Juliana Yuri Nagata

Antibacterial photodynamic therapy for dental caries: evaluation of the photosensitizers used and light source properties.

Photodynamic therapy studies have shown promising results for inactivation of microorganisms related to dental caries. A large number of studies have used a variety of protocols, but few studies have analyzed photosensitizers and light source properties to obtain the best PDT dose response for dental caries. This study aims to discuss the photosensitizers and light source properties employed in PDT studies of dental caries. Three questions were formulated to discuss these aspects. The first involves the photosensitizer properties and their performance against Gram positive and Gram negative bacteria. The second discusses the use of light sources in accordance with the dye maximum absorbance to obtain optimal results. The third looks at the relevance of photosensitizer concentration, the possible formation of self-aggregates, and light source effectiveness. This review demonstrated that some groups of photosensitizers may be more effective against either Gram positive or negative bacteria, that the light source must be appropriate for dye maximum absorbance, and that some photosensitizers may have their absorbance modified with their concentration. For the best results of PDT against the main cariogenic bacteria (Streptococcus mutans), a variety of aspects should be taken into account, and among the analyzed photosensitizer, erythrosin seems to be the most appropriate since it acts against this Gram positive bacteria, has a hydrophilic tendency and even at low concentrations may have photodynamic effects. Considering erythrosin, the most appropriate light source should have a maximum emission intensity at a wavelength close to 530 nm, which may be achieved with low cost LEDs.

Photosensitizer and light diffusion through dentin in photodynamic therapy

Abstract. Photodynamic therapy has been considered a potential antimicrobial modality against oral infections, including dental caries. A model to estimate the penetration of both photosensitizers and light through human dentin, a factor of interest in photodynamic therapy, is proposed. The photoacoustic spectroscopy technique was used to evaluate in vitro dentin permeability of three different photosensitizers. Using the dentin optical absorption and scattering coefficients, it was possible to propose a semi-quantitative model predicting both photosensitizer and light doses within dentin. The graphic illustrations obtained provided guidelines that may be useful in photodynamic therapy protocols used as antimicrobial tools in caries lesions.

Singlet oxygen production by combining erythrosine and halogen light for photodynamic inactivation of Streptococcus mutans

BACKGROUND Photodynamic inactivation of microorganisms is based on a photosensitizing substance which, in the presence of light and molecular oxygen, produces singlet oxygen, a toxic agent to microorganisms and tumor cells. This study aimed to evaluate singlet oxygen quantum yield of erythrosine solutions illuminated with a halogen light source in comparison to a LED array (control), and the photodynamic effect of erythrosine dye in association with the halogen light source on Streptococcus mutans. METHODS Singlet oxygen quantum yield of erythrosine solutions was quantified using uric acid as a chemical-probe in an aqueous solution. The in vitro effect of the photodynamic antimicrobial activity of erythrosine in association with the halogen photopolimerizing light on Streptococcus mutans (UA 159) was assessed during one minute. Bacterial cultures treated with erythrosine alone served as negative control. RESULTS Singlet oxygen with 24% and 2.8% degradation of uric acid in one minute and a quantum yield of 0.59 and 0.63 was obtained for the erythrosine samples illuminated with the halogen light and the LED array, respectively. The bacterial cultures with erythrosine illuminated with the halogen light presented a decreased number of CFU mL(-1) in comparison with the negative control, with minimal inhibitory concentrations between 0.312 and 0.156mgmL(-1). CONCLUSIONS The photodynamic response of erythrosine induced by the halogen light was capable of killing S. mutans. Clinical trials should be conducted to better ascertain the use of erythrosine in association with halogen light source for the treatment of dental caries.

Clinical Perspective of Electrospun Nanofibers as a Drug Delivery Strategy for Regenerative Endodontics

Recent progress in endodontics, particularly encouraging regenerative outcomes achieved by evoked bleeding therapy in the treatment of necrotic immature permanent teeth, clearly suggests that establishment of a regenerative-based clinical strategy is closer than ever before. In this context, an efficient disinfection of the root canal system, mainly through the eradication of microbial biofilms, is a crucial step. Accordingly, numerous bacterial biofilm models have been used in vitro as an attempt to simulate the clinical conditions. To offer a comprehensive update on progress in the field, this review provides an overview of biofilm role in endodontic disease and in vitro biofilm models, the importance of disinfection, a brief review on antibiotic-containing polymer nanofibers and their antimicrobial properties, and future perspective of this novel intracanal drug delivery strategy in regenerative endodontics. Limitations in reproducing in vivo conditions will always exist; however, creating a laboratory-based biofilm model that very closely simulates clinical situations makes in vitro research reliable and the first step towards translation of new therapies.

Antimicrobial Efficacy of Triple Antibiotic–eluting Polymer Nanofibers against Multispecies Biofilm

&NA; The elimination of microbial flora in cases of immature permanent teeth with necrotic pulp is both key and a challenging goal for the long‐term success of regenerative therapy. Recent research has focused on the development of cell‐friendly intracanal drug delivery systems. This in vitro study aimed to investigate the antimicrobial action of 3‐dimensional (3D) tubular‐shaped triple antibiotic–eluting nanofibrous constructs against a multispecies biofilm on human dentin. Polydioxanone polymer solutions, antibiotic‐free or incorporated with metronidazole, ciprofloxacin, and minocycline, were electrospun into 3D tubular‐shaped constructs. A multispecies biofilm consisting of Actinomyces naeslundii, Streptococcus sanguinis, and Enterococcus faecalis was forced inside the dentinal tubules via centrifugation in a dentin slice in vitro model. The infected specimens were exposed to 2 experimental groups (ie, 3D tubular‐shaped triple antibiotic–eluting constructs and triple antibiotic paste [TAP]) and 2 control groups (7‐day biofilm untreated and antibiotic‐free 3D tubular‐shaped constructs). Biofilm elimination was quantitatively analyzed with confocal laser scanning microscopy. Confocal laser scanning microscopic (CLSM) analysis showed a dense population of viable (green) bacteria adhered to dentin and penetrated into the dentinal tubules. Upon 3D tubular‐shaped triple antibiotic–eluting nanofibrous construct exposure, nearly complete elimination of viable bacteria on the dentin surface and inside the dentinal tubules was shown in the CLSM images, which was similar (P < .05) to the bacterial death promoted by the TAP group but significantly greater when compared with both the antibiotic‐free 3D tubular‐shaped constructs and the control (saline). The proposed 3D tubular‐shaped antibiotic‐eluting construct showed pronounced antimicrobial effects against the multispecies biofilm tested and therefore holds significant clinical potential as a disinfection strategy before regenerative endodontics. HighlightsAntibiotic nanofibers led to significant biofilm death.Antibiotic nanofibers are a more cell‐friendly disinfection strategy than triple antibiotic paste (TAP).Dental pulp stem cell proliferation was higher (day 7) on fiber‐treated dentin compared with TAP.