Tooth sites will be recorded by tooth number, type of surface (mesial, distal,occlusal), cavitated, non-cavitated, healthy. Radiographs will similarly be scored.Although contrast agents are classified as drugs this is not a study of drug properties or effect on cells since the properties of the agent are already well know and its safety record well established. This study will be recording the radiopacity of the contrast agent on healthy tooth surfaces, non-cavitated tooth surfaces and cavitated tooth surfaces. The outcome for each surface type will be presence or absence of a radiopacity on a radiograph which will be made at the one and only visit for each study subject. The radiograph contains the data from the intervention (placement of contrast agent) and the outcome will be assessed some weeks later after the completion of the data collection.