Retrospective Cohort Study of the Predictors of Implant Failure in the Posterior Maxilla

Purpose: The purpose of this study was to retrospectively analyze a cohort of patients who had implants placed in the posterior maxilla and assess and identify the predictors of implant failure. Materials and Methods: With institutional review board approval, dental records from a population of patients who had maxillary posterior implants placed were used to create a database. Independent variables were divided into continuous (age of the patient at stage-one implant surgery [S1], time between extraction and S1, time between extraction and sinus augmentation, time between sinus augmentation and S1, time between S1 and stage-two implant surgery [S2], and the time between S2 and restoration of the implant) and categorical (gender, American Society of Anesthesiologists [ASA] status, current smoking status, implant position, implant proximity, residual crestal bone height, implant length and diameter, and sinus augmentation technique and materials). The dependent variable was implant failure, which was defined as complete removal of the implant. Simple logistic regression was used to assess the influence of each of the predictors on implant failure (P .05). Results: The final database included 504 maxillary posterior implants with an overall survival rate of 93.2% over a mean follow-up period of 35.7 months. For the continuous variables, the age of the patient at S1 was statistically associated with implant failure (P = .028), as was the time between extraction and S1 (P = .014). For the categorical variables, ASA status (P .001), implant proximity (P = .043), residual crestal bone height (P .001), implant diameter (P = .050), sinus augmentation technique (P = .002), and sinus graft materials (P .001) were statistically associated with implant failure. Conclusion: Within the limitations of this retrospective study, the results suggest that there are risk factors associated with maxillary posterior implant failure. Implants placed in areas with inadequate residual crestal bone height that required sinus augmentation were statistically associated with implant failure. Keywords: dental implants, implant failure, posterior maxilla, predictors, retrospective cohort study, risk factors