Fatigue testing is used in implant dentistry to determine the strength and longevity of an implant system. The governing standards are ISO 14801 – Dynamic Fatigue Test for Endosseous Dental Implants and U.S. FDA Class II Special Controls Guidance Document: Root-form Endosseous Dental Implants and Endosseous Dental Implant Abutments. Generally, larger diameter implants with thicker walls have higher strength and fatigue life than smaller diameter implants of the same material. In addition to the diameter size, the material type plays a major role in increasing the strength and fatigue limit of implants. The ability of titanium and titanium alloy to resist corrosion is a result of the formation of an insoluble and continuous titanium oxide (TiO2) layer on the surface (Figure 1). The titanium oxide layer prevents oxygen penetration, protects the material from any impurities and permits a compatible layer of biomolecules to attach. The excellent biocompatibility of titanium and titanium alloy is the result of the nature of this surface layer.
All BioHorizons titanium implants and prosthetic components are made from Ti-6Al-4V ELI (Grade 23), a higher-purity (“Extra- Low Interstitial”) version of Ti-6Al-4V. The lower limits of iron, carbon and oxygen (Table 1) improve ductility, fracture toughness, and fatigue crack propagation. This alpha-beta titanium alloy has superior damage and mechanical properties compared to pure titanium and standard grade Ti-6Al-4V. In comparison, Commercially Pure (CP) titanium comes in 4 Grades. The difference between Grade 1, which is fully annealed, and Grade 4 titanium is the amount of cold work performed to increase the strength (Table 2). While the tensile strength of CP titanium can be improved by a cold-work process, this procedure makes the material more brittle. Because of the complex loading found in implant dentistry, brittle failure of higher grades of CP titanium must be considered.
Figure 1. Formation of an insoluble titanium oxide layer on the surface of metal titanium
Table 1. Ti-6Al-4V ELI is a higher purity version of Ti-6Al-4V for improved ductility, fracture toughness and fatigue crack propagation.
* The percentage of titanium is determined by the difference
Table 2: Ti-6Al-4V ELI produces Ultimate Strength and Yield Strength greater than all 4 Grades of CP Titanium