Frequency of maxillary sinus septa: varies between different reports (10 to 36%), being more common in patients who are edentulous.
There are 3 dental basins on the floor of the maxillary sinus separated by ridges:
(1) anterior (over the premolars)
(2) middle (over the first and second molars)
(3) posterior (over the third molar)
The basins form when the bony floor sinks down between the dental roots during tooth eruption.
A septa
(1) develops from the ridges between the basins
(2) may develop during the various stages of dental eruption
(3) is present if the height of the ridge is greater than 2.5 mm
(4) is complete if it spans the entire sinus, else is termed incomplete
The septae have been classified by different authors, but a key factor is whether the septa is secondary to loss of the adjacent teeth or primary (not associated with loss of teeth).
The presence and measurement of a septa is best determined on CT scan. as panoramic scans are unreliable.
The presence of a septa will influence how surgery is conducted. One approach is to cut out the septa, while another is to place sinus windows on both side of the septa rather than having one large window.
