Real Time ISE Study on the effects of metal ions on the demineralization of Hydroxyapatite Discs

Abstract

Objective The main aim of the study was to investigate the effects of metal ions, Zn²⁺, Cu²⁺, and Sr²⁺ on the demineralization solution of Hap discs, as well as to monitor changes in calcium concentrations in real-time to evaluate how these metal ions affect the demineralization process. Materials and Methods Hydroxyapatite (HAp) discs were divided into 9 groups (n=2). Each HAp disc was initially immersed in 50 mL of a demineralization solution for 2 hours. Following this demineralization phase, the discs were treated with varying concentrations of zinc chloride (ZnCl₂), copper chloride (CuCl₂), and strontium chloride (SrCl₂) solutions at concentrations of 1800 ppm, 180 ppm, and 18 ppm for each metal ion. The demineralization process was monitored using Ion Selective Electrode (ISE) technology, which measured the release of calcium ions (Ca²⁺) from the discs every minute at a controlled temperature of 37.0±1.0°C. Results The study found that all three metal ions had an inhibitory effect on the demineralization of hydroxyapatite, with the ability to inhibit calcium activity being concentration-dependent for all ions. Zinc demonstrated the highest inhibitory effect, particularly at 1800 ppm, where it reduced the rate of calcium loss by 71%. Copper and strontium also exhibited significant inhibitory effects, with copper showing a 65% reduction at 180 ppm and strontium achieving a 60% reduction at 1800 ppm. This effect is attributed to the ability of metal ions to incorporate into the HAp lattice and surface deposition. Conclusions The study suggests that these metal ions Zn²⁺, Cu²⁺, and Sr²⁺ can effectively inhibit the rate of hydroxyapatite demineralization, indicating their potential use in preventive dental treatments. These ions could offer a strong protective effect against dental caries when incorporated into dental care products.