Survival rate for implants placed in the posterior maxilla with and without sinus augmentation: a comparative cohort study

BACKGROUND: The reduced bone height and proximity of the maxillary sinus are the most common limitations for placement of dental implants in the posterior maxilla. Reconstruction of the atrophic posterior maxilla can be performed with a sinus augmentation procedure. The aim of this cohort study is to compare the survival rate of implants placed in augmented sinus to implants placed in native bone in the posterior maxilla. METHODS: This study was designed as a prospective cohort study and included consecutively treated patients. Patients who required the sinus augmentation (test group) were treated according to the two-stage technique. Patients were scheduled for follow-up evaluation at 3, 6, and 12 months after implant placement and then every 6 months for ≤ 6 years. RESULTS: One hundred and five patients with 393 implants were enrolled in the study. Two hundred and one implants were placed after preliminary sinus floor grafting in 41 patients. The control group contained 64 patients with 192 implants that were placed in pristine bone of the posterior maxilla. The cumulative implant survival rates were 86.1% and 96.4%, respectively. The difference between the two groups was highly significant (P <0.005). CONCLUSIONS: These findings show that implants placed in augmented sinuses had a lower survival rate compared to implants placed in pristine bone. All the implant failures in the augmented sinuses occurred before the prosthetic rehabilitation. Moreover, it should be considered that most of the failures were observed in few patients, thus suggesting cluster behavior.