Pericoronitis is the inflammation of the tissue that is partially covering a partially erupted tooth in the mouth. Often it occurs with partially erupted wisdom teeth that don’t have space to erupt into the mouth fully, but sometimes it can even happen with the eruption of the first or second molars. The gum tissue that partially covers an erupting tooth is called an operculum, and the inflammation of that tissue is called pericoronitis. Pericoronitis is diagnosed based on signs and symptoms gathered during a clinical analysis, as well as a potential x-ray taken to rule out any other causes.