New electrochemical techniques for probing phase transfer dynamics at dental interfaces in vitro.
Phase transfer reactions such as dissolution, precipitation, sorption, and desorption are important in a wide range of processes on dental hard tissue surfaces. An overview is provided of several new complementary electrochemical techniques which are capable of probing the dynamics of such processes at solid/liquid interfaces from millimeter- to nanometer-length scales, with a variable time resolution down to the sub-millisecond level. Techniques considered include channel flow methods with electrochemical detection, which allow reactions at solid/liquid interfaces to be studied under well-defined and calculable mass transport regimes. Scanning electrochemical microscopy allows the chemical activity of interfaces to be mapped at higher spatial and temporal resolutions. This technique, which utilizes a scanning ultramicroelectrode, has been used extensively for the study of dissolution processes of ionic crystals, as well as in imaging the action of fluid-flow-blocking agents on dentin surfaces, which act via precipitation. So that interfaces at the nanometer level can be probed, an integrated electrochemical-atomic force microscope has been developed which enables the local solution conditions to be controlled electrochemically while topographical changes are mapped simultaneously.