Hardness of Bovine Teeth Applied With Fluoride Varnish Under Demineralization/Re-mineralization Cycle

Objectives: The purpose of this study was to evaluate the effect of fluoride varnishes on the Vickers hardness of bovine teeth under the demineralization/re-mineralization cycling using experimental and commercial fluoride varnishes.
Methods: Experimental fluoride varnish that contains 5 wt% NaF were fabricated in the laboratory. 5 mg of experimental fluoride varnish and two commercial fluoride varnishes (V-varnish: Vericom, Cavity shield: 3M) were applied on the bovine anterior incisors impregnated in acrylic resin. In control group, no varnish was applied. Vickers hardness was measured on the labial surface of bovine teeth, before and after immersing in caries causing solution for 3 days, 24 hours after applying fluoride varnishes, and at 10^th day and 20^th day of demineralization/re-mineralization cycle. Sample size of each group was 10. The data of hardness was analyzed with Kruskal-Wallis test and Tukey test for post-hoc at α=0.05.
Results: The Vickers hardness of bovine teeth were not significantly different before and after caries inducing solution in all groups (P>0.05). Twenty four hours after fluoride varnish application, and at 10th day and 20th day of demineralization/re-mineralization cycle, the hardness of experimental fluoride varnish was the highest, followed by V-varnish group (P<0.05). Cavity shield and control group showed significantly lower hardness (P<0.05) and there were no significant differences between these two groups (P>0.05).
Conclusions: The highest hardness of experimental fluoride group after applying fluoride varnish and even after demineralization/re-mineralization cycle for 20 days suggests that experimental fluoride varnish can be used as an effective fluoride varnish to resist demineralization and to facilitate re-mineralization.