Factors associated with the survival rate of 4,556 dental implants –a practice-based multicenter retrospective cohort study

Aim: the objective of the study was to evaluate the influence of systemic and local factors as implant and prosthesis characteristics on the survival rate of dental implants through a practice-based multicenter retrospective cohort study. Methods: the sample consisted of 1417 patient records, with 4556 implants placed. Dental records were analyzed considering patients who received dental implants in a period up to 20 years. The complete loss (removal) of the implant was considered a failure. Cox proportional-hazards models were used to evaluate the influence of variables (systemic - age, sex, smoking; local – arch region, previously failed site; implant - shape, length, diameter, thread form, insertion torque; prosthesis - load type, prosthodontics type) on the condition of failed implant. The Backward stepwise selection was then performed based on the probability of the Wald statistic. The measure of effect was the hazard rate (HR). Results: a total of 144 implants were lost by the patients (3.2%). The survival rate of the dental implants was 96.8% in a mean time of 5 years. For both Backward stepwise and Enter method, variables that negatively influenced the survival of dental implants were higher total medications (HR=1.511), male sex (HR=1.733), posterior (HR=1.903) and anterior (HR=1.991) maxillary region, previously failed site (HR=3.012), short length (HR=1.742), immediate load (HR=1.896), and overdenture rehabilitation (HR=15.761). Higher survival rate was observed for anterior mandibular region (HR=0.245) and medium (regular) diameter implants (HR=0.450). Age, total diseases, smoking, implant shape, thread form and torque variables did not influence the models. Conclusion: it was possible to conclude that either systemic and local patient factors or implant and prosthesis characteristics influence the survival of dental implants.