Endodontic antimicrobial photodynamic therapy: safety assessment in mammalian cell cultures.
OBJECTIVE
The purpose of this study was to assess the in vitro synergistic effect of methylene blue (MB) and red light on human gingival fibroblasts and osteoblasts with parameters similar to those that may be applied in a clinical setting for endodontic disinfection.


METHODS
Both cell types were sensitized with 50 microg/mL MB followed by exposure to red light at 665 nm for 5 minutes with an irradiance of 10, 20, and 40 mW/cm(2). After photodynamic therapy (PDT), cell viability and mitochondrial activity were evaluated by the neutral red and MTT assay, respectively. The assessment of PDT-induced apoptosis was investigated by western blot analysis using cleaved poly(ADP-ribose) polymerase-specific antibodies.


RESULTS
Light at 20 and 40 mW/cm(2) with MB had modest effects at 24 hours on osteoblasts in both assays, whereas sodium hypochlorite completely eliminated cells. Western blot analysis revealed no signs of apoptosis in either cell type.


CONCLUSIONS
The data suggest that there is a safe therapeutic window whereby PDT can inactivate endodontic pathogens without affecting host cell viability.
Applied Molecular Photomedicine Laboratory, The Forsyth Institute, Boston, MA 02115-3799, USA.
Yan
Y
Xu
Mark J
MJ
Young
Ricardo A
RA
Battaglino
Leslie R
LR
Morse
Carla Raquel
CR
Fontana
Tom C
TC
Pagonis
Ralph
R
Kent
Nikolaos S
NS
Soukos
D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004396:Coloring Agents; D003786:Dental Pulp Cavity / Q000187:drug effects*; D004203:Disinfection / Q000379:methods*; D005347:Fibroblasts / Q000187:drug effects; D005881:Gingiva / Q000166:cytology / Q000187:drug effects; D006801:Humans; D054023:Lasers, Semiconductor / Q000627:therapeutic use*; D008422:Materials Testing; D008751:Methylene Blue / Q000627:therapeutic use; D008928:Mitochondria / Q000187:drug effects; D009499:Neutral Red; D010006:Osteoblasts / Q000187:drug effects; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000627:therapeutic use; D012390:Root Canal Therapy / Q000379:methods*; D012449:Safety; D013778:Tetrazolium Salts; D013844:Thiazoles; D013997:Time Factors
D004396:Coloring Agents; D017319:Photosensitizing Agents; D013778:Tetrazolium Salts; D013844:Thiazoles; D009499:Neutral Red; C022616:thiazolyl blue; D008751:Methylene Blue