Many children grind their teeth during the night which can cause parents to worry, and become afraid that the habit will damage their children's teeth. Some parents may be concerned whether this is a sign of other health problems. In Chinese medicine bruxism is referred to as lie chi, and indicates the grinding of the upper and lower teeth which produces noise. In ancient medical texts it is referred to by many different names. The Essential Prescriptions of the Golden Coffer (Jin Gui Yao Lue) and the Discussions on the Origins and Symptoms of all Diseases (Zhu Bing Yuan Hou Lun) refer to bruxism as xie chi. From the Tang and Song dynasties onward the terms, ga chi, nie chi and yao chi were also used.