This new technology uses a hand-held laser to detect decay at the earliest stages. Even very small lesions can be identified, enabling you to protect and preserve tooth structure. The laser works by passing a small light through the top, or occlusal surface of the tooth in order to determine the fluorescence of the tooth. Essentially, the more fluorescence a tooth has, the more decay is present. The diagnodent will assign a number based on the amount of fluorescence detected. A small number is indicative of a healthy tooth, whereas a large number is indicative of a tooth that needs restoration.