[Permanent constriction of the jaw due to idiopathic bilateral hyperplasia of the coronoid process].

Bilateral hyperplasia of the coronoid processes of the mandible is not frequent and concerns most always males between the ages of 14 and 16. The restricted opening movement is caused by impingement of the process on the medial and anterior surfaces of the zygomatic arch. The diagnostic is made by a good radiography. The treatment is surgery by intraoral approach. The coronoid processes are removed on the two sides with postoperative physiotherapy. The results are good and permanent.