Discoloration of dental pellicle by tannic acid.

The ability of tannic acid to discolor pellicle was studied in vitro and in vivo. Freshly extracted teeth were submerget in solutions of tannic acid, and in the clinical study individuals rinsed three times daily with 0.1% or 0.2% tannic acid. It was fount that 0.2% tannic acid caused brownish discolorations within 10-12 days both in vitro and in vivo. Discolored pellicle material collected from the in vivo test group was shown to contain furaldehyde after hydrolysis. The origin of the furaldehyde is not ascertained, but could be due to the presence of dietary deposits, transformation of pellicle pentoses, or from reactions between reducing sugars and amino compounds.