Morphological changes and viability of Streptococcus mutans biofilm treated with erythrosine: A confocal laser scanning microscopy analysis.

Antimicrobial photodynamic therapy (a-PDT) is a modality that aims to induce microorganisms through visible light, a photosensitizer, and molecular oxygen. This therapy has shown promising results in controlling cariogenic biofilm in vitro and in vivo counterparts. This study investigated bacterial viability and morphological characterization of Streptococcus mutans mature biofilms after combination of erythrosine and a high potency dental curing light. Biofilms were formed on saliva-coated hydroxyapatite disks in batch culture. The samples were performed in triplicates. Fresh medium was replaced daily for five days and treated using 40 µM of E activated by HL 288 J/cm2 and total dose of 226 J at 1200 mW/cm2. Phosphate buffer saline and 0.12% of chlorhexidine were used as negative and positive control, respectively. After treatment, biofilms were assessed for microbial viability and morphological characterization by means of bio-volume and thickness. COMSTAT software was used for image analysis. Data were analyzed using two-way ANOVA followed by Tukey test with significance level 5%. The application of a-PDT and CHX treatments decreased S. mutans bacterial viability. The image analysis showed more red cells on biofilms when compared to other groups, demonstrating photobacterial killing. Erythrosine irradiated with a high potency curing light can potentially act as an antimicrobial tool in the treatment of cariogenic biofilms. The morphology and viability of microorganisms were impacted after treatment. Treatment with photodynamic therapy may be able to reduce the bio-volume and viability of bacteria present in biofilms. CLINICAL RELEVANCE AND RESEARCH HIGHLIGHTS: The use of the a-PDT technique has been applied in dentistry with satisfactory results. Some applications of this technique are in stomatology and endodontics. In the present study, we sought to understand the use of photodynamic therapy in the control of biofilm and the results found are compatible with the objective of microbiological control proposed by this technique, thus raising the alert for future studies in vivo using the combination of a-PDT with erythrosine, since they are easily accessible materials for the dental surgeon and can be applied in clinical practice.

Effect of Combining Erythrosine with a High-Power Dental Curing Light Appliance on the Viability of a Planktonic Culture of Streptococcus mutans.

Objective: The aim of this in vitro study was to evaluate the effectiveness of antimicrobial photodynamic therapy (aPDT) composed of the association of the photosensitizer (PS) erythrosine irradiated by a high-intensity dental light source against a culture of Streptococcus mutans, comparing this effect with that of a 0.12% chlorhexidine solution. Materials and methods: For this purpose, planktonic suspensions of S. mutans were subjected to experimental conditions in which three different concentrations of erythrosine (E) (2, 4, and 8 µM) associated with three different doses emitted by the light source (L) (48, 96, and 144 J/cm2) were crossed, corresponding to the exposure times of 40, 80, and 120 sec, respectively, delivered in pulsed mode. The following experimental conditions were evaluated: G1-treatment with dye and light source (E+L+); G2-treatment with the dye only (E+L-); G3-treatment with the light source only (E-L+); G4-absence of dye and light (negative control); and G5-0.12% chlorhexidine (positive control). After treatment, aliquots of each group were plated on blood agar, then the colony forming units per milliliter (CFU/mL) later counted. The results were subjected to ANOVA and Tukey tests, considering the level of significance of 5%. Results: Group aPDT showed complete eradication of microorganisms as from the concentration of 4 µM irradiated for 40 sec, demonstrating statistically significant difference in comparison with the negative control group (p ≤ 0.05) and efficacy similar to that of the 0.12% chlorhexidine group (p ≥ 0.05). Conclusions: The authors concluded that the light-polymerizing appliance used in pulsed mode, associated with the PS erythrosine, was efficient for the control of S. mutans in a planktonic suspension in a short period of irradiation time.

Effect of rewetting solutions on micropush-out dentin bond strength of new bioceramic endodontic material.

