I’ve been firing ceramic for over 15 years. Before I was a CEREC user, I used to hand-stack my own ceramics on many of my restorations. It wasn’t the most efficient thing in the world, but I was able to gain a wealth of knowledge to the art/science of stacking ceramic.
One thing that I learned is that you MUST have a high quality oven that has a vacuum. The old saying of “getting what you paid for” never rang truer. Dental ceramic ovens are highly precise equipment that are able to control very high temperatures in a fast setting.
An oven that I cannot recommend more, is the Ivoclar Vivadent CS oven. It is extremely efficient, and preprogrammed for Ivoclar Vivadents CAD/CAM materials: Empress CAD, Emax CAD, and their respective glazes. The best feature of the oven is its simple use for doctors that are not up to speed with modifying their firing cycles. It is as simple as hitting a button and the oven does the rest.
There may be cheaper ovens, but none of them works as seamlessly in the CAD/CAM dental office! Firing EMax CAD works the best with this oven, and I use one myself.