Root caries incidence increases with age as the gums recede. As the number of older people increases it is anticipated that root caries will become more prevalent. Conventional methods using a sharp explorer can damage the healthy root surface which is much softer than enamel. X-rays cannot detect early root caries. This research is to develop a diagnostic instrument for early detection of root caries when intervention may halt the carious process and possibly reverse it. It was shown that ultrasonic imaging can distinguish artificial lesions in dentin at the very beginning of attack. In Phase I a laboratory instrument will be constructed to investigate the genesis of artificial lesions resembling root caries and possible intervention techniques. The equipment will be used in the subsequent Phase II. Phase II will be given to the development of a clinical instrument. The important aspect of this later stage will be the design and fabrication of an ultrasonic probe that can be used in the mouth to image the carious root lesion.