Comparative Analysis of Ion Release from Conventional, CAD/CAM-Milled, and 3D-Printed Denture Base Resins Under Acidic and Neutral Conditions

Abstract

Ions released from denture base resins under oral conditions may affect biocompatibility and material stability, particularly at low pH. This study quantified inorganic ion release from three denture base resins—conventional heat-cured PMMA, pre-polymerised CAD/CAM-milled PMMA, and a 3D-printed resin—under simulated oral conditions. Disc specimens (n = 3 per group) were immersed in artificial saliva at pH 4.0 or 7.0 (37 °C) for 24 h or 30 d. Eluates were analysed for Ca, K, Mg, Na, Ti, Fe (ICP-OES) and Zn, Ni, Cu, Cr, Cd, Pb (ICP-MS). Solution concentrations are reported in mg L−1 or µg L−1; cumulative release is normalised per g of resin (mg g−1). Ca, Na, K, Mg, Zn, Ni, Cu, Cr, Fe and Ti were detected; Cd and Pb were below the detection limit. After 30 d at pH 4.0, total release ranked: conventional ≈ 2.8 mg g−1 > 3D-printed ≈ 1.2 mg g−1 > CAD/CAM ≈ 0.6 mg g−1; values were lower at pH 7.0. Material and pH significantly affected most ions (p < 0.001), whereas time affected only Na. Metals were in the µg L−1 range (Ni ≈ 0.008 mg L−1). CAD/CAM showed the lowest total release, consistent with higher chemical stability under simulated oral conditions; 3D-printed was intermediate, and conventional PMMA the highest.