An X-ray (radiograph) is like a photograph. The image on the radiograph is created when X-rays pass through the mouth, more X-rays are absorbed by the denser parts (such as teeth and bone) than by soft tissues (such as cheeks and gums) before striking the film. Because fewer X-rays penetrate the teeth to reach the film teeth appear lighter. Cavities and gum disease appear darker because of more X-ray penetration. Because many diseases exist beneath the visible oral tissue and cannot be detected without the use of radiographs, a radiograph is a valuable tool for the dentist to safely and accurately detect hidden abnormalities. X-rays pose a far smaller risk to your health than undetected and untreated dental problems.