It’s amazing what you can produce in a dry mill nowadays
Although we have two wet mills in the milling centre for abutments, bars, screw-retained cases and glass ceramics, we have five dry mills for all else.
‘All else’ is a growing list!
Milling wax in the digital lab
Wax is milled by most digitised laboratories, it’s difficult to match the results by hand.
Designing on screen means the coping thickness can be controlled, and the cement space can be ‘distributed’ to allow greater room around the occlusal or incisal edge, down to zero at the margins for a snug fit.
The wax is largley plastic, so unlike normal wax it remains rigid at room temperature, particularly important for bridgework.
The futures of Zirconia
Zirconia is increasingly popular and growing worldwide. When first introduced it had the strength and some translucency, but not enough to challenge traditional porcelain. But the material scientists went to work developing greater translucency and we now have pre-coloured zirconia available and even multilayer pre-coloured is widely available.
The latest development sees yet another type of zirconia: known as ‘3D’ this gives a strength gradient, a translucency gradient and is colour multilayered. This combines the aesthetics with more strength. Our own 3D Multilayer, called EXPLORE , has all the advantages of 3D but with added fracture toughness.
So you can design a crown on-screen, send it to the mill and with a little fissure staining and glaze the case is finished. Strength, translucency, colour and ease of manufacture, it is no wonder, full contour work has grown and grown. The pictures show a full contour all zirconia crown milled in one piece, on a Roland, roots as well!
This is a hybrid ceramic from Upcera, the largest zirconia manufacturer in the world. Other companies are offering Hybrids too. I believe Hybrids have a big future…just mill and polish for a great result! Unlike Lithium Disilicates, adding, adjusting and polishing (even after fitting) is simplicity itself.
Another material to save us time. Easily dry milled, pre-coloured to the Vita range, also available in multilayer. This is now a very popular material for temps.
Yes, it’s possible to mill models from this. It does take a long time to mill a model though. Probably not the best way forward!
Another new material
We have been testing a new material that could replace some chrome partials.
Launch was at the IDS in Cologne 2017. Ultaire has been developed by a major company in the US, Solvay, trials are ongoing.
Polyether ether ketone (PEEK) is another group of materials that are certainly tough, but again, easy to dry mill.
This is a another hybrid ceramic for inlays, onlays and veneers. There are several available, Vita Enamic is another well known example. Although part ceramic, a dry mill has no problem with it, as long as you use diamond coated milling burs
This is metal in disc form and can be easily milled. It has to be sintered either in an Argon atmosphere or under a strong vacuum in a special furnace. We have our own brand X-Sinter
Which mill is best for you?
So a large range of materials can be dry milled. If you wish or need to mill Lithium Disilicate you will definately need a wet mill, preferably one dedicated to this material. And certainly for Chrome Cobalt and Titanium a more substantial wet mill would be the essential choice.
There are reasons for considering a ‘universal’ mill and also reasons it is not an ideal solution.
Many of us have heard the word ‘futureproofing’, but that may not be a good idea. In essence, buy what you actually need may be a better approach, digitising the types of work you have now, rather than spending extra on a machine capability that you may or may not need in the future. But more importantly, always check on all the running costs to support your choice, these can really bite you and move valuable bottom line to your supplier. A recent purchaser of a large mill believed it was open in every aspect. That is until he needed to get his spindle replaced or repaired. The machine supplier had fitted a spindle with an agreement that replacement could only be only through them. This was unknown to the buyer. The cost was high with no repair/exchange offered at less than full price. Ouch!