Which sinus is involved in a patient with a toothache and sinusitis
Dental infections are an important source of maxillary sinusitis. 
Roots of premolar and molar teeth are related to the floor of sinuses and may be separated only by a thin layer of mucosal covering. 
A peripheral dental abscess may burst into the sinus or the root of a tooth during extraction may be pushed into the sinus.
In the case of oroantral fistula following tooth extraction bacteria from the oral cavity enter the maxillary sinus.
Maxillary
Ethmoid
Frontal
Sphenoid