Side effects from mouthwashes and medications
You would think that mouthwash would be the last thing to stain teeth. However, washes and rinses with chlorhexidine and cetylpyridinium chloride can do just that, according to WebMD. Additionally, certain medications can lead to discoloration, including antibiotics tetracycline and doxycycline when given to children under eight years of age, as well as antihistamines, antipsychotics, and high blood pressure drugs.
Overbrushing
Overbrushing has the opposite effect than what people think. It strips the enamel, making the tooth look more yellow and more prone to cavities. And be wary of fads when it comes to oral hygiene. Dr. Reid explains that “using abrasive toothpastes, such as charcoal toothpaste, [can] lead to thinning of the enamel, making the teeth appear darker as the dentin layer begins to show through more.”