Periodontal probes are used to measure the pocket depth of the gums around each tooth. A healthy gum will have less than 2 mm of pocket depth.
The probe acts like a ruler, and has markings along its side measured out in millimeters. To measure the depth of your tooth’s pocket, your dentist gently places the probe into this pocket and makes note of the depth. From time to time, you may hear your dentist say a number or write down a number.