Crestal sinus lifting technique is a simple less invasive procedure. Nevertheless, it suffers a serious disadvantage of being a blind technique. Thus, perforation can easily occur without being detected which will lead to later implant failure especially when bone graft is added [1, 12,13,14]. We used endoscopic-assisted evaluation as a dependable method to assess the safety of the Schneiderian membrane elevation from the same crestal osteotomy site. Others used a more invasive technique by doing a window on the lateral sinus wall [15, 16].

Considering the relation between the membrane thickness and its perforation risk, our results showed a higher liability of perforation in membranes less than 2 mm thickness. Thus, we advocate that any membrane thickness less than 2 mm should not be elevated using a blind crestal osteotomy. Consequently, the membrane thickness should be precisely estimated using at least a preoperative CBCT prior to any anticipated blind elevation technique [10].

The use of lateral endoscopic approach [15, 17], despite being safe with minimal complications, can be substituted with the crestal one as in our study. The crestal endoscopic approach has some surpassed advantages. It saves the patient undue lateral bony osteotomy and membrane access perforation while using an already available access (crestal osteotomy site). An endoscope of 1.9 mm launched on 2.4 mm trocar can readily fit on the 3 mm crestal osteotomy width. Moreover, it gives direct magnification to the sinus membrane through the osteotomy site, and it is more precise in detecting almost microscopic perforations that may be even spared during lateral endoscopic examination. The raising of the sinus membrane in a closed approach proved to be a safe technique as long as there is appropriate membrane thickness more than 2 mm [5, 7]. The crestal elevation is not a technique and osteotome design dependent procedure, but it is rather a membrane structured dependent method. Endoscopic crestal evaluation represents a precise valuable and easy tool when routinely available as chair side equipment for detecting any perforations and hence modify decision making after lifting procedures.