Effects of methylene blue and curcumin photosensitizers on the color stability of endodontically treated intraradicular dentin

Effect of Experimental Bleaching Gels With Enzymes on Composite and Enamel

INTRODUCTION AND AIMS

Potential secondary or toxic effects of peroxide-based whitening gels have driven the search for alternative methods that use natural compounds with gentle action on tooth enamel that provide remineralizing benefits.

METHODS

This study introduces four innovative experimental whitening gels (GC, G1, G3, G4) formulated with enzymes (Bromelaine and Papaine) and natural extracts, along with SiO2. The efficacy of these gels was tested on nanohybrid dental composite (EsCOM100, Spident Company) and dental enamel stained with coffee and natural juice (Tedi) over 10 days. The structural changes in samples before and after bleaching were examined using scanning electron microscopy and atomic force microscopy. Additionally, cytotoxicity tests were conducted on the gels using mesenchymal stem cells from human dental pulp (dMSC) and human keratinocytes (HaCaT). Antibacterial activity was assessed on five strains (Streptococcus mutans. Porphyromonas gingivalis; Enterococcus faecalis; Escherichia coli; Staphylococcus aureus).

RESULTS

Coffee and natural juice stains significantly increase the roughness of composite and enamel surfaces by forming deposits. The enzymatic action of bromelain and papain effectively disorganizes and removes these clusters, significantly reducing surface roughness.

CONCLUSION

Notably, the gel containing papain and nanostructured SiO2 proved to be the most effective in removing coffee stains from both composite surfaces and enamel. On the other hand, the gel with bromelain and nanostructured SiO2 was the most efficient in removing natural juice stains. The absence of SiO2 in the experimental gels slightly decreased the enzymes' effectiveness in stain removal. The antibacterial activity observed in the experimental gels is attributed solely to the enzymatic compounds.

Color Changes in Artificially Induced Incipient Caries after Photodynamic Therapy with Different Concentrations of Methylene Blue and Toluidine Blue and Irrigation with Water and Hypochlorite

Aim

The aim of this study was to assess the color changes in artificially induced incipient caries after photodynamic therapy (PDT) using different concentrations of methylene blue and toluidine blue, along with irrigation using water and hypochlorite.

Materials and Methods

Forty-two sound human premolar teeth were used to create two artificial incipient carious lesions. One lesion was placed on the buccal surface and the other on the lingual surface. The color of these artificial incipient carious surfaces was determined using the CIE L  ∗ a  ∗ b  ∗ color system. The teeth were then randomly assigned to 12 groups (n = 7) based on the PDT method. These methods included methylene blue with concentrations of 50, 100, and 150 µg/mL, followed by water irrigation, methylene blue with concentrations of 50, 100, and 150 µg/mL, followed by hypochlorite solution irrigation, toluidine blue with concentrations of 50, 100, and 150 µg/mL, followed by water irrigation, and toluidine blue with concentrations of 50, 100, and 150 µg/mL, followed by hypochlorite solution irrigation. The teeth underwent a colorimetry procedure again, and the resulting color changes were calculated. A three-way ANOVA was performed to analyze the effects of laser wavelength, concentration of the light-absorbing material, and irrigation solution on ΔE.

Results

The results showed that the color changes caused by toluidine blue photosensitizer at a concentration of 100 µg/mL, with both water and hypochlorite irrigation, were not noticeable to the naked eye (ΔEwater = 3.04, ΔEhypochlorite = 2.00). However, in the other study groups, the color changes were perceptible (ΔE > 3.3). There were no significant differences in ΔE between different concentrations of methylene blue and toluidine blue when using either water or hypochlorite irrigation (P  > 0.05). A significant difference was observed between methylene blue and toluidine blue at a concentration of 100 µg/mL with water irrigation (P=0.006). Additionally, a significant difference was found between methylene blue and toluidine blue at a concentration of 100 µg/mL with hypochlorite irrigation (P=0.049). However, no significant differences were observed between methylene blue and toluidine blue at other concentrations with either water or hypochlorite irrigation (P  > 0.05).

Conclusion

In conclusion, tooth color in teeth with incipient caries did not change significantly after PDT using toluidine blue (the photosensitizer) at a concentration of 100 µg/mL with either water or 1% hypochlorite solution irrigation for 5 s.

Evaluation of the effects of different photosensitizers used in antimicrobial photodynamic therapy on tooth discoloration: spectrophotometric analysis

BACKGROUND

Tooth discoloration is a common concern in antimicrobial photodynamic therapy (aPDT) using various photosensitizers (PS). Toluidine Blue (TB), Methylene Blue (MB), Phthalocyanine (Pc), and 2-mercaptopyridine-substituted zinc phthalocyanine (TM-ZnPc) are among those studied, but their relative impacts on tooth discoloration remain unclear.

