Long-time measurements of calcium release by dental resin-based composites using a liquid-contact calcium ion-selective electrode.

Liquid-contact ion-selective electrodes have been successfully applied in electrochemical analysis over the past 60 years and remain a highly reliable platform in modern analytical chemistry. Owing to their structural simplicity, low fabrication cost, and reproducible operational behavior, these sensors offer an attractive and robust alternative for real-time measurements when their key analytical parameters are thoroughly understood. In this study, we fabricated and characterized a micro calcium ion-selective electrode (micro-ISE) based on a commercial membrane cocktail containing the ETH-1001 ionophore. Critical operational parameters were systematically evaluated to tailor the microelectrode for localized sensing, including expected measurement error, background electrolyte influence, signal stability, memory effects, and accuracy. The microsensor was subsequently positioned 20 μm above dental composite samples designed for dentin remineralization with varying inorganic compositions (100% CaHPO4/0% glass, 50% CaHPO4/50% glass, and 0% CaHPO4/100% glass) to map dynamic calcium release over the first 2 h of immersion in an aqueous solution. Sensor accuracy and precision were independently validated by ICP-OES, confirming the micro-ISE's suitability for localized ion flux monitoring.