Nasopalatine duct cyst developed in association with dental implant treatment: A case report and histopathological observation
A 45-year-old male patient visited our clinic in May 2005 due to detachment of a porcelain-fused-to-metal crown on the left maxillary central incisor, which had been connected at another clinic in 2000.\nThere were no special findings in his physical and extraoral conditions. On intraoral examination, mesiodistal fracture lines were found on the remaining tooth structure. A swelling and slight redness were observed on the peripheral soft tissue, but there were no acute symptoms such as purulence or pain [Figure and ].\nRadiographic examination showed no inflammatory symptoms, such as an increased periapical space, bone resorption, or periapical radiolucency, thus, the inflammation was judged confined almost exclusively in the gingival tissue. A nasopalatine foramen was found adjacent to the apex of the maxillary left central incisor [].\nThe maxillary left central incisor had a root fracture and required extraction. After a careful consultation about various treatment options, the patient desired implant treatment. Because there existed no obvious signs of acute inflammation or any other symptoms of the soft and hard tissue, postextraction immediate implant placement was planned. Prior to the implant treatment, the patient was subjected to meticulous scaling of all the remaining teeth and oral hygiene instruction session.\nIn May 2005, the maxillary left central incisor was extracted. After careful curettage of the extraction site, the mucoperiosteal flap was reflected. There was no resorption of the labial bone and an implant (TiOblast, Astra Tech, Mölndal, Sweden, ø 4.5 mm, length 13 mm) was placed into the fresh extraction socket with good primary stability. The osteotomy was made so that the implants would be located centrally in relation to the socket; however, careful drilling was conducted in order to preserve the buccal wall. The gap between the fixture and the socket wall was filled with autogenous bone particles collected during the surgery. The wound was closed after a releasing incision. On the periapical radiograph taken immediately after implant surgery, the implant appeared to interfere with the nasopalatine canal [].\nThe implant was restored with the definitive crown in November 2005. No abnormality was found during quarterly maintenance visits after the implant surgery, however, at the maintenance visit in November 2007, the patient complained about swelling on the palate. Clinical examination detected pulsation on the palate and an oval-shaped radiolucency having unclear boundary around the apex of the dental implant detected on the periapical radiograph. A computed tomography (CT) scan confirmed the radiolucency of a size of 10 mm × 10 mm × 9 mm, which surrounded the apical portion of the implant, reaching to the nasopalatine canal [Figure –]. Although the patient had no spontaneous pain, the lesion seemed to be enlarging and it was judged that early removal of the cyst was necessary. Because the implant was immobile, with no signs of peri-implant bone resorption, it was decided not to remove the entire implant but to resect the apical portion of the implant lodged inside the cyst, and remove the entire lesion. The surgery was performed in November 2007. Flap incision was designed to be away from the expected lesion area so that the incision will not overlap with the bone defect after the cyst removal. Mucogingival flap was elevated and resorption of the labial bone was observed. After removing the thinned cortical bone and detaching the cyst wall on the palatal side, the apical portion of the implant (approximately 3 mm) lodged inside the cyst was resected using a carbide bur. Thereafter, the entire cyst, including the resected implant, was removed en bloc. It was evident that the nasopalatine neurovascular bundle was incorporated into the cyst []. The wound was closed by repositioning the mucoperiosteal flap, and no bone grafting materials were used to fill the defect.\nThe histopathological findings showed that the wall of the cystic lesion comprised of cuboidal, ciliated columnar and stratified squamous epithelium with underlying connective tissue. The cysts that form adjacent to oral mucosa of the incisal foramen was lined mainly by stratified squamous epithelium, whereas the lining close to the incisal foramen was lined by cuboidal and ciliated columnar epithelium, and there were no signs of inflammatory cell localization within the observed biopsy []. Thus, based on the clinical and histological findings, the lesion was diagnosed as nasopalatine duct cyst developed in association with the dental implant placement.\nAfter the cyst removal, the patient has been carefully followed by clinical, radiographic examinations (both periapical and CT) during maintenance visits scheduled every 4 months. The current status after 28 months after the cyst removal shows no signs of implant mobility, marginal gingival recession, or peri-implant inflammation. Compared with the radiographic findings before the cyst removal, the radio-opacity of the original lesional area seemed to have increased. The bone defect measured on the CT after the cyst removal is 4 mm × 3 mm × 4 mm, comparably smaller to the preoperative radiograph, suggesting a favorable healing [].