AIM

This study aimed to compare the effects of TB, MB, Pc, and TM-ZnPc in aPDT on tooth discoloration, utilizing a controlled experimental setup.

MATERIALS AND METHODS

The study comprised seventy-five single-rooted incisors with root canals. Following meticulous preparation, a standardized area on the crown surface was designated for examination, and precise measurements of the initial tooth colors were recorded. Samples were randomly divided into five groups: Negative control, MB, TM, Pc, and TM-ZnPc. Photoactivation was performed using LED light, and color measurements were taken at multiple time points up to 90 days. Data were converted to Lab* color values of the CIE Lab* color system (International Commission on Illumination, Vienna, Austria), and ΔE values were calculated. Statistical analysis was performed using Two-way ANOVA and Post-Hoc Tukey tests (p < 0.05).

RESULTS

At day 7 and 30, TM-ZnPc and Pc caused less discoloration compared to MB and TB. TM-ZnPc caused more tooth discoloration compared to Pc (p < 0.05). Compared to baseline, MB and TM-ZnPc caused more tooth discoloration at 30 days and TB caused more tooth discoloration at 90 days (p < 0.05). No significant difference was observed in terms of tooth discoloration at all periods evaluated after Pc application (p > 0.05). All photosensitizers tested in the study caused tooth coloration.

CONCLUSION

All PS induced clinically detectable tooth discoloration, with TB and MB causing more significant discoloration compared to Pc and TM-ZnPc at certain time points. TM-ZnPc and Pc demonstrated more stable coloration levels over time, suggesting their potential reliability in aPDT applications. This study highlights the importance of selecting appropriate PS to minimize tooth discoloration in aPDT, with Pc showing promise in this regard.

The impact of methylene blue photosensitizer, aPDT and a calcium hydroxide-based paste on the physicochemical and mechanical characteristics of root canal dentin and the bonding interface of fiberglass posts

PURPOSE

To investigate the influence of methylene blue (MB)-mediated antimicrobial photodynamic therapy (aPDT) and calcium hydroxide (CH) medication on the mechanical characteristics, degree of conversion (DC), quantification, and volume of gaps at the adhesive interface of glass fiber posts (GFPs) luted to distinct thirds of root canal dentin. Additionally, the microhardness (MH), elastic modulus (Eit), morphology, and chemical structure of the intraradicular dentin were assessed.

MATERIALS AND METHODS

6 experimental groups were formed by sorting 102 bovine incisors. Canals receiving deionized water irrigation as a negative control; canals receiving deionized water irrigation and filled with CH as a positive control; groups treated with CH + MB at 50 and 100 mg/L without irradiation; and groups treated with CH + MB at 50 and 100 mg/L irradiated by red laser for 60 s (660 nm; 100 mW; 6.5 J; 72 J/cm2). MH, Eit, and DC properties were evaluated for both the resin cement layer and root dentin substrate (n = 8). Volume and quantification of gaps at the bonding interface (n = 6), and dentin morphology and chemical content were investigated (n = 3). Data were analyzed using a repeated-measures 2-way ANOVA followed by Tukey post hoc analysis (α = 0.05).

RESULTS

The distinct intraradicular thirds and treatment with MB-mediated aPDT, whether activated or not, in combination with CH, had a significant impact on the mechanical characteristics of the root dentin. This effect was also observed in the MH, Eit, DC, quantification, and volume of gaps at the luting interface (P < .05). In general, a higher concentration of MB, whether activated by a red laser or not, led to lower values in the mechanical properties of the root dentin, as well as in MH, Eit, and DC at the adhesive interface (P < .05). Additionally, these groups exhibited higher values for quantification and volume of gaps at the luting substrate (P < .05). Scanning electron micrographs and energy dispersive X-ray spectra showed qualitative similarity among all groups, except for the negative experimental control group.

CONCLUSIONS

MB-mediated aPDT at 50 mg/L, in combination with CH, demonstrated favorable physico-chemical and mechanical characteristics in intraradicular dentin, along with satisfactory mechanical features and the adhesive interface integrity for GFPs at all intraradicular depths.

CLINICAL SIGNIFICANCE

MB-mediated aPDT at a concentration of 50 mg/L combined to CH medication represents a suitable choice for photosensitization in the context of intracanal disinfection following the biomechanical procedure and prior to luting of intraradicular restorations.

