Introduction: When the implant surgeon has the patient with severely atrophied upper posterior maxilla with substantially enlarged pneumatized sinus, the surgeon has to open up the sinus laterally to perform sinus augment surgery other than Crestal Approach Sinus Lift surgery.

I was thinking which portion of the implant is most crucial to establish initial stability and during implant sustainment? My opinion is clinical and empirical point of view is apical end portion of last 3 threads of the implant. The reasons are explained as following: