Your teeth are the hardest substance in your body and are made up of enamel, dentin, and cementum. Gnashing is a term used to describe the grinding or clenching of teeth, usually done unconsciously. This can be caused by stress, anxiety, or other medical conditions. Gnashing of teeth can lead to damage to the enamel and other parts of the teeth, so it is important to be aware of this behavior and take steps to reduce it.