16/02/2026
🚫 Clinical Strategy to Interpret Probing Depth (PD) and Clinical Attachment Level (CAL)
One of the most important — and often misunderstood — concepts in periodontal diagnosis is the difference between probing depth (PD) and clinical attachment level (CAL).
☑️ In the image, all three teeth present the same probing depth: 6 mm. However, each scenario represents a different level of periodontal destruction. The key lies in the position of the gingival margin relative to the cementoenamel junction (CEJ).
🔷 Case 1 – CAL = 3 mm
The gingival margin is positioned coronal to the CEJ, typically due to inflammation or gingival enlargement. Although the probing depth measures 6 mm, part of this value corresponds to a pseudopocket. The true loss of attachment is limited to 3 mm.
🔷 Case 2 – CAL = 6 mm
The gingival margin coincides with the CEJ. In this situation, the probing depth accurately reflects the amount of attachment loss. Therefore, PD equals CAL.
🔷 Case 3 – CAL = 9 mm
There is gingival recession, meaning the gingival margin is apical to the CEJ. While the probing depth remains 6 mm, the clinical attachment loss is greater because recession must be added to the probing depth. This represents more advanced periodontal destruction despite having the same PD as the other cases.
☑️ Key Clinical Message
Probing depth alone does not determine disease severity. Accurate periodontal diagnosis requires evaluating PD in relation to the CEJ to calculate the true clinical attachment level.
In daily practice, this assessment can be challenging due to limited visibility, patient discomfort, saliva control, and anatomical variations. However, mastering this concept significantly improves diagnostic accuracy and periodontal treatment planning.
👉 Understanding the relationship between PD and CAL marks a critical step in developing advanced periodontal clinical reasoning.
