In each patient, one sinus was chosen at random and filled with DFDBA (Tissue Regeneration Corporation, Iran).

The contra lateral sinus was filled with Algipore (Dentsply, USA).

A crestal incision was made on the mucosa of the edentulous ridge. The flap was elevated carefully and extended labially to expose the bone. A vertical releasing incision was made in the mesial end of the flap as needed. The mucoperiosteal flap was extended to expose the alveolar ridge and the lateral wall of the maxillary sinus. Then, a window was prepared using the piezoelectric device (Mectron, Italy); the Schneiderian membrane was then elevated conservatively according to the technique described by Vercellotti (2001).

The sinus membrane was meticulously detached and pushed superiorly to allow for the placement of bone graft material.

Baseline and 9 months radiographs were scanned with an Agfa scanner at 1200 dpi with a 12-bit grayscale and stored in JPEG format. Changes in bone height were calculated in each case. Two reference points, one at the lowest part of the ridge crest and the other at the highest part of sinus floor, were selected in two radiographs (baseline and after 9 months) and their distance was calculated in 0.1mm scale using computer.

Changes in radiographic density after sinus grafting were evaluated using densitometry.