What are sinter beads made of? Are some inferior to others? Why such a huge price difference between brands? Why two different sizes?
There are two types, alumina beads and zirconia beads. Alumina beads work but not as well as the zirconia beads. There are 2 different ways of making the zirconia beads. From these two methods, there are either pearly beads or chalky beads. If you are using white zirconia, either bead type will usually work just fine. However I have heard that if you are sintering shaded zirconia you must use pearly beads to keep the zirconia from forming white spots. For some reason the chalky beads seem to absorb into the colored zirconia, causing white spots. While some people have told me they have had no problems with using chalky beads and shaded zirconia together, many labs have.
Smaller 0.5mm beads are good for bridges as they give you even sintering. The 2mm can be used for any restoration.
Price difference depends on the purity level of the zirconia sintering beads. The more pure the more expensive they tend to be.
Hope this helps. If you like, call me and I can provide more details over the phone.