I have a question about the new BruxZir crowns that are being offered. Since I sell burs and cutting equipment a common question from a dentist using a new material is "How do I adjust this new material for occlusion?" or "How do I remove this old restoration?" I was having one of these conversations about the BruxZir material and the dentist told me that his lab advised to keep the crown about 1mm out of occlusion. The lab's reason for this is to help prevent opposing tooth wear from the super hard BruxZir material. I personally can't imagine that this approach would be anything but trouble down the road. Most likely causing eruption of the opposing dentition.
Has anyone else run up against this material? I'm curious if it is really as hard as the lab says it is and what you are advising your customers!
no experience with Bruxzir; if it is as hard as you claim then it will be a terrible material for use in the mouth. I have cut Zirconia well with a product called diagen from Bredent. It cuts smoothly, without chipping and no sparks! Its a lab bur-stone and I don't think it is intended to be used in the mouth.
Thank you for the help! The Diagen is a great bur! We sell something very similar here at Brasseler called the Porcela-Pro. Sintered diamonds like these will leave a nice smooth surface and yes...no sparking!
I'll keep researching more on the BruxZir. Do we have anyone from Glidewell on here?
Our milling center offers our own version of full contour zirconia restorations that we call Full-Z. Here's a link to a document we give our customers that lists a number of burs that we suggest for making any adjustments.
We use fine diamond burs and ceramic polishers depending on the amount of adjustment being made. SS White and Premier make some very nice, long lasting diamonds! (Critical when a zirconia is what you work on 90% of the time!)
I agree, 1 mm out of occlusion is a bit much. We're normally seeing 0.2mm or so out of occlusion.
Zirconia is an extremely hard material, but it's not so much the hardness as the roughness that affects wear on opposing dentition. Think of a metal file and a piece of soft pine. The metal file is definitely a harder material than the pine. The file has two sides, a smooth side and the side with the rasps or grooves. Rub the smooth side against the wood.... You won't see much deformation... Now flip the file over. The material hardness hasn't changed, but the roughness has. Now rub it against the wood... Definitely will see it wear down the softer material.
To my knowledge, there have not been any recently published studies to specifically address the wear of zirconia on tooth enamel. The preliminary data I've seen on studies currently in process show that the wear on opposing dentition by full contour zirconia crowns (Full-Z, Bruxir, etc...) that have been polished or glazed, is very comparable to that of traditional PFM restorations.
Zirconia is definitely a hard material.... When you hit it with a diamond hard enough, you WILL see the sparks fly! Water spray is critical when making adjustments with high-speed diamonds to keep the material cool and not induce microfractures. Not necessary with the polisher....
Chris and Mary,
Thank you both for your replies! The next time I am in a conversation with a doctor about adjusting a full contour zirconia crown I will definitely recommend the proper polishing tools. Chris - I like that you point out it's the roughness of a material that causes opposing tooth wear. This is a great reason to make sure that our customers polish their crowns correctly after adjusting!