Calcium Release From Bioactive Endodontic Cements: An in-vitro ISE Study

Objectives: Bioactive endodontic cements (BECs) are contain calcium and silicate. They require an aqueous environment to release calcium ions onto dental tissues forming a hydroxyapatite interface. A strong interface will enhance stability of the material, improving prognosis. Real-time measurement of calcium ion release from materials involves kinetic studies often requiring complex spectroscopic equipment. Previously, calcium ion-selective electrodes (Ca²⁺-ISEs) have been used to measure calcium ion release from dental hard tissues as a proxy measurement for demineralization. The aim was to measure the ‘free’ calcium ions released into water from BECs applied into a simulated perforation cavity.
Methods: Midroot dentin was sectioned horizontally into 2mm thick slices. Simulated perforation cavity of 1.3mm wide prepared by instrumenting the lumen of discs using GG burrs #1-5. Cements mixed in 1:1 ratio, placed inside the cavity using a hand plugger, rinsed, and the samples immersed in 10mL stirred deionized water (pH=7.0). Ca²⁺-ISEs (Nico2000, UK) were calibrated using CaCl₂ solutions made from analytical grade chemicals, and used to continually measure the increase in free calcium ion concentration every 60s for 12h.
Results: Ca²⁺-ISEs can continually measure increases in free calcium ion concentration from BECs. Time dependent data showed a 0.04mmol/L (per hour) Ca²⁺ concentration that remained stable for MTA Cem (Nexobio, Korea) group. For MTA Angelus (Angelus, Brazil), the concentration increased 0.02mmol/L in first 2 hrs and proceed to 0.07mmol/L. Whereas Endosequence BC RRM (Brasseler, USA) showed an increase in concentration of 0.04mmol/L in first 2 hrs, proceeding to 0.09mmol/L in 12 hrs. The control group concentration was 0.005 mmol/L.
Conclusions: ISEs provide a rapid and practical measurement to compare the kinetics of calcium ion release from different bioactive endodontic cements. The BC RRM group showed the fastest release in first 2 hrs but release similar levels to MTA Angelus in 12hrs.