Final answer:
Enamel is the most radiopaque tooth tissue because of its density and high mineral content, making it the hardest material in the body.
Step-by-step explanation:
The most radiopaque tooth tissue is enamel. This is because enamel is the hardest material in the body, designed to withstand the force of biting and chewing. The crown of a tooth, which is visible above the gum line, is covered with enamel. Underneath the enamel is a layer of dentin, which is a bone-like tissue that extends throughout the crown and into the root of the tooth around the pulp cavity. The root is also covered by cementum, but it is the enamel that appears the most radiopaque on X-rays due to its higher density and mineral content.