Purpose: The purpose of this study was to evaluate the feasibility of the outfracture osteotomy sinus graft technique with the evaluation of 8.5 year survival rate of the implants placed in the atrophic edentulous posterior maxillary area. Methods: One hundred and seventy-six cases of 145 patients who visited our center from August 2004 to February 2013 and were diagnosed as atrophic edentulous maxillary alveolar ridge, were selected and underwent sinus graft with outfracture osteotomy sinus graft technique. Feasibility of the outfracture osteotomy sinus graft technique was investigated with clinical and radiographic evaluation to assess the survival rate of the total dental implants in augmentation sinus surgery. Total fixture number available in follow-up period was 320, in which the lost 15 patients were excluded out of 160 patients. Results: Eight point five year cumulative survival rate was 95.6% with 14 failures of total 320 fixtures. The average follow-up period was 28 months 16 days with the minimum and maximum follow-up periods of 4 months 5 days and 94 months 10 days, respectively. Conclusion: Traditional infracture technique is a popular method for an augmentation sinus surgery. The authors modified this classical method by outfracturing and readapting the bony window after sinus graft, with excellent treatment results evidenced by high survival rate, which proves the feasibility of the newly-designed outfracture osteotomy sinus graft technique.