The variable shows the number of individuals registered with a BSI index of 2–4 in the relevant patient group. BSI index (plaque and mucosa index) for groups C1 and C2. The BSI index is the sum of two indices: Plaque Index (BI) + Mucosa Index (SI) = BSI. Each of these indices is graded from 1 to 4, where 1 describes the normal condition, meaning absence of plaque and absence of inflammation in the mucosa and gums.