Remineralisation of enamel with silver diamine fluoride and sodium fluoride

Abstract

Objectives: To evaluate the remineralising effect of topical application of 38% silver diamine fluoride (SDF) solution, 5% sodium fluoride (NaF) varnish and adjunctive application of SDF solution and NaF varnish on artificial enamel caries lesions. Methods: Forty-eight demineralised enamel specimens from 12 sound molars were allocated into 4 groups. Group 1 received 38% SDF solution and 5% NaF varnish. Group 2 received 38% SDF solution. Group 3 received 5% NaF varnish. Group 4 received deionized water. After pH cycling for 21 days, the surface morphology was studied by scanning electron microscopy (SEM). Energy dispersive spectroscopy (EDX) was performed for elemental analysis. Crystal characteristics were assessed by X-ray diffraction (XRD). Lesion depth and mineral density of specimens were studied using micro-computer tomography (Micro-CT). The crystallization reaction was performed by incubating hydroxyapatite powder with NaF solution (900 ppm fluoride) or SDF solution (900 ppm fluoride) for 24 hours. The precipitates formed were studied by transmission electron microscopy (TEM) and EDX. Results: SEM showed the surface destruction in group 4 but not the other 3 groups. EDX found the fluoride weight percentage (mean±SD) from group 1 to 4 were 1.23±0.14, 1.33±0.19, 1.18±0.20 and 0.92±0.05 respectively (Group 1,2>3>4, p<0.001). Micro-CT showed the lesion depth (mean±SD) of group 1 to 4 were 132.20±21.13mm, 131.00±22.40mm, 150.03±18.71mm and 181.52±29.76mm (Group 1,2<3<4; p<0.001), respectively. Mineral density (mean±SD) of the lesion from group 1 to 4 were 1.66±0.15gHApcm-3, 1.67±0.27gHApcm-3, 1.37±0.18gHApcm-3 and 1.07±0.22gHApcm-3 (Group 1,2>3>4; p<0.001). XRD revealed precipitates of silver chloride in group 1 and 2. TEM and EDX indicated that silver was incorporated into hydroxyapatite crystal in SDF treated hydroxyapatite powder. Conclusions: Application of SDF solution promoted the formation of an apatite-rich surface layer and inhibited enamel demineralisation. However, the addition of NaF varnish to SDF solution did not produce a superior remineralising effect than SDF solution alone.