Mechanism of Action of TiF4 on Dental Enamel Surface: SEM/EDX, KOH-Soluble F, and X-Ray Diffraction Analysis

This in vitro study aimed to evaluate the action of TiF4 on sound and carious bovine and human enamel. Sound (S) and pre-demineralised (DE) bovine and human (primary and permanent) enamel samples were treated with TiF4 (pH 1.0) or NaF varnishes (pH 5.0), containing 0.95, 1.95, or 2.45% F for 12 h. The enamel surfaces were analysed using SEM-EDX (scanning electron microscopy/energy-dispersive X-ray spectroscopy) (n = 10, 5 S and 5 DE) and KOH-soluble fluoride was quantified (n = 20, 10 S and 10 DE). Hydroxyapatite powder produced by precipitation method was treated with the corresponding fluoride solutions for 1 min (n = 2). The formed compounds were detected using X-ray diffraction (XRD). All TiF4 varnishes produced a coating layer rich in Ti and F on all types of enamel surface, with micro-cracks in its extension. TiF4 (1.95 and 2.45% F) provided higher fluoride deposition than NaF, especially for bovine enamel (p < 0.0001). It also induced a higher fluoride deposition on DE samples compared to S samples (p < 0.0001), except for primary enamel. The Ti content was higher for bovine and human primary enamel than human permanent enamel, with some differences between S and DE. The XRD analysis showed that TiF4 induced the formation of new compounds such as CaF2, TiO2, and Ti(HPO4)2·H2O. In conclusion, TiF4 (>0.95% F) interacts better, when compared to NaF, with bovine and human primary enamel than with human permanent enamel. TiF4 provoked higher F deposition compared to NaF. Carious enamel showed higher F uptake than sound enamel by TiF4 application, while Ti uptake was dependent on the enamel condition and origin.

Alkali-soluble fluoride deposition on enamel after professional application of topical fluoride in vitro

Since the efficacy of topical fluoride products is related to the fluoride (F) availability and its reactivity with enamel, this study was conducted. The F concentration of the following materials was verified: I- acidulated phosphate fluoride (APF) gel (1.23% F), II- APF foam (1.23% F) and III- Varnish (2.26% F). Forty blocks of bovine enamel were divided into 4 groups and treated according to the materials described, being one of them used as control. Loosely bound fluoride (''CaF2'') was determined on enamel after extraction with 1.0M KOH and analyzed by ion-selective electrode. Total F concentration found in gel was 12,642, in foam 12,755 and in varnish 23,183 mg F/g. All products formed statistically higher amounts of ''CaF2'' on enamel compared to the control group (p < 0.05), but the difference between them was not significant (p > 0.05). Thus, ''CaF2'' formation was not proportional to the total F content in the products, suggesting that the pH and the vehicle used are more important.