Periodontal pockets form when the gingival sulcus deepens due to the accumulation of bacteria and subsequent destruction of the supporting periodontal tissues. Pockets are classified as gingival, suprabonny, or intrabony based on the location of the base of the pocket relative to the underlying bone. Bacteria in the pocket cause inflammation and tissue destruction through the release of toxins and enzymes. Left untreated, pockets can deepen and cause increased bone and tissue loss. Probing is used to measure pocket depths and monitor periodontal disease progression and response to treatment.