Should You See the Tooth Under the Crown?

Question

I recently had a crown put on a tooth. Some of the tooth underneath remains exposed. I asked the dentist before it was permanently glued about it and was told it is okay and would allow me to clean the area better. The more I think about it, the more concerned I feel about it. Is it "good crown fit" to have the tooth exposed at the gum line?

John Schmid, DDS, LVIF · Answer

Utgrad,

	It really depends on what materials were used and where the restoration is.  Newer materials allow us to place all porcelain crowns / on-lays away from the gum line.  This is by virtue of the fact that bonds strengths of porcelain fused to tooth structure are a lot higher than those of conventional crowns cemented in.  With these bond strengths we no longer have to rely on mechanical retention to keep crowns in, meaning we don't have to remove as much tooth structure. 

	In the back it is common to have margins above the gum line when using these newer materials.  Not only is it more hygienic for the patient but it helps with isolation during the bonding process (which is very technique sensitive).  Sometimes the margin where the porcelain stops and the tooth starts can show.  This is not a problem if 1) it is totally closed and sealed 2) it does not show during conversation or smiling.

	Obviously in the front we want to hide margins either by carefully blending to the natural color of the teeth or by placing the margin at or below the gum line.

	The short answer is,  if it is modern adhesive dentistry in the posterior then it is fine and probably will help preserve gum health and prevent recurrent decay.  If not and you have reason to believe it is not an all ceramic/ resin restoration then you may want to have it looked at.

	 

	Hope this helps,

	John Schmid DDS LVIF

Norman Huefner, DDS · Answer

In general not placing crowns down or under the gum line is healthier for the tooth and gums, thus many dentists who try to conserve as much tooth structure as possible (i.e. do less drilling on the teeth) will oftentimes leave the margin (edge of the crown) above the gum line.  If done this way, it is often better done on back teeth that you don't see.  However, it is usually esthetically unacceptable to leave the crown margin above the gum line for both the upper and lower front teeth, teeth and crowns that can easily be seen when smiling.  With side teeth (mostly bicuspids), it may just depends on whether or not you see it.

	If a dentist plans on placing the margin above the gum line that is usually discussed with the patient to avoid misunderstandings and make sure the patient likes the what the crown looks.  As a matter of fact, most dentists will actually show the patient the crown and ask if is acceptable to them before cementing it into place.

Murray Bruckel, DDS (retired) · Answer

If it is a porcelain fused to metal crown, then the answer is no.  If its a non metallic crown and its in the back, then its ok

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