Pericoronitis (from the Greek peri, "around", Latin corona "crown" and -itis, "inflammation") also known as operculitis, is inflammation of the soft tissues surrounding the crown of a partially erupted tooth,including the gingiva (gums) and the dental follicle. The soft tissue covering a partially erupted tooth is known as an operculum, an area which can be difficult to access with normal oral hygiene methods. The synonym operculitis technically refers to inflammation of the operculum alone.

Pericoronitis is caused by an accumulation of bacteria and debris beneath the operculum, or by mechanical trauma (e.g. biting the operculum with the opposing tooth). Pericoronitis is often associated with partially erupted and impacted mandibular third molars (lower wisdom teeth), often occurring at the age of wisdom tooth eruption (15-24 years old).Other common causes of similar pain from the third molar region are food impaction, pulpitis from dental decay and acute myofascial pain.

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