Dental Education Lecture: Drawbacks of Joined Crowns

Little Ming fell and broke one front tooth at the age of 9.  It has been repaired several times since.  Two or three year ago, a crown was placed on the broken tooth (#9) and joined to that of the tooth #10 (Fig.1).  The gums are reddish around the crown of #9 (arrowheads).

Since the tooth #9 has severe damage.  A post (P, Fig.2) was inserted before placement of the joined crowns (* showing outlines of crowns).  She cannot floss the joined area (**, double arrowheads) so that there is a big tartar (single arrowhead) above the joined area.  

In brief, we have to remove the joined crowns, a bad idea.  When they are gone, extensive tartar is noted along the surface of the tooth 10 next to the tooth #9 (Fig.3: arrowheads).  #9 has a large filling (F).  The remaining tooth structure is quite limited.   The tooth #8 has a crack (arrowheads).  Both the teeth #8 and 10 have slight discoloration, suggesting the nerve being dead.  We need to do root canal.

Every single tooth needs to be supported by itself.  Joined crowns create a lot of problems.  We cannot floss the narrow space.  Consequences are gum bleeding and formation of tartar as mentioned above.  When a tooth is severely destructed, it is better to be extracted and restored with an implant.  Or use brace mechanism to bring the tooth out so that sound tooth structure is above the gum line to support a crown.

Fig.4 arrowhead shows that the tartar shown in Fig.2 is removed after removal of the joined crowns.  We are doing root canal for #8 and 10.

Xin Wei, DDS, PhD, MS 1st edition 12/14/2009, last revision 04/16/2012