Temporomandibular arthritis, an inflammation caused by damage to the temporomandibular joint, may result from excessive mouth opening, trauma, and oral therapy. 1. Excessive opening of the mouth: Opening the mouth too wide during daily eating or talking may cause excessive stretching of the soft tissues around the TMJ, resulting in inflammation. 2. Trauma: If the temporomandibular joint is damaged due to trauma such as jaw impact, the damaged joint surface may cause arthritis. 3. Oral treatment: A small number of patients undergo oral treatment, such as orthodontic treatment, which may lead to minor damage to the temporomandibular joints due to the change of the force in the oral cavity, and the damage is gradually aggravated in daily life, causing arthritis. It is recommended that patients with arthritis should consult a doctor in time to get a clear diagnosis and treatment under the doctor’s guidance.