Sonic-assisted antibacterial photodynamic therapy: a strategy for enhancing lateral canal disinfection.

BACKGROUND: Bacterial infections in lateral canals pose challenges for root canal treatment. This in vitro study aims to evaluate the antibacterial efficacy of sonic-assisted methylene blue mediated antimicrobial photodynamic therapy (MB-aPDT) against Enterococcus faecalis (E. faecalis) in infected lateral canals. METHODS: Sixty-five premolars infected with E. faecalis in lateral canals were randomly divided into five groups (n = 13) and treated with : (1) 5.25% NaOCl (positive control); (2) Saline (negative control); (3) Sonic-assisted MB-aPDT; (4) 3% NaOCl + MB-aPDT; (5) 3% NaOCl + sonic-assisted MB-aPDT, respectively. The antibacterial efficacy was evaluated by the colony- counting method (CCM) and scanning electronic microscope (SEM). RESULTS: Both 5.25% NaOCl and the 3% NaOCl + sonic-assisted MB-aPDT exhibited the most effective while comparable antibacterial effects without significant statistical difference (P > 0.05). Furthermore, the antibacterial effect of the 3% NaOCl + MB-aPDT group was significantly higher compared to that of the sonic-assisted MB-aPDT group (P < 0.05). The SEM results demonstrated notable morphological alterations in E. faecalis across all experimental groups, except for the negative control group. CONCLUSION: The concentration of NaOCl can be reduced to a safe level while preserving its antibacterial efficacy through the synergism with the sonic-assisted MB-aPDT in this study.

In vitro effect of Er: YAG laser irradiation in caries cavity preparation on biobehaviors of adjacent human dental pulp cells in the pulp chamber.

The erbium-doped yttrium aluminum garnet (Er: YAG) laser has been successfully applied in caries removal; however, little is known about proper parameters of Er: YAG laser on different conditions of caries removal, especially the influence of Er: YAG irradiation on human dental pulp cells (hDPCs). Here, we tested the effects of Er: YAG laser at different output energy levels (100, 200, 300, 400, and 500 mJ) on biobehaviors of hDPCs. To simulate clinical deep caries conditions, hDPCs were cultured on the pulpal side of 500-µm-thick dentin disks in an in vitro pulp chamber model. Temperature change, structural change, and ablation depth of dentin disk were also recorded. The findings suggested that the biological behaviors of hDPCs are strongly correlated with the energy output of the Er: YAG laser. Er: YAG laser irradiation at 100 mJ may be proper and safe for deep caries removal since it would not cause any adverse effect on hDPCs biobehaviors.

An easily achievable strategy to promote the penetration of methylene blue into dentinal tubules.

BACKGROUND: One critical issue that impairs the therapeutic effects of antimicrobial photodynamic therapy (aPDT) in root canal disinfection is the insufficient penetration of photosensitizer into dentinal tubules. Therefore, this study aimed to compare the treatments in enhancing photosensitizers' penetrability for aPDT in root canal therapy. METHODS: Thirty premolars with a single root canal were randomly divided into three groups (n = 10), using Methylene blue (MB) as a photosensitizer and treated with different approaches: sonic-assisted diffusing group, ultrasonic-assisted diffusing group and the control without treatment. All specimens were observed by stereomicroscope to measure the penetration depth of MB into dentinal tubules. RESULTS: Both sonic and ultrasonic treatments substantially improved the penetrability of MB. The former achieved a deeper penetration depth than the latter did in the same region of root (P<0.05). Regarding the dye penetration depths at different root regions, the control group showed a declining trend from coronal to apical. In contrast, the penetration depths of sonic and ultrasonic-assisted diffusing groups from highest to lowest were middle > coronal > apical (P<0.05). CONCLUSIONS: This study showed that both sonic and ultrasonic treatments remarkably promoted MB's penetration depth into dentinal tubules. Maximum penetration was achieved when treated with a sonic approach.

Antimicrobial Photodynamic Effect of Cross-Kingdom Microorganisms with Toluidine Blue O and Potassium Iodide.

