Polishing Zirconia Crowns
Technical advisor and CDT Tony Megale shows you how to make occlusal adjustments on a full-contoured zirconia crown. Tony takes you through the steps and tools used to achieve the required high luster.
The Importance of Polish
In its unpolished state, zirconia is highly abrasive and will cause significant wear to the opposing dentition. When zirconia is polished correctly, it creates minimal wear on the opposing teeth.
If a zirconia restoration requires adjustment in the mouth, re-polishing can be a time-consuming task to do correctly. Before adjusting the polished zirconia, if only minimal adjustments are required, it’s worth considering an adjustment to the opposing dentition instead.
What About Glaze?
Some other labs may only glaze the occluding surfaces of their zirconia, but glaze can wear off quickly and once it does, the highly abrasive zirconia is exposed. When properly polished, zirconia retains its polished surface indefinitely. O’Brien Dental Lab produces all of its zirconia restorations with a thoroughly and properly polished occlusal surface.
What The Experts Say
According to Dr. Gordon Christensen, zirconia should not be glazed because “research has shown glaze quickly wears and roughens which wears opposing dentition” (Christensen, 2014).
Christensen, G. (2014). The Zirconia Revolution: Here to Stay or Not?. Gordon J. Christensen Clinicians Report, 7, 1-2.
Today we’re going to be talking about polishing full-contoured zirconia crowns after making occlusal adjustments. Keep in mind, if looks like only minor adjustments need to be made, you can consider adjusting the opposing dentition before altering the zirconia.
You will also want to ensure that the patient does not close down heavily on the crown while you are checking the contacts and occlusion. You only want very light occlusal contact until the crown has been cemented.
It’s very important to restore the zirconia to a very highly polished luster.
If you do need to make any adjustments to the zirconia crown, it’s important to know that once the surface of the zirconia has been roughened, it will not become smooth over time. Rough zirconia will cause excessive wear on the opposing teeth so it must be avoided. Highly polished zirconia, however, has minimum wear on the opposing tooth structure.
This is why it’s important that once you have altered any of the polished surface of the zirconia crown, that you make sure that all the roughened areas are mechanically smoothed utilizing rubber wheels and rubber points. You must then finish with polishing paste to achieve a high luster.
The occlusal surface of any zirconia restoration should never be glazed.
There are several great polishing systems available such as Dialite® ZR rubber wheels and rubber points, Ceramo-Dotz, and ZirconBrite polishing paste.
All these polishing systems can be used, chairside, for roughed zirconia, as well as e.max, PFMs (porcelain fused to metal) and composite restorations.
When reducing high points on a zirconia crown, use a Dialite® ZR rubber wheel, or a football-shaped finishing diamond to make these adjustments.
Once the occlusal has been adjusted use a medium polishing wheel, or a medium polishing point to shine and remove all the roughness from the surface of the zirconia crown.
Next utilize a fine polishing wheel or a fine polishing point to high shine the entire occlusal surface, making sure there is no rough areas remaining on the crown.
The last step is to use a Ceramo-Dotz point or a ZirconBrite polishing paste to bring the zirconia surface to a high luster. Then clean and cement.
Something to be cautious of is that excessive pressure with a handpiece or heat generation can cause flaws which can lead to propagation of cracks and even failure of the crown during this process.
And as always, we’d be more than happy to re-polish the crown for you at the laboratory.