The odontogenic keratocyst has been well documented and extensively studied. It is of particular interest because of its high recurrence rate and aggressive nature. The material for this study consisted of 70 cases of odontogenic keratocysts in predominantly ethnic Chinese patients who were treated from 1981 to 1996. The cases were retrospectively studied to compare characteristics of the lesion in this population with those in previous reports. Most of the patients in this series were 21 to 30 years of age. Association with an impacted mandibular third molar was found in more than 50% of the cases. The recurrence rate was 20% for 35 patients with a follow-up period of at least 5 years. The follow-up period for the whole series ranged from 1 to 16 years. Treatment was surgical enucleation with peripheral ostectomy. There were no significant differences in characteristics with respect to presentation and prognosis between this series and those described in previous publications.
Mandibular swellings may occur as a result of many benign lesions of odontogenic or non-odontogenic origin. Ameloblastomas are benign tumours of odontogenic origin, whose importance lies in its potential to grow into enormous size with resulting bone deformity, it is a slow-growing, persistent, and locally aggressive neoplasm. The unicystic ameloblastoma (UA) represents an ameloblastoma variant, presenting as a cyst clinically and radiographically, but showing typical ameloblastomatous epithelium lining histologically. It commonly occurs in second and third decades of life and is rare in children under 12 years of age, and better response to conservative treatment. It shares many clinical and radiographic features with odontogenic cysts/tumours and/or periapical disease of endodontic origin. Reported here is an unusual case of unicystic ameloblastoma involving the crown of an unerupted mandibular first premolar in a 9-year boy in an uncommon location, which was misdiagnosed as periapical lesion of inflammatory origin clinically, and as a dentigerous cyst radiographically. This highlights the importance to routinely submit the removed surgical specimen for histopathological examination.