Every time I am sitting at my AC and move to the Mill Preview screen, I stare at the option to mill in Veneer Mode. I feel like a little boy in Catholic school about to do something wrong and Sister Mary Catherine appears and hovers over me, tall and imposing, ready to smack me on the knuckles if I even think about choosing Veneer Mode. Actually, it's really not that bad. Veneer Mode has its place and actually serves a very valuable role in providing the strongest, most intimate-fitting restorations.
Formerly Endo Mode, Veneer Mode is a user-defined option that eliminates overmilling and provides us with the thickest possible restoration. Let's first understand overmilling and then we can realize how Veneer Mode can get us into trouble.
Overmilling is something that the software needs to do to allow our restorations to fully seat. It compensates for preparations that are not able to be milled by the burs we have available to us. Therefore the burs will overmill some areas, resulting in porcelain that may be thinner than we want. This can affect the strength and the cosmetics of a restoration. Prepping properly is the way to avoid overmilling.
As we have said, Veneer Mode will override the software’s desire to overmill, and the result in a perfect world with a perfect CEREC prep is a nice intimate fit and the thickest porcelain as dictated by the design. Now, we all try to prep perfectly but we are fighting many obstacles. If we mill in Veneer Mode and the prep is not perfect, we will have a beautiful restoration that will not seat. So, what are our options? We want a tight-fitting restoration with minimal overmilling, but we also want it to seat fully, or it's worthless.
What I do with all of my anterior restorations is first to try my hardest to prep as perfectly as possible and smooth the prep as much as possible, removing any sharp transitions and angles. Then I throw caution to the wild, risk the wrath of Sister Mary Catherine and choose the Veneer Mode option. At try-in, I test the fit. If I bind and am unable to seat, I go back to the AC and at Mill Preview I choose the Model Box option and see where I am binding. Then, using a diamond bur on the high speed and copious water spray, I carefully relieve the binding areas.
In effect, I become the overmiller but just slightly. I relieve the spot as accurately as possible, occasionally several times until the restoration fully seats. This, I feel gives me the best of both worlds, a very precisely milled restoration that seats fully on the prep. Don't be afraid to mill in Veneer Mode for anteriors. Just watch your knuckles when you choose it.
John Adams on June 20, 2012 at 12:01 pm
Confession is good for the soul.
Jeffrey Caso (Faculty) on June 20, 2012 at 7:32 pm
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