Tooth discoloration is a side effect of most mouth rinse solutions. It impairs the aesthetic appearance especially of the front teeth. The aim of this pilot study is to determine a time point when visible discoloration appears in the front teeth. Therefore, participants of this study will rinse twice daily with chlorhexidine mouth rinse for 10 days. To elicit a more pronounced discoloration, participants will rinse with black tea right after the chlorhexidine rinse. Discoloration will be measured daily by discoloration index, by spectrophotometry, and by the use of a digital photo.