Potencial biomodificador de colágeno dentinário e de preservação da camada híbrida por diferentes ligninas

Abstract

The union between adhesive and dentin substrate may not be long-lasting when it comes to conditioning and washing adhesive systems, due to the composition of this substrate and since the collagen fibers exposed by acid conditioning are not completely infiltrated by the adhesive monomers, providing the action of various degradation mechanisms of the hybrid layer (CH). In this sense, biomodifying agents (BA) are one of the strategies used to minimize the impacts caused by CH degradation mechanisms, highlighting some polyphenols, such as Proanthocyanidins (PAC), from grape seed extract. Lignin, in turn, is a natural polymer originating from waste from the paper industry that has great potential for the formation of cross-links due to its chemical structure, having the ability to form hydrogen bonds or other covalent bonds with the dentin collagen. Therefore, this study aimed to evaluate the biomodifying effect of different lignins on the adhesive procedure on dentin, as well as on the bond strength of an adhesive system to this substrate. For this, the study factors under investigation were: (1) Ethanolic lignin 2 w/w% [LIGe]; (2) Aqueous lignin 2 w/w% [LIGa]; (3) PAC 6.5 p/w%; (4) Cardanol 2 w/w% [CARD]; in addition to the use of (5) Distilled water [negative control]. 40 healthy and extracted human third molar teeth were selected, where, for the biomodification procedure, dentin bars measuring 1.7 x 0.5 x 6 mm in size were made. The dependent variables of the study were Modulus of Elasticity (ME), quantitatively evaluated using the 3-point bending method (n=10), Mass Variation (VM) [n=10] and Biodegradation Rate (TB) [n=10 ], measured, respectively, by a universal testing machine and a precision analytical balance. For the restorative test, specimens in the form of resin-dentin sticks with a cross-sectional area of 1mm2 were manufactured and subjected to the Bond Strength (RU) test by microtensile (n=12). For the ME test, two-way ANOVA was used for repeated measures, while for RU, ANOVA was used. A non-parametric Kruskal-Wallis analysis was adopted for VM and TB. All tests were carried out adopting a significance level of 5% (p<0.05). PAC and CARD showed the best results for ME, followed by LIGa and LIGe, respectively. The negative control group demonstrated inferior results to the test groups for ME and RU. There were no statistical differences between the groups for MV and biodegradation rate. LIGa and PAC showed the best results for RU, but PAC demonstrated a significant reduction after aging, while LIGa was maintained. LIGe and CARD showed statistically similar results for RU and remained similar to LIGa after aging. It is concluded that the different lignins represent promising BAs, especially LIGa, as they maintained the stability of CH over time and presented the potential for the formation of highly stable bonds due to their ability to interact with water.