What kind of stain may become intrinsic over time?

Tobacco stains can indeed become intrinsic over time due to the nature of how they interact with the tooth surface. Initially, tobacco-related stains may manifest as extrinsic stains on the enamel, which means they are located on the outer layer of the teeth and can typically be removed through professional cleaning or good oral hygiene practices.

However, with prolonged exposure to tobacco and other associated materials, these stains can penetrate deeper into the tooth structure. As the enamel becomes demineralized or if there are any abrasions or micro-cracks, the pigments from the tobacco can seep into the dentin, which is the layer beneath the enamel. Once the stains are incorporated into the structure of the tooth, they become intrinsic stains and are far more resistant to removal through standard dental cleaning methods.

This transformation highlights the importance of educating patients about the long-term effects of tobacco use on oral health and aesthetics. In contrast, the other types of stains listed, such as black line stains, green stains, and endogenous stains, are generally categorized differently in terms of their properties and origins, making them less likely to transition from extrinsic to intrinsic without the specific conditions associated with tobacco use.