This is an Odontogenic Cyst.
Etiology : Infected tooth leading to pulpal necrosis.Toxins exist through apex leading to peri apical inflammation. This inflammation stimulates the epithelial rest cells of Malassez which are found in the apical periodontal ligament. Resulting in the formation of periapical granuloma,which can get infected.When there is insufficient blood supply this undergoes liquefaction necrosis and granuloma becomes a cyst. These cyst are seen in the apex of the root stumps ,fractured or infected tooth.
( what is a granuloma ? ans:A highly vascularized tissue containing a profused infiltrate of immunologically competent cells. )
Radiographic features: well-delineated - Marked radio-opaque rim (granuloma or other neoplasm can also have this features with similar radioluscent area in the peri-apical area. So the lesion should be larger than 2 cm in diameter and rarely in radicular cyst there will be any resorption of the root apex..
Treatment : Extraction of the affected tooth with careful curettage.In some cases Root canal treatment with apicoectomy of the cystic lesion.. Untreated radicular cyst enlarges in size with resorption of the surrounding bones.Expansion of the cortical plate is seen as in dentigerous cyst. (Under prophylactic antibiotics)
(Hyaline bodies or Rushton bodies are seen in the mucous secreting epithelium under microscope. This cyst is often found in the vicinity of the maxillary sinus,)
Case study: 25/11/2010. A young patient of the age 27 years had come to the hospital with a complain of pain in the maxillary anterior region. He states a history of such pain from last 3 years, which was sudden in onset and relieved under medication. Patient had no external swelling before until this day. External appearance :- slight swelling in his left side of the face with slight reddened area just under the malar prominence .Intra-oral findings : No visible findings in the buccal mucosa in the affected side but when palpated in the same area ,it was tender and a medium size spherical mass was felt . The OPG and Occlusal Radiographs confirmed the presence of the mass ,just at the apical area of the root stumps in the affected side.The mass later was confirmed to be a Radicular Cyst from the report.
The too affected was 25,which involved the mesial root of 26 and distal part of the root of 24 .It also in the area of the palate surrounding the Root stumps.
Radicular Cyst along with Peri-Apical Infection . 24 and 26 were tender upon percussion .