Ultrasonic measurement of dental enamel demineralization

The DONAR (digital ultrasonic system) has been used to continuously measure the displacement, due to etching by hydrochloric acid, of the surface of bovine enamel and to monitor the development of a demineralized layer. Conventional pulse echoes are used to measure displacements of the order of micrometres with an uncertainty no greater than 0.1 μm. The demineralized zone in one instance attained a maximum thickness of 5 μm and was much less in other experiments.