A filling is a repair to an otherwise healthy, intact tooth. The term “filling” implies that the repair should be contained within the boundaries of that tooth. In other words, the filling should be surrounded by natural tooth structure insofar as it is possible. In practice, of course, dentists frequently replace large sections of teeth with large, bulky fillings. As the filling gets larger and larger, the amount of natural tooth structure necessary to retain the filling decreases. The ultimate consequence of this is that the filling becomes a rickety patchwork of artificial materials that is inherently weak and may break out at any time.
Furthermore, as the natural tooth structure becomes thinner, replaced by more filling material, it becomes more and more likely to break off necessitating an even larger repair. The larger a filling is, the more technically difficult it is for the dentist to do, and the larger the tooth/filling interface. This means that very large fillings are likely to be unstable and to leak over time leading to recurrent decay and replacement with even larger fillings. This process of patching or replacing already large fillings is what we call “patchwork dentistry“.
In most situations, patchwork dentistry ultimately leads to the loss of the tooth, or at minimum to very expensive methods of repair. If your dentist recommends placing a
crown on the tooth, he is attempting to stop this cycle of recurrent decay, breakage and repair before it becomes necessary to do a root canal and post and core in order to have anything left above gum line to repair.
A crown is a cast metal covering, generally overlain with porcelain, which is placed over the tooth in order to hold it together and to withstand the forces of chewing. Sometimes the entire crown is made out of porcelain in order to attain the greatest esthetic (appearance) value possible. The crown may even be made entirely out of gold if that is the wish of the patient. While no dentist can guarantee that a crown will repair the tooth forever, it is still the very best restoration possible for a severely damaged tooth, and may be the only way that some severely damaged teeth can be repaired at all.
The following is a list of reasons that a crown might be more appropriate than a filling:
- A tooth should be crowned if the filling would make up more than half the bulk of the clinical crown of a tooth (that part above the gum line).
- A tooth should be crowned if the filling would make up more than half of the surface area of the clinical crown.
- A tooth should be crowned if the clinical crown is
crackedor seriously mechanically weakened.
- A tooth should be crowned if the filling is very deep under the gum line since a filling under these circumstances is difficult to do and is more likely to leak. This leads to recurrent decay a year or two later.
- All back teeth with root canals should be crowned as the tooth structure tends to become brittle after the living nerve is no longer present.
- All front teeth that have root canals and also have large fillings should be crowned.
- Teeth that are unsightly (ugly) and embarrass the patient should be crowned. This is especially true in front teeth that have root canals.
- Teeth with circumferential decay (decay at the gum line that encircles more than one surface of the tooth) should be crowned in view of the near impossibility of properly repairing this type of decay with simple fillings.
- Teeth that are worn down due to attrition from bruxing (grinding and clenching) are often best crowned.
When the dentist says you need a crown, you really ought to think twice before rejecting the advice!
Even though a good dentist can repair almost any tooth with a filling, he or she may recommend a crown instead. Lots of people choose the filling anyway since it is always cheaper. This is often a bad choice. Very large fillings are technically very difficult to do! You may leave the office with what looks and feels like a tooth only to find that a year or two down the line, there is recurrent decay under the filling. It may be near impossible for the dentist to make the filling contact the tooth next to it leaving a gap which jams food between the teeth. Pieces of the tooth or the new filling may break off over time. The filling may even have required just enough removal of tooth structure to cause the nerve to die which will lead to a root canal followed by a crown, or even an extraction. These problems are not the fault of the dentist.
There is a limit to what even the best and most conscientious dentist can accomplish with a very large, difficult filling. Opting for a filling on a tooth that the dentist feels needs a crown may be opting for an extraction a year or two later.