Expert: Dr. Randolph Myerson - 12/22/2009

Question
I just took my 5 year old daughter for her regular dental check up.  Her teeth are healthy with one exception.  Her last toddler molar on the lower right side has been steadily sinking back into her gum line.  I wasn't notified of this problem at any previous check ups, but the dentist relates that they have been "watching it."  It's apparent that something is going wrong with this tooth, but I find the treatment a bit scary and would appreciate some advice.

Her dentist has recommended putting a cap (taller than usual) on the tooth.  He says that the tooth is possibly fused to the jaw bone, and that the cap would provide a corrected bite that could possibly loosen the tooth and raise it up again.  In order to put the cap on, he will have to go down into the gum line to prepare the tooth for the cap.  He is suggesting sedation along with local anesthesia for the procedure.  This is the part that I find particularly scary.

I'm thinking logically, that something has to be done.  We can't have that tooth sink farther in and cause additional problems.  I'm just wondering if this cap therapy is the most common and successful treatment.  Also, there is not decay on the tooth.

Answer
The condition you are describing is called "ankylosis".  The primary molar is fused to the bone.  It is not actually sinking into the bone.  In reality all the other teeth are continuing to erupt except the ankylosed molar which is left behind.  In time the other teeth and the gums will emerge past the ankylosed tooth and this creates a difficult problem in the future.  At some point the ankylosed tooth will have to be removed before extraction becomes complicated.  Then a space maintainer may have to be placed to prevent the other teeth from drifting into the extraction space.
Placing a crown on the ankylosed tooth is not really the best way to manage this situation.  First, it is not likely that it will result in loosening the ankylosed molar.  As the other teeth continue to emerge the ankylosed molar will again be out of contact with the opposing teeth.  I find a much better solution is to add to the height of the ankylosed tooth with bonded composite resin material until it is again in contact with the opposing teeth.  This procedure is not as drastic as the crown and can often be accomplished without sedation and local anesthetic.  An added advantage is that it is possible to add composite resin as needed in the future.  Still, at some point the ankylosed molar will probably have to be extracted, but this way it may be possible to delay that extraction for some time.