Innovative development of dental alloys for state-of-the-art technologies

The focus of this blog post is primarily on alloys that are used in subtractive manufacturing – an area that MINDFAB also covers. While there is a wide range of PM (precious metal) and NPM (non-precious metal) alloys for casting alloys, the choice of alloys for subtractive (and also additive) manufacturing is much more limited. Only a few pioneers, such as Hafner with gold milling or CADdent with their revolutionary Gold LaserMelting technology, have brought PM alloys into the digital era.

Since the translation of PM from analog to digital technology has little appeal in the industry, this trend suggests that the share of PM alloys will continue to decline in the future. For this reason, MINDFAB does not currently offer PM alloys, as they are difficult to integrate into the digital workflow. However, indirect approaches to solutions exist, such as the use of cast material in 3D printing – stay tuned.

The classification as a non-precious alloy is basically made for any metal alloy without precious metal. In the dental context, however, this term is closely associated with cobalt-chrome (CoCr) alloys, which are also known as “dental steel”.

Although titanium alloys are also included in non-precious alloys, the term “non-precious” is mainly associated with cobalt-chrome in the dental context. This can easily cause confusion among non-dental technicians.

NEM alloys developed specifically for casting technology have been optimized and modified for use in subtractive manufacturing. In the case of cobalt-chrome alloys, the cobalt content varies between 60 and 68%, depending on the manufacturer, and the chromium content between 25 and 30%. Either molybdenum (Mo, 5-7%) or tungsten (W, 8-9%) is added as a significant minor component. The processing of other alloys by means of milling technology is rarer; here, titanium alloys – irrespective of the degree of purity – are particularly worthy of mention.

With these, water cooling is necessary and veneering is more difficult. However, the biocompatibility of these alloys is outstanding, which is why they are used in the field of implant prosthetics. In this context, we recommend the use of MINDFAB’s alloy, FAB Titanium G5. This is a Grade 5 alloy, which has an ideal combination of biocompatibility and mechanical properties.

In contrast to cast alloys, milling alloys must fulfill one thing above all: they must be easy to mill – and not with large industrial milling machines, but with the smaller and less expensive models in the dental sector.

The quality of the milling results with milling alloys is significantly influenced by the thermal post-processing of the milling blanks, in addition to the chemical composition, which is adapted in comparison to the casting technique. Each manufacturer has an individual process for this, which ensures consistent quality.

Likewise, the method of manufacturing the blanks, whether individual casting or ingot casting – in a so-called mold – has an influence on the properties of the alloys. Blanks from ingot casting generally have a more homogeneous structure, due to slower cooling. FAB Cobalt-Chrome T4 is produced in this way and therefore exhibits more consistent properties than blanks produced by single casting.

The FAB Cobalt-Chrome T4 alloy contains 6% molybdenum. This admixture gives the alloy a certain softness, making it particularly suitable for smaller milling machines with lower spindle power. But paradoxically, this does not necessarily mean that CoCr-Mo alloys are also advantageous in terms of tool life. The lower hardness of this alloy means that it is more prone to smearing and causes the cutting edges of the milling cutters to stick together more quickly. In contrast, this problem does not occur with the “harder” CoCr-tungsten alloys. However, this variant poses another challenge: if the blank used is not absolutely carbon-free, tungsten and carbon form tungsten carbide.

Since this technical ceramic is one of the hardest materials of all and is therefore used in high-quality carbide tools, it has a counterproductive effect in blanks as an impurity and quickly leads to tool breakage. However, when CoCr-W alloys are truly free of carbon, they offer mechanical properties that are superior: Yield strength, tensile strength, and maximum elongation at break are higher than CoCr-Mo alloys. Therefore, restorations made from these alloys tend to be designed somewhat thinner-walled. Currently, MINDFAB may not yet carry a carbon-free CoCr-W alloy in its range, but who knows what the future holds? This possibility is still open and could soon provide for exciting developments.

The choice of alloy for milling and veneering depends on individual preferences. The veneering properties are largely controlled by the chromium component. Oxide formation not only passivates the chromium on the surface, but its oxides combine well with the main component of veneering ceramics, SiO₂.

The molybdenum or tungsten content, on the other hand, affects the veneering only slightly. It is important that the coefficient of thermal expansion (CTE) of the alloy matches the veneering ceramic to avoid cracks. Slow cooling helps to minimize temperature differences and reduce unwanted stresses.

The world of dental alloys at MINDFAB is characterized by our commitment to continuous improvement of your added value. Our many years of experience enable us to apply our expertise to serve the industry. With a clear view of your requirements, we work to develop suitable solutions for our customers.

As a reliable partner, we are at your side to make your health care business a success. Trust MINDFAB – your reliable provider and expert in the dental industry.