Which type of stain originates from sources outside the tooth?

The correct answer is exogenous stain, which refers to stains that come from external sources and adhere to the tooth's surface. These stains can result from various factors, including dietary choices (like coffee, tea, and red wine), tobacco use, and certain medications. They accumulate on the enamel and are typically more easily removed compared to intrinsic stains, which are caused by factors originating from within the tooth itself, such as dental fluorosis or trauma.

Intrinsic stains, by definition, originate within the tooth structure, presumably due to environmental influences at the developmental stage or due to systemic conditions affecting tooth formation. Endogenous stains are specifically a subset of intrinsic stains that arise during tooth development due to factors like genetics or systemic health issues.

While yellow stain refers to a specific coloration seen on teeth that could be classified under exogenous stains, it doesn't encompass the broader category of stains from external sources that include a variety of colors and causes. Thus, exogenous stain effectively captures the idea of any stain that comes from outside the tooth rather than those that originate internally.