An in vitro study on the efficacy of hydrogen peroxide mediated high-power photodynamic therapy affecting Enterococcus faecalis biofilm formation and dispersal

Evaluation of riboflavin, nanocurcumin, and hydrogen peroxide under light conditions: Reduction of mature dental biofilms and enamel mineral loss

BACKGROUND

Biofilms are a potential harbor for many microorganisms. The aim of this study was to test the efficacy of riboflavin (Rib), nano-micelle curcumin (NC), and hydrogen peroxide (HP), alone and in combination with the respective light (light-emitting diode (LED) or 980 nm diode laser) on the reduction of Streptococcus mutans and Lactobacillus acidophilus dual-species biofilms and their effect on the enamel mineral loss.

MATERIALS AND METHODS

The biofilms were formed on saliva-coated enamel slabs. Then, the biofilms were treated with antimicrobial photodynamic therapy (PDT) based on LED, Rib, and NC photosensitizers and with HP also based on a 980 nm diode laser (n = 8 per group). A crystal violet assay was performed to determine the reduction of the dual-species biofilms. The enamel slabs were analyzed for calcium and phosphorus content by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX).

RESULTS

While HP-PDT showed a reduction of 37% (p < 0.001), PDT with NC resulted in an even greater reduction of dual-species biofilms (40%, p < 0.001) than HP- and Rib-mediated PDT. In the EDX test, no significant difference was found between the control group and the treatment groups.

CONCLUSIONS

The use of natural photosensitizers such as NC in PDT has an effect that may be potentially important in reducing caries-causing bacteria.

Microbiological and Imaging-Based Evaluations of Photodynamic Therapy Combined with Er:YAG Laser Therapy in the In Vitro Decontamination of Titanium and Zirconia Surfaces

The oral cavity's soft and hard tissues create a conducive environment for microbial proliferation and biofilm development, facilitating the colonization of prosthodontic and implant materials such as titanium (Ti) and zirconia (Zr). This study aimed to compare the efficacy of conventional decontamination methodologies (i.e., chemical and mechanical, using 0.12% digluconate chlorhexidine (CHX) solution-treatment and airflow) to adjunctive laser-based interventions on Ti and Zr substrates inoculated with Staphylococcus (S.) aureus ATCC 25923. Additionally, this investigation sought to elucidate the impact of these treatments on temperature variations and surface integrity, analyzing the laser irradiation effects on these prevalent dental materials. Experimental configurations were delineated for both Ti and Zr samples across four groups: (1) a conventional treatment group (CV); (2) a photodynamic therapy group (PDT); (3) an Er:YAG laser treatment group (Er); (4) a combined PDT and Er:YAG treatment group (PDTEr). Also, a negative control group (C) that received no treatment was considered. The decontamination of the inoculated disc samples was evaluated by quantifying the microbial colonies in colony-forming units per milliliter (CFU/mL). Temperature variations on the surface of the samples were determined during laser treatments. Surface modifications were investigated using scanning electron microscopy (SEM) and optical coherence tomography (OCT). For statistical analysis, Fisher 95% confidence intervals, Hsu's MCB method, and the Kruskal-Wallis test were applied. With regard to the 105 CFU/mL of the negative control group, results indicated average values equal for each study group to (1) 2.66 CFU/mL for Ti and 2 CFU/mL for Zr for the CV group; (2) 0.33 CFU/mL for Ti and 1 CFU/mL for Zr for the PDT group; (3) 1.25 CFU/mL for Ti and 0 CFU/mL for Zr for the Er group; (4), and 0 CFU/mL for both Ti and Zr for the PDTEr group. Therefore, the combined PDT and Er:YAG treatment (PDTEr) and the singular PDT modality outperformed conventional decontamination methods in eradicating S. aureus biofilms from both Ti and Zr surfaces. Notably, the PDTEr regime achieved a comprehensive elimination of microbial colonies on treated substrates. Surface examination employing OCT demonstrated discernible alterations in the surface morphology of samples subjected to Er:YAG and combined PDT and Er:YAG treatments. Temperature checks during treatments showed no major changes, suggesting the applied laser methods are safe. In conclusion, PDTEr and PDT eliminated bacteria more effectively, but Zr surfaces were more resilient, making them better for microbe-controlling applications. Also, the study demonstrated that the (less costly but lower resolution) OCT method can replace SEM for such investigations.

