| Root form dental implants are a common solution used today to replace missing teeth. However current designs still suffer from a number of limitations. Angled abutments are used for incisors, where maximum human bite forces are normally 200 N. The aim of this study was to evaluate the mechanical performance of a novel dental implant system by fatigue testing straight and 15-degree angled abutments. It was hypothesized that the novel thread design will dissipate the load evenly throughout the implant allowing the system to withstand normal chewing forces. Implants with 4.2mm diameter were tested according to ISO 14801 in specimen holders tilted 30oand 25o, respectively, to illustrate worst case scenarios. Three straight and three angled abutment systems with screws torqued to 35 Ncm, were subjected to a load-to-failure test. This maximum load was decreased by 20% increments for cyclically loading implants at 2 Hz in air at room temperature until failure or run-out (2,000,000 cycles). Three implants were tested at each load to generate an S-N curve and endurance limit. Implant systems were then polished and etched to examine grain boundaries, determine the orientation of the original manufacturer cut and their potential effects on the mechanical properties of the implants' material (Ti alloy). Systems with straight abutments produced a mean load-to-failure of 603 N, an endurance limit of 121 N and a maximum bending moment of 665 Nmm. Systems with angled abutments yielded 487 N, 195 N and 906 Nmm, respectively. Microstructure studies showed a polycrystalline alpha structure with different grain orientations for the implant body and smaller alpha-beta structure for the abutment and screw. Cyclic loading was an initial study to evaluate the mechanical properties of the novel thread designed to provide sufficient area to dissipate the load evenly throughout the entire implant. The endurance limit of the angled abutment fell within the "safe" range, while the straight system showed a lower value. Surface treatment, diameter size and material enhancement through grain refinement may affect the strength of the implant construct. |
