IOSR Journal of Dental and Medical Sciences (IOSR-JDMS) e-ISSN: 2279-0853, p-ISSN: 2279-0861. Volume 12, Issue 1 (Nov.- Dec. 2013), PP 45-48 www.iosrjournals.org www.iosrjournals.org 45 | Page An Aggressive Orthokeratinized Odontogenic Cyst of the Mandible: A Case Report. Dr. Ajay Kumar Pillai; Dr M.K.Gupta; Dr Shubhangi Jedhe Mhaske; Dr. Mrinal Satpathy; Dr Santosh Kumar Singh Department of Oral & Maxillofacial Surgery; People’s University, Bhopal, Madhya Pradesh, India; Prof & HOD, Oral & Maxillofacial Surgery, People’s Dental Academy, Bhopal, Madhya Pradesh, India. Prof & HOD, Oral & Maxillofacial Pathology, People’s Dental Academy, Bhopal, Madhya Pradesh, India. Department of Oral & Maxillofacial Surgery; People’s University, Bhopal, Madhya Pradesh, India; Sr. Lecturer, Department of Conservative dentistry, People’s University, Bhopal, Madhya Pradesh, India. Abstract: Orthokeratinized odontogenic cyst (OOC) is a developmental cyst that occurs in the jaw. it was initially defined by the world health organization as the orthokeratinized variant of odontogenic keratocyst (OKC). However, studies have shown that OOC has a peculiar clinicopathologic aspects when compared with other developmental odontogenic cysts, especially OKC's. The orthokeratinized odontogenic cyst is a distinct clinicopathologic entity and is histologically characterized by a thin, uniform, epithelial lining with orthokeratinization. Clinically, the orthokeratinized cyst is a single cyst, shows a predilection for males, and is most often found in the second to the fifth decade. It is not a dentigerous cyst but is often mistaken for a dentigerous cyst because of its association with unerrupted or impacted tooth in the posterior mandible. It exhibits lower clinical aggressiveness compared to its counterpart OKC. The purpose of the article is to present a case of large aggressive OOC in the anterior mandible and to highlight the importance of, distinguishing it from the more commonly occurring OKC or keratocystic odontogenic tumour (KCOT). Key Words: Jaw cysts; Odontogenic cyst; Odontogenic keratocyst; Dentigerous cyst. I. Introduction Orthokeratinized odontogenic cyst (OOC) is a developmental cyst that occurs mostly in the maxillary corpus, it was initially defined by the world health organization in 1992 as the uncommon orthokeratinized type of odontogenic keratocyst (OKC) (Sciubba JJ et al, 1999). The lesion has been termed variously as an "orthokeratinized variant of OKC’’ or a ‘‘jaw cyst with orthokeratinization". The world health organization's new classification of the year 2005 for head and neck tumors has designated OKC as keratocystic odontogenic tumor (KCOT) and reclassified it as a neoplasm in view of its intrinsic growth potential and propensity to recur. According to this new classification, OOC should not be part of the spectrum of KCOT and should be distinguished from the latter (Wright JM, 1981; Philipson HP, 2005). II. Case Report:- A 25 year old systemically healthy female patient came up with the complaint of tenderness and slight swelling in the lower front jaw region, of duration of 1 month. On examination, it revealed to be a mild diffused swelling of approximate size 3 x 2 cm (Figure 1) over anterior mandible region, causing mild facial asymmetry. On palpation, swelling was firm with associated tenderness. Intra oral examination(Figure 2, 3) revealed the swelling extending from left premolar region to right lateral incisor, with obvious midline crossing. On palpation, mild buccal plate expansion & with multi lobular consistency of the bony plate was evident, also tenderness on palpation was present. There was no apparent overlying mucosal changes or signs of fluctuation. The associated teeth had variable degree of labio-lingual tipping of crown, but all teeth were found to be vital in subsequent vitality test. Orthopantomogram (OPG) (Figure 4) revealed a well defined radiolucency with sclerotic and scalloped margins extending from periapical region of lower premolar to premolar region crossing arches, multi loculer in appearance, with thinning of lower border of mandible. Also associated impacted supernumery tooth like structure was noted in the superior periphery of the lesion (Figure 4). Further Occlussal radiograph (Figure 5) revealed both buccal and lingual plate expansion with the lesion. Her past medical history was of no relevance and general physical status was good. Lab findings included routine blood and biochemical investigations. Later to confirm the diagnosis, deep intrabony incisional biopsy was done, which revealed (Figure 6) it to be a orthokeratinized odontogenic cyst, with typical histopathological appearance.