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. 2020 May;36(5):687-697.
doi: 10.1016/j.dental.2020.03.007. Epub 2020 Mar 30.

Chlorhexidine-modified nanotubes and their effects on the polymerization and bonding performance of a dental adhesive

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Chlorhexidine-modified nanotubes and their effects on the polymerization and bonding performance of a dental adhesive

Sara Kalagi et al. Dent Mater. 2020 May.

Abstract

Objectives: The purpose of this study was to synthesize chlorhexidine (CHX)-encapsulated aluminosilicate clay nanotubes (Halloysite®, HNTs) and to incorporate them into the primer/adhesive components of an etch-and-rinse adhesive system (SBMP; Scotchbond Multipurpose, 3M ESPE) and to test their effects on degree of conversion, viscosity, immediate and long-term bonding to dentin.

Methods: CHX-modified HNTs were synthesized using 10% or 20% CHX solutions. The primer and the adhesive components of SBMP were incorporated with 15wt.% of the CHX-encapsulated HNTs. Degree of conversion (DC) and viscosity analyses were performed to characterize the modified primers/adhesives. For bond strength testing, acid-etched dentin was treated with one of the following: SBMP (control); 0.2%CHX solution before SBMP; CHX-modified primers+SBMP adhesive; SBMP primer+CHX-modified adhesives; and SBMP primer+CHX-free HNT-modified adhesive. The microtensile bond strength test was performed after immediate (24h) and long-term (6 months) of water storage. Data were analyzed using ANOVA and Tukey (α=5%) and the Weibull analysis.

Results: DC was greater for the CHX-free HNT-modified adhesive, whereas the other experimental adhesives showed similar DC as compared with the control. Primers were less viscous than the adhesives, without significant differences within the respective materials. At 24h, all groups showed similar bonding performance and structural reliability; whereas at the 6-month period, groups treated with the 0.2%CHX solution prior bonding or with the CHX-modified primers resulted in greater bond strength than the control and superior reliability.

Significance: The modification of a primer or adhesive with CHX-encapsulated HNTs was an advantageous approach that did not impair the polymerization, viscosity and bonding performance of the materials, showing a promising long-term effect on resin-dentin bonds.

Keywords: Adhesives; Aluminosilicate clay; Bonding; Dentin; Halloysite; Microtensile; Nanotube.

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Figures

FIGURE 1.
FIGURE 1.
Percentage of the failure modes obtained for each group after 24 hours and 6 months of water storage.
FIGURE 2.
FIGURE 2.
Representative SEM micrographs (100× and 5,000× of magnification) for each group tested in the study at both periods tested (immediate and long-term). A: adhesive layer; D: dentin substrate; R: resin composite; DT: dentinal tubule.
FIGURE 3.
FIGURE 3.
Survival plots for each group tested. Each plot illustrates the relation between the survival probability (Weibull model) and microtensile bond strength values (in MPa). The bond strength values obtained in 24 h were averaged with those from the 6-months period.

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