Two white lines in the mouth may be caused by occlusal lines or lichen planus. 1. Bite line: this is a normal physiological phenomenon, upper and lower teeth in the oral cavity when biting will be on both sides of the mucous membrane friction, mucous membrane keratinization in the oral cavity there will be two white lines, usually no symptoms, do not need to do any treatment. 2. Lichen planus: this is a very common disease, its etiology is unknown, but in the inner mouth may appear slightly elevated white thread-like stripes, can be interwoven into a network or into a short radial elevation, there may be chronic desquamative gingivitis, and even discomfort or pain. The condition can be treated with low concentrations of antibiotics such as retinoic acid or tetracycline, and specific medications can be obtained by visiting your doctor.