Linea alba in the mouth of a 70 year old female patient. Linea alba is a white line that can be seen in the mouth and it is often mistaken for a scar. It occurs when the mucous membranes of the mouth heal from an injury and collagen is deposited during the healing process. Common causes of this condition include biting the cheek, braces, oral piercings and teeth grinding. While most of the time, linea alba will go away on its own, it may persist and get thicker over time. Therefore, it should be managed to ensure it does not cause any complications.