Intra-articular injection of parathyroid hormone in the temporomandibular joint as a novel therapy for mandibular asymmetry.

Mandibular asymmetry (MA) is one of the most common craniofacial malformations. However, there is no optimal technique for this malformation nowadays. A novel technique for both children and adults with less disadvantages is a must. Parathyroid hormone (PTH) is a straight-chain polypeptide secreted by the parathyroid gland that regulates calcium metabolism. PTH has both anabolic and catabolic effects on bone formation, depending on its mode of administration. Furthermore, the mandible is characterized by the most delayed growth and the most postnatal growth of all the facial bones. The condyle, the major growth site of mandible, grows by proliferation of cartilage in the condylar head and endochondral bone formation. Condylar cartilage is present throughout postnatal life, taking part in endochondral ossification and having a special multidirectional capacity for growth potential and remodeling throughout life. Based on the double effects of PTH on bone formation and characters of mandibular development and growth, it is hypothesized that intermittent or/and continuous intra-articular injection of PTH in the temporomandibular joint be a novel therapy for mandibular asymmetry for both children and adults. It can achieve early treatment of MA to avoid many secondary deformities and keep away from many complications resulting from current techniques or systematic administration of PTH.