Hans-Joachim Burkhardt
Master Dental Technician
Germany
Every dental technician has at some point come into contact with waxes from the German company Renfert from Hilzingen, a family business with tradition, which also has obligations. The name Renfert is synonymous with high and consistent quality, reliability, and this over many decades. Renfert waxes are only a small part of the product range.
The recipes for the waxes are of course well hidden, but this much is known:
They consist of natural waxes, paraffins, natural and artificial resins, colour pigments and adjusting agents for hardness and melting temperature. Sometimes more than 20 different substances are alloyed to form useful, finely tuned materials. For development and quality control there are specialized wax chemists who combine raw materials to the desired end product. It is strange that there are dental technicians who prefer to melt their own mixture.
Dental waxes are high-performance materials that must be handled accordingly to take full advantage of their properties. Overheating is the biggest problem here, and today this can best be regulated with electric probes. Even soot from the Bunsen burner can cause undesirable colour effects in pressable ceramics.
Renfert waxes have become indispensable in our laboratory. Whether it be casting and modelling waxes, finished wax parts, waxes for model casting, wax wires or waxes that are available in several shades for training to better understand the function of the tooth – Renfert has the right product for every application.
Renfert goes digital.
In the meantime, the classic method of modelling and casting has been replaced to a large extent by digital production methods in many laboratories. Nowadays, more and more people are modelling digitally and milling the mould from plastic or wax blanks, which are then cast or pressed. The advantages are clear: reproducibility, perhaps less time required and consistent quality of the object with little rework.
Renfert’s many years of experience give it a big head start in dental waxes. Nevertheless, after long market studies and product analyses, it has only now been decided to offer the digitally equipped laboratory a corresponding product, the “EASY blank wax”. Since there are already a lot in the market, the first question is why another supplier is needed. But thats what should makes you curious, because if Renfert comes up with it now, it must be something extraordinary!
What do we expect from our millable waxes:
- Does it fit into our clamping system and how can it be attached? That is actually a succinct question. But it becomes important when waxes shrink, are not temperature-stable or are simply too soft.
- Can I use my usual milling cutters or do I have to buy my own milling cutter set? Single or multiple cutters, carbide or diamond?
- Which strategy do I have to use for milling, do the cutters stick together, do I have to cool or lubricate? Can I use my extraction system or do my filters stick?
- Can I add something by hand?
- Does it burn without residue?
Question after question. Renfert has enclosed a 5-page questionnaire on the test material to answer these and many other questions. They obviously take the product very seriously.
To make a long story short: We have handled the Renfert wax blank with our milling machines just like all other soft materials – the same milling cutters and the same milling strategy as for zirconium and sintered metal. The milling cutters are 2-edged diamond coated and we mill dry. Surprisingly, there were no streaks or lumps, instead clean small crumbling chips that were easily picked up by the suction system. The result was accordingly. The surface obtained was smooth and the edges sharp, as far as the milling strategy allowed. The cutters also remained clean.
We removed the ridges of the milling cutters with a carbide tip (Lindemann milling cutter) and then finished them with HM milling cutters (Img. 1). All toothings can be used which are also suitable for other soft materials (Img. 2). Thinning of the crown margins also works very well because the wax has sufficient stability. We even assume that we can reduce the angle and thickness of the margin area considerably.
Img. 1
Img. 2
The chosen blue color is homogeneous through and through. So it is obvious that the wax quality is the same and there is no segregation during production. Distortions due to different mixtures should therefore not occur. Tests have shown fits in larger objects within the range of what is technically possible. Layer thicknesses can be easily recognised by the coloring, which makes it easy to improve the milling result.
Occlusal can be refined as desired, either by scraping or by waxing up with modelling wax. For all those for whom milled crown margins are not precise enough, the correction by removing and reapplying cervical wax remains.
Sprueing of casting canals, embedding and casting or pressing does not require any adjustment of investment material or expansion values. At best one does everything “as usual”. However, there is a small downer. The wax – like most casting waxes – cannot be scanned. This is probably due to the residue-free combustion, that is why no clouding substances as for example zinc oxide or titanium oxide are allowed to be contained. In this we also see the difference between modelling waxes and casting waxes. Designated scanning waxes contain a larger proportion of opacifying agents.
The cast or pressed workpieces did not show any reactions with the investment material. The surface of the castings was as we had embedded them. There were no inclusions and no distortions or other changes in shape could be detected (Img. 3 and 4). Feguramed One-micro and C130MO as well as Class 4 triple-bed investments were used for casting. Zubler Concept Vest with only a very low reaction layer and JP-Vest without reaction layer were used for pressing. All, except C130MO, were used in the Speed process.
Img. 3
Img. 4
Of course, we compared milled parts from Renfert wax blanks as well as the finished products with work from blanks of other manufacturers and found first-class results throughout. Even if we lack the possibilities of a more detailed examination in the laboratory, we still have a very positive impression.
In summary, it can be said that Renfert wax blanks combine the following properties: smooth surfaces, high edge stability with the usual milling strategy, clean objects and milling cutters, correctable with modelling waxes, suitable for speed casting or speed pressing. A good product at a fair price.
