Field studies will be carried out in the Fall of 1980 to collect further plaque samples for descriptive microbiology of subjects in low and high caries areas. These samples will also be used to study the physiology of oral bacteria as affected by trace elements in water supplies. To continue studies on the possible ways of using strontium, with fluoride, as an anti-caries agent. In vitro studies on dissolution and subsequent remineralization will continue with Sr-F solutions. Analytical studies on the availability of trace elements from vegetables and soils in N.W. Ohio will continue. The morphology studies of strontium on tooth development will be completed.