During probing, the distance from the gingival margin to the CEJ is found to be -1 mm (the gingival margin is 1 mm CORONAL to the CEJ). The probing depth is 4 mm. What is the clinical attachment level (CAL)?

The formula for CAL depends on the position of the gingival margin relative to the CEJ: When the gingival margin is CORONAL to the CEJ (tissue overgrowth / pseudopocketing): CAL = Probing Depth MINUS the gingival margin-to-CEJ distance. CAL = 4 mm - 1 mm = 3 mm. When the gingival margin is APICAL to the CEJ (recession): CAL = Probing Depth PLUS the recession measurement. When the gingival margin is AT the CEJ: CAL = Probing Depth. The negative value (-1 mm) means the gingival margin covers the CEJ by 1 mm, indicating gingival enlargement or inflammation has moved the margin coronally. This REDUCES the apparent CAL. A CAL of 3 mm confirms minimal attachment loss, consistent with gingivitis rather than periodontitis. This is a frequently tested calculation on INBDE.