The proposed test is intended to enable dentists to differentiate between cavitated and non-cavitated tooth decay in the areas where teeth are in contact (interproximal surfaces). In these areas, dentists cannot visually inspect for caries, and currently bitewing X-rays (BWs) only correctly detect the presence of enamel decay 15-25% of the time. This low sensitivity can lead to late treatment resulting in unnecessarily large fillings, crowns, pain, root canals, and possible later loss of teeth.

Tooth sites will be recorded by both 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 known 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.

Inclusion Criteria:

• Must have a minimum of 2 adjacent teeth so that interproximal surfaces of interest are in contact and hidden from direct visual examination.

The occlusal plane plane should be normal so that the interproximal contact regions are normal.

English or Spanish speaker.

Exclusion Criteria:

• Pregnant women. A person who has participated in a similar study involving dental radiography within the last 12 months.

Fillings must not be present in the regions of interest.