Bruxism is a habit of grinding or clenching the teeth. 44 million Americans suffer from chronic bruxism. Clenching means you tightly hold your top and bottom teeth together. Grinding occurs when you slide your upper and lower teeth back and forth over each other. There are a few symptoms that are characteristic of bruxism. People who suffer from bruxism may or may not experience the following: headaches, sore jaw muscles, frequent toothaches, facial pain, worn or fractured enamel, loose teeth or fatigue.