Contemporary "All-on-4" concept.

Restoration of the atrophic edentulous maxilla and mandible with implant retained prostheses has involved the use of axially placed implants in regions of the maxilla and mandible based on the adequate availability of bone, often using a staged surgical approaches. Anatomic limitations including pneumatized maxillary sinus, proximity of the inferior alveolar nerve and lack of available native bone have many clinicians performing traditional grafting procedure prior to implant placement. Utilization of the "All-on-4" concept has overcome these anatomic restrictions by allowing placement of 2 vertical and 2 angled implants in the premaxilla and anterior mandible. This technique has enabled immediate placement of full arch fixed restoration at the time of implant surgery if sufficient torque is achieved. It has biomechanical advantages including increasing in A-P spread, enhancing load distribution with cross arch stabilization, shorten cantilever, longer implants to be placed by titling them posteriorly, and maintenance of marginal bone height. High implant survival rates of in the maxilla (92.5-100%), in the mandible (93-100%) and restoration (99.2-100%) prove that the "All-on-4" concept is a viable treatment option for edentulous patients with atrophic alveolar ridges circumventing these traditional grafting procedures. Published by Elsevier Inc.