Astra Tech and Branemark system implants:: a 5-year prospective study of marginal bone reactions

This paper describes the 5-year results of a comparative study between Astra Tech and Branemark system implants. The aim was to compare the systems primarily with regard to bone level changes, and also with regard to other variables of interest. Sixty-six patients with edentulous jaws were included in the study. Randomisation schedules were used to allocate the patients to the two implant systems. 184 Astra Tech implants with a titanium-blasted surface and 187 Branemark implants with a turned surface were used. The implants were inserted with a two-stage technique and the insertion followed the routines for the respective implant system. All patients were provided with full-arch fixed bridges. All patients were followed up with clinical and radiographic examinations from fixture insertion to the 5-year follow-up. The total mean bone level change in the upper jaw between fixture insertion and the 5-year examination was -1.74+/-0.45 mm at the Astra implants and -1.98+/-0.21 at the Branemark implants. The corresponding values for the lower jaw were -1.06+/-0.19 for Astra and -1.38+/-0.17 for Branemark. The major postoperative changes of the marginal bone level took place between fixture insertion and baseline. During this period, there was also a different pattern of bone remodelling between the implant systems. Between baseline (prosthesis connection) and the 5-year examination, the marginal bone level changes were small, with no difference between the implant systems. The implant stability was examined with the supraconstructions removed. At the 5-year examination, the survival rate for Astra Tech implants was 98.4% and for the Branemark implants it was 94.6%. The difference was not statistically significant.