Crown is not a Panacea
Probably because crown is expensive, it is thought to be a panacea. It should protect our tooth! But the crown only protects the portion of the tooth which is covered by the crown.
Mrs. Thomas has had a crown for a molar for a long time (Fig.1 C). The gums in the back of the molar have receded (white line). The white arrow indicates where the crown coverage stops. So the area between the arrow and line is NOT protected.
Five years later, the back surface of the molar develops cavities (Fig.2 arrowheads). Finally the tooth is taken out. The cavities are large and nasty (Fig.3 arrowheads).
What should we do to protect the area which is covered by the crown? In fact, we should floss the back surface of the last teeth in our mouth and brush the gum line.
Fig.2 shows cavities in the back surface of the tooth in that area immediately next to the gum line. This area is best to be cleaned by flossing.
Fig.3 demonstrates cavities below the crown (C), i.e., along the gum line on the cheek side. This region is best serviced by brushing at gum line.
We should not forget these two hidden areas.
Xin Wei, DDS, PhD, MS 1st edition 03/06/2012, last revision 03/06/2012