Dental restoration does not last forever. On the average a crown should
last about 15 to 20 years. There are many reasons for the crowns to fail.
The most common causes are:
1. The outer porcelain covering is separated from the inner metal substructure.
2. The cement layer is dissolved and therefore failing to seal and protect
the remaining of the tooth.
3. New cavity occurs or old cavity recurs
Occasionally a crowned tooth can get a new cavity. Such carious lesion typically starts below the crown's edges or at the gum line. While it's true that cavities never pass through the crown, they can begin at the crown borders. Often the dentist refers to this area as the "margin" because this where the crown and tooth meet.
The marginal areas of the crowns are difficult to keep clean. The bacteria
living in the plaque at these places cause new cavity. If the cavity is
small, it can be easily fixed with a dental filling. However, when the
the lesion is more advanced, going deeper toward the pulp and spreading
wider to the area in between the teeth, a new crown needs to be made to
replace the old one.
The usual signs and symptoms of the failing crown are:
1. Tooth sensitivity to hot and cold
2. Painful chewing
3. Bleeding gum
4. Bad breath
5. Crown movement
Our Houston dentist recommends that once the old crown has several failing
signs, it should be remake right away. A delay will cause further damage
to the already-compromised tooth and and require additional extensive treatment,
such as the root canal therapy, before the new crown can be made.