Nanotube-modified dentin adhesive—Physicochemical and dentin bonding characterizations
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Fig. 1
Representative FE-SEM (A) and (B) TEM micrographs of the as-received aluminosilicate clay nanotubes (Halloysite, Dragonite-1415JM®, Applied Minerals, New York, NY). Note the overall uniform rod-like tubular structure and the unique hollow (white arrows) structure with approximately 100–150 nm in width and an estimated length in the range 300–1500 nm.
Fig. 2
Representative SEM micrographs of the fractured surfaces of (A and B) the unfilled control adhesive and (C and D) 20 wt.% HNT-modified adhesive.
Fig. 3
Representative SEM micrographs of the resin–dentin interfaces for the control (A and B) (no HNTs) and the (C and D) 20 wt.% HNT-incorporated SMBP adhesives. C = composite resin, A = adhesive layer, RT = resin tags, and D = dentin. Note relatively shorter and apparently rougher resin tags for the 20 wt.% HNT-incorporated adhesive when compared to the control suggesting the presence of HNTs.
Fig. 4
Degree of conversion (%) and Knoop microhardness for the different evaluated groups. *means p < 0.001 compared to the control.
Abstract
Objective
The aim of this study was to investigate the effect of aluminosilicate clay nanotubes (Halloysite, HNT) incorporated into the adhesive resin of a commercially available three-step etch and rinse bonding system (Adper Scotchbond Multi-Purpose/SBMP) on dentin bond strength, as well as the effect on several key physicochemical properties of the modified adhesive.
Methods
Experimental adhesives were prepared by adding five distinct HNT amounts (5–30 wt.%) into the adhesive resin (w/v) of the SBMP dentin bonding system. Bond strength to human dentin, microhardness, and degree of conversion (DC) of the modified adhesives were assessed.
Results
From the shear bond strength data, it was determined that HNT incorporation at a concentration of 30 wt.% resulted in the highest bond strength to dentin that was statistically significant (p = 0.025) when compared to the control. Even though a significant increase in microhardness (p < 0.001) was seen for the 30 wt.% HNT-incorporated group, a significantly lower DC (p < 0.001) was recorded when compared to the control.
Significance
It was concluded that HNT can be incorporated up to 20 wt.% without jeopardizing important physicochemical properties of the adhesive. The modification of the SBMP dentin bonding agent with 20 wt.% HNT appears to hold great potential toward contributing to a durable dentin bond; not only from the possibility of strengthening the bond interface, but also due to HNT intrinsic capability of encapsulating therapeutic agents such as matrix metalloproteinase (MMP) inhibitors.
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