Is the chlorophyll derivative Zn(II)e(6)Me a good photosensitizer to be used in root canal disinfection?

Background: The aim of this study was to assess antimicrobial efficacy and cytotoxic outcomes of a chlorophyll based photosensitizer (PS) Zn(II)chlorin e(6) methyl ester (Zn(II)e(6)Me), when applied to human dentin discs and root blocks infected with 48 h biofilms. The results were compared with the ones obtained with FotoSan (R) (commercial Toluidine Blue O formulation) and 3% sodium hypochlorite (NaOCl). Methodology: Dentin and root blocks were infected with mixed biofilms of Enterococcus faecalis and Candida albicans; exposed for 15 min to 0.1 mg/mL of Zn(II)e(6)Me or FotoSan (R) and then irradiated with red light (627 nm, 75 mW, 3150 J/cm(2)) for 90 s or treated with NaOCl. Biofilm removal was calculated with safranin red assay and biofilm cells viability with XTT (R) assay. The PSs cytotoxicity was evaluated over human apical papilla primary cell line (hAPCs) with AlamarBlue (R) assay and cell morphology assessed with widefield fluorescence microscopy. Results: At dentin discs, the chlorophyll derivative performed better in biofilm removal (59.1%) than FotoSan (R) agent (57.5%), however, with lower efficacy than NaOCl (68.1%) (P = 0.0185). Conversely, at the root block, the chlorophyll Zn(II)e(6)Me (79.7%) present better antimicrobial efficacy than NaOCl (75.5%) and the disinfection pattern was more consistent at inner and outer samples for the former. No dark or photoinduced cytotoxic outcomes were detected for Zn(II)e(6)Me over human cells at 24 and 48 h when compared with other PSs (FotoSan (R), Rose Bengal and 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin - TMPyP). Conclusions: The chlorophyll derivative Zn(II)e(6)Me showed adequate antimicrobial efficacy, performing better in mixed biofllm removal than FotoSan (R) in both experimental conditions. No cytotoxic effects over human apical papilla cells were identified for this chlorophyll derivative, subsequently it deserves further evaluation to assess its potential use in endodontic therapy.