The word “radiopaque” simply means that a substance is opaque, or cannot be seen through, under radiation. The most common example of something radiopaque is the human skeleton. Bones cannot be seen through under radiation, which is why x-rays are such an effective way of visualizing bones. Human skin, eyes, and other soft tissues are radiotransparent or radiotranslucent, which means they either will not be visible under radiation or they will be faint and easily seen through. Radiopaque substances are often used in the medical field for diagnostic purposes, such as drinking barium before an x-ray to visualize the normally radiotranslucent intestines. In dentistry, radiopaque materials include dental implants, braces, amalgam fillings, and some cosmetic restorative materials. The different levels of radiopacity of fillings, enamel, pulp, tooth decay, gums, and other oral structures help dental professionals diagnose a number of conditions including caries, cysts, gum disease, impacted wisdom teeth, and more.