Two Most common Cysts Associated With Impacted Wisdom Teeth

Dentigerous Cyst
A dentigerous cyst or follicular cyst is an odontogenic cyst- thought to be of developmental origin - associated with the crown of an unerupted (or partially erupted) tooth.  Meaning that the cyst-like tissue may cover a portion or the entire crown of the tooth. The cyst cavity is lined by epithelial cells derived from the reduced enamel epithelium of the tooth forming organ. Regarding its pathogenesis, it has been suggested that the pressure exerted by an erupting tooth on the follicle may obstruct venous flow inducing accumulation of exudate between the reduced enamel epithelium and the tooth crown.  This can account for the fluid material in the cyst cavity.
Histologically a normal dental follicle is lined by enamel epithelium, whereas a dentigerous cyst is lined by non-keratinized stratified squamous epithelium. Since the dentigerous cyst develops from follicular epithelium it has more potential for growth, differentiation and degeneration than a radicular cyst. Occasionally the wall of a dentigerous cyst may give rise to a more ominous mucoepidermoid carcinoma. Due to the tendency for dentigerous cysts to expand rapidly, they may cause dehiscence or pathologic fracture of jaw bone.
The usual radiographic appearance is that of a well-demarcated radiolucent lesion attached at an acute angle to the cervical area of an unerupted tooth. The border of the lesion may be radiopaque. The radiographic differentiation between a dentigerous cyst and a normal dental follicle is based merely on size. Radiographically, a dentigerous cyst should always be differentiated from a normal dental follicle. Dentigerous cysts are the most common cysts with this radiographic appearance.  However, histological analysis is a more definitive method of identification. Radiographically the cyst appears unilocular with well defined margins and often sclerotic boarders. Infected cysts show ill-defined margins.
The most common location of dentigerous cysts are the Mandibular 3rd Molars and the Maxillary Canines, and they rarely involve deciduous teeth and are occasionally associated with odontomas.


Ameloblastoma

Ameloblastoma is a rare, benign tumor of odontogenic epithelium (ameloblasts, or outside portion, of the teeth during development) much more commonly appearing in the lower jaw than the upper jaw.  The lesion usually is associated in the lower posterior mandible and can be affiliated with any molar tooth in this region.
While these tumors are rarely malignant or metastatic (that is, they rarely spread to other parts of the body), and progress slowly, the resulting lesions can cause severe abnormalities of the face and jaw. Additionally, because abnormal cell growth easily infiltrates and destroys surrounding bony tissues, wide surgical excision is required to treat this disorder.
Ameloblastomas are often associated with the presence of unerupted teeth. Symptoms include painless swelling, facial deformity if severe enough, pain if the swelling impinges on other structures, loose teeth, ulcers, and periodontal (gum) disease. Lesions will occur in the mandible and maxilla,although 75% occur in the ascending ramus area and will result in extensive and grotesque deformitites of the mandible and maxilla. In the maxilla it can extend into the maxillary sinus and floor of the nose. The lesion has a tendency to expand the bony cortices because slow growth rate of the lesion allows time for periosteum to develop thin shell of bone ahead of the expanding lesion. This shell of bone cracks when palpated and this phenomenon is referred to as "Egg Shell Cracking" or crepitus, an important diagnostic feature. Ameloblastoma is tentatively diagnosed through radiographic examination and must be confirmed by histological examination (e.g., biopsy). Radiographically, it appears as a lucency in the bone of varying size and features—sometimes it is a single, well-demarcated lesion whereas it often demonstrates as a multiloculated "soap bubble" appearance. Resorption of roots of involved teeth can be seen in some cases, but is not unique to ameloblastoma. The disease is most often found in the posterior body and angle of the mandible, but can occur anywhere in either the maxilla or mandible.
Ameloblastoma is often associated with bony-impacted wisdom teeth—one of the many reasons some dentists recommend having them extracted