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Collagen Cross-Linking Lignin Improves the Bonding Performance of Etch-and-Rinse Adhesives to Dentin
Journal article   Open access   Peer reviewed

Collagen Cross-Linking Lignin Improves the Bonding Performance of Etch-and-Rinse Adhesives to Dentin

Diego Martins de Paula, Diego Lomonaco, Antônio Moisés Parente da Ponte, Karen Evellin Cordeiro, Madiana Magalhães Moreira, Massimo Giovarruscio, Salvatore Sauro and Victor Pinheiro Feitosa
Materials, Vol.15(9), p.3218
04/29/2022
DOI: 10.3390/ma15093218
PMCID: PMC9101521
PMID: 35591547
url
https://doi.org/10.3390/ma15093218View
Published (Version of record) Open Access

Abstract

To evaluate the biomodification ability of lignin used as pre-treatment in human dentin before the application of an etch-and-rinse adhesive. Experimental hydroethanolic solutions with different cross-linking agents were used: 6.5% proanthocyanidins (PAC, from grape-seed extract); 2% cardanol (CARD, from cashew-nut shell liquid); lignin (LIG, from eucalyptus) at 1, 2 or 4% concentrations. The negative control (NC) was ethanol 50 v%. Extracted molars were prepared, and dentin microtensile bond strength (μTBS) was evaluated after 24 h water storage or 10,000 thermocycling aging. Further specimens were processed for SEM nanoleakage, micropermeability confocal microscopy evaluation and in situ degree of conversion (DC) through micro-Raman spectroscopy. Demineralized dentin sticks were submitted to a three-point bending test to evaluate the elastic modulus (E) before and after 1 min biomodification using the tested solutions. Moreover, it was also evaluated the mass changes and hydroxyproline (HYP) release after 4-weeks of water storage. Vibrational collagen crosslinking identification was evaluated through micro-Raman spectroscopy. The results were analyzed by analysis of variance (ANOVA) and Tukey’s test (α = 0.05). A significant reduction in μTBS was observed in groups NC (p < 0.001) and CARD (p = 0.026). LIG-4% showed no significant reduction in μTBS after aging (p = 0.022). Nanoleakage micrographs showed hybrid layer protection with all agents, but reduced micropermeability was attained only with lignin. Polymerization was negatively affected in the presence of all tested cross-linking agents, except LIG-1%. Lignin and cardanol increased the dentin E values, but only lignin reduced the mass loss in dentin specimens. Effective collagen crosslinking (1117 cm−1 and 1235 cm−1) was detected for all agents. HYP release was significantly lower with LIG-1% than NC (p < 0.001). Lignin was able to perform collagen cross-linking and prevent the degradation of unprotected dentin collagen, thereby improving the bonding performance of the composite restorations performed in this study.
 Dentistry cardanol lignin collagen cross-linking dentin proanthocyanidin

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