In-vitro evaluation of the remineralization effectsof fissure sealants with bioactive glass particles in nanoand micro sizes

The aim of this study was to evaluate and compare the effect of commercial fissure sealant materials modified with bioactive glass (BAC) particles with different sizes (nano, micro, hybrid) on the demineralization resistance of the enamel and its contribution to the remineralization. In our study; 45 caries-free permanent molar teeth were separated from their roots and embedded in epoxy resin. Then they were randomly divided into 5 groups and artificial initial caries lesions were created on the occlusal surfaces of the teeth with demineralization solution. After demineralization, the hardness and elasticity modulus values of samples were measured by nanoindentation analysis. Commercial fissure sealants (Helioseal F Plus Ivoclar Vivadent Schaan Liechtenstein) were applied to the control group. The experimental fissure sealants were applied to 3 groups; MICRO BAC (15 wt% of micro-sized bioactive glass+ Helioseal F Plus), NANO BAC (15 wt% of nano-sized bioactive glass+ Helioseal F Plus), HYBRID BAC (a combination of micro- (7.5 wt%) and nano-sized (7.5 wt%) bioactive glass + Helioseal F Plus). Fissure sealants were not applied to the negative control group. A second nanoindentation analysis was performed after a 7-day pH cycle. Then % surface hardness recovery values were calculated. One sample from each group was examined by SEM EDS and the mean ion percentages of the enamel adjacent to the fissure sealants were calculated. The statistical analysis was performed by using SPSS 23.0 program (IBM, Chicago, USA), Shapiro Wilk test, one-way analysis of variance, Duncan test and t test. The results were evaluated at p <0,05 significance level. In all groups, the average nanohardness values after the pH cycle were higher than nanohardness values after demineralization, But the difference was statistically significant only in the NANO BAC group (p=0,036). The highest average surface hardness recovery value was in the MICRO BAC group, followed by; HYBRID BAC, CONTROL, NANO BAC, and NEGATIVE CONTROL groups. But no statistically significant difference was found between the groups (p=0,820). No statistically significant difference was observed between the elastic modulus values after demineralization and after pH cycle, in all groups (p>0,05). According to SEM-EDS results; the average Ca (at%, wt%) value was; highest was the NANO BAC and the lowest was the NEGATIVE CONTROL sample. The average P(at%, wt%) values; highest was the CONTROL and lowest was the NEGATIVE CONTROL sample. The mean wt % Ca/P was higher in the samples containing BAC than the samples in the control and negative control, the highest value was in the NANO BAC sample. Nano BAC particles added to resin-based fissure sealants increase the resistance of the enamel tissue adjacent to the fissure sealant against demineralization and significantly contribute to its remineralization. Keywords: nano bioactive glass, resin-based fissure sealant, nanoindentation, demineralization, remineralization