What is NOT true about tobacco smoking?

Tobacco smoking has various effects on oral health, including its impact on the immune system and bacteria in the mouth. The statement that smoking is caries immuno-suppressive is not accurate because tobacco use is actually associated with an increased risk of dental caries and other oral diseases. One of the mechanisms by which smoking negatively impacts oral health is through its immunosuppressive effects, which can lead to a diminished response to bacteria that contribute to cavities and periodontal diseases.

Moreover, tobacco contains substances that alter oral flora, promote growth of harmful bacteria, and affect the body's inflammatory responses. The correct answer highlights that while tobacco use may impact immune function, it does not have a protective effect against caries—rather, it exacerbates the risk of dental diseases.

The other aspects cover how tobacco smoking influences bacterial growth, affects the body’s stress responses, and alters immune mechanisms, thereby enhancing susceptibility to infections and further complicating oral health.