ABSTRACT
Sufficient bonding between the framework of the cast alloy and the denture base resin is essential for the clinical success of removable partial dentures. In this study, we investigated whether the silane and alkali treatments improve the chemical bonding between two nickel-chromium alloys and acrylic resin and thus the shear bond strength. A silane solution was prepared using 3-methacryloxypropyltrimethoxysilane. The alloy specimens were treated with silane and alkali, preparing four experimental groups: untreated (UT), silane treated (ST), alkali treated (AT), and alkali/silane treated (AST) groups. In addition, the contact angles and surface roughness of the alloy surfaces of the four groups were measured. The acrylic resin was bonded to the alloy specimens, and then the resin was polymerized to form a bonded specimen. After measuring the shear bond strength, the failure modes were examined using scanning electron microscopy. Results for all groups were analyzed using two-way ANOVA followed by Tukey's multiple comparison test at a significance level of 0.05. The statistical analysis showed no significant differences in Ra value for all groups (p>.05). In the two alloys, the contact angle of the AT group was significantly lower than that of the other groups (p<.05), and that of the AST group was significantly higher than that of the ST group (p<.05). In both alloys, the ST and AST groups showed the higher shear bond strengths (p<.05), while the UT and AT groups showed the lower values. The UT and AT groups showed complete adhesive failure at the fractured surfaces. In this study, the silane treatment was effective to improve the shear bond strength, but the alkali treatment did not show any significant effect.
ABSTRACT
The purpose of this study was to compare the accuracy of the working models fabricated by the subtractive and additive processing methods based on the 3-dimensional reconstruction model. A total of 20 models were fabricated with subtractive processing method from polymethyl methacrylate (PMMA) blocks using the stereolithography (STL) file of master gypsum model and another 20 models were fabricated with additive processing method using 3D printer with 0.025 mm of a layer thickness. The CAD-reference-model (CRM) and CAD-test-model (CTM) were superimposed by a software for accuracy analysis (Geomagic Qualify 13), where the STL files were transformed to point cloud data and the surface data (CRM and CTM) were subjected to initial alignment and followed by re-alignmented according to best-fit superimposition. The distances between surface data and all points, in this process, were converted to the root mean square (RMS) and averaged. In the experimental results, It was shown that the accuracy is higher in work model fabricated by additive processing method compared to one fabricated by subtractive one (p < 0.05). In addition, it is considered that the working model fabricated by subtractive processing method is to be clinically applicable by improving the improper reproducibility of the tooth surface and depressed area.