Abstract
Objective: the aim of the present study was to evaluate the influence of adding different concentrations of chitosan to an experimental two-step etch-and-rinse adhesive system on the bond strength and failure mode to dentin. Material and Methods: thirty-two flat dentin surfaces were obtained from extracted human third molars and divided into four groups (n=8) for application of the adhesive systems: AD - conventional two-step adhesive system (Adper Single Bond 2); EXP – experimental two-step etch-and-rinse adhesive system; Chi0.2% - EXP with addition of 0.2% Chitosan; Chi0.5% - EXP with addition of 0.5% Chitosan. Resin composite build-ups were made and the composite/dentin specimens were sectioned to obtain rectangular beams with a bond area of approximately 1mm2. After 24 hours, the sticks were submitted to microtensile bond strength tests in a universal test machine. The fracture pattern was evaluated under a stereoscopic loupe at 40X magnification. Results: one-way analysis of variance showed that the type of adhesive system had no significant effect on the bond strength values (p = 0.142), showing the mean bond strength values (standard deviation), in MPa, for the groups as follows: AD=20.1 (5.4); EXP=16.6 (2.3); Chi0.2%=16.1 (2.8); Chi0.5%=16.9 (2.3). In all the groups there was predominance of cohesive fractures in dentin, representing 68 to 82% of the failure modes. Conclusion: the addition of 0.2 or 0.5% of chitosan had no influence on the bond strength and failure mode of an experimental two-step etch-and-rinse adhesive system to dentin.KeywordsChitosan; Dental Adhesives; Failure Mode; Microtensile Bond Strength.
Highlights
When using adhesive systems, total-etch or self-etch approaches can be used to obtain bond strength to dentin: while totaletch adhesives require a separated etching step, self-etch adhesives contain acidic monomers that simultaneously demineralize and infiltrate dentin [1,2]
Total-etch or self-etch approaches can be used to obtain bond strength to dentin: while totaletch adhesives require a separated etching step, self-etch adhesives contain acidic monomers that simultaneously demineralize and infiltrate dentin [1,2]. They are presented in different forms of bond to dentin strategies, the main constituents of adhesive systems are the methacrylate-based monomers, with the most commonly used type being those based on bisphenol A glycidyl methacrylate (Bis-GMA), UDMA, TEGDMA and hydroxyethyl methacrylate (HEMA) (Hiydroxyethyl Methacrylate) [3,4,5,6]
One-way analysis of variance demonstrated that the type of adhesive system had no significant effect on the bond strength values (p = 0.142) (Table 2)
Summary
Total-etch or self-etch approaches can be used to obtain bond strength to dentin: while totaletch adhesives require a separated etching step, self-etch adhesives contain acidic monomers that simultaneously demineralize and infiltrate dentin [1,2]. With the purpose of preventing the passage of free monomers in the direction of the pulp, or to diminish the damage they cause, some components may be incorporated into the adhesive systems or restorative materials [6]. One of these components is chitosan, which is a hydrophilic biopolymer obtained from chitin, a polysaccharide existent in the shells of crustaceans and on the cell wall of fungi. It is a very versatile polymer that is modifiable to improve the use of its biological and physical-chemical properties [10]
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