Fig. 1
From: Crestal endoscopic approach for evaluating sinus membrane elevation technique

A trephined hole (4 mm bone) in the lateral wall of the maxillary sinus to allow entrance of the endoscope
From: Crestal endoscopic approach for evaluating sinus membrane elevation technique
A trephined hole (4 mm bone) in the lateral wall of the maxillary sinus to allow entrance of the endoscope