AIM OF THE STUDY For more than twenty years the IMZ-system has been in clinical use, since 1995 modified as IMZ-TwinPlus. The aim of this prospective clinical trial was to analyse the success of the latter implant system, which is an automatically threading cylindrical titanium screw with a deep structured surface (Fa. FRIATEC AG, Mannheim, BRD). Investigated parameters were the peri-implant situation of the soft tissues, the bone loss and the rate of implant failure after a maximum period of 4.5 years of clinical use. MATERIAL AND METHODS From 1995-2000 sixty-eight patients were provided with a total of 278 IMZ TwinPlus screw implants for various indications (mainly alveolar ridge atrophy). 191 implants were inserted without any, 35 implants with a loco-regional and another 52 implants after comprehensive reconstructive osteoplastic surgery. 38 patients with 155 implants were re-examined using a standardised protocol to evaluate peri-implant hard- and soft tissue situation as well as the patient's subjective assessment of the treatment. RESULTS With a maximum of 54 months the mean observation period was 30 months. The implant failure rate has risen to 6% so far (n = 18 in 12 patients). Two patients bearing 7 implants have passed away. One patient with 4 implants was lost to follow up. 249 implants were still under function at examination, thus the in situ rate was 91%. The Kaplan-Meier survival rate after 54 months proved 91%. DISCUSSION To our knowledge there are at present no other data published on the survival rate of the IMZ TwinPlus implant system. The results of this study evaluate a survival rate similar to the classical IMZ cylinder implant and other implant systems for the analysed observation period. CONCLUSIONS After a maximum observation period of 4.5 years the IMZ TwinPlus implant system showed results in the range of other well-established implant systems. Designed to resist rotation of the superstructure the IMZ TwinPlus screw implant widens the range of indications in comparison to the classical IMZ cylinder implant system.