We get patients from time to time who say, “I was eating breakfast this morning, oatmeal, and suddenly there was something crunchy and half my tooth is missing. How did that happen?” Well it is pretty simple. Teeth are brittle and a property of brittle materials is that they are subject to fracture. It’s like the windshield of your car. You get a small nick or crack from a rock, and the crack grows until, if you don’t replace the windshield first, the windshield will break. This is called crack propagation, or simply the crack grows. In the mouth we sometimes chew things that crunch and when they do crunch can place a great deal of force on the teeth. Things like chewing on ice, the un-popped popcorn kernels in the bottom of the bowl, or the last little pea size bit of candy left over when you suck on a jaw breaker or atomic fireball. When we chew, we compress our food between our teeth and stress builds up and if what we are compressing is exceptionally hard, all the stress built up will release all at once and the teeth will actually slam together. This will produce sometimes a flaw or crack in the enamel of the tooth, the outside hard material called the crown.
As we chew and force is applied daily, the cusp of the opposing tooth acts as a wedge, and the crack will continue to grow. Crack propagation, remember? It is when this crack grows through the enamel and then into the softer inner portion of the tooth, the dentin, and it is then that we begin to have real trouble. Through special light conditions we can see the crack growing into the tooth and threatening to fracture the tooth in half.
When the crack grows enough it will break, catastrophically, and you may find a piece or two in your food.