The cytotoxic effect of TiF₄ and NaF on fibroblasts is influenced by the experimental model, fluoride concentration and exposure time

by Priscila Maria Aranda Salomão, Flávia Amadeu de Oliveira, Paula Danielle Rodrigues, Luana Polioni Al-Ahj, Kellen Cristina da Silva Gasque, Pia Jeggle, Marilia Afonso Rabelo Buzalaf, Rodrigo Cardoso de Oliveira, John Michael Edwardson, Ana Carolina Magalhães

Titanium tetrafluoride (TiF₄) has shown promising effect in preventing tooth lesions. Therefore, we compared the cytotoxicity of TiF₄ with sodium fluoride (NaF) (already applied in Dentistry) considering different fluoride concentrations, pH values and experimental models.

Step 1) NIH/3T3 fibroblasts were exposed to mediums containing NaF or TiF₄ (from 0.15 to 2.45% F), both at native and adjusted pH, for 6 h. Step 2) NIH/3T3 were exposed to NaF or TiF₄ varnishes with 0.95, 1.95 or 2.45% F (native pH), for 6, 12 or 24 h. We applied MTT (1^st and 2^nd steps) and Hoescht/PI stain (2^nd step) assays. Step 3) NIH/3T3 were exposed to NaF or TiF₄ varnish (2.45% F), at native pH, for 6 or 12 h. The cell stiffness was measured by atomic force microscopy (AFM).

Step 1) All cells exposed to NaF or TiF₄ mediums died, regardless of the F concentration and pH. Step 2) Both varnishes, at 1.90 and 2.45% F, reduced cell viability by similar extents (33–86% at 6 h, 35–93% at 12 h, and 87–98% at 24 h) compared with control, regardless of the type of fluoride. Varnishes with 0.95% F did not differ from control. Step 3) TiF₄ and NaF reduced cell stiffness to a similar extent, but only TiF₄ differed from control at 6 h.

Based on the results of the 3 experimental steps, we conclude that TiF₄ and NaF have similar cytotoxicity. The cytotoxicity was dependent on F concentration and exposure time. This result gives support for testing the effect of TiF₄ varnish in vivo.