Streptococcus mutans (S. mutans) and Candida albicans (C. albicans) are prominent microbes associated with rapid and aggressive caries. In the present study, we investigated the antimicrobial efficacy, cytotoxicity, and mechanism of toluidine blue O (TBO)-mediated antimicrobial photodynamic therapy (aPDT) and potassium iodide (KI). The dependence of KI concentration, TBO concentration and light dose on the antimicrobial effect of aPDT plus KI was determined. The cytotoxicity of TBO-mediated aPDT plus KI was analyzed by cell counting kit-8 (CCK-8) assay. A singlet oxygen (1O2) probe test, time-resolved 1O2 detection, and a 1O2 quencher experiment were performed to evaluate the role of 1O2 during aPDT plus KI. The generation of iodine and hydrogen peroxide (H2O2) were analyzed by an iodine starch test and Amplex red assay. The anti-biofilm effect of TBO-mediated aPDT plus KI was also evaluated by counting forming unit (CFU) assay. KI could potentiate TBO-mediated aPDT against S. mutans and C. albicans in planktonic and biofilm states, which was safe for human dental pulp cells. 1O2 measurement showed that KI could quench 1O2 signals, implicating that 1O2 may act as a principal mediator to oxidize excess iodide ions to form iodine and H2O2. KI could highly potentiate TBO-mediated aPDT in eradicating S. mutans and C. albicans due to the synergistic effect of molecular iodine and H2O2.

Laser activated irrigation with SWEEPS modality reduces concentration of sodium hypochlorite in root canal irrigation.

INTRODUCTION: Shockwave enhanced emission photoacoustic streaming (SWEEPS) of Er: YAG laser has been proposed to improve the disinfecting efficacy of endodontic treatments. The purpose of this in vitro study was to compare the effects of different concentrations of sodium hypochlorite (NaOCl) combined with SWEEPS root canal irrigation on the removal of Enterococcus faecalis (E.faecalis) in infected bovine root canals. MATERIALS AND METHODS: Forty-eight bovine root canals infected with E.faecalis were randomly divided into six groups. The root canals were irrigated by normal saline (NS) in combination with conventional needle irrigation (CI) , NS and different concentrations of NaOCl (0.5%, 1.0%, 2.0%, and 5.25%) in combination with SWEEPS. Then, the remaining live microbes from all specimens before and after root canal irrigation were collected and recovered via plate counting of the colony-forming unit (CFU). The CFU data were statistically analyzed by the Kruskal-Wallis H test. RESULTS: After root canal irrigation, the viable count in each group was significantly reduced (P < 0.05). The bacterial reduction in NS+CI and NS+SWEEPS groups was significantly lower than that in other groups (P < 0.05), and there was no significant difference among the other groups, or between these two groups (P > 0.05). CONCLUSIONS: This study showed that SWEEPS used for root canal irrigation can enhance the effect of low-concentration NaOCl while ensuring the antimicrobial effect.

Hydrogen peroxide potentiates antimicrobial photodynamic therapy in eliminating Candida albicans and Streptococcus mutans dual-species biofilm from denture base.

BACKGROUND: Candida albicans (C.albicans) is the primary pathogen of denture biofilm. Moreover, it could establish a cross-kingdom relationship with bacteria to enhance its virulence and resistance to antifungal drugs. This study aimed to investigate the efficacy of antimicrobial photodynamic therapy (aPDT) in combination with hydrogen peroxide (H2O2) against C.albicans and Streptococcus mutans (S.mutans) dual-species biofilm formed on polymethyl methacrylate (PMMA) disk, and explore its involved mechanisms. METHODS: C.albicans and S.mutans were grown on PMMA disk for 48 h to form biofilm and received different treatments. The treatments included:1) phosphate-buffered saline (PBS) group,2) 100 mM H2O2 group,3) aPDT group,4) aPDT+ H2O2 and 5) H2O2+aPDT group. Colony forming units (CFU), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), and scanning electron microscope (SEM) were used to evaluate the antimicrobial effects. Extracellular polysaccharide substance (EPS) production and observation, cell permeability of biofilm, and uptake of toluidine blue O (TBO) by biofilm were assessed to investigate the involved mechanism. RESULTS: There was no significant difference between PBS group and H2O2 group in viable microorganisms and metabolic activity of biofilm. The treatment protocols containing aPDT group reduced microorganism numbers and metabolic activity when compared to PBS group or H2O2 group (P<0.05). H2O2+aPDT treatment showed the highest antimicrobial efficacy in comparison with other treatments (P<0.05). Pretreatment with H2O2 could decrease EPS production and enhance cell permeability, leading to increased TBO uptake in biofilm. CONCLUSION: Pretreatment with H2O2 improved aPDT efficiency in eliminating dual-species biofilm from PMMA disk by reducing EPS amount, enhancing cell permeability, and increasing TBO uptake.

