Bruxism is a term used for teeth grinding or excessive jaw-clenching. Many people do it unconsciously, both during the day and while they sleep. While bruxism can be mild and harmless for some people, extreme bruxism can cause a range of problems, from increased tooth erosion to headaches and jaw problems. It can be caused by factors as varied as anxiety and stress, as a side effect to some medications, or a misalignment of parts of the jaw.