[Opacity of composites and hard tooth substance on X-ray].

The opacity of eleven composites, enamel, and dentin was determined quantitatively using densitometric measurements of X-rays. The reference material was aluminium 99.5% which was exposed with each film. Opacity values were 215% for enamel and 118% for dentin. Three of the composite materials demonstrated an opacity similar to enamel, one similar to dentin. The other materials showed higher values than enamel. Consequently, the majority of composites reaches opacity values necessary for the diagnosis of secondary caries.