A periodontal pocket is a pocket formed on the surface of the gum and the root of the tooth. The normal gum is attached to the alveolar bone, and only about 2 mm of the upper part of the free gum is attached to the surface of our teeth without any attachment. If the alveolar bone is receding downward, or if the gums are overgrown by more than 2mm, we call this a periodontal pocket. Pseudo periodontal pockets are those where there is only a change in the depth of the periodontium, but no resorption of the alveolar bone, and true periodontal pockets are those where the alveolar bone does recede downward, exposing the enamel bone boundary. In true periodontal pockets, the doctor can use a periodontal probe to probe the distance between the bottom of the pocket and the enamel bone boundary to calculate the extent of true alveolar bone resorption.