Atmospheric pressure plasma jet treatment enhances the effect of Alloy Primer on the bond strength between polymethyl methacrylate and stainless steels: application for retention of magnetic attachment to resin denture base

Magnetic attachment system is used to embed in polymethyl methacrylate (PMMA) resin denture base to improve denture stability. However, dislodgement of magnetic attachments from denture base is a major clinical problem. This study is to evaluate the bond strength between PMMA and stainless steel using metal primer and atmospheric pressure plasma jet (APPJ) treatment. Stainless steel discs were treated with Single Bond Universal Adhesive; Palfique Universal Bond; Alloy Primer; heat treatment with Alloy Primer; and 10-s, 20-s, and 30-s APPJ treatment with Alloy Primer. The shear bond strength between PMMA and surface-treated stainless steel was measured using universal testing machine. The effects of N2 flow rate (60, 50, 40, 30 SLM), thermal cycling, and air quenching on shear bond strength were also investigated. The surface of each disc was examined using X-ray photoelectron spectroscopy and a goniometer. Finally, the temperature of plasma with various N2 flow rates was measured and the optical emission spectra of the plasma were measured using spectrometer. Alloy Primer produced the highest bond strength. APPJ treatment was effective at enhancing bond strength by cleaning the surface of contaminants. Moreover, APPJ treatment with air quenching increased surface O2-/OH- and Fe2O3/FeOOH ratios, reducing the negative influence of thermal cycling on bond strength. Alloy Primer with 20 s of APPJ treatment with a 50-SLM N2 flow rate and air quenching was the most effective at increasing bond strength.