How do you calculate the Root Caries Index?

• A. (Decayed root surfaces + Filled root surfaces) / (Total root surfaces) × 100
• B. (Decayed + Filled root surfaces) / (Total exposed root surfaces) × 100
• C. (Decayed root surfaces) / (Total exposed root surfaces) × 100
• D. (Filled root surfaces) / (Total teeth) × 100

Answer: (B)

Root caries index measures how much of the exposed root surface has caries experience. To calculate it, count all root surfaces that are decayed or have fillings due to root caries, divide that by the total number of exposed root surfaces, and multiply by 100 to express as a percentage. This formulation captures both current decay and past treatment on the roots while standardizing for the amount of root surface actually at risk. Using the total number of root surfaces (including unexposed ones) would distort the rate since unexposed roots can’t develop caries, and counting only decayed surfaces ignores surfaces that have already been filled. Using total teeth in the denominator doesn’t align with root-surface exposure and caries assessment.