Double-Layer Surface Modification of Polyamide Denture Base Material by Functionalized Sol-Gel Based Silica for Adhesion Improvement

Abstract

Purpose

Limited surface treatments have been proposed to improve the bond strength between autopolymerizing resin and polyamide denture base materials. Still, the bond strength of autopolymerizing resins to nylon polymer is not strong enough to repair the fractured denture effectively. This study aimed to introduce a novel method to improve the adhesion of autopolymerizing resin to polyamide polymer by a double layer deposition of sol-gel silica and N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (AE-APTMS).

Materials and Methods

The silica sol was synthesized by acid-catalyzed hydrolysis of tetraethylorthosilicate (TEOS) as silica precursors. Polyamide specimens were dipped in TEOS-derived sol (TS group, n = 28), and exposed to ultraviolet (UV) light under O₂ flow for 30 minutes. UV-treated specimens were immersed in AE-APTMS solution and left for 24 hours at room temperature. The other specimens were either immersed in AE-APTMS solution (AP group, n = 28) or left untreated (NT group, n = 28). Surface characterization was investigated by fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM). Two autopolymerizing resins (subgroups G and T, n = 14) were bonded to the specimens, thermocycled, and then tested for shear bond strength with a universal testing machine. Data were analyzed with one-way ANOVA followed by Tukey's HSD (α = 0.05).

Results

FTIR spectra of treated surfaces confirmed the chemical modification and appearance of functional groups on the polymer. One-way ANOVA revealed significant differences in shear bond strength among the study groups. Tukey's HSD showed that TS_T and TS_G groups had significantly higher shear bond strength than control groups (p = 0.001 and p < 0.001, respectively). Moreover, bond strength values of AP_T were statistically significant compared to controls (p = 0.017).

Conclusion

Amino functionalized TEOS-derived silica coating is a simple and cost-effective method for improving the bond strength between the autopolymerizing resin and polyamide denture base. Clinical implications: Amino-functionalized silica coating could represent a more applicable and convenient option for improving the repair strength of autopolymerizing resin to polyamide polymer.

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