The posterior residual ridge, from approximately the premolar area through the tuberosity, is supplied principally by the posterior superior alveolar artery (6). Branches of this fairly strong artery pass within bone through nerve canals to supply the alveoli and outside bone, on the buccal surface of the upper arch, to supply the gingiva.

Both anterior and posterior superior alveolar arteries have branched into numerous, tiny vessels in the operative site. These

41