To preserve the whiteness of your teeth when consuming colored beverages like coffee, use a straw to avoid direct contact between the pigments and the enamel of your front teeth.

noli's read

This tip relies on the physical logic of fluid dynamics: bypassing the anterior teeth reduces direct exposure of the visible enamel to chromogenic compounds, such as coffee tannins. Practitioner networks like University General Dentists and Colgate do, in fact, recommend this method to limit surface stains (level of evidence: expert opinion). However, the idea that this provides total protection for the teeth is exaggerated. Once in the mouth, the beverage mixes with saliva, and the tongue can act as a reservoir for pigments, subsequently redistributing them across the entire dentition. Furthermore, using a straw for very hot beverages is discouraged due to the risk of oral burns. Finally, although the tip is anatomically consistent, it is not supported by any robust clinical or observational studies that have compared the long-term progression of tooth shade in coffee drinkers who use straws versus those who do not.

the sources

No named source held this one up — that absence is part of the verdict.