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
Habitual aspect Italian, and Portuguese do not have a grammatical form that is specific to the habitual aspect. In the past tense, they have a form called the imperfect, which combines the past tense with the imperfective aspect; it is used to indicate that a past ongoing process was habitual or continuous. Cantonese, a Sinitic language, has a dedicated particle to express the habitual aspect, 開 "hoi1", which follows the verb. This is unlike Mandarin and some other Sinitic languages, which have no grammatical indicators of the habitual aspect, but may express habituality via circumlocution. Habitual aspect In linguistics, the aspect of