In Vitro Effect of Photodynamic Therapy With Curcumin in Combination With Photobiomodulation Therapy by 660 nm on the Viability of Human Gingival Fibroblasts

<b>Introduction:</b> This study aimed to assess the effect of repeated irradiations of 660 nm photobiomodulation therapy (PBMT) after photodynamic therapy (PDT) with curcumin on the viability of human gingival fibroblasts (HGFs). <b>Methods:</b> In this in vitro, experimental study, HGFs were cultured and assigned to five groups: One control group with no intervention and four experimental groups of PDT with curcumin, PBMT (660 nm laser irradiation) immediately after PDT, PBMT immediately and 24 hours after PDT and PBMT immediately and 24 hours and 48 hours after PDT. Cell viability was assessed after 1, 4, and 7 days using the methyl thiazolyl tetrazolium (MTT) assay. Data were analyzed by one-way ANOVA. <b>Results:</b> On day 1, the control group had no significant difference with one-time (<i>P</i>=1.00), two-time (<i>P</i>=1.00), and three-time (<i>P</i>=0.88) laser irradiation groups. On day 4, the difference between the control and one-time (<i>P</i><0.001), two-time (<i>P</i><0.001) and three-time (<i>P</i>=0.02) laser irradiation groups was statistically significant, suggesting more cell viability in test groups. On day 7, the three-time laser irradiation group showed significant cell viability compared to the other two test groups but not with the control group (<i>P</i>=0.98). <b>Conclusion:</b> PBMT with 660 nm laser irradiation after PDT with curcumin would increase the viability of HGFs by increasing the frequency of irradiation.