How rare or common is a sinus infection due to a tooth problem?

Sinus inf & teeth: While it is very common for a sinus infection to cause facial pain or a sensation that feels just like a toothache (if the lower, maxillary sinus are involved; they sit right about the roof of your mouth and teeth), it is quite rare for an infection starting in the tooth (root area) to spread up through the bone to the sinus, but it can happen.

Uncommon: The teeth are usually separated from the sinus by bone and a membrane. It is unusual for a tooth infection to spread through both of those barriers, though not impossible. A tooth infection can, however, feel as if it is going into the sinus because the nerves can be closely connected.