Sandblasting fully anatomic lithium disilicate crowns with Renfert’s Basic quattro IS. A field report by Oliver Brix, Bad Homburg in Germany.
When you think about sand-blasting images of leftover investment material, dull or roughened surfaces and moulds spring to mind. But sand-blasting is much more than this. Because the more precise a sandblaster operates the more flexibly it can be used, like Renfert’s Basic quattro IS for example. In this field report Oliver Brix shows us how even occlusal surfaces of IPS e.max CAD crowns in a blue condition can be formed.
Sandblasting has become an integral part of the daily lab routine. There could be no removal of muffle traces in the casting and pressing techniques without sandblasting. Precise conditioning or removal of impurities also belong to the job of a modern sandblasting unit. However the precise preparation of occlusal surfaces of ceramic crowns through sandblasting is relatively unknown (Fig.1).
Sandblasting fully anatomic
01 A monolithic IPS e.max CAD posterior tooth crown after precise sandblasting. All fine anatomical details can be seen clearly.
02 The Basic quattro IS is robust, ergonomic and easy to use. A highlight is the large sandblasting chamber, which allows a clear view of the work at hand.
03 Several nozzles allow efficient working. Whether coarse or fine sandblasting, with different nozzles all tasks can be fulfilled.
04 The Cobra abrasive with a grain size of 25 μm is perfect for working on layered ceramics and monolithic IPS e.max CAD crowns.
Fissures and occlusal surfaces can be easily accentuated using a suitable sandblasting unit like the Basic quattro IS with a fine abrasive (Cobra, AL2O3, 25 μm), as well as a fine 0,4 to 0,6 mm nozzle (Fig. 2 to 4). We have been applying this process successfully in our lab for many years. (Fig. 5 + 6)
05 At a pressure of 2 to 3 bar fissures are tightened with focused blasting and cusp elements are blasted out. As the abrasive of the Quattro IS is dosed very precisely and it has no lead and follow-up times, material can be removed systematically. The special light in the sandblasting chamber which is part of Renfert’s “PerfectView” system, as well as a reduced dust development allow a clear view of the object.
06 IPS e.max CAD crowns ground from left to right with a Zenotec mini: Directly from the grinding machine, partly blasted distal parts (the difference can be seen clearly) and a “finished contoured crown”. The soft transitions and fine cavities show off the possibilities of sandblasting.
In order to apply this process successfully it is important to have a sandblasting unit without any lead and follow-up times that can begin and end the process immediately and precisely. This way it is guarenteed that only the surfaces that are to be treated come in contact with the sandblast. The Renfert sandblaster guarantees this with its “Immediate Stop” functionality (IS), that’s where the name Basic quattro IS comes from.
However, the modification of monolithic IPS e.max CAD crowns (before crystalization) using sandblasting is a new differentiated approach. With a little practice it offers a modern and efficient working process for posterior teeth. The sandblasting technique described here opens up completely new possibilities to optimize the CAD/CAM based fabrication and functional dental prosthesis. The fundamental idea is to add missing details to CAD/CAM fabricated posterior teeth using sandblasting instead of a rotating instrument (Fig. 8 to 14). The details of this technique are described in the image galleries.
07 Patient work: Seven IPS e.max CAD crowns (HT blanks) ground with the Organical Desktop. The approximate and centric, as well as eccentric contacts are refinished with a diamond grinder. It is generally recommended to prepare the external form, as well as the edges before crystalizing.
08 The occlusal surfaces are contured with 0,4 and 0,6 mm nozzles at a pressure of 2 to 3 bar. Centric contacts are left mainly unchanged and made smaller or given more clearance if necessary.
09 The IPS e.max CAD crowns were crystalized according to the manufacturer’s instructions (Ivoclar Vivadent).
10 The finished, color accentuated, fully anatomical lithium disilicate crowns after polishing.
11 This photo was taken with a diffuser in order to better highlight the sandblasted crowns.
12 Detailed view of the 3rd and 4th quadrants. With a little practice the sandblasting technique becomes an efficient and simple method to accentuate monolithic IPS e.max CAD crowns.
13 The integrated crowns in place. If you didn’t know how it was done you would never guess that the occlusal surfaces have been sandblasted.
The technique introduced here distinguishes itself through great rationality and precision. The combination of digital workflow and manual perfection offers a real alternative to the classic manufacturing process. Of course we must mention that a waxed up and pressed monolithic crown continues to be the standard, but……”who knows”……