The Effect of Photodynamic Therapy on Enterococcus spp. and Its Application in Dentistry: A Scoping Review

Enterococci spp. are Gram-positive bacteria that cause mild to severe infections, many associated with the oral cavity, such as periapical infections and healthcare-associated infections (HAIs). Many of these infections become serious diseases that are difficult to resolve, specifically when multidrug-resistant (MDR) strains cause them. In recent years, the number of MDR strains of Enterococcus spp. has increased significantly. This increased prevalence of MDR strains produces significant pressure to generate more antimicrobial therapies, but there is a decline in the production of new antibiotics, driving the development of complementary therapies, such as photodynamic therapy (PDT). PDT combines a photosensitizer agent (PS), light, and oxygen to cause photooxidative stress in bacterial cells. PDT can eradicate Enterococcus spp. contaminations, improve the classic cleaning processes, and eradicate the bacteria in dental pieces. PDT's effectiveness can be improved with nanoparticles that function as carriers. Our work aims to describe the advances in PDT against Enterococcus spp. as a complement to antibiotic therapy, focusing on infections by Enterococcus faecium and Enterococcus faecalis, dental hygiene, and using nanoparticles to improve the antimicrobial effect. A systematic bibliographic search without a meta-analysis was conducted on various databases, using inclusion and exclusion criteria to identify the most relevant research. Of the 193 non-redundant articles found, 65 were selected for a systematic review, from which a summary table was created and a manual description was made. Photodynamic therapy for treating E. faecium and E. faecalis is a widely studied area, with promising results concerning bactericidal effectiveness and reductions in biofilm formation, particularly in regard to dental hygiene. Because most of the studies were conducted in vitro or ex vivo, the results indicated that there were not sufficient data to initiate clinical trials for safety and efficacy studies on humans.

Simultaneous Dual-Wavelength Laser Irradiation against Implant-Adherent Biofilms of Staphylococcus aureus, Escherichia coli, and Candida albicans for Improved Antimicrobial Photodynamic Therapy

The efficiency of antimicrobial photodynamic therapy (PDT) might be improved by using multiple wavelengths. This study investigates the sensitivity of implant-adherent biofilms of Staphylococcus aureus, Escherichia coli, and Candida albicans to indocyanine green (ICG)-808 nm diode laser, toluidine blue O (TBO)-635 nm diode laser, and hydrogen peroxide (HP)-980 nm diode laser and their combination when irradiated with dual-wavelength laser irradiation (simultaneously 980-635 nm or 980-808 nm). After an incubation period of 72 h, the infected implants were randomly divided into seven different treatment modalities: Control, HP, HP-PDT, TBO-PDT, HP-TBO-PDT, ICG-PDT, and HP-ICG-PDT. After the treatments, the colony-forming units (CFUs)/mL and reactive oxygen species (ROS) generation were determined. All evaluated disinfection methods were significantly effective against the three investigated bacteria compared to the control. The combined treatment of HP-ICG-PDT or HP-TBO-PDT had the greatest antibacterial effect compared to each treatment alone. There were statistical differences between HP-ICG-PDT and ICG-PDT or HP-TBO-PDT and TBO-PDT for all three bacteria studied. PDT with simultaneous dual-wavelength laser irradiation is an efficient strategy to improve the therapeutic effect of PDT.

Medicinal benefits, biological, and nanoencapsulation functions of riboflavin with its toxicity profile: A narrative review

Riboflavin is a precursor of the essential coenzymes flavin mononucleotide and flavin adenine dinucleotide. Both possess antioxidant properties and are involved in oxidation-reduction reactions, which have a significant impact on energy metabolism. Also, the coenzymes participate in metabolism of pyridoxine, niacin, folate, and iron. Humans must obtain riboflavin through their daily diet because of the lack of programmed enzymatic machineries for de novo riboflavin synthesis. Because of its physiological nature and fast elimination from the human body when in excess, riboflavin consumed is unlikely to induce any negative effects or develop toxicity in humans. The use of riboflavin in pharmaceutical and clinical contexts has been previously explored, including for preventing and treating oxidative stress and reperfusion oxidative damage, creating synergistic compounds to mitigate colorectal cancer, modulating blood pressure, improving diabetes mellitus comorbidities, as well as neuroprotective agents and potent photosensitizer in killing bloodborne pathogens. Thus, the goal of this review is to provide a comprehensive understanding of riboflavin's biological applications in medicine, key considerations of riboflavin safety and toxicity, and a brief overview on the nanoencapsulation of riboflavin for various functions including the treatment of a range of diseases, photodynamic therapy, and cellular imaging.