Cysts of the Oral and Para-oral Region PDF

Chapter 3 Cysts of the Oral and Para-oral Region Chapter ILOs: 1. Define cyst and pseudocyst. 2. Identify pathogenesis and histogenesis of cysts. 3. Classify different types of cysts. 4. Recognize clinical features, histopathology, radiographic picture and behavior...

Chapter 3 Cysts of the Oral and Para-oral Region Chapter ILOs: 1. Define cyst and pseudocyst. 2. Identify pathogenesis and histogenesis of cysts. 3. Classify different types of cysts. 4. Recognize clinical features, histopathology, radiographic picture and behavior of odontogenic cysts. 5. Recognize clinical features, histopathology, radiographic picture and behavior of non-odontogenic cysts. 0  Cysts of the Oral and Paraoral Region Cysts of the Oral and Para-oral Region Definition: A cyst is a pathological cavity lined with epithelium and having fluid or semi-solid contents occurring in either hard or soft tissues. Some cysts may not be epithelial-lined and therefore are not true cysts and termed: Pseudocysts. Cysts are more common in the jaws than in any other bone because of the many epithelial rests remaining in the tissues after dental development. Classification: I- Odontogenic cysts: These arise from odontogenic epithelial remnants associated with the development of teeth. A. Periodontal cysts 1- Inflammatory: i. Apical (radicular), lateral and residual cysts ii. Inflammatory Collateral Cysts: Paradental and Mandibular buccal bifurcation cysts 2- Developmental: i. Lateral developmental cyst ii. Botryoid odontogenic cyst iii. Gingival cyst of adults iv. Gingival cyst of newborn (Dental lamina cyst of Newborn/Bohn's nodules) B. Dentigerous cyst: (Central, lateral, circumferential); cysts of eruption. C. Odontogenic keratocyst D. Orthokeratinized Odontogenic cyst 1  Cysts of the Oral and Paraoral Region E. Calcifying odontogenic cyst (COC, Gorlin's cyst). II- Non-Odontogenic cysts: A- Cysts of vestigial ducts Nasopalatine tract Cysts: i.Incisive Canal Cyst ii.Cyst of palatine papilla B- Fissural Cysts: 1- Median Cysts: In the maxilla: Median palatal cyst In the mandible: Median mandibular cyst 2- Globulomaxillary cyst 3- Nasolabial cyst III- Pseudocysts: A. Simple bone cyst B. Aneurysmal bone cyst C. Static bone cyst IV- Soft tissue cysts of the floor of mouth and neck: A. Dermoid and epidermoid cysts. B. Thyroglossal tract cyst. C. Cervical lymphoepithelial cyst (Branchial cleft cyst). D. Mucous retention, mucous extravasation cysts and Ranula I- Odontogenic Cysts Odontogenic cysts affect the tooth-bearing region of the jaws. The epithelium associated with odontogenic cysts is derived from one of the following sources: 1. Enamel organ. 2. Reduced enamel epithelium. 3. Epithelial rests of Malassez. 2  Cysts of the Oral and Paraoral Region 4. Remnants of the dental lamina (epithelial rests of Serre’s). A- Periodontal cysts I- Inflammatory periodontal cyst Etiology: This cyst is the most common odontogenic cyst and represents 65% of all cysts. It results from inflammatory hyperplasia of the epithelial rests of Malassez in the periodontal ligament following death of the pulp. Periapical cysts usually develop from a preexisting periapical granuloma. Stimulation is caused by the inflammatory process within the granuloma. Classification: It is classified as follows: a) Apical or Periapical cyst: These are the cysts which are present at root apex. b) Lateral radicular cyst: These are the cysts which are present at the opening of lateral accessory root canals of offending a tooth. c) Residual cyst: These are the radicular cysts that remain even after extraction of the offending tooth. Pathogenesis: Pathogenesis of radicular cyst can be summarized into three phases: 1- Phase of initiation: It is generally agreed that the epithelial lining of these cysts is derived from epithelial cell rests of Malassez in periodontal ligaments. The mechanism of stimulation of epithelial cells may be due to inflammation in periapical granuloma or some products of dead pulp, which may initiate the process and at the same time it evokes an inflammatory reaction. 2- Phase of Cyst Formation It is a process by which a cavity becomes lined by proliferating epithelium. The most widely accepted theory suggests that the initial 3  Cysts of the Oral and Paraoral Region reaction leading to cyst formation is a proliferation of epithelial rests in periapical area involved by granuloma. This proliferation continues and the epithelial mass increases in size. The dividing cells are that of the periphery, corresponding to the basal layer of surface epithelium. The cells of the central portion of mass become separated further and further from nutrition so they fail to obtain sufficient nutrition. The central cells eventually degenerate, becoming necrotic and liquify. This creates an epithelium-lined cavity filled with fluid. 