The Simple index measures the presence or absence of a condition. Which of the following is an example of a Simple index?

• A. Plaque control record
• B. Dental caries index
• C. Gingival recession index
• D. Oral hygiene index

Answer: (A)

A Simple index records only whether a condition is present or absent on each unit, giving a yes/no result rather than a measure of amount or severity. The plaque control record fits this pattern because, after staining, each tooth surface is simply marked as having plaque or not, and the overall score reflects the proportion of surfaces with plaque. The other indices assess more than presence/absence: the dental caries index sums decayed, missing, and filled surfaces to reflect caries experience; the gingival recession index measures depth of recession; and the oral hygiene index rates the amount of debris or calculus, which are graded quantities rather than a binary presence/absence.