Bruxism is the medical term for grinding, gnashing or clenching your teeth. The condition affects both children and adults. Some people with Bruxism unconsciously clench their teeth together during the day, often when they feel anxious or tense. This is different from tooth grinding or clenching that occurs at night, which is called sleep Bruxism. Most children, who are bruxers, do so at night, while adults are either daytime or nighttime bruxers.