How can tea , coffee or tobacco is harmful for teeths?

Staining: One of the main harms of these 3 things are staining. Tobacco, whether it's smoked or chewed, is one of the worst offenders of staining teeth and then coffee, and tea are right behind it. Tobacco can also lead to oral cancer. If you drink tea or coffee don't sip it all day, and brush your teeth after you do drink it. This can help prevent staining, and if you smoke consider quitting.

Extrinsic stain: The predominant effect on teeth is their tendency to cause dark deposits to accumulate on their surfaces. This doesn't harm them, but can be unsightly. The documented health effects of tea and coffee are mixed, depending on who is sponsoring the research (i suspect juan valdez is behind some of the recent health claims for coffee). Of course, tobacco is well known to be injurious to general health.