Best dental clinic in 200 feet radial road. What Causes Teeth Discolouration? Teeth discolouration can happen for a variety of reasons, including: *Diet: Coffee, tea, wine, and certain foods can stain teeth over time. *Smoking: Tobacco use is a common cause of yellowing or dark stains. *Aging: Enamel naturally thins with age, exposing the yellow dentin underneath. *Medications: Some antibiotics and treatments can cause internal staining. *Poor Oral Hygiene: Inadequate brushing and flossing can lead to surface stains.