An oroantral fistula (OAF) is an epithelialized oroantral communication (OAC), which refers to an abnormal connection between the oral cavity and the antrum. The creation of an OAC is most commonly due to the extraction of a maxillary tooth (typically a maxillary first molar) which is closely related to the antral floor. A small OAC up to 5 millimeters may heal spontaneously, but a larger OAC would require surgical closure to prevent the development of a persistent OAF and chronic sinusitis.
Classification
Signs and symptoms
When looking in the mouth, a communication in the upper jaw (i.e. a hole) can be seen connecting the mouth to the maxillary sinus. Sometimes this can be the only sign, as pain is not always present.
Symptoms One symptom is a same-side nose blockage (unilateral nasal obstruction). When an OAC or OAF is present, the passage to the maxillary sinus can results in infection and inflammation. This subsequently results in mucus build up presenting as a unilateral nasal blockage. Sinusitis may also be present as a pain in the middle of the face. Pain can also be referred to the upper teeth and be mistaken for toothache. Another symptom is the movement of fluid from the mouth through the communication and into the maxillary sinus, as the maxillary sinus is connected to the nose and therefore fluid can come out of the nostrils when drinking. There may be variations in the noises made by the voice and nose, particularly a whistling sound made when speaking. Taste may possibly be affected.
Signs A visible hole between mouth and sinus is one of the major signs. There may be fracturing on the floor of the maxillary sinus creating a communication to the oral cavity, which may be seen following trauma. Furthermore, air bubbles, blood, or mucoid secretion around the orifice can be seen as air passes from the sinus into the oral cavity through the communication.
Diagnosis Diagnosis is usually based on clinical examination and reported symptoms. Therefore, an understanding of the patient's history and symptoms is crucial in the diagnosis of an oroantral fistula. A Valsalva test (nose blowing test) may also be issued to diagnose an oroantral fistula. In a Valsalva test, the patient is asked to pinch their nostrils together and open their mouth and then blow gently through the nose. The clinician must observe if there is passage of air or bubbling of blood in the post-extraction alveolus, as the trapped air from closed nostrils is forced into the mouth through an oroantral communication. Gentle suction applied to the socket often produces a characteristic hollow sound. However, there are differing opinions about the appropriateness of carrying out this test. By performing it, a small OAC may be made bigger, thus preventing spontaneous healing. Imaging can also be useful in the diagnostic process; however, radiographs only reveal the fistula if there is a breach in the bony floor of the antrum. Even if there is a breach in the bony floor, then the Schneiderian membrane may still be intact. Depending on the size of the potential communication and in what context, a small radiograph inside the mouth may be sufficient (a periapical) to indicate any break in the bone of the sinus floor which may indicate an OAC. Panoramic radiographs can also be used to confirm the presence of an OAC. If simple radiographs are deemed not to give enough information, cone beam computed tomography (CBCT) (special x-ray equipment that can scan in 3 dimensions) may be used. Imaging can help locate the communication, determine the size of it and can give an indication as to whether there is any sinusitis and foreign bodies in the sinus.
Causes
Extraction of maxillary teeth The maxillary sinus is known for its thin floor and close proximity to the posterior maxillary (upper) teeth. The extraction of a maxillary tooth (typically a maxillary first molar which lies close to the lowest point of antral floor although any premolar or molar can be affected) is the most common cause of an OAC (which can then progress to an OAF as described above). Extraction of primary teeth are not considered a risk of OAC due to the presence of developing permanent teeth and the small size of the developing maxillary sinus.
Other causes Other causes of an OAC are maxillary fractures across the antral floor (typically Le Fort I), displacement of posterior maxillary molar roots into antrum, and direct trauma. An OAC can happen for many other more unusual reasons, such as acute or chronic inflammatory lesions around the tip of a tooth root which is in close proximity with the maxillary antrum, destructive lesions/tumors of the maxilla, failure of surgical incisions to heal (e.g. Caldwell-luc antrostomy), osteomyelitis of the maxilla, careless use of instruments during surgical procedures, Syphilis, implants and as a results of complex surgery (for example removal of a large cysts or resections of large tumors) involving the maxilla.
Diagnosis Clinical examination and x-rays can help diagnose the condition. Tests used to diagnose this condition include:
Valsalva test (nose blowing test): Ask the patient to pinch the nostrils together and open the mouth, then blow gently through the nose. Observe if there is passage of air or bubbling of blood in the post extraction alveolus as the trapped air from closed nostrils is forced into the mouth through any oroantral communication. Gentle suction applied to the socket often produces a characteristic hollow sound. Perform a complete extra- and intra-oral examination using a dental mirror under good lighting, look for granulation tissue in the socket and openings into the antrum. Panoramic radiograph or paranasal computed tomography can help to locate the fistula, the size of it and to determine the presence of sinusitis and other foreign bodies. Other methods like radiographs (occipitomental, OPG and periapical views) can also be used to confirm the presence of any oroantral fistulas. To test the patency of communication the patient is asked to rinse the mouth or water is flushed in the tooth socket. Unilateral epistaxis is seen in case of collection of blood in the sinus cavity. Do not probe or irrigate the site, because it may lead to sinusitis or push foreign bodies, such as contaminated fragments, or oral flora further into the antrum. Hence, leading to the formation of a new fistula or widen an existing one.
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