numerous studies have found that GA can help to manage various conditions, including bacterial infections, tumors, immunomodulation, expectorants, diuretics, diaphoresis, ulcers, dermatitis, proliferation, and gastritis. These conditions all involve lipid peroxidation and inflammatory response. In this review, we have covered the biomedical applications of GA. Moreover, we also emphasize the therapeutic potential of guaiazulene derivatives in pre-clinical and clinical settings, along with their underlying mechanism(s).

CONCLUSION

GA and its related compounds exhibit therapeutic potential in several diseases. Still, it is necessary to investigate their potential in animal models for various other ailments and establish their safety profile. They might be a good candidate to advance to clinical trials.

Efficacy of antimicrobial photodynamic therapy (aPDT) in reducing cariogenic bacteria in primary deciduous dentine

AIM

The aim is to systematically review the efficacy of aPDT in minimizing cariogenic bacteria in primary dentine when compared to tooth preparation and endodontic debridement.

MATERIALS AND METHODS

The focused question was: Is aPDT (intervention) effective in minimizing the cariogenic bacteria (outcome) in deciduous dentine (participants) after caries removal when compared to before aPDT or mechanical caries removal alone (controls). The keywords that were used were: 'antimicrobial photodynamic therapy', 'dentine', 'primary teeth' and 'deciduous teeth' in different combinations. Following the exclusion of the irrelevant studies, eight (seven clinical studies and one in vitro study) studies were included in the review. The data from each study was extracted and the quality of each article was assessed.

RESULTS

In four out of the eight studies, aPDT with methylene blue or toluidine blue had improved the efficacy of microbial reduction in deciduous dentine when compared to conventional root canal treatment or caries removal. In four studies, no significant improvement in microbial reduction was observed following aPDT compared to caries removal or endodontic debridement without aPDT. Four studies received an overall quality grading of 'medium', three studies were assessed as having a 'low' quality and only one study received an overall grading of 'high' quality.

CONCLUSION

Within the limitations of this review, aPDT may improve the anti-bacterial efficacy of restorative and endodontic procedures in deciduous teeth. However, due to lack of long-term clinical trials and robust study designs, the efficacy of aPDT in minimizing cariogenic bacteria in deciduous dentine is debatable.

Photodynamic Inactivation of an Endodontic Bacteria Using Diode Laser and Indocyanine Green-Loaded Nanosphere

Apical periodontitis, an inflammatory lesion causing bone resorption around the apex of teeth, is treated by eradicating infectious bacteria from the root canal. However, it has a high recurrence rate and often requires retreatment. We investigated the bactericidal effect of antimicrobial photodynamic therapy (aPDT)/photodynamic antimicrobial chemotherapy (PACT) using indocyanine green (ICG)-loaded nanospheres coated with chitosan and a diode laser on a biofilm of Enterococcus faecalis, a pathogen of refractory apical periodontitis. Biofilm of E. faecalis was cultured in a porcine infected root canal model. ICG solution was injected into the root canal, which was then irradiated with a laser (810 nm wavelength) from outside the root canal. The bactericidal effect was evaluated by colony counts and scanning electron microscopy. The result of the colony counts showed a maximum 1.89 log reduction after irradiation at 2.1 W for 5 min. The temperature rise during aPDT/PACT was confirmed to be within a safe range. Furthermore, the light energy transmittance through the root was at a peak approximately 1 min after the start of irradiation, indicating that most of the ICG in the root canal was consumed. This study shows that aPDT/PACT can suppress E. faecalis in infected root canals with high efficiency.

In vitro and in vivo biological activities of azulene derivatives with potential applications in medicine

Azulene is an aromatic hydrocarbon that possesses a unique chemical structure and interesting biological properties. Azulene derivatives, including guaiazulene or chamazulene, occur in nature as components of many plants and mushrooms, such as Matricaria chamomilla, Artemisia absinthium, Achillea millefolium, and Lactarius indigo. Due to physicochemical properties, azulene and its derivatives have found many potential applications in technology, especially in optoelectronic devices. In medicine, the ingredients of these plants have been widely used for hundreds of years in antiallergic, antibacterial, and anti-inflammatory therapies. Herein, the applications of azulene, its derivatives and their conjugates with biologically active compounds are presented. The potential use of these compounds concerns various areas of medicine, including anti-inflammatory with peptic ulcers, antineoplastic with leukemia, antidiabetes, antiretroviral with HIV-1, antimicrobial, including antimicrobial photodynamic therapy, and antifungal.

Bactericidal effect of antimicrobial photodynamic therapy (aPDT) on dentin plate infected with Lactobacillus acidophilus

This study aimed to examine bactericidal effects of a new antimicrobial photodynamic therapy (aPDT) on dentin plates infected with Lactobacillus acidophilus (L. acidophilus). First, we measured the amount of reactive oxygen species (ROS) produced when new photosensitizer (PS), acid red (AR), and brilliant blue (BB) were irradiated with a semiconductor laser. ROS generated from each PS solution by laser irradiation was calculated as the total light emission amount (Relative Light Unit, RLU) using a chemiluminescence measuring device. Second, we examined bactericidal effects of the aPDT on dentin plates infected with L. acidophilus. The bactericidal effects on each group were evaluated by colony count assay and adenosine triphosphate assay. The experimental groups comprised two laser irradiation groups (650 nm laser, 650laser; and 940 nm laser, 940laser), two PS groups (BB and AR), four aPDT groups (650 nm laser irradiation with BB, 650laser-BB; 650 nm laser irradiation with AR, 650laser-AR; 940 nm laser irradiation with BB, 940laser-BB; 940 nm laser irradiation with AR, 940laser-AR), and a control. The ROS in all aPDT groups was significantly higher than in the control. RLU in all groups applied with laser irradiation was significantly lower than that in the control. However, only 650laser-BB showed significantly lower colony counts than the control. 650laser-BB was the most effective in sterilizing the infected dentin plates.

Comparison of photodynamic therapy with methylene blue associated with ceftriaxone in gram-negative bacteria; an in vitro study

The resistance of microorganisms increases the need for new antimicrobial therapies. The aim of this study was to evaluate the in vitro action of photodynamic therapy and its combination with ceftriaxone in third generation cephalosporin resistant gram-negative bacteria. Clinical strains of Klebsiella pneumoniae, Enterobacter aerogenes and Escherichia coli were obtained, incubated with MB for 15 min combined or not with ceftriaxone and irradiated with fluence of 10 and 25 J/cm². MB internalization was evaluated by confocal microscopy. Cell viability was assessed by counting colony forming units and bacterian metabolism by the resazurin test. MB has been observed within cells, although not in all bacteria. PDT-MB alone and combined with Ceftriaxone reduced bacterial growth by approximately 1 log at 10 J/cm² of fluence and 4 logs by 25 J/cm², with a significant difference from the control group. The reduction in bacterial growth between the treated groups was similar, without significant difference between them. The Resazurin test showed lower bacterial metabolic activity in the treated groups, but it did not allow to observe difference between fluences. It was concluded with this study that the internalization of MB was not observed in all cells of K. pneumoniae, E. aerogenes and E. coli strains. There was less bacterial metabolic activity in the treated groups, with no variation between different fluences. PDT-MB 25 J/cm² alone and combined with Ceftriaxone showed antimicrobial action, but the PDT-MB/Ceftriaxone combination had no potentiating effect.

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.