The maxillary sinus is connected to the nose and therefore fluid can come out of the nostrils when drinking· Change in sounds produced from the nose and the voice – specifically a whistling sound whilst speaking· Taste can be affected

Signs
· Visible hole between mouth and sinus
· Fracture of the floor of the maxillary sinus creating a communication to the oral cavity (e.g. as seen following trauma).· 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
- Patient history - Diagnosis is usually based on clinical examination and reported symptoms. Therefore, a good history and understanding of the patient’s symptoms is key. - Undertake a complete extraoral and intraoral examination using a dental mirror alongside good lighting. When assessing the socket following an extraction look for granulation tissue in the socket which may represent normal healing. Assess for the presence of visible an opening/hole between the oral cavity and the maxillary sinus. - Imaging can be useful. However, radiographs only show 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 assess for 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. - Normally clinicians should be cautioned against probing or irrigating the site a newly formed OAC as this may reduce the chance of spontaneous healing. - Valsalva test (nose blowing 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 any 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. It can be argued that by performing this test, a small OAC may be made bigger thus preventing spontaneous healing. Causes
Extraction of maxillary teeth
The maxillary sinus is known for its thin floor and close proximity to the posterior maxillary (upper) teeth.