Aplicação da biomassa residual da indústria do papel na odontologia adesiva

Abstract

Lignin is a natural polymer not tested in restorative dentistry with great potential for crosslinking with dentin collagen fibers. The aim of this thesis was: (1) to evaluate the cross-linker capacity of Lignin in the demineralized human dentin assayed as pre-treatment of composite resin restorations; (2) to evaluate the effects of the incorporation of natural cross-linkers in phosphoric acid into the microtensile bond strength (μTBS) and nanoleakage (NL) to two-step etch&rinse adhesive. In study 1, experimental solutions with Proanthocyanidin 6.5% (PAC), Cardanol 2% (CARD), Lignin (LIG) at concentrations of 1, 2, 4% were manipulated. The negative control was the solution without cross-linkers (NC). Quantitative tests, used after the composite resin restorations using the pretreatment solutions (1-minute), were μTBS (n=5) tested 24h and after thermocycling, in-situ conversion degree (DC, n=3) of hybrid layer and qualitative tests to NL and micropermeability in Confocal microscopy. Dentin bars were used for quantitative tests three points bending test(n = 12) before (baseline) and after 1-minute biomodification; mass variation (n=12) after 48 hours and 4 weeks of treatment; Hydroxyproline (HYP) test after 4 weeks of degradation in water and for qualitative analysis by micro-Raman spectroscopy (n=3) of the peaks formed after the biomodification treatment. In study 2, experimental phosphoric acids were manipulated and incorporated with 2% of cross-linkers: LIG, CARD and PAC. NC without cross-linkers and commercial control (CC) were also used. FTIR spectroscopy was used to detect collagen cross-linking in etched dentin specimens. The quantitative test μTBS (n = 7) with analysis of the fracture mode (24 hours and aging) and the qualitative analysis of NL were also performed. The results of both studies were analyzed with ANOVA or ANOVA of repeated measurements and Tukey's post-hoc (p<0.05). The results of study 1, LIG and PAC maintained their μTBS, NL and micropermeability images showed hybrid layer protection. Only LIG1 did not disturb the GC in situ. LIG2, LIG4 and CARD increased the modulus of elasticity of the demineralized dentin bars. LIG1 and LIG2 reduced dentine bar mass loss. Peaks 1117 cm-1 and 1235 cm-1 (cross-linking) were shown with micro-Raman. LIG1 released less HYP. The results of study 2 showed peaks of cross-linking in FTIR analysis. LIG and CARD maintained μTBS and showed little silver in NL after aging. The adhesive fracture mode was higher. Therefore, LIG was able to perform cross-links with the demineralized collagen fibers applied as pre-treatment and incorporated into phosphoric acid, preventing the degradation of unprotected dentin and increasing the longevity of the restorations.