Effects of sub-lethal doses of photo-activated disinfection against Porphyromonas gingivalis for pharmaceutical treatment of periodontal-endodontic lesions

Expression patterns of <em>oxyR</em> induced by oxidative stress from <em>Porphyromonas gingivalis</em> in response to photo-activated disinfection

“… 19 In these circumstances, sPAD can not only eliminate the microorganisms but also considerably influence microbial pathogenicity through changes in gene expression of the virulence factor and increase the resistance to antimicrobial agents. 9 , 11 , 12 Nevertheless, in addition to sPAD not helping the treatment of root canal infections, it also may cause treatment failure and the emergence of secondary endodontic infections.…”

“…According to the previous studies, 9 – 11 stock solutions of TBO and MB (both items were purchased from Sigma-Aldrich) at final concentrations of 0.1 mg/mL and ICG (Santa Cruz Biotechnology Co., Ltd; Shanghai, China) stock solution at a final concentration of 1.0 mg/mL were prepared as photosensitizers in sterile 0.9% (wt/vol) NaCl. Prior to use, the photosensitizers were filtered with a sterile syringe filter of 0.22 μm pore size and were kept under dark conditions.…”

“…sPAD was determined by measuring the minimum inhibitory concentration (MIC) of photosensitizers and sublethal dose of diode laser irradiation time against P. gingivalis isolates according to our previous study. 9 In short, the wells of 96-well, flat-bottomed, sterile polystyrene microplates (TPP, Trasadingen, Switzerland) were filled with 100 μL of 2×BHI broth and 100 μL of each photosensitizer at 2×MIC, and individually diluted in serial 2-fold to 1/8× MIC. One hundred microliters of each fresh suspension of the 16 clinical P. gingivalis isolates in final concentrations of 5.0×10 5 CFU/mL was then inoculated into each well.…”

“…Eventually, the microplates were incubated in an anaerobic atmosphere in the dark at room temperature for 5 min and were then immediately exposed to a sublethal dose of light sources, depending on the type of photosensitizer according to our previous study. 9 We placed a black paper sheet under the microplates to avoid beam reflection from the table top during irradiation. Instantly, 10 μL of each well containing the diluted series was cultured in enriched BHI plates and incubated in anaerobic conditions at 37°C for 48 h, and the CFU/mL values were determined using the method of Miles et al 13 The lowest concentrations of photosensitizers with the shortest irradiation time of diode laser in the last well showing growth were defined as the (maximal) sPAD.…”

“…Endodontic pathogens such as P. gingivalis may be exposed by a sublethal dose of PAD (sPAD; i.e., a combination of sub-minimum inhibitory concentration of photosensitizers and/or a sublethal dose of diode laser irradiation time) at the site of infection during endodontic treatment, which not only does not eradicate or inactivate the P. gingivalis but also may affect a broad range of its features and virulence factors. 7 , 8 Some studies 9 – 11 have provided evidence for the effects of sPAD with different photosensitizers and the corresponding wavelengths of light on the count and biofilm formation ability of P. gingivalis , but the sPAD effects on the expression of P. gingivalis virulence factor genes, including those that are involved in response to oxidative stress, are still missing. The aim of this study was to assess the effects of sPAD treatment in vitro on oxyR gene expression of clinical P. gingivalis isolates surviving photodynamic treatment.…”