O’Learly plaque index


  1. Dry teeth
  2. Apply disclosing solution with cotton tip applicator
  3. Rinse once
  4. Older plaque appears darker in color (blue)
  5. Examine each tooth surface and record plaque on surfaces along the cervical 1/3rd of the tooth.
  6. Compute PI score


  1. Count number of surfaces with plaque (numerator)
  2. Determine the total number of surfaces available (# of teeth X 4) (denominator)
  3. PI = (# of surfaces with plaque X 100) / (Total # of available surfaces)
  4. PI of less than or equal to 10% is recommended.