Multivariate study of factors influencing primary dental implant stability

Objective: The purpose was to determine by multivariate analysis in a large series of dental implants the variables associated with primary endosseous dental implant stability (DIS). Material and methods: A 10-year retrospective study was conducted of 1084 Branemark (R) implants placed in 316 patients. Clinical variables (age, gender, smoking habit, and periodontal status), implant diameter, implant length, and Periotest (R) values (PTVs) were analyzed in bivariate and multivariate studies in order to determine their influence on DIS, using a cut-off PTV value of -2. Results: The site of implant insertion showed the strongest association with primary DIS failure among the study variables. Implants in the anterior mandible had a 6.43-fold lower risk of primary DIS risk vs. those at other sites [95% confidence interval (CI) 3.28-12.61], and implants in the maxillary had a 2.70-fold higher risk of primary DIS failure vs. those in the mandible (95% CI 1.82-4). Among other variables, females had a 1.54-fold higher risk of primary DIS failure vs. males (95% CI 1.88-2.22) and implants < 15 mm in length had a 1.49-fold higher risk of failure vs. longer implants (95% CI 1.09-2.04). Conclusion: According to these findings, primary DIS failure is more likely in females, at sites other than the anterior mandible, and with dental implants shorter than 15 mm, at least when non-threaded titanium implants are used. These data may be of value in the identification of patients at a high risk of primary DIS failure with immediate implant loading.