Teeth are not like bones. No bone in our bodies is more than 10 years old. That’s because bones are constantly remodeling according to the stresses placed on them by our physical activities. Teeth however, once erupted into the mouth and fully formed remain the same. Chewing, clenching, grinding and trauma are among the stresses that teeth endure.
Those loads applied many times a day cause the tooth to deform slightly and recover to original form. Those deformations over time result in fatigue micro-cracks in the tooth structure that with repeated cycles eventually join other micro-cracks and eventually after many micro-cracks join one another, a piece of the tooth will break away. It could be a small piece of the tooth that breaks off or it could be a more serious split that exposes the nerve endings.