The aim of this study is to present the clinical data from the use of implants that were placed and restored in four independent private dental offices. In part I, the survival rate was calculated and the failure causes were associated with some potential risk factors. In part II, the surgical and prosthetic complications were also recorded and associated both with failures and clinical factors. During 1990-2002 (mean observation 4.6 years), 1692 dental implants were placed and restored in 405 patients in 4 private clinics following the same treatment protocol. The prosthetic restorations included fixed partial dentures, single crowns, and overdentures. The results were statistically analyzed and survival rate probability curves were calculated according to Kaplan-Meier analysis. Part I: Seventy-four implants (4.4%) in a total of 1692 implants failed. The mean of time elapsed before removal of the failed implants was 40 months. The failure rate was higher in the maxilla in patients with metabolic diseases, in D4 bone quality, in smokers, and in patients with insufficient oral hygiene. Part II: Surgical complications happened to 65 implants (3.8%). Prosthetic complications appeared in 152 implants (9%). The overall survival rate (95.6%) in a period of 1 to 12 years is comparable to other studies. The early failures represented a high percentage of failures. Peri-implantitis was the main cause of late failures. The results of this study indicate that the use of implants in private clinics is a safe and predictable method for the treatment of partially or completely edentulous patients, if the proper clinical protocol is followed. The need of a severe recall program must also be emphasized.