Gum disease is diagnosed by your dentist or dental hygienist during your appointment. This type of exam should always be part of your regular dental check-up. A periodontal probe is gently used to measure the pocket, or sulcus, between the tooth and the gums. The depth of a healthy sulcus measures three millimeters or less and does not bleed. Your dentist or hygienist will use pocket depths, the amount of bleeding, inflammation and tooth mobility to determine how healthy your gums are.