Cooling Is the Key to Faster Sintering
Zirconia laboratory increases production by decreasing post-processing time
By Nannette Boyd, CDT
This year Derby Dental Lab will celebrate its 30-year anniversary. As “early adopters” of zirconia and CAD/CAM technology in dentistry, we have been milling and sintering zirconia restorations in-house for more than 15 of those years. In 2001, we purchased a zirconia system, which at the time was CAM technology only, and began evolving our methods with new materials and machinery.
It’s hard to believe that we were able to be successful and productive with a milling time of more than 35 minutes for a single crown and 80 minutes for a 4-unit bridge, plus a sintering unit that could manage only 20 to 30 units per day. It took us a few years, but by 2008, our zirconia copings and crowns accounted for 25% of our fixed restorations, while today that number is nearly 90%.
Clearly, new materials and milling processes contributed to our increased production, but what has remained almost unchanged in the zirconia world is the post-processing—the sintering of the material. There have been enhancements in furnaces and heating elements, as well as some attempts to speed up that process like the microwave approach, but overall we have all come to accept the 6 to 8 hour sintering process as normal. Fortunately, most zirconia on the market today will allow for a “speed sintering” cycle of a small batch of single units and provide recommended heating programs, which we have utilized with great results. But while the speed sintering cycle achieves the final sintering temperature at a faster rate and shorter hold time, the cooling process takes just as long as the 6 to 8 hour programs we run overnight. So, unfortunately, the “speed” of these programs is dictated by the cooling of the muffle.
We recently found ourselves in the market for a new sintering unit and decided upon the new SinterPro from Whip Mix for a number of reasons. First and most importantly, the reliability and durability of Whip Mix equipment are proven. The unit also offers several unique features that were key to our decision, including the ActivCool feature that allows for controlled cooling of the muffle and a large muffle size, which can accommodate stacking of multiple trays for higher throughput of sintered units.
The SinterPro features 30 user programs, plus four stages, which optimize program flexibility. Similarly, having both a short tray for single units and short span bridges and a deep tray for other bridges gives us added production flexibility. Its ActivCool feature offers three cooling methods—Natural Cool, Controlled Cool, and Fast Cool—so we can control the cooling speed our zirconia needs.
With the Whip Mix SinterPro unit and its ActivCool feature, we can have rush cases sintered and ready for final finishing in just a little over 3 hours, and at the end of the day are still able to load up to four trays with 60+ units for the standard overnight sintering cycles. Although the SinterPro has only been in our production line-up for a short time, it is already proving itself to be a consistent, reliable, high-quality piece of laboratory equipment.
Disclaimer: The statements and opinions contained in the preceding material are not necessarily those of the editors, publisher, or the Editorial Board of Inside Dental Technology.
About the Author
Nannette Boyd, CDT
Derby Dental Lab