Is there an expiration date for a crown?


The other day one of my most curious patients   asked " Is there an age when a crown should be redone?" I answered no, not really, but she suggested I write a post about this. The truth is there is no simple answer. I actually don't have a hard and fast rule about when a crown needs to be redone. Sure if I can detect recurrent decay or can get a small tip of my dental explorer wedged between the crown margin and its tooth, I will often suggest replacing a crown. In other cases, it can be difficult to figure out what is going on underneath an older crown. Crowns are radioopaque so dentists can't really see whats hiding underneath on a radiograph.

Sometimes when I have occasion to remove an older crown that has been functioning well I can detect a partial washout of my dental cement around the terminal one mm or so of the crown. When this is observed the tooth adjacent to the washout may even show some decay present .

Traditional dental cements have some water solubility and the gap between the crown margin and tooth is in the order of twenty microns or more. Even microscopic gaps can allow some wash out over time and if a patient is prone to decay these older crowns can develop recurrent decay in some spots that may not be detectable until decay becomes extensive.

So this leaves dentists and their patients with a quandary. What should be done with very old crowns (over fifteen years old)? I tend to leave them alone, unless there is an additional reason for replacement. Often as a crown ages the gingiva recedes away from the margin of the crown and some  patients do experience adjacent recurrent decay adjacent to their crowns. Some crowns eventually develop fractures of their porcelain and some metal crowns just "wear out" ( the metal on the occlusal surface develops perforations). These can all be a good reason to recommend a new crown. Another reason to replace a crown is esthetic. As people age the teeth adjacent to a crown can darken but most crowns do not. Actually some actually lighten, since some of the pigment in extrinsic glazes can wear off over time. Also when the gum recedes, often an unaesthetic rim of metal can be observed at the terminus of a ceramometal crown and patients  find it unaesthetic.

Newer composite cements are less prone to washout, but time will tell how they will hold up.  Some of the earlier composite cements have show some tendency to degrade over time ( at least in their adherence to the underlying tooth structure).  As to the answer to my curious patients question, I tend to leave crowns alone if I have no evidence a problem, regardless of their age. If it ain't broke, I don't fix it is my standard line.  Not all dentists feel the same way and some may advocate replacing older crowns if a patient can afford it. I can't say with certainty that they are wrong or right, but if a patient is interested in replacing older crowns or bridges I might be inclined to go ahead and redo them with a more modern and better looking version. I really do  not have a hard and fast rule where older crowns are concerned.  Usually I discuss it with my patients and explain that  some older crowns may indeed have some hidden problem but I don't advocate replacing all older crowns especially when many of my elderly patients have a number of crowns that are over 15 years old.

I should add that for the most part my approach works well, but on occasion, I do find an older crown has had ongoing undetected recurrent decay and when this occurs for one of my patients who has a number of older crowns, I am look at these aging restorations with more suspicion and may replace ones that I suspect could be at risk as well.  Patients who have a higher caries risk  and have older crowns often have a higher rate of recurrent decay and should be handled in a different manner than a patient who rarely experiences decay.

from Ask Dr. Spindel - http://lspindelnycdds.blogspot.com/2019/01/is-there-expiration-date-for-crown.html - http://lspindelnycdds.blogspot.com/

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