Sunday, August 2, 2009

Can a permanent crown be altered once it has been cemented?

One of my front teeth had to be replaced with a permanent crown. As a result, the crown stands out and is really noticeable. It is quite bulky in appearance in comparison to my other teeth. Could it be reshaped somehow?

Can a permanent crown be altered once it has been cemented?
Hi..While reshaping an seated crown is sometimes tried, it shouldn't be. The usual amount of grinding on the veneer face of the crown to effect a noticeable change, leaves the veneer material susceptible to easy staining and the overall appearance is seldom ever even close to what it should be. Unless your natural tooth was already way out front before the crown was put on, there is no excuse for it to look that way now. The dentist owes you a new crown made right. Don't take excuses, if your natural tooth was in good alignment before it had to be prepped for a crown, either the DDS failed to remove enough tooth structure to give the Lab Tech enough room to create the crown properly, "OR" the Lab Tech screwed up, either way your entitled to have it done correctly...Good luck and I wish you well.
Reply:Yes it can, but I'm not sure how they do it I heard they have to pull it out like a tooth but they somehow are able to melt the cement 1st. Like drill a hole in the tooth melt the cement, then pull it out. They will have to make a new crown but it can be done. But say it's not painful.
Reply:I'm a dentist.





First off, it is common practice for the doctor to provide you with a mirror so that you can see the crown in your mouth before he/she cements it in. If the doctor gave you a mirror and you approved the cosmetics and fit, then you bear almost all of the culpability. If not, then the doctor owes you a new crown.





Often (but not always), bulky crowns are the result of someone not doing their job properly.








Preparing a tooth for a crown, believe it or not, is not as simple as it sounds. The ultimate goal is to have a prosthesis that is the same size as a natural tooth. This requires the doctor to adequately reduce the size of the natural tooth on which the crown will be placed, and for the lab tech who makes the crown to produce a crown that is not too thick. Along the way to achieving this goal, there are some numbers to consider.





A typical crown prosthesis is made of a dark gray metal substructure (i.e. "coping") covered with tooth-colored porcelain.





Metal, being the stronger of the two materials, need only be 1/3 to 1/2 millimeter in thickness. Hence, if you were having a gold or silver crown placed on your tooth, the doctor would only need to remove 1/3 or 1/2 millimeter from the surfaces of your tooth. Porcelain, on the other hand, must be (ideally) 1mm to 2mm thick. On an area where the porcelain will endure biting forces, 1.5 to 2mm is required. On areas where no biting forces are required, 1 to 1.5mm will do.





Sound complicated? There's even more to consider! Getting a crown to look like a natural tooth requires the use of different kinds of porcelain. In case you didn't know, the outer layer of your teeth (i.e. the enamel) is not completely opaque (like a white coffee mug). It is translucent. This means that some of the incident light hitting your teeth bounces right off the surface of the enamel while some of the light passes part-way through the enamel before bouncing back. This is why your teeth have somewhat of a pearly appearance rather than a matte appearance (i.e. like a white coffee mug). In order to duplicate this pearly appearance, the lab tech must use different kinds of porcelain in different areas of the crown. There are completely opaque porcelains, bulk/shade porcelains, and there are translucent porcelains, and a shiny glaze that gives crowns their gloss. They are applied to the crown in that order...ideally.





Opaque porcelains must be laid down first against the metal coping in order to hide the dark gray color of the metal. Translucent porcelains cannot accomplish this. It only takes 1/2mm of opaque porcelain to cover up the metal.





After the opaque porcelain is laid down, the more tooth-like porcelains can be laid down. As you can imagine adding more porcelain means adding bulk to the crown prosthesis.





But what if the doctor only reduced the tooth by 1.5mm everywhere? Well, the lab tech has a decision to make: either 1. keep adding porcelain to make the crown look naturally translucent but at the same time too bulky, or 2. limit the amount of porcelain he puts on the crown in order to make the crown shaped and contoured like a natural tooth, while at the same time resulting in a crown that is not adequately translucent.





Now, it is also possible that your crown does not have a metal coping. Instead, it may have some sort of white ceramic coping, which makes achieving cosmesis easier...although the same considerations as I mentioned above must still be made.





Everything I've described above addresses what can happen if the doctor does not adequately shave down the tooth. This is a very common occurrence, I am sad to say.





Now, it is also entirely possible that the doctor adequately reduced the tooth and the lab-tech simply did a lousy job of making the crown. That is also a very common occurrence, I am also sad to say.





So, can your crown be adjusted, you ask? Not without drilling away the the glaze and the translucent porcelains, which will negatively affect the appearance of the crown. How much it affects the appearance of the crown depends on how much of each type of porcelain was laid down, as well as how much needs to be drilled away.





Let your doctor give it a try. The cosmetic result may turn out to be adequate. If you don't like it, he/she can always cut off the crown and get you a new one.





Again, this is why you should have seen the crown in a mirror before it was cemented in. That's why I do it for all crowns that are to go in cosmetic areas--so that the onus is on the patient should they be unhappy with the cosmetic result.




hotels reviews

No comments:

Post a Comment