Background and Objectives: This study was performed to compare the use of methylene blue (MB) and rose bengal (RB) in antimicrobial photodynamic therapy (PDT) targeting Enterococcus faecalis (E. faecalis) bacteria in planktonic and biofilm forms with potassium iodide (KI) potentiation. Study Design/Materials and Methods: E. faecalis bacteria in planktonic form were exposed to antimicrobial PDT protocols activating MB and RB, with or without KI potentiation, following laser irradiation with different exposure times, 60 mW/cm 2 laser power, and different photosensitizer agent (PS)/potentiator concentrations to observe relationships among the variables. Two continuous-wave diode lasers were used for irradiation (red light: λ = 660 nm and green light: λ = 565 nm). The pre-irradiation time was 10 minutes. The vitality of E. faecalis biofilm was assessed by confocal laser scanning microscopy, and the morphology was determined by scanning electron microscopy. The effects on the proliferation of stem cells from the apical papilla (SCAPs) were analyzed by cell counting kit-8 assay. The staining effect of antimicrobial PDT on dentin slices was investigated. Statistical analysis using a one-way analysis of variance was done. Results: KI-potentiated RB and MB antimicrobial PDT both effectively eradicated E. faecalis bacteria in planktonic and biofilm forms. The minimum bactericidal concentrations of PSs (±100 mM KI) were obtained through PDT on planktonic E. faecalis, and the optimal light parameters were 60 mW/cm 2 , 6 J/cm 2 for 100 seconds. KI-potentiated PDT effectively strengthened the ability to inhibit E. faecalis biofilm with 86.50 ± 5.78% for MB (P = 0.0015 < 0.01) and 91.50 ± 1.75% for RB (P = 0.0418 < 0.05) of bactericidal rate, with less toxicity for SCAPs (P < 0.001) and less staining. KI could reduce the staining induced by antimicrobial PDT on dentin slices. Conclusion: A combination of KI and antimicrobial PDT may be a useful alternative to conventional disinfection methods in endodontic treatment. MB and RB antimicrobial PDT at much lower concentrations with KI could hopefully achieve disinfection effects comparable with those of 1.5% NaClO while causing few adverse effects on SCAPs. KI helps to avoid staining problems associated with high concentrations of photosensitizer agents. Lasers Surg. Med.

Background: Pulpitis is a complicated chronic inflammatory process which in a dynamic balance between damage and repair. Extracellular matrix plays an important regulatory role in wound healing and tissue repair. The aim of this study was to explore role of the epigenetic mark, enhancer of zeste homolog 2 (EZH2) on the degradation of extracellular matrix during pulpitis. Methods : Quantitative polymerase chain reaction was used to assess the expression of matrix metalloproteinases (MMPs) and type Ⅰ collagen in HDPCs upon EZH2 and EI1 stimulation. The mechanism of EZH2 affecting extracellular matrix was explored through quantitative polymerase chain reaction and Western blot. A rat model of dental pulp inflammation was established, and the expression of type Ⅰ collagen in dental pulp under EZH2 stimulation was detected by immunohistochemical staining. Results :EZH2 upregulated the expression of MMP-1, MMP-3, MMP-8 and MMP-10 and decreased the production of type Ⅰ collagen in HDPCs, while EI1 had the opposite effect .EZH2 activated the Nuclear Factor-κB(NF-κB)and p38 signaling Pathways in HDPCs, the inhibition of which reversed the induction of MMPs and the suppression of type Ⅰ collagen .EZH2 can downregulated the type Ⅰ collagen levels in an experimental model of dental pulpitis in rats. Conclusion: EZH2 promotes extracellular matrix degradation via Nuclear Factor-κB(NF-κB)and P38 signaling pathways in pulpitis.EZH2 can decrease the type Ⅰ collagen levels in vivo and vitro.