3- Phase of Cyst Enlargement Experimental work provided evidence that osmosis contributes in increasing the cyst’s size. Remnants of cellular debris are found within the cyst lumen, producing an increase in osmotic pressure of the cystic fluid, as a result of the breakdown of complex tissue proteins into a larger number of molecules of more simple proteins. The result is fluid transport across the epithelial lining and connective tissue, that act as a semi-permeable membrane, in an attempt to equalize the osmotic pressure; and so, enlargement occurs. This growth stimulates osteoclastic bone resorption thus enlarging the bony cavity and allowing further expansion of the cyst. Osteoclastic bone resorption is also stimulated by bone resorbing factors from the inflammatory cells and cellular elements within the peripheral portion of the lesion. a- Apical (periapical, radicular) Clinical Features: Age: Adult life (third to the sixth decades). Sex: More frequent in men. Site: Maxilla especially the anterior region. Most radicular cysts are asymptomatic and are discovered during routine dental radiographic examination. As they enlarge they cause slowly 4  Cysts of the Oral and Paraoral Region progressive painless swellings often on the labial or buccal side. If infection occurs, the swelling becomes painful and may rapidly increase in size secondary to inflammatory edema. The swelling is rounded and at first hard. Later, when bone has been reduced to eggshell thickness, a crackling sensation may be felt on pressure. Finally, part of the overlying bone is resorbed entirely, leaving a soft fluctuant swelling, bluish in color, beneath the mucosa. The tooth related to the periapical cyst is usually a non-vital tooth. Radiographically: Round or ovoid well-defined radiolucency surrounded by a narrow radio-opaque margin. The radio-opaque margin may not be apparent if the cyst is actively enlarging. The cyst ranges from 5mm to several centimeters in diameter. The dead tooth, from which the cyst has arisen, often has a large carious cavity or a filling. Root resorption of the offending tooth or adjacent teeth may be noted. Infection of a cyst causes the outline to become hazy. Distinction between a small radicular cyst and a periapical granuloma radio-graphically is difficult. 5  Cysts of the Oral and Paraoral Region Periapical Cyst. Well- Periapical Cyst. circumscribed radiolucency Radiolucency associated associated with the apex of with the maxillary central the mandibular central incisor, with significant root incisor. (1) resorption. (1) Histopathologic Features: Epithelial lining: The epithelial lining of apical periodontal cysts is usually a stratified squamous epithelium. In a newly formed cyst, the epithelium is hyperplastic, showing acanthosis (20 cell layers) with over vascularized connective tissue and many inflammatory cells are seen in the connective tissue. In fully formed, old cysts, the epithelial lining becomes more regular and flattened as inflammation decreases and the connective tissue contains few inflammatory cells. In case of intense inflammation, the epithelial lining of the cyst may be discontinuous and is frequently missing over these areas. 6  Cysts of the Oral and Paraoral Region Connective tissue: The underlying connective tissue is composed of parallel bundles of collagen fibers with variable numbers of fibroblasts and capillaries. Inflammatory cell infiltration is also present. Towards the epithelium, polymorphonuclear leucocytes predominate. Deeper within the connective tissue lymphocytes are more common. In the connective tissue wall of the cyst, foci of dystrophic calcification, cholesterol clefts and enlarged blood vessels may be found. Degenerated plasma cells may be present and are known as Russel bodies. Multinucleated foreign-body giant cells may frequently be seen close to cholesterol clefts and hemosiderin within the connective tissue wall. Occasionally a mass of cholesterol erodes through the lining epithelium and is extruded into the cyst lumen. The source of cholesterol seems to be due to local tissue damage. Collection of lipid-filled macrophages (foam cells) are present. Cyst Lumen The lumen of the cyst usually contains fluid, which stains eosinophilic. Sometimes the lumen may contain cholesterol in great amounts. Chemically, cystic fluid contains serum albumin, globulin, cholesterol and nucleoproteins. 