Evaluation of the effect of different remineralization agents on the surface and subsurface microhardness of demineralized enamel

In this study, the effects of different remineralization agents applied on enamel samples on the treated area and the adjacent area were evaluated by using surface and subsurface microhardness analysis. 60 enamel samples of 4x9x3 mm in size obtained from bovine incisor teeth were divided into 5 groups (n = 12). After the samples were embedded in acrylic blocks and polished with 320, 600 and 1200 grid abrasive discs, initial microhardness values were measured. 9 mm long enamel samples are divided into 3 equal parts, and assigned as the treatment area, the adjacent area and the covered area. Samples were subjected to pH cycle for 5-days, after covering their 1/3 part with an acid-resistant varnish. Then, microhardness measurement of demineralized enamel samples were done and recorded. Remineralization agents were applied to the treatment areas of the samples in each groups: Group 1: BioMin F (BioMin Technologies Ltd., London, England) toothpaste, Group 2: Colgate Triple Effect (Colgate Palmolive Co., Ltd., China) toothpaste, Group 3: FCP COMPLEX (US Patent 8956596) solution, Group 4: Fluor Protector (IVOCLAR VIVADENT AG, Schaan, Liechtenstein) varnish and Group 5: Control (artificial saliva). After the varnish on the samples was removed with acetone, surface microhardness measurements were made from the treatment area (T) and 150 µm (K1), 300 µm (K2) and 450 µm (K3) in the adjacent area. Then samples with, 4mm width were divided into two parts for subsurface microhardness measurement and one of the samples obtained was polished with 320, 600 and 1200 grid abrasive discs. Subsurface microhardness was measured and recorded from 20, 50, 100 and 200 µm depths of each region (T, K1, K2, K3, C) in the samples. The data obtained were analyzed using SPSS 23.0 program. According to the surface microhardness evaluation, the microhardness increase was in the order of T> K1> K2> K3. BioMin F toothpaste provided the greatest increase in surface microhardness, followed by FCP COMPLEX, Colgate and Fluor Protector materials, respectively. According to subsurface microhardness assessments; while the lowest microhardness values were seen at 20 µm depth, these values increased with depth, and at 200 µm depth the values were close to those of normal enamel. BioMin F and Colgate toothpastes were the materials which increased the subsurface microhardness value, the most, followed by FCP COMPLEX solution and Fluor Protector varnish application was found to be ineffective. While BioMin F and FCP COMPLEX materials showed successful results in surface microhardness evaluation, both toothpastes showed similar good results in subsurface microhardness evaluation. Fluor Protector varnish application showed the lowest values in both evaluations. Key Words: BioMin F, FCP COMPLEX, adjacent enamel, fluoride.