۱٫ Introduction

The maxillary cysts lined by pseudostratified columnar epithelium (respiratory epithelium) can show different pathologic conditions and hinder the diagnosis, thus challenging the clinician and pathologist. These lesions include mucocele of the maxillary sinus and surgical ciliated cyst.The latter develops after a surgical procedure, such as maxillary sinus surgery (e.g., Caldwell-Luc), orthognathic surgery, and trauma caused by dental extraction [1–۳]. In some cases, a radicular cyst can also be included in the differential diagnosis of these lesions. In fact, although its cavity is lined by a nonkeratinized stratified squamous epithelium, it can be partially or totally lined by a respiratory epithelium [4–۷]. We report the case of an unusual cyst on the maxillary right first molar (tooth #16) region, in which the cavity was totally lined by respiratory epithelium. Interestingly, no previous history of surgical treatment of the sinus, trauma, or dental extraction was observed.

۲٫ Case Presentation

We report the case of a 35-year-old healthy male who consulted our Oral Surgery, Implantology and Pathology Emergency Department with a chief complaint of pain in the posterior maxillary right region. He reported no history of trauma or surgery in the maxillofacial region and was not known for recurrent sinusitis. The clinical examination revealed a generalized periodontitis. Tooth #16 presented a periodontal pocket extending to the root apices with pus coming out from the gingival sulcus. The mobility of the teeth was grade 3, the vitality was negative, and the percussion was positive. The patient was not swollen and did not have any systemic symptomatology. A severe generalized horizontal bone loss associated with local vertical lesions and furcation involvement in the first quadrant was seen on the panoramic radiography. The diagnosis of a combined endodontic periodontal lesion was inferred.