7  Cysts of the Oral and Paraoral Region Periapical Cyst. Cyst lined by stratified squamous epithelium. Note connective tissue wall, which contains a chronic inflammatory infiltrate and numerous cholesterol clefts. (1) Differential Diagnosis: Periapical granuloma if the radiolucency is small. Periapical scar or surgical defect in areas of previously treated. Early phase of periapical cemental dysplasia in anterior mandibular area, but related teeth are usually vital. Microscopic Variations in Cyst Walls: Pseudo-stratified ciliated columnar epithelium. This may be seen in periapical cysts of maxillary teeth, which involve the maxillary sinus. Dystrophic calcification as haematoxyphilic-calcified deposits may be found in the epithelium and connective tissue. Keratinized lining (para-or orthokeratin). Hyaline bodies or Rushton bodies may be found within the epithelial lining; (Thin, linear, curved bodies, amorphous in structure, eosinophilic in reaction). The origin of such bodies is controversial. Some believe that they are of haematogenous origin 8  Cysts of the Oral and Paraoral Region arising from thrombus formation in small capillaries, being formed chiefly from their red blood cells as a rouleaux phenomenon. Others believe that they have an odontogenic origin. Periapical Cyst. Squamous epithelial cyst lining exhibiting numerous irregular and curvilinear Rushton bodies. (1) Treatment: If the cyst is small, enucleation of the cyst and apicectomy of the involved tooth. If the cyst is medium size, remove the tooth and enucleate the cyst. Large cysts need marsupialization to avoid the antrum or important structures as the inferior dental nerve. Larger cysts need enucleation and bone chips to fill the cavity. b- Inflammatory Lateral Periodontal Cysts Inflammatory lateral periodontal cysts are less common than periapical ones. They form along the lateral aspect of the root of a pulpless tooth as a result of opening of a lateral root canal and irritation of periodontal tissue. 9  Cysts of the Oral and Paraoral Region Lateral Inflammatory Cyst. Inverted pear-shaped radiolucency between the maxillary lateral incisor and cuspid (arrow). The lateral incisor ultimately proved to be nonvital. (1) Lateral Inflammatory Cyst. A rounded radiolucency between bicuspid and first molar extending laterally from the mesial root of the first molar (Courtesy of Dr. Carroll Gallagher). (1) c- Residual Cyst The pulpless tooth from which a periapical cyst has arisen may be extracted and the cyst may persist in the jawbone. It's one of the most common causes of swelling of the edentulous jaw. Residual cysts may cause trouble by interfering with the fitness of dentures, and sometimes enlarge to the extent of weakening the jaw with possible risk of jaw fracture. 10  Cysts of the Oral and Paraoral Region Residual Periapical Cyst. Well-circumscribed radiolucency of the maxilla at the site of previous tooth extraction. (1) II-Inflammatory Collateral Cysts: Odontogenic cysts located on the buccal or distal aspect of a tooth, usually a mandibular molar. It has two main types: a) A paradental cyst arises on the distal surface of a partially erupted lower third molar. Usually associated with a history of long standing pericoronitis, with associated symptoms of pain, swelling, trismus. The associated tooth is vital. Radiographic Features: Well-circumscribed radiolucent area on the distal side of a partially erupted lower third molar. b) Mandibular buccal bifurcation cyst arises subgingivally on the buccal aspect of lower first or second molars. Presents as a painless swelling, but infection can result in pain and suppuration. The tooth is usually tilted buccally, with deep periodontal pockets. Cyst formation may be exacerbated by a down-growth of enamel on the buccal aspect of the involved tooth or by food impaction. 11  Cysts of the Oral and Paraoral Region Radiographic Features: Well-demarcated buccal radiolucency, which may extend to the lower border of the mandible. A periosteal reaction with laminated new bone formation may be visible. Buccal Bifurcation Cyst: Axial computed tomography (CT) image showing a circumscribed radiolucency buccal to the roots of the mandibular first molar (Courtesy of Dr. Robert Clark). (1) Histopathologic Features: Not specific and is indistinguishable from that of a radicular cyst. The Inflammatory collateral cyst is lined by a hyperplastic layer of nonkeratinized stratified squamous epithelium. Cholesterol clefts and foamy macrophages may be seen in the cyst wall. The lining may be attached at the cementoenamel junction or be continuous with the epithelium of the peri-coronal tissues, forming an invagination or pocket protruding down the root of the tooth. 12