Implant-abutment interface design affects fatigue and fracture strength of implants

Failures of implant-abutment connections are relatively frequent clinical problems. The aim of this study was to evaluate the influence of long-term dynamic loading on the fracture strength of different implant-abutment connections.

Six implant systems were tested: two systems with external connections (Brånemark, Compress) and four systems with internal connections (Frialit-2, Replace-Select, Camlog, Screw-Vent). Fracture strength was tested in two subgroups for each system: one subgroup with (dyn) and the other without prior dynamic loading (contr). Each subgroup consisted of eight specimens with standard implant-abutment combinations for single molar crowns. Dynamic loading was performed in a two-axis chewing simulator with 1,200,000 load cycles at 120 N.

Median fracture strengths in Newton (N) and 25th and 75th percentiles [in brackets] were: Brånemark: dyn=729 [0;802]/contr=782 [771;811], Frialit-2: dyn=0 [0;611]/contr=887 [798;941], Replace-Select: dyn=1439 [1403;1465]/contr=1542 [1466;1623], Camlog: dyn=1482 [1394;1544]/contr=1467 [1394;1598], Screw-Vent: dyn=0 [0;526]/contr=780 [762;847] and Compress: dyn=818[0;917]/contr=1008 [983;1028]. In some dyn subgroups, failures of the implant-abutment connection occurred already during dynamic loading: three specimens of the Brånemark and Compress groups and six specimens of the Screw-Vent and the Frialit-2 groups failed during dynamic loading. Statistically significant differences (P< or =0.05) in fracture strength could be found between groups with different connection designs.

Implant systems with long internal tube-in-tube connections and cam-slot fixation showed advantages with regard to longevity and fracture strength compared with systems with shorter internal or external connection designs.