The phrase "do dentists say you have cavities when you don't" refers to the unethical practice of dentists falsely diagnosing patients with cavities to increase their income. This can involve misinterpreting dental X-rays or exaggerating the severity of existing cavities.
This practice is not only dishonest, but it can also lead to unnecessary and expensive dental treatments. Patients who are told they have cavities may undergo painful and invasive procedures, such as fillings or root canals, that are not actually necessary. This can result in long-term damage to the teeth and gums.