Bruxism occasional tooth grinding. It has been shown that the majority (86%) of sleep bruxism episodes occur during periods of sleep arousal. One study reported that sleep arousals which were experimentally induced with sensory stimulation in sleeping bruxists triggered episodes of sleep bruxism. Sleep arousals are a sudden change in the depth of the sleep stage, and may also be accompanied by increased heart rate, respiratory changes and muscular activity, such as leg movements. Initial reports have suggested that episodes of sleep bruxism may be accompanied by gastroesophageal reflux, decreased esophageal pH (acidity), swallowing, and decreased salivary flow. Another report suggested
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 ±