What does probing depth measure?

• A. The depth from the gingival margin to the base of the sulcus or pocket
• B. The depth from the CEJ to the base of the pocket
• C. The distance from the mucogingival junction to the base of the pocket
• D. The depth of tooth decay

Answer: (A)

Probing depth measures the depth of the gingival sulcus or periodontal pocket by recording the distance from the gingival margin to the base of that sulcus or pocket with a periodontal probe. This millimeter reading reflects how much periodontal support has been lost to disease—the deeper the pocket, the more extensive the attachment loss. In healthy conditions, sulci are shallow, typically about 1 to 3 mm. The other references, like the distance from the cementoenamel junction to the base of the pocket, describe clinical attachment level, which can differ from probing depth if gingival recession or overgrowth is present. Probing depth is also not a measure of tooth decay or the distance from the mucogingival junction to the pocket base.