On This American Life, a dentist talks about the increasing frequency of people with newly cracked and broken teeth. He has seen an acute change in the last three or four months. People are grinding and clenching their teeth while sleeping. This is usually caused by stress, and it usually goes away when the stress lifts. But in times of high stress, whether in someone's personal life or due to the state of today's economy, the grinding can be so severe as to break a tooth. The dentist is seeing a lot more people with job pain and resulting broken teeth.