Mandibular first premolar with five root canals: a case report.

BACKGROUND: Understanding the anatomical morphology of the root canal is key for successful root canal treatment. The aims of this case presentation are to report a unique case of root canal treatment involving five root canals in the mandibular first premolar and to highlight the importance of variation in root canals of mandibular first premolars in clinical practice. CASE PRESENTATION: A 25-year-old male with intermittent pain in relation to the lower right posterior teeth over 3 weeks was diagnosed with symptomatic pulpitis in tooth #44. Four root canals were found, including mesiobuccal, distobuccal-1, distobuccal-2, and distolingual roots, and the Mtwo rotary system was used for root canal preparation. The four root canals were filled after 2 weeks, when a fifth canal was found, located in the buccal cavity. The fifth canal was confirmed to be the mesiolingual root canal by cone beam computed tomography (CBCT) and was found to be curved. After completion of the root canal filling, CBCT was performed, and a three-dimensional root canal image was reconstructed. After 1 week of observation, the tooth was repaired using composite resin filling. CONCLUSIONS: This is the first case presentation of a fifth canal of the mandibular first premolar and advances our understanding of variations in the anatomy of the mandibular first premolar. This case report provides a reference for the treatment of mandibular first premolars.

Pretreatment of Root Canal with Photodynamic Therapy Facilitates Adhesion, Viability and Differentiation of Stem Cells of the Apical Papilla.

This study was to test the hypothesis that root canal pretreated with photodynamic therapy (PDT) would promote stem cells from the apical papilla (SCAP) adhesion, proliferation and differentiation without affecting smear layer removal and microhardness of root canal. Standardized root canals were randomized into four groups (n = 30/group): (1) sodium hypochlorite(NaOCl) group, (2) NaOCl + ethylene diaminetetraacetic acid (EDTA) group, (3) NaOCl + PDT group, (4) NaOCl + EDTA + PDT group. After treatments, smear layer removal and microhardness of root canal were evaluated. SCAP with hydroxyapatite-based scaffolds were seeded into root canals for 7 days. SCAP adhesion was observed by scanning electron microscope (SEM), and viable cells were calculated by CellTiter-Glo Luminescent kit. Platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF) expression of SCAP were evaluated by Quantitative Reverse Transcriptase-Polymerase Chain Reaction. There was no significant difference in the smear layer removal and microhardness of root dentin between the groups with and without PDT treatment (P > 0.05). SCAP with elongated cytoplasmic processes and cell-cell contact were observed on the dentin surfaces treated with PDT. Elevated cell viability, PDGF and VEGF expression were found in root canal treated with PDT (P < 0.05). Under the experimental conditions, PDT could provide positive microenvironment for SCAP growth.

Antimicrobial effects of photodynamic therapy with antiseptics on Staphylococcus aureus biofilm on titanium surface.

BACKGROUND: S. aureus biofilm plays a predominant role in the establishment and development of peri-implantitis. It is suggested to combine different modalities as peri-implantitis treatment. The aim of this study was to evaluate the disinfection efficacy of combined application of antiseptics with PDT on Staphylococcus aureus (S. aureus) biofilm formed on titanium(Ti) disks with different surface roughness. METHODS: S. aureus biofilm was incubated on polished and sandblasted large-grit acid-etched (SLA) Ti surfaces for 48 h. 72 contaminated Ti disks (36 polished, 36 SLA) were randomly divided into 6 different groups as follows: (a) PBS, (b) 0.2% chlorhexidine digluconate (CHX), (c) 3% hydrogen peroxide (H2O2), (d) PDT, (e) 0.2% CHX + PDT, and (f) 3% H2O2+PDT. Colony forming unit (CFU) was measured to determine antimicrobial effects. Biofilm structure was assessed using scanning electron microscopy (SEM) and confocal laser scanning microscope (CLSM). RESULTS: All disinfection methods significantly reduced bacteria amounts compared to control group on both polished and SLA Ti surfaces (P < 0.001). PDT demonstrated stronger decontamination ability in eliminating S. aureus from Ti surfaces than CHX and H2O2 did (P < 0.05). The combined CHX or H2O2 with PDT treatment were more effective in bacterial disinfection than a single administration of these treatments (P < 0.001). CONCLUSION: The combination of CHX or H2O2 administration with PDT was more effective in eradicating S. aureus on both polished and SLA Ti disks in comparison with either treatment alone, suggesting that combined usage of antiseptics with PDT could be a more efficient method for the treatment of peri-implantitis.

