The maxillary sinuses are behind your cheeks and on top of the upper teeth. Sinuses are likeempty rooms that have nothing in them.
Some of the roots of the natural upper teeth extend up intothe maxillary sinuses. When these upper teeth are removed,
there is often just a thin wall of boneseparating the maxillary sinus and the mouth. Dental implants need bone to hold them in place.
Whenthe sinus wall is very thin, it is impossible to place dental implants in this bone.