Chitosan-Based Extrafibrillar Demineralization for Dentin Bonding

Abstract

Instability of resin-dentin bonds is the Achilles’ heel of adhesive dentistry. To address this problem, a chelate-and-rinse extrafibrillar dentin demineralization strategy has been developed that keeps intrafibrillar minerals within collagen fibrils intact to prevent activation of endogenous proteases that are responsible for collagen degradation within hybrid layers. The objective of the present study was to evaluate the potential of using chitosan >40 kDa as an antimicrobial extrafibrillar dentin-chelating agent to enhance bond durability. Transmission electron microscopy provided evidence for retention of intrafibrillar minerals and smear plugs in dentin conditioned with 1 wt% chitosan. Analyzed by Kruskal-Wallis analysis of variance, Dunn’s statistic, and separate Mann-Whitney tests, tensile bond strengths to wet- and dry-bonded dentin indicated that chelating dentin with chitosan for 60 s prior to bonding did not result in a significant decline in resin-dentin bond strength when compared with that of phosphoric acid etching ( P > 0.05). Gelatinolytic activity within the hybrid layers was examined via in situ zymography after 24-h storage or after thermomechanical cycling and analyzed with 3-factor analysis of variance. After 24 h, enzymatic activity was detected only within completely demineralized phosphoric acid–etched dentin, with values derived from dry bonding significantly higher than those derived from wet bonding ( P < 0.05). Negligible fluorescence was detected within hybrid layers when dentin was conditioned with chitosan, even after thermomechanical cycling, as compared with the controls. Reduction in water permeability in chitosan-conditioned dentin, attributed to smear plug retention, also fostered long-term bond stability. Antibacterial testing performed with live/dead staining indicated that the acetic acid–solubilized chitosan possessed antibacterial activities against 3 single-species biofilms: Streptococcus mutans, Actinomyces naeslundii, and Enterococcus faecalis. Taken together, the new chitosan-based extrafibrillar demineralization strategy retains intrafibrillar minerals, reduces endogenous protease-initiated collagen degradation, prevents water permeation within hybrid layers, and kills bacteria on dentin surfaces, which are crucial factors for enhancing resin-dentin bond durability.

Effect of chitosan nanoparticles on microtensile bond strength of resin composite to dentin: an in vitro study

“…This agrees with Gu L et al [19] who concluded that chitosan-based extrafibrillar demineralization reduces endogenous MMPinitiated collagen degradation, prevents water permeation within hybrid layers. Resin-dentin interface should be optimally sealed to prevent water movement.…”

Effect of chitosan on resin-dentin interface durability: A 2 year in-vitro study

“…The ability of chitosan to preserve bond integrity was inferred in previous literature reports. [28][29][30][31][32]49,50 On the other hand, Daood et al in 2013 stated that although chitosan has improved the structural stability of the demineralized dentin collagennetwork, exaggerated chitosan accumulation within collagen fibrils may hinder proper resin infiltration and results in defective hybrid layer formation. 28 Crosslinkers increase the stiffness of collagen fibrils and consequently interferes with the ability of collagenases to unwind the collagen peptides.…”

“…[28][29][30] In addition, chitosan has a wide range of antibacterial activity and was claimed to increase dentinal surface wettability which may provide a great advantage if used to treat the demineralized dentin prior to adhesive application. 31,32 Due to its outstanding properties, modification of demineralized dentin using chitosan could be of great importance in dentin bonding. Although previous studies [22][23][24][25][26][27][28][29][30] have proved the importance of collagen network strengthening in providing a more stable and durable bonded interface, the effect of chitosan on dentinal collagen has not been fully investigated yet.…”

Evaluation of a Collagen-Reactive Monomer with Advanced Bonding Durability

“…The gelatinolytic activity of the bonding interface was evaluated, as described in a previous study (Gu, Cai, et al 2019). Three teeth were used for each adhesive.…”

“…Collagen exposure is indispensable for resin hybridization, regardless of the protocol followed—etch and rinse, self-etch, or the so-called extrafibrillar demineralization (Gu, Cai, et al 2019). Chemical modification of the collagen matrix by biomimic crosslinking has been suggested as an additional dentin pretreatment step to protect collagen (Bedran-Russo et al 2014; Cai et al 2018).…”