Chlorhexidine is currently the most applied antimicrobial active substance, especially in dentistry. Due to its proven track record of clinically alleviating gingivitis, this active substance has established itself as the gold standard in infection treatment and prevention over the past few decades.
The cationic chlorhexidine adheres to the negatively charged surfaces in the oral environment, i.e., salvia, skin or membrane layers. As a result, the active ingredient remains in the mouth for several hours. Due to it surface-active proberties, it prevents proteins from adhering to the tooth surface, thereby destroying the foundations on which detal plaque forms. However, mouth rinses containing chlorhexidine have the potential to lead to discolorations when combined with colorants from food and beverages. An in vitro study at Fraunhofer IMWS investigated the formation and removal of discoloration from a materials science perspective. The study was commissioned by project partner GSK Consumer Health Care (now Haleon).
The aim of the study was to investigate the discoloration potential of different beverages when combined with chlorhexidine in an in vitro test model in order to obtain a data basis that allows for simple recommandations of alternative beverages to avoid discoloration during chlorhexidine treatment. The developed test model simulatied a period of 14 days application oh the mouth rinse. For this purpose, half dental crowns were subjected to cyclic exposure of artificial salvia and mouthwash in combination with a series of beverages. In addition to the exposure only treatment, the samples were brushed in a brushing simulator to evaluate the effect of mechanical cleaning. The study concluded that the risk of tooth discoloration when using chlorhexidinecontaining products is reduced if highly staining beverages are not consumed during treatment. Black tea and red wine caused the most severe discoloration. Significant discoloration was also observed when ginger-lemon tea, coffee (both with and without milk), tea with milk, and lager beer were used. After the teeth were exposed to highly staining beverages, the scanning electron microscopy evaluation showed the formation of a surface layer. The mechanical resistance of the discoloration varied depending on the beverage, with that of black tea being the most resilient. Adding milk to tea and coffee changed the discoloration layer and significantly reduced the adhesion to the tooth surface