To evaluate the influence of rewetting solutions on bond strength to root dentin of conventional gutta-percha (GP) or niobium phosphate glass-based gutta-percha (GNb) associated with a bioceramic sealer. The root canals of 80 human mandibular premolars were prepared using nickel-titanium instruments and irrigation with sodium hypochlorite and EDTA. The teeth were randomly divided into four groups according to the gutta-percha used: GNb or GP associated with EndoSequence BC Sealer (BC) and the solution for rewetting dentin before filling (distilled water; phosphate buffer saline solution - PBS; simulated body fluid - SBF; or no solution). The root canals were filled with a single cone using warm vertical condensation. Micropush-out bond strengths associated with the filling materials in slices from middle root thirds was determined 30 days after root filling. The failure mode was analyzed with stereoscopic lens. The data were statistically analyzed by two-way ANOVA and Holm-Sidak test (p < 0.05). There was significant difference in the types of gutta-percha (p < 0.001) and in the different rewetting solutions (p = 0.003). The interaction between gutta-percha and rewetting solutions was not significant (p = 0.53). The SBF solution provided an increase in bond strength for both gutta-percha solutions. The GNb+BC (3.42 MPa) association increased bond strength when compared with GP+BC (2.0 MPa). The use of SBF as a dentin rewetting solution increased bond strength in the groups studied. Association of GNb with bioceramic sealer was beneficial, increasing the bond strength to dentin when compared with the association with GP.

Effect of rewetting solutions on micropush-out dentin bond strength of new bioceramic endodontic material

Abstract To evaluate the influence of rewetting solutions on bond strength to root dentin of conventional gutta-percha (GP) or niobium phosphate glass-based gutta-percha (GNb) associated with a bioceramic sealer. The root canals of 80 human mandibular premolars were prepared using nickel-titanium instruments and irrigation with sodium hypochlorite and EDTA. The teeth were randomly divided into four groups according to the gutta-percha used: GNb or GP associated with EndoSequence BC Sealer (BC) and the solution for rewetting dentin before filling (distilled water; phosphate buffer saline solution - PBS; simulated body fluid - SBF; or no solution). The root canals were filled with a single cone using warm vertical condensation. Micropush-out bond strengths associated with the filling materials in slices from middle root thirds was determined 30 days after root filling. The failure mode was analyzed with stereoscopic lens. The data were statistically analyzed by two-way ANOVA and Holm-Sidak test (p < 0.05). There was significant difference in the types of gutta-percha (p < 0.001) and in the different rewetting solutions (p = 0.003). The interaction between gutta-percha and rewetting solutions was not significant (p = 0.53). The SBF solution provided an increase in bond strength for both gutta-percha solutions. The GNb+BC (3.42 MPa) association increased bond strength when compared with GP+BC (2.0 MPa). The use of SBF as a dentin rewetting solution increased bond strength in the groups studied. Association of GNb with bioceramic sealer was beneficial, increasing the bond strength to dentin when compared with the association with GP.

Streptococcus mutans photoinactivation using a combination of a high potency photopolymerizer and rose bengal.

BACKGROUND: Long treatment periods to reach a substantial inactivation of microorganisms are one of the critical challenges in the photodynamic therapy field. METHODS: Planktonic suspensions of Streptococcus mutans were treated in different groups: presence of rose bengal (RB at 2µM) and light exposure by a new high potency photopolymerizer (L at wavelength=440-480nm; dosimetry=96J/cm(2) - 40s of irradiation; potency density=1200mW/cm(2); dosage=48J) - RB+L+ (PDT), just with dye - RB+L-, just with light - RB-L+ and absence of light and dye RB-L- (control group). Aliquots of each group were transferred to Petri dishes to colony counting (CFU/mL) with the data transformed in log10. The results were submitted to ANOVA and Tukey test at 5%. RESULTS: PDT group presented total eradication of microorganisms showing statistical difference with all the other groups (5.82log reduction≅99%). CONCLUSION: The high potency photopolymerizer in pulsed emission at an extra short irradiation and low concentration of rose bengal could be considered as a progressive alternative to the control of S. mutans suspensions.