Photodynamic Action of Curcumin and Methylene Blue against Bacteria and SARS-CoV-2-A Review

Coronavirus disease 19 (COVID-19) has occurred for more than four years, and the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causing COVID-19 is a strain of coronavirus, which presents high rates of morbidity around the world. Up to the present date, there are no therapeutics that can avert this form of illness, and photodynamic therapy (PDT) may be an alternative approach against SARS-CoV-2. Curcumin and methylene blue have been approved and used in clinical practices as a photosensitizer in PDT for a long time with their anti-viral properties and for disinfection through photo-inactivated SARS-CoV-2. Previously, curcumin and methylene blue with antibacterial properties have been used against Gram-positive bacteria, Staphylococcus aureus (S. aureus), and Gram-negative bacteria, Escherichia coli (E. coli), Enterococcus faecalis (E. faecalis), and Pseudomonas aeruginosa (P. aeruginosa).

METHODS

To conduct a literature review, nine electronic databases were researched, such as WanFang Data, PubMed, Science Direct, Scopus, Web of Science, Springer Link, SciFinder, and China National Knowledge Infrastructure (CNKI), without any regard to language constraints. In vitro and in vivo studies were included that evaluated the effect of PDT mediated via curcumin or methylene blue to combat bacteria and SARS-CoV-2. All eligible studies were analyzed and summarized in this review.

RESULTS

Curcumin and methylene blue inhibited the replication of SARS-CoV-2. The reactive oxygen species (ROS) are generated during the treatment of PDT with curcumin and methylene blue to prevent the attachment of SARS-CoV-2 on the ACE2 receptor and damage to the nucleic acids either DNA or RNA. It also modulates pro-inflammatory cytokines and attenuates the clotting effects of the host response.

CONCLUSION

The photodynamic action of curcumin and methylene blue provides a possible approach against bacteria and SARS-CoV-2 infection because they act as non-toxic photosensitizers in PDT with an antibacterial effect, anti-viral properties, and disinfection functions.

Antibacterial potential of riboflavin mediated blue diode laser photodynamic inactivation against Enterococcus faecalis: A laboratory investigation

OBJECTIVES

This study aimed to evaluate the inactivation potency of riboflavin-mediated blue diode laser photodynamic inactivation (PDI) against Enterococcus faecalis at planktonic and biofilm stages and also investigated its effect on the tooth color change.

MATERIALS AND METHODS

The antibacterial and antibiofilm activities of riboflavin mediated PDI against E. faecalis were investigated. The numbers of colony-forming units (CFUs)/mL were calculated. Teeth discoloration were evaluated using the CIE L*a*b* based color difference (ΔE).

RESULTS

Antibacterial analysis indicated that the blue diode laser irradiation at 12, 18, 24, and 30 J/cm² alone and different concentrations of riboflavin solution (6.25 to 100 μM) reduced the number of CFU/mL of E. faecalis, but the reduction was not statistically significant (P > 0.05). Depending on the riboflavin concentration and the light dose, there can be as much as a 1-log effect on CFU/mL. In addition, E. faecalis biofilm was more affected with 30 J/cm² irradiation dosage and 100 μM riboflavin than other groups. Meanwhile, bacterial suspensions treated with 5.25% sodium hypochlorite (NaOCl) showed maximum biofilm inhibition and colony number reduction, compared with the control. The teeth exhibited clinically acceptable color change after riboflavin treatment at concentration ranging from 6.25 to 50 μM (ΔE < 3.7).

CONCLUSIONS

The riboflavin mediated PDI process is somewhat less effective than NaOCl but perhaps less toxic to tissues. It might be feasible to repeat the riboflavin + light treatment to further promote efficacy.

Influence of antimicrobial photodynamic therapy on the bond strength of endodontic sealers to intraradicular dentin: A systematic review and meta-analysis

BACKGROUND

The objective of this systematic review and meta-analysis (SRMA) was to investigate the influence of antimicrobial photodynamic therapy (aPDT) on the bond strength of endodontic sealers to intraradicular dentin.

METHODS

This SRMA followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and was registered in the International Prospective Registry of Systematic Reviews (PROSPERO) (CRD42022319856). A population, intervention, control, and outcome (PICO) question was formulated: "Does antimicrobial photodynamic therapy decrease the bond strength of root canal sealers?". A literature search was performed in PubMed/MEDLINE, Embase, Web of Science, Scopus, Cochrane Library, and ProQuest databases until July 2022. Joanna Briggs Institute Critical Assessment Guidelines for Quasi-Experimental Studies were used for quality assessment. The meta-analysis was based on the inverse variance (IV) method (p<0.05).

