How is CAL calculated when there is gingival overgrowth?

• A. CAL = PD - (CEJ-GM)
• B. CAL = PD + (CEJ-GM)
• C. CAL = GM - CEJ
• D. CAL = PD

Answer: (A)

CAL is the distance from the cementoenamel junction (CEJ) to the base of the pocket. When gingival overgrowth occurs, the gingival margin sits above the CEJ, so the CEJ–gingival margin distance is negative. To get the true attachment level, you subtract this negative margin from the pocket depth, which is the same as adding the amount the margin is coronal to the CEJ to the pocket depth. That is why CAL = PD − (CEJ − GM) is used. For example, if the probing depth is 3 mm and the gingival margin sits 1 mm coronal to the CEJ (CEJ−GM = −1 mm), CAL = 3 − (−1) = 4 mm. The other forms either ignore the margin position, use the wrong sign, or mix up distances, so they don’t accurately reflect attachment when the gingival margin is displaced coronally.