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Why Did My Crowns Get Black Lines?

Face it: A crown or a veneer or a filling is an artificial material. We can certainly make improvements in your smile, but in so many ways, we cannot improve the original equipment. And a crown that looks great on day one, may not look as good ten years out.

There are several reasons that you see a black line around crowns:

1)      Crowns  fabricated from the 1970’s up until now were usually fabricated by applying porcelain over a gold coping – this was the state-of-the art. With time, as your gums have receded, the edge of the gold coping appears and you see a dark line. Sometimes, the color discrepancy is even worse because the yellow/brown tooth root is now visible. The latest crowns are all porcelain and this problem is much less apparent than in the past.

2)      No matter how precise our dental work is, a gap can occur between the tooth and the artificial portion. We are often talking about a gap that is no wider than 50-100 microns – that’s .05-0.1 millimeters). If bacteria get in the area and cause staining, the line will be very apparent. It’s especially visible if you have a high smile line

3)      Sometimes a gap will occur between bonding adhesive and the tooth. Again, stain infiltrates under the gap and this is visible.

So what’s the solution?

Usually, replacement of the crown/filling is the best solution. If you try to cover the line with a patch, it never looks quite right.

Let’s say that your crown looks fine, but the natural teeth have darkened with age. You might want to try bleaching the natural teeth to bring them back to the same color they were when you were “twenty something”.

And a dirty little secret: People who have invested thousands of dollars in their smiles will likely have to repeat the process 10 or 20 years down the road as they age.

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