Sameer Puri D.D.S. There have been lots of discussions over the years regarding the shrinkage of e.max restorations out of the oven. The typical complain is that “My contacts were great during try in but after firing, I had open contacts.”
If this sounds familiar, then likely there are two possible scenarios to the apparent shrinkage. 1- Calibrate your oven. If your oven is not calibrated properly and instead of 840 degrees, your restorations are firing at 842 degrees as an example, then you will have more shrinkage than what is planned for. 2- Ensure that you do not have large unsupported pieces of porcelain. The larger the mass, the larger the potential distortion if all things are not supported properly. According to the manual by Ivoclar, there is .2% shrinkage and that shrinkage is already taken into consideration by the software. "CAD/CAM processing As densification of about 0.2% occurs in IPS e.max CAD during crystallization, this factor has been taken into account in the respective software of the tested CAD/CAM system. Consequently, the milled IPS e.max CAD restorations demonstrate a high accuracy of fit after crystallization. The fabrication steps are described in the directions for use and user manuals of the different CAD/CAM systems. The instructions of the manufacturers must be followed” So support your restorations well with Object Fix, calibrate your oven and ensure that there are not large masses of emax unsupported. These things can potentially lead to unintended distortion. But normally, one should experience no dimensional change whatsoever that will affect the fit and the finish of the restorations with e.max.
