"All-on-Four" immediate-function concept with Brånemark System implants for completely edentulous mandibles: a retrospective clinical study.

BACKGROUND Immediate-function Brånemark System implants (Nobel Biocare AB, Gothenburg, Sweden) have become an accepted alternative for fixed restorations in edentulous mandibles, based on documented high success rates. Continuous development is ongoing to find simple protocols for their use. PURPOSE The purpose of this study was to develop and document a simple, safe, and effective surgical and prosthetic protocol for immediate function (within 2 hours) of four Brånemark System implants supporting fixed prostheses in completely edentulous mandibles: the "All-on-Four" concept. MATERIALS AND METHODS This retrospective clinical study included 44 patients with 176 immediately loaded implants, placed in the anterior region, supporting fixed complete-arch mandibular prostheses in acrylic. In addition to the immediately loaded implants, 24 of the 44 patients had 62 rescue implants not incorporated in the provisional prostheses but incorporated in final prostheses later on. RESULTS Five immediately loaded implants were lost in five patients before the 6-month follow-up, giving cumulative survival rates of 96.7 and 98.2% for development and routine groups, respectively. The prostheses' survival was 100%, and the average bone resorption was low. CONCLUSIONS The high cumulative implant and prostheses survival rates indicate that the "All-on-Four" immediate-function concept with Brånemark System implants used in completely edentulous mandibles is a viable concept.