Ⅰ. INTRODUCTION
The pathologic potential of the pericoronal tissues of impacted third molars to develop cysts and tumours were reported in many cases. The possible pathology was found to be dentigerous cysts, followed by odontogenic keratocyst, and tumours like ameloblastoma1,3). There was a case report that even after 3.5 years of the surgical extraction of the third molar, amelobastoma had been found at the same site4). However, ameloblastoma secondary to third molar extraction and subsequent sagittal split ramus osteotomy (SSRO) had not been reported. In this case report, we describe
In this case report, we describe our experience in the management of the ameloblastoma following SSRO procedure and reviewed the possible causes and treatment.
Ⅱ. CASE REPORT
A 30 year old female patient was presented with hypoplastic maxilla and prognathic mandible and impacted third molar teeth. The patient underwent extraction of the impacted third molar teeth at a local dental clinic. Five months later, Le Fort I osteotomy and SSRO had been planned to correct the facial deformities. There had been no pathological evidence of bony lesion at the extraction site of right mandibular 3rd molar before the orthognathic surgery (Fig 1. A). The postoperative healing was favourable after one year follow-up of two jaw surgery (Fig 1. B, C).
At 6 years after the orthognathic surgery, the patient reported with a complaint of swelling and pain on the previous surgical site of SSRO on the right side. Radiographic findings revealed that the presence of a radiolucency on the right mandibular angle area with expansion and thinning of cortical plates (Fig 2) suggesting ameloblastoma. According to the histologic examination of Incisional biopsy, dentigerous cyst with ameloblastic changes was noted. Microscopically, stratified squamous epithelium composed of 3 to 5 cell layers and ameloblastomatic changes under the basal layer of widened epithelium lining.
Based on initial pathological findings and radiographic features, marginal resection of a unilocular soft tissue mass (3.5 × 2.5 × 2.5 cm) had been performed and mandibular right second molar was extracted. The tumour was surgically removed clearly under general anaesthesia. Plate on the previous operation site was also removed and intermaxillary fixation was performed to prevent traumatic fracture for a week postoperatively. There was no evidence of recurrence after removal of the tumour at 4 years after the surgery (Fig 3). According to the permanent biopsy, the pathological specimen was proved to be the ameloblastoma (basal cell type). The specimen was composed of uniform basaloid cells and no stellated reticulum was seen in the central portion of the follicles (Fig 4).
Ⅲ. DISCUSSION
Surgical removal of impacted third molars is one of the most frequent procedures carried out in oral and maxillofacial surgery. Impacted (unerupted or partially erupted) third molars are familiar to be associated with the occurrence of pathological conditions. The most common type of cyst was dentigerous cyst whereas the most common tumours associated with the dental follicle of impacted third molars are ameloblastoma1). Epithelial odontogenic tumours and odontogenic cysts are derived from epithelial cells in the oral tissues such as remnants of odontogenic epithelium, dental follicles and the surface epithelium of the oral mucosa. Differences in the proliferation ratio of these oral epithelial cells may play an important role in the pathogenesis of epithelial tumors and odontogenic cysts5).
Previous investigation on radiographic and immunohistochemical study revealed that odontogenic epithelium in dental follicle of unerupted third molars might be actively proliferating6). According to the analysis of 104 unerupted third molars, the incidence of pathological conditions such as odontogenic keratocyst and ameloblastoma was 1.92% and 0.96%2). Other report had shown that the incidence of ameloblastoma to develop around impacted third molar teeth has been reported as 0.27%3).
The absence of symptoms related with impacted third molars does not correspond to the absence of pathology. It had been suggested that among the dental follicle from asymptomatic third moalrs, 23% had pathologic conditions. Clinically, there may be no signs or symptoms of cyst formation in asymptomatic impacted third molars7). Therefore, the decision to remove third molars prophylactically should be based on an evaluation of the balance between the probability of retained third molars causing problems in the future and the uncertainty or benefits of surgery carried out earlier compared with later3). However, the current report suggests that even after extraction of the third molar, there might be a possible development of secondary ameloblastoma.
The SSRO is the most common and useful method to correct the mandibular deformities. Pathological process of the current case would be postulated as follows; the remnants of the epithelial lining from the previous dental follicle or dentigerous cyst of an impacted third molar tooth would be entrapped at the bony gap of SSRO and this might potentially be transformed into an ameloblastoma. To our knowledge, this is the first report of an ameloblstoma after the 3rd molar extraction and sagittal spit ramus osteoyomy.
The current ameloblastoma had been diagnosed as “basal cell type” ameloblastoma, which is a very rare variant of ameloblastoma demonstrates the findings of cutaneous basaloid squamous cell carcinoma but has the pathological findings of conventional ameloblastoma8). Since the reported cases are very rare, recurrence rate had not been identified9). Based on the unique history of disease development and treatment course, long-term follow up would be needed.
Ⅳ. CONCLUSION
There had been some reports mentioning the pathologic potential of the pericoronal tissues of impacted third molars to develop pathological lesions. This case report emphasizes the long term follow up of the SSRO and a rare possibility of ameloblastic change at the site of uneventful healing following the orthognathic surgery and third molar extraction.
