A comparison of fluoride uptake, enamel surface hardness and surface remineralization using three different fluoride varnishes: in vitro study

OBJECTIVES: To compare the efficacy of fluoride varnishes for their ability to deliver fluoride and re-mineralize human enamel in vitro. METHODS: Three 5% NaF varnishes were used in this study: I. ProFluorid (VOCO), II. Vanish (3M ESPE), III. StarBright (Nanova Biomaterials) and IV. artificial saliva solution as a control. Twenty-four extracted intact adult teeth were randomly divided into 4 groups (n=12 per group). Each group was tested under two protocols (n=6 for each protocol). In Protocol A, artificial lesions were created by immersing the sound teeth in Coca Cola for 20 mins at 37 °C for demineralization (DM). Then a fluoridation step was performed by applying 3 mg of fluoride varnish as a thin layer (RM1). For the control group, artificial saliva was applied. All specimens were submerged in 30 mL of artificial saliva for 24 hr at 37°C. Following the treatment period, extra F varnish was removed from each specimen using chloroform moistened cotton swab and all teeth were then cleaned with deionized water for 10 seconds. The fluoridation cycle was repeated once more (RM2). For subgroups under Protocol B, tooth specimens with sound enamel were treated with two cycles of fluoridation (RM1 and RM2), then exposed to Coca Cola for 20 mins demineralization (DM). Surface micro-hardness of each tooth was measured at three random locations using Knoop hardness and fluoride content of each tooth was analyzed under (SEM/EDS) at baseline, after each fluoride varnish application, and demineralization treatment. The mean Knoop hardness and fluoride content by weight were calculated and the differences within treatment groups were analyzed by JMP Pro 13 using ANOVA. RESULTS: The application of all fluoride varnishes significantly increased the fluoride content of the lesioned enamel (p<0.05). ProFluorid varnish had increased the enamel surface hardness significantly compared to the other two varnishes (StarBright and Vanish), and the difference was statistically significant (p < 0.05). CONCLUSIONS: This study concludes that application of NaF varnish twice can significantly increase the fluoride content in enamel in both remineralization and protection cases, However, the twice application would increase surface hardness of enamel in artificial caries protocol only