Odontogenic cysts of the maxillary sinus refer to cysts formed from developmental abnormalities or pathological changes in the upper teeth that extend into the maxillary sinus. These are categorized into dentigerous cysts and radicular cysts.
Dentigerous Cyst
Dentigerous cysts (also known as follicular cysts) surround the crown of an unerupted tooth or a supernumerary tooth and are attached to the cervical portion of the tooth. They most commonly occur in the mandible, accounting for more than 75% of dentigerous cysts, and are less frequently encountered in the maxilla. These cysts typically originate from a single tooth germ and usually contain a single tooth. However, they may also arise from multiple tooth germs, containing multiple teeth. The peak incidence occurs between the ages of 10 and 40, with a higher prevalence in males than females.
Etiology and Pathology
An unerupted tooth retained within the alveolar bone can stimulate ameloblasts, leading to their proliferation and secretion, resulting in cyst formation. The tooth enamel becomes enclosed within the cyst. The cyst wall consists of fibrous tissue and is lined by flat or low cubic epithelium. The cystic fluid is yellow or brown in color, containing cholesterol crystals and exfoliated epithelial cells. While these cysts grow slowly, they can gradually expand. As the cyst enlarges, it may compress and thin the surrounding bone.
Clinical Manifestations and Diagnosis
As the cyst enlarges, swelling may occur in the affected cheek and in the lip-gingival region. The skin and gingival mucosa over the swelling appear normal, and the surface is smooth, with a sensation resembling a ping-pong ball or the fragility of an egg shell. Symptoms such as nasal obstruction on the affected side and upward displacement of the eyeball may occur. Examination of the upper dentition often reveals a missing tooth, most commonly the canine, premolar, or incisor. Radiographic imaging of the sinuses shows an expanded maxillary sinus cavity on the affected side, with a cystic shadow containing the outline of a tooth. Aspiration of mucus from the swelling confirms the diagnosis.
Treatment
Treatment typically involves removal of the cyst and the associated tooth through a transnasal endoscopic approach, such as inferior meatal antrostomy or the pre-lacrimal recess approach. Traditional treatment involves the Caldwell-Luc operation, whereby the cyst and affected tooth are completely removed while preserving the normal mucosa of the maxillary sinus.
Radicular Cyst
Radicular cysts are the most common odontogenic cysts. They are usually located on the labial surface of the root of an upper incisor, canine, or molar tooth.
Etiology and Pathology
They originate from root infections or pulp necrosis, leading to the formation of a periapical granuloma or abscess. Subsequently, epithelial cells grow into the lesion and form an epithelial lining for the cyst. The affected tooth root extends into the cystic cavity. The cyst wall comprises connective tissue and is lined with squamous epithelium. The cystic fluid is yellow and may be serous or mucous, containing cholesterol crystals. Secondary infection of the cyst can result in fibrosis.
Clinical Manifestations and Diagnosis
Enlargement of the cyst may lead to facial swelling. Radiographic imaging of the sinuses reveals a small, round cystic shadow around the periapical region of the affected tooth root within the maxillary sinus cavity, accompanied by surrounding bone resorption.
Treatment
The Caldwell-Luc operation is used to remove the cyst. If the affected tooth remains stable and salvageable, root apex resection or root canal therapy may be performed to prevent cyst recurrence. If preservation of the tooth is not feasible, extraction of the affected tooth should be performed concurrently.