A comparative evaluation of ion release characteristics of three different dental varnishes containing fluoride either with CPP-ACP or bioactive glass.

Objective: To compare ion release characteristics of three different dental varnishes either containing CPP-ACP and fluoride (CPP-ACPF, MI Varnish GC, Japan), bioactive glass and fluoride (BGAF, Dentsply Sirona USA) or fluoride alone (NUPRO White, Dentsply Sirona USA) using fluoride-Ion Selective Electrode (F-ISE), Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES), X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), F and P Magic Angle Spinning-Nuclear Magnetic Resonance (MAS-NMR).

Methods: A thin layer (0.0674±0.0005g) of each varnish (20×25mm in area) was spread on a roughened glass slide (n=7). They were separately immersed in 10ml Tris buffer (0.06M, pH=7.30), and changed after 1, 2, 4, 6, 24 and 48h. Fluoride-ion concentration at each time using the F-ISE, whilst calcium and phosphate release were investigated using ICP-OES. XRD, FTIR. MAS-NMR analyses were also performed before and after immersion.

Results: The cumulative F-ion release was significantly higher in CPP-ACPF (1.113mmol/g)>BGAF(0.638)>F(0.112) (p<0.001). The cumulative calcium and phosphorus were higher in the CPP-ACPF (0.137mmol/g, 0.119) than BGAF (0.067, 0.015) (p<0.001) respectively. The XRD and F MAS-NMR confirmed the presence of NaF peaks in all cases before immersion. There were less prominent signal and appearance of fluorapatite crystals after immersion. F MAS-NMR revealed CaF formation after immersion in both CPP-ACPF and BGAF. P MAS-NMR showed phosphate signals in both CPP-ACPF and BGAF before immersion. FTIR failed to show any signs of apatite formation.

Significance: Both CPP-ACP and bioactive glass enhanced ion release without compromising the bioavailability of fluoride. The CPP-ACPF varnish had the most promising ion release.