Fatigue strength AS AN INDICATOR OF THE SAFETY OF AN ABUTMENT

6. March 2020

WHAT MAKES AN ABUTMENT SECURE?

The safety of abutments is influenced by several aspects. Here are a.o. to call:

• Mechanical properties,

• Hygienic properties.

By mechanical properties we understand topics such as:

• Choice of material or material properties,

• Compatibility,

• Design and construction guidelines,

• Best Practice in Strength of Materials.

In the area of hygienic properties, we take care of the “purity” of our parts upon delivery. This means that there must be no residues of auxiliary materials on the surfaces. We also ensure that there are no residues from the cleaning process. We prove this by validating special laboratories.

The material of our choice is titanium grade 5 (Ti6Al4V), which has proven to be suitable as an abutment material over many years. There are also components made from Ti6Al7Nb (often referred to as TAN). Compared to Ti6Al4V, the tensile strength is around 5% higher and the yield strength is around 2.5% higher. In fatigue strength tests according to DIN EN ISO 14801, we were unable to determine any difference.

We will deal with compatibility elsewhere.

FATIGUE STRENGHT IN ACCORDANCE WITH DIN EN ISO 14801

Dental implants, abutments and abutment screws are continuously and dynamically loaded over the course of “their life”.Virtually every movement of the jaw causes forces to be transferred into the bone via the crown, abutment, abutment screw and the dental implant. Among the various types of stress, this is an increasing stress. DIN EN ISO 14801 describes, among other things. the construction of an experiment that represents a chewing simulation. A combination of dental implant, abutment, abutment screw and a matching cap is dynamically loaded at 15 Hz (15 loads per second) with a defined force. The assembly is clamped at an angle of 30° to the direction of load. The dental implant is embedded in a special epoxy resin and protrudes 3 mm from it. In the experimental setup, the 3 mm represent peri-implant bone resorption.

The samples are loaded with a certain force until they fail or the test is terminated after 5,000,000 cycles. If a part or an assembly can withstand 5 million load cycles, it is considered to be operational. It then doesn't matter whether there are another 5 or 10 million load cycles. The results of the tests are Wöhler curves that provide information on the fatigue strength of a product or assembly.

HELIOCOS PRODUCTS IN COMPARISON

We test our products as well as the original products or products of our competitors. Our abutment is screwed together with our abutment screw and an original dental implant. In the comparative tests, an original abutment is screwed to the original dental implant with the associated screw. The same product groups and the same implant platform are compared.

We have carried out these tests for years because certain statistics have to be guaranteed. We tested a total of 17 combinations. Our products achieve at least the survival level of the comparable products. In the majority of the combinations, the Heliocos abutments have a higher fatigue strength than the comparable products.

For this reason we can say that, at least from the perspective of fatigue strength, our products are at least as good as the comparable products, but often significantly better.