The friction of a jewel against the cheek, tongue or lip can wear or fracture tooth enamel and result in tooth loss, irritation, bleeding and receding gums.
In addition, oral piercings are an open door to bacteria and numerous risks of infection (puss, poisoning, allergic reaction, herpes, hepatitis, HIV, etc.), which can affect your overall health and leave sequelae that can last for a number of years.