Photodynamic Inactivation of Cariogenic Pathogens Using Curcumin as Photosensitizer.

OBJECTIVE: This investigation assessed the susceptibility of Streptococcus mutans and Lactobacillus acidophilus to Photodynamic Therapy (PDT) when grown simultaneously in dentine carious lesions. BACKGROUND DATA: PDT is a technique that utilizes light to activate photosensitizers in the presence of oxygen to produce reactive radicals. MATERIALS AND METHODS: A culture medium of 1% glucose, 2% sucrose, 1% young primary culture of L. acidophilus 108 CFU/mL, and S. mutans 108 CFU/mL was utilized to inoculate the bacterial induced caries on human dentine slabs. Different concentrations of the photosensitizer (0.75, 1.5, 3.0, 4.0, and 5.0 g/L) were activated through exposure to the light-emitting diode source with a central wavelength of 450 nm and a fluency of 5.7 J/cm2. Two light intensities (19 and 47.5 mW/cm2) were tested. Four different groups were analyzed: L-D- (control group), L-D+ (drug group), L+D+1 (PDT group 1, light intensity of 19 mW/cm2), and L+D+2 (PDT group 2, light intensity of 47.5 mW/cm2). ANOVA/Tukey tests were utilized to compare groups (α = 5%). RESULTS: Both light intensities required 5.0 g/L of curcumin for significant bacterial reduction (p < 0.05). No significant effect was found for L-D+, thus proving the absence of a potential inherent toxicity. CONCLUSIONS: Curcumin has a toxic effect on microorganisms at appreciable concentrations upon photoactivation. However, it was required to use the maximum concentration of the drug for a successful procedure.

Effect of pH values of two bleaching gels on enamel microhardness.

This study evaluated the influence of bleaching gel pH and the effect of remineralizing gels after bleaching in different time intervals. Sixty bovine incisors were divided into 2 groups (n = 30). Group 1 was bleached with a 35% hydrogen peroxide (HP) acid gel and Group 2 was bleached with a 35% HP neutral gel. Each group was then divided into 3 subgroups (n = 10) according to the post-bleaching treatment used: storage in artificial saliva, application of a fluoride gel, or application of a gel consisting of fluoride, potassium nitrate, and nanostructured calcium phosphate. Specimens were stored in artificial saliva, and enamel microhardness was evaluated at 24 hours and 15 days postbleaching. Vickers microhardness data were analyzed by means of 2-way ANOVA, with repeated measurements and Bonferroni's post-hoc test. Twenty-four hours after bleaching, no significant differences were found between the bleaching gels. At 15 days postbleaching, Group 2 samples demonstrated a significant reduction in microhardness. No significant differences were found between the remineralizing gels, though all of the postbleaching treatments after the use of 35% neutral gel were able to re-establish baseline microhardness. It was concluded that neutral bleaching gel significantly reduced enamel microhardness 15 days after bleaching and that the use of remineralizing gels did not significantly enhance the microhardness of bleached enamel. However, in clinical situations, the acquired enamel pellicle protects tooth surfaces, and postbleaching, decalcified enamel would undergo recalcification. This study indicates that it is important to consider the bleaching agent's pH and composition when treating patients with reduced salivary secretion.

Photodynamic effects of curcumin against cariogenic pathogens.

BACKGROUND DATA: The presence of Streptococcus mutans and Lactobacillus acidophilus in dental structure is an indicator of a cariogenic biofilm. Photodynamic therapy is a technique that involves the activation of photosensitizers by light in the presence of oxygen, resulting in the production of reactive radicals capable of inducing cell death. Reduction of bacteria levels can provide additional means of preventing dental caries. OBJECTIVE: The present study evaluated the susceptibility of planktonic cultures of S. mutans (ATCC 25175) and L. acidophilus (ATCC-IAL-523) from the Adolfo Lutz Institute (IAL) to photodynamic therapy after sensitization with curcumin and exposure to blue light at 450 nm. METHODS: Bacterial suspensions of S. mutans and L. acidophilus isolated (as single species) and combined (multspecies) were prepared and then evaluated. Four different groups were analyzed: L-D- (control group), L-D+ (drug group), L+D- (light group), and L+D+ (photodynamic therapy group). Two different concentrations of curcumin were tested (0.75 and 1.5 g/L) associated with a 5.7 J/cm(2) light emission diode. RESULTS: Significant decreases (p<0.05) in the viability of S. mutans were only observed when the bacterial suspensions were exposed to both curcumin and light. Then, reductions in viability of up to 99.99% were observed when using 1.5 g/L of the photosensitizer. The susceptibility of L. acidophilus was considerably lower (21% and 37.6%) for both curcumin concentrations. CONCLUSIONS: Photodynamic therapy was found to be effective in reducing S. mutans and L. acidophilus on planktonic cultures. No significant reduction was found for L-D+, proving the absence of dark toxicity of the drug.

Overall-mouth disinfection by photodynamic therapy using curcumin.

BACKGROUND DATA: Photodynamic therapy is a technique that involves the activation of photosensitizers by light in the presence of tissue oxygen, resulting in the production of reactive radicals capable of inducing cell death. OBJECTIVE: The present study assessed the overall susceptibility of pathogens of salivary flora to photodynamic therapy after sensitization with curcumin and exposure to blue light at 450 nm. METHODS: A randomized trial was executed with 13 adult volunteers. Three different groups were analyzed: L-D- (no light, no drug; control group), L-D+ (treated only with the drug; curcumin group) and L+D+ (treated with drug and light; photodynamic therapy group). Non-stimulated saliva samples were collected for bacterial counts at baseline and after the experimental phase, and adverse events experienced were recorded. Serial dilutions were performed, and the resulting samples were cultured on blood agar plates in microaerophilic conditions. The number of colony-forming units was then determined. RESULTS: There was a considerable difference between the two experimental groups with regard to effectiveness of bacterial reduction. In the L-D+ group, the bacterial decline was considerably smaller (9%) than in the L+D+ group, with a 68% decrease in bacteria. A statistically significant reduction in the bacterial population was observed only in the photodynamic therapy group (p<0.05). CONCLUSIONS: Photodynamic therapy was found to be effective in the reduction of salivary microorganisms. No significant reduction was found for the group in which only curcumin was used, proving the absence of dark toxicity of the drug. This work shows that overall disinfection of the mouth can be done with a simple procedure involving photodynamic action.