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. Complications
OAF is a complication of oroantral communication. Other complications may arise if left untreated. For example:

Candidal infection
Chronic maxillary sinus infection of bacterial origin
Osteomyelitis
Rhinosinusitis
Sinus pathologyTherefore, OAF should be dealt with first, before treating the complications. Prevention
Whilst in some circumstances, preventing development of an OAF following extraction of a tooth can be difficult, careful assessment is important.
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.