Bruxism of bruxism. Clenching the teeth is generally displayed by humans and other animals as a display of anger, hostility or frustration. It is thought that in humans, clenching the teeth may be an evolutionary instinct to display teeth as weapons, thereby threatening a rival or a predator. The phrase "to grit one's teeth" is the grinding or clenching of the teeth in anger, or to accept a difficult or unpleasant situation and deal with it in a determined way. In the Bible there are several references to "gnashing of teeth" in both the Old Testament, and the New Testament, where
Grinding (abrasive cutting) work in the machining fields, the term "cutting" is often understood to refer to the macroscopic cutting operations, and "grinding" is often mentally categorized as a "separate" process. This is why the terms are usually used separately in shop-floor practice. Lapping and sanding are subsets of grinding. Selecting which of the following grinding operations to be used is determined by the size, shape, features and the desired production rate. "Surface grinding" uses a rotating abrasive wheel to remove material, creating a flat surface. The tolerances that are normally achieved with grinding are ± for grinding a flat material and ±