RESULTS

Out of an initial 345 articles, 8 in vitro studies were included, published between 2013 and 2022. The studies were qualitatively analyzed; two studies showed a positive effect, two studies a negative effect, and the other studies showed no effect on bond strength of endodontic sealers to intraradicular dentin. Seven of the studies were included in the SRMA, which indicated that there was no significant difference in bond strength when using aPDT (P = 0.90; MD: -0.03; 95% CI: -0.46 to -0.41). There was a high level of evidence for each meta-analysis outcome.

CONCLUSION

It can be concluded that the use of aPDT as a method of root canal disinfection does not negatively influence the bond strength of endodontic sealers in the root canal.

Efficacy of curcumin-mediated photodynamic therapy for root canal therapy procedures: A systematic review

BACKGROUND

This systematic review aimed to investigate the effectiveness of CUR-mediated PDT (Curcumin mediated PDT) as an adjunct to conventional chemo-mechanical debridement and/or standard PDT of the RC system with endodontic infections.

METHODS

The focused research question was: "Whether the application Curcumin mediated PDT as an adjunct is more effective than the traditional chemo-mechanical debridement and/or standard PDT of the RC system alone for improving antibacterial and/or mechanical features among subjects undergoing RCT?". An electronic literature search was performed in Scopus, PubMed, and Web of Science. In vitro reports utilizing Curcumin mediated PDT as an adjunct to conventional chemo-mechanical debridement considering permanent dentition assessing the antibacterial and/or mechanical effect were included.

RESULTS

Eighteen articles were included in the review, out of which 13 studies assessed the antibacterial activity, while 5 evaluated the mechanical properties. Most of the studies concluded that Curcumin mediated PDT had a significant antibacterial activity than the conventional chemo-mechanical debridement and/or standard PDT. Four of the five studies suggested that Curcumin mediated PDT had no impact on the push-out bond strength of root dentin. Furthermore, the significant heterogeneity in the data from the included studies did not permit the author to carry out a meta-analysis.

CONCLUSION

There is potential for application of Curcumin mediated PDT as an adjunct to the conventional chemo-mechanical debridement and/or standard PDT in reducing the bacterial load, however, Curcumin mediated PDT has minimal effect on enhancing the pushout bond strength of fiber posts to radicular dentin. Moreover, clinical studies are required to provide a more conclusive opinion on the efficacy of Curcumin mediated PDT for RCT procedures.

Antimicrobial efficacy, optical properties and flexural strength following antimicrobial photodynamic therapy over vacuum-formed orthodontic retainers

BACKGROUND AND AIMS

Vacuum-formed retainers (VFRs) are widely used in dental practices because of their superior esthetics. However, simultaneous maintenance of their hygiene, mechanical and optical properties is challenging. This study aimed to evaluate and compare the disinfection efficacy of antimicrobial photodynamic therapy (aPDT), chlorhexidine (CHX), sodium hypochlorite (NaOCl) and water over VFRs specimens, along with their effect on flexural strength and color stability.

MATERIALS AND METHODS

Fabricated VFRs of thicknesses 1 mm and 2 mm were contaminated with S. mutans and C. albicans. Brain Heart Infusion agar was used to seed Streptococcus Mutans whereas Candida Albicans was seeded in Sabourand Dextrose Agar. The contaminated retainers were divided into four groups and decontaminated using four different treatment protocols: aPDT, CHX, NaOCl and water, with 10 specimens per group. Microbial viability following decontamination, was assayed using MTT. To assess the color stability, pre and post decontamination color difference of 10 specimens was recorded using a spectrophotometer by blinding technique. The flexural strength of 10 specimens was measured using a universal testing machine by a standardized 3-point flexural strength (FS) test.

RESULT

aPDT showed the highest reduction in the viability of S. mutans (28%) and C. albicans (20%) species in 1 mm thickness group while the second highest reduction following disinfection with CHX (40%) in followed by NaOCl disinfection (50%). On comparison between 1 mm and 2 mm, a statistically significant difference was noted for S. mutans in aPDT (p = 0.033) and NaOCl (p = 0.028) groups, and for C. albicans, a significant difference was noted within NaOCl (p = 0.001) and CHX (p = 0.043) groups. For FS, a statistically significant difference (p < 0.05) was observed between aPDT and the rest of the groups, whereas there was no statistically significant difference in the flexural strength between the CHX, NaOCl and water groups (p > 0.05) in both 1 mm and 2 mm specimens. Between 1 mm and 2 mm specimens, no statistically significant difference in the mean color difference was noted after any disinfection protocol (p > 0.05).

CONCLUSION

Antimicrobial photodynamic therapy showed a remarkable reduction in candidal and bacterial viability over VFRs. aPDT treated VFR specimens showed increased flexural strength and a higher color difference post treatment compared to other reagents.