Measurement of Potassium Ion Diffusion through Dentine Using ISE

Abstract

Objective: To measure the in vitro concentration of potassium ions (K + ) on the opposite side of the dentine samples in real-time, using Potassium Ion Selective Electrodes (K + ISE).Method: An assembly array was designed and different sections (n=4) of dentine were acid etched in 6% citric acid and ultra-sonicated for five minutes. They were subsequently fixed into a polypropylene tube using impression dental material and immersed into simulated dentine fluid (SDF) which consisted of 0.01 mol/dm 3 potassium chloride (KCL) solution. The K + ISE was placed external to the polypropylene tube, to measure changes in the potassium ion concentration [K + ] in the SDF for 60 hrs continuously. Application of potassium nitrate (KNO 3 ) solutions of concentrations between 0.05-3 mol/dm 3 were applied to the exposed dentine samples in separate experiments.Results: Minimal changes in [K + ] (<5 mmol/dm 3 ) in the SDF (the opposite side of the sample) were measured by the K + ISE when applying less than 600 mmol/dm 3 of KNO 3 solutions to the dentine sections. However, significant changes (P<0.05) in [K + ] of 5-25 mmol/dm 3 were measured in the SDF when applying a KNO 3 solution of concentration more than 600 mmol/dm 3 to the dentine samples, indicating greater penetration of K + through the dentine matrix. Conclusion:ISE may be used to measure ionic transfer in dentinal tubules although questions arise due to the sensitivity of the ISE and its suitability. However, it was demonstrated that increasing the concentration of an applied KNO 3 solution to exposed dentine increased the [K + ] in the SDF which was on the opposite side in the dentine disk model and premolar tooth with a cut cavity. This was also the case when the fluid flow was in the opposite direction to diffusion. This study demonstrates that ISE may be suitable for real-time diffusion experiments in dentine for possible future research into dental therapeutics which involve ion exchange.