Disinfect Porphyromonas gingivalis Biofilm on Titanium Surface with Combined Application of Chlorhexidine and Antimicrobial Photodynamic Therapy.

Various antimicrobial modalities have been proposed to treat peri-implantitis but resulted in limited outcomes. The aim of this in vitro study was to evaluate the disinfection efficacy of combined application of chlorhexidine digluconate (CHX) and antimicrobial photodynamic therapy (aPDT) of titanium surfaces previously contaminated with Porphyromonas gingivalis biofilm. P. gingivalis biofilms were grown on 32 polished and 32 sandblasted large-grit acid-etched (SLA) titanium surfaces. Titanium disks were allocated into four groups as follows: (1) immersed in phosphate-buffered saline (PBS), (2) immersed in 0.2% CHX, (3) application of aPDT and (4) immersed in 0.2% CHX and subsequent aPDT. Residual bacteria were determined by microbial culture analysis and by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) imaging. Combination protocol (CHX+ aPDT) was the most effective in eradicating P. gingivalis (P < 0.05) on both polished and SLA surfaces. There was no significant difference in the number of remaining P. gingivalis between polished titanium disks and the SLA ones in four groups (P > 0.05). Under the limitation of this study, combined technique of preceding application of CHX and subsequent aPDT was shown to be an efficient method in reducing P. gingivalis numbers in both polished and SLA titanium surfaces.

Minimizing Concentration of Sodium Hypochlorite in Root Canal Irrigation by Combination of Ultrasonic Irrigation with Photodynamic Treatment.

Concentration of sodium hypochlorite (NaOCl) is positively correlated with its effectiveness in root canal disinfection but negatively correlated with its biocompatibility. The objective of this in vitro study was to compare the bactericidal effects among ultrasonic irrigation with different concentration of NaOCl alone or together with photodynamic treatment (PDT) against Enterococcus faecalis (E. faecalis) in infected root canals. One hundred and twenty bovine root canals contaminated with E. faecalis were randomly distributed into 12 groups treated with different disinfection methods: PDT, ultrasonic irrigation with NaOCl at different concentrations (0.5%, 1.0%, 2.0%, 2.5% and 5.25%), and ultrasonic irrigation with NaOCl at different concentrations plus PDT. Data of microorganism load were collected before and after disinfection and analyzed by one-way ANOVA and LSD tests. Significantly enhanced antibacterial effects were noticed in groups treated by PDT plus 2.0% or 2.5% NaOCl irrigation (P < 0.05). No statistical differences existed in bactericidal efficacy among groups of PDT plus ultrasonic irrigation with 2.0%, 2.5% or 5.25% NaOCl, and ultrasonic irrigation with 5.25% NaOCl alone (P > 0.05). Our study confirmed the feasibility to reduce the concentration of NaOCl to a safer level while maintaining its antibacterial efficiency through synergistic effect of PDT with NaOCl ultrasonic irrigation.

Comparative antibacterial efficacy of photodynamic therapy and ultrasonic irrigation against Enterococcus faecalis in vitro.

Enterococcus faecalis poses a challenge to the efficacy of traditional root canal disinfection methods. This study was aimed to establish a synergistic root canal disinfection strategy combining ultrasonic irrigation with photodynamic therapy (PDT) together and to test its antibacterial efficacy against E. faecalis. Twenty-seven bovine root canals infected with E. faecalis were randomly divided into three groups and treated with different disinfection methods as follows: ultrasonic irrigation with 2.5% NaOCl, methylene blue (MB)-mediated PDT, or combined ultrasonic irrigation and PDT as described above. Quantification of E. faecalis was performed on the root canals before and immediately after the disinfection treatment. Residual bacteria were determined by counting colony-forming units. Samples were randomly selected from the three groups, and the morphology of residual bacteria inside the dentinal tubules was studied by scanning electron microscopy. The number of surviving E. faecalis in the group treated with the combination method was significantly lower (P < 0.05) than those in the ultrasonic irrigation-treated or PDT-treated groups. Similar results were found in the morphological studies of the three groups. The results of our study highlighted the importance of combination of ultrasonic irrigation and PDT to produce significant antibacterial efficacy against E. faecalis during root canal disinfection.