This is a common complication, which may occur during an attempt to extract the upper back teeth or roots (premolars & molars).
The mouth-sinus communication (oro-antral communication) may be confirmed by observing the passage of air or bubbling of blood from the post- extraction socket when the patient tries to exhale gently through their nose while their nostrils are pinched (Valsalva test). If the patient exhales through their nose with great pressure, there is a risk of causing oro-antral communication, even though communication may not have occurred initially, such as when only the lining (mucosa) of the maxillary sinus is present between the tooth socket and the sinus.
Mouth-Sinus communications (oroantral communications) may be the result of:
Closeness of the root tips to the floor of the sinus (maxillary antrum). The bony portion above the root tips is often very thin or may even be absent, whereupon oro-antral communication is inevitable during extraction of the tooth, especially if the socket is 'cleaned' unnecessarily.