Figure 1 shows human dental plaque exposed to 5% sucrose in situ for 5 min, after which Gram's iodine (0.33% iodine in 0.66% KI) was applied. The sucrose solution was applied to the left central incisor while the right central incisor served as a control. Iodine selectively binds to alpha-1,4 glucans (iodophilic polysaccharide, i.e., glycogen or amylose) which results in brown to purple staining.

The ability of oral bacteria to store iodophilic polysaccharide or glycogen-like molecules inside their cells is associated with dental caries since these storage compounds may extend lactic acid formation, which decalcifies tooth structure.

Figure 2 represents a x1,000 magnification view of human dental plaque exposed to 5% sucrose in situ for 5 min, after which the material was removed and prepared in a Gram's iodine (0.33% iodine in 0.66% KI) wet mount for microscopic observation. Iodine selectively binds to alpha-1,4 glucans (iodophilic polysaccharide, i.e., glycogen or amylose), which results in brown to purple staining. The stained cells represent oral bacteria with intracellular iodophilic polysaccharide.