Probing depth is the measurement from which points?

• A. From the gingival margin to the base of the sulcus or pocket
• B. From the CEJ to the base of the pocket
• C. From the CEJ to the gingival margin
• D. From the mucogingival junction to the base of the pocket

Answer: (B)

Probing depth tells us how far a sulcus or periodontal pocket extends apically from the edge of the gingiva. To measure it, you place the periodontal probe at the gingival margin and record the distance down to the base of the sulcus or pocket. This direct measure reflects how deep the pocket has formed around the tooth.

The cemento-enamel junction to the base of the pocket is used to determine clinical attachment level, which combines pocket depth with any gingival recession or overgrowth. So while CAL uses the CEJ as a fixed reference, probing depth itself is measured from the gingival margin to the base of the pocket.