Efeito da aplicação de primers experimentais à base de flavonoides nas propriedades adesivas e mecânicas da dentina hígida e afetada por cárie

Abstract

The aim of this study was to evaluate the effect of experimental flavonoid primers on bond strength, nanohardness, elastic modulus, and micromorphology of bonding interfaces created on sound and caries-affected dentin using one commercially available universal bonding agent applied in the etch-and-rinse mode. Flat midcoronal dentin surfaces were exposed in 182 permanent molars. Ninety-one molars were stored in water while the other 91 molars were kept in a BHI/Sucrose solution (pH 4.0) with Streptococcus mutans strain for 14 days to induce artificial caries-affected dentin. Forty-nine teeth were randomly assigned to 7 groups (n=7) according to the experimental primer applied to each dentin surface condition (sound or caries-affected dentin): Control, in which no primer was applied (CON), Hydroalcoholic solution with surfactant Placebo (PLA), Proanthocianidin (PRO), Quercetin (QER), Naringin (NAR), Rutin (RUT) and Hesperidin (HES). After etching, rinse and drying the dentin surfaces, the primers were actively applied for 1 min to rewet the dentin surface. After bonding and restorative procedures, specimens were sectioned in the long axis to obtain rectangular sticks (0.9 mm2) that were subjected to microtensile tests (μTBS) at a crosshead speed of 1 mm/min, either 24 h or after 25.000 cycles in a thermocycling machine (5ºC / 55ºC). For nanohardness and elastic modulus (n=3), the specimens were longitudinally sectioned to obtain 2 flat silces (1,2 mm) and were analyzed in a nanohardness device with a Berkovich indenter either after 24 h or after 25.000 (5 ºC / 55 ºC) thermal cycles. For the dye assisted microinfiltration qualitative analysis 21 teeth (n=3) was performed with a Confocal Scanning Laser Microscope (CSLM), both adhesive system and resin composite were mixed with 0.2% (weight) Rhodamine B prior to the restorative procedure and two flat slices were obtained for analysis in 24 h and after 25.000 thermal cycles. The bonding interfaces were immersed in a 0,1%. Fluorescein solution for 4 hours. Four images of bonding interface per specimen where obtained in each experimental time (24 h and 25.000 cycles) at 5 and 10 􀀂m depth. The data were analyzed using two-way repeated measures ANOVA and Bonferroni post-hoc test ( = 0.05). Results. PLA and RUT showed the highest TBS values in sound teeth at both intervals (24h and ageing) (p>0.05), while RUT and NAR showed the highest TBS values in carious teeth in both stages. CLSM analysis showed signs of microinfiltration for all groups. PLA, RUT, NAR and PRO showed areas of no infiltration in both experiments and intervals. Nanomechanical properties were influenced by experimental groups in deep, dependending on the flavonoid used. Conclusion: The use of flavonoids may be an alternative for therapeutic substances in sound or carious dentin to improve their properties and longevity in the adhesive interphase.