Odontogenic keratocysts can occur at any age but are most frequent in individuals between 10 and 40 years of age, have a male predominance, and typically are located within the posterior mandible. Differentiation of the odontogenic keratocyst from other odontogenic cysts is important because it is locally aggressive and has a high recurrence rate. On histologic examination, the cyst lining consists of a thin layer of parakeratinized or orthokeratinized stratified squamous epithelium with a prominent basal cell layer and a corrugated luminal epithelial surface. Treatment requires aggressive and complete removal; recurrence rates of up to 60% are associated with inadequate resection.
In contrast with the developmental cysts just described, the periapical cyst has an inflammatory etiology. These extremely common lesions occur at the tooth apex as a result of long-standing pulpitis, which may be caused by advanced caries or trauma. Necrosis of the pulpal tissue, which can traverse the length of the root and exit the apex of the tooth into the surrounding alveolar bone, can lead to a periapical abscess. Over time, granulation tissue (with or without an epithelial lining) may develop. Periapical inflammatory lesions persist as a result of bacterial infection or necrotic tissue in the area. Successful treatment, therefore, necessitates the complete removal of the offending material followed by restoration or extraction of the tooth.
Odontogenic tumors are a complex group of lesions with diverse histologic appearances and clinical behaviors. Some are true neoplasms, either benign or malignant, while others are thought to be hamartomas. Odontogenic tumors are derived from odontogenic epithelium, ectomesenchyme, or both. The two most common and clinically significant tumors are ameloblastoma and odontoma.
Ameloblastomas arise from odontogenic epithelium. They are typically cystic, slow-growing and, despite being locally invasive, have an indolent course. The cysts are lined by palisading columnar epithelium that overlies a loose stroma with stellate cells. Odontoma, the most common type of odontogenic tumor, arises from epithelium but shows extensive deposition of enamel and dentin. Odontomas are cured by local excision.
Thejawsareacommonsiteofepithelium-linedcystsderivedfromodontogenicremnants.
Theodontogenickeratocystislocallyaggressive,withahighrecurrencerate.
Theperiapicalcystisareactive,inflammatorylesionassociatedwithcariesordentaltrauma.
Themostcommonodontogenictumorsareameloblastomaandodontoma.
The esophagus develops from the cranial portion of the foregut. It is a hollow, highly distensible muscular tube that extends from the epiglottis to the gastroesophageal junction, located just above the diaphragm. Acquired diseases of the esophagus run the gamut from lethal cancers to the persistent “heartburn” of gastroesophageal reflux that may be chronic and incapacitating or merely an occasional annoyance.
Atresia, fistulas, and duplications may occur in any part of the gastrointestinal tract. When they involve the esophagus, they are discovered shortly after birth, usually because of regurgitation during feeding. Prompt surgical repair is required. Absence, or agenesis, of the esophagus is extremely rare. Atresia, in which a thin, noncanalized cord replaces a segment of esophagus, is more common. It occurs most frequently at or near the tracheal bifurcation and usually is associated with a fistula connecting the upper or lower esophageal pouches to a bronchus or the trachea. This abnormal connection can result in aspiration, suffocation, pneumonia, or severe fluid and electrolyte imbalances.