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Advances in Milling Chrome Cobalt

Interestingly, the saying “If you have a hammer everything is a nail”  truly seems to apply to CAD CAM for dental labs. That said, companies developing mills feel they need to mill every indication and material possible. Understandably, the more indications the more viable the ROI and thus, the mill. That said, it’s important to recognize, when automating or milling an indication or material, what is the best manufacturing solution.

For some time I have been of the opinion that milling CrCo has not the best process or even viable for manufacturing frameworks from this material. We certainly know that milling is one of the most accurate of all manufacturing processes, however CrCo is extremely hard and thus requires heavy duty machinery and has a high tool cost. A recent advancement in automation includes SLM or Selective Laser Sintering for CrCo. This process requires expensive output equipment and results in a finished surface that has a roughness that is less desirable when compared to casting and milling. In addition, SLM margins are rounded, resulting in post processing to get just adequate marginal integrity. As you may know, CrCo is significantly harder than what would be desirable in a dental alloy, so finishing and polishing are difficult and time consuming. That said, until now there really was no real viable, high quality automated solution for most labs to automate CrCo frameworks and full crowns in house.

The recently patented development of Ceramill Sintron by Amann Girrbach (AG) now provides labs a cost effective process for milling CrCo on site. In fact, most any 4 or 5 Axis mill can be used. This presintered CrCo disc is almost wax like and is milled in most any dry 4 or 5 axis mill. Due to the presintered state and soft composition, tool cost is close to $0 and wear and tear on mills is minimal. Sintron is somewhat similar to our current zirconia processing. Mill time is about 15 minutes per unit. Post processing and spru removal is very quickly achieved with little wear to rotary instruments. Unlike SLM the final product has improved fit, margin Integrity and surface quality. Another inherent advantage of  Sintron, the post sintered hardness is about 2/3 that of cast, SLM  or milled CrCo making finishing and polishing of the Sintron less labor intensive. In fact, Sintron handles more like a cast gold alloy and is polished to a mirror finish. Indications include an economical full gold crown replacement and frameworks up to 14 units.

Sintron does require sintering after milling. The sintering must be done in an Argon atmosphere thus requiring a specific sintering furnace. The Argotherm sintering furnace from AG (available through CAP) sinters Sinton in about 6 hours.

Sintron discs are now available in 71mm and 98mm discs, several different thicknesses, and can be purchased from our online store: http://shop.cap-us.com/sintron/

CAP’s Milling Center will be making Sintron frameworks and copings available in February for a cost of $17.  Currently CAP is the only distributor of Sintron.

For more information on Ceramill Sintron visit: http://cap-us.com/products/ag-sintron/

or call 800-496-9500 (option 9)

Thanks for reading

Bob Cohen, CDT

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