These are far easier to remove than most people give credit for. I have heard everything from 10+ minutes of drilling, to buying expensive zirconia burs. These are all insane options when there is a very easy, cheap solution.
Just for fun I timed one I removed today, full zirconia crown of about 2mm thickness. 16 seconds total to cut, 3 seconds to apply spread pressure to crack and remove. Under 20 seconds total to remove the crown in total. It too me longer to remove the cement on the tooth.
All you need is a FINE diamond (red) of your preferred shape. I like the 856-016 barrel. Basically what you want is something that just barely fits your crown spreader or screw driver. Lots of water, decent pressure, and just cut.
Why does this work? Zirconia will destroy large diamonds on course burs, the adhesive layer just breaks them off. However, fine diamonds don’t have this issue and will actually CUT zirconia. The remaining course diamonds will get clogged quickly as well. Think of zirconia like plywood, the sawdust created from cutting it will get everywhere. Fine diamonds are small enough to not get clogged if you use adequate water.
Zirconia specialty burs – If you look with a microscope, a “zirconia burr” has almost exactly the same size/shape diamonds as a regular fine diamond burr. Like a lot of things in dentistry, they just repackage it with a new name and charge three times more.
This also works with old course diamonds that have been worn down slightly if the wear is in loss of diamond size and not quantity. For me though, I prefer just to use a new fine diamond and not waste the time trying to sort “old” vs new black diamonds and always have a consistent cut.
So next time you see a zirconia crown you have to cut off, take a breath, pull out a fine barrel diamond, and cut it off faster than any other material….all without buying something new or fancy.