Dentoalveolar Abscess Caused by Pericoronitis of an Erupting First Molar

<b>Background</b>: Pericoronitis is defined as inflammation of the soft tissues around the crown of an erupting tooth or a tooth with incomplete eruption, most commonly during eruption of the third molars. Pediatric dentists frequently encounter pericoronitis of the first molar, most of which resolve spontaneously. We describe the case of a 7-year-old girl who was referred to our hospital with intractable swelling in the right buccal region. <b>Case Presentation</b>: Intraoral examination showed an erupting right mandibular first molar and facial examination revealed swelling and an accumulation of pus in the cheek region. Radiographic examination revealed no pathological findings; therefore, it was diagnosed as a cheek abscess, and the region was incised that day. However, the symptoms recurred 3 weeks later, and cone-beam computed tomography detected a bone defect in the right mandibular first molar region, confirming a diagnosis of dentoalveolar abscess caused by pericoronitis of the first molar. The swelling resolved after incision of the abscess, and bone recovery was confirmed by X-ray in the follow-up period. <b>Conclusions</b>: Erupting first molars is at risk of pericoronitis, which may sometimes progress to a dentoalveolar abscess. Dental professionals should be alert to this possibility and should advise pediatric patients and their guardians to maintain good oral hygiene around erupting molars.