Which statement correctly describes the role of PD in CAL calculation when recession is present?

• A. PD is the only factor used to calculate CAL
• B. PD is a component used with GM-CEJ distance to calculate CAL
• C. PD is not used in CAL calculations
• D. PD is equal to GM

Answer: (B)

When there is gingival recession, you can’t rely on probing depth alone to know how much attachment has been lost. CAL represents the distance from the CEJ to the base of the pocket, so you need both how deep the pocket is and how far the gingival margin has receded.

The depth of the pocket (probing depth) tells you how far the base of the pocket is from the gingival margin. But recession moves the gingival margin apically, away from the CEJ. To get the true attachment loss from the CEJ to the base of the pocket, you add the recession distance (the GM-CEJ measurement) to the probing depth: CAL = PD + GM-CEJ. This is why the statement describing PD as a component used with the GM-CEJ distance to calculate CAL is the correct approach. For example, if PD is 5 mm and recession is 2 mm, CAL is 7 mm.

PD alone would underrepresent attachment loss in recession, and PD is not equal to GM. The essential idea is that CAL combines pocket depth with recession measurement to reflect true attachment loss, not just the depth of the pocket.