Reasons why dentists place crowns on teeth that have had root canal treatment.
After a tooth's root canal therapy has been finished, some type of permanent dental restoration still needs to be placed.
With some cases, a simple filling might suffice. In other instances, the treating dentist may feel that a dental crown is indicated (possibly including the placement of a post and core).
This page outlines factors that need to be taken into consideration when making a decision about which type of restoration makes the best choice.
Why can a crown be a better choice than a filling?
A) The tooth may need strengthening.
Teeth that have had root canal therapy can be fragile, possibly significantly so. This is because many of the teeth that require it have already experienced some type of traumatic event (such as having a large cavity or sustaining damage from fracture).
A history of such an event, in addition to a dentist's need to create an access cavity through which they perform their root canal work, means that by the time a tooth's treatment has been completed, a fair amount of tooth structure may have been lost.
In those cases where the dentist feels that a substantial amount of weakening effect has taken place, they will be concerned that the tooth might crack or break when placed under normal functioning loads. If so, the integrity of the root canal filling, or the survival of the tooth itself, might be placed at risk.
As a solution, a dentist will often recommend that a dental crown should be placed. Dental crowns provide a strengthening effect that can help to prevent fracture.
B) Crown placement creates a predictable seal for a tooth.
Another common reason for the recommendation of a crown instead of a filling has to do with the fact that a crown creates an excellent seal for a tooth.
A dental crown, more than any other type of restoration, can help to predictably prevent this type of event.
Dental research confirms the benefit of dental crowns.
Several studies have evaluated the outcomes of teeth that have had root canal treatment and then were, or were not, crowned. Here are the findings of some of those studies.
1) Aquilino (2002) - This study evaluated the experiences of 400 endodontically treated teeth and found that those that were not crowned after the completion of their treatment were lost at a rate 6 times greater than teeth that had dental crowns placed.
2) Nagasiri (2004) - This study evaluated 220 molars that did not receive dental crowns after root canal treatment. The survival rates of these teeth at 1, 2 and 5 years were 96%, 88% and 36% respectively.
3) Lynch (2004) - This study evaluated 176 endodontically teeth for a three year period following the completion of their treatment. The following survival rates were observed for teeth with the following types of restorations: cast restoration (dental crown) - 92%, amalgam restorations ("silver" filling) - 67%, composite restorations (tooth bonding) - 35%.
Do all root canalled teeth require a dental crown?
The type of dental restoration that is used to restore a tooth after root canal therapy will depend upon the dentist's interpretation of its needs. This restoration must help to protect the integrity of the root canal treatment, as well as the tooth itself.
Increasingly, placing a dental crown on an endodontically treated molar has become the "standard of care" in dentistry. In some cases, however, and especially for front teeth, the simple placement of a dental filling may suffice. Since this determination will vary on a case-by-case basis, you simply need to defer to the judgment of your dentist.
Examples.
It is possible that a front tooth, one with a conservative access cavity and no other history of significant tooth structure loss (such as a previous cavity for filling), might be successfully restored just with the placement of a white filling (dental bonding).
Back teeth (premolars and molars), especially those that have modest to large access cavities and/or large fillings, are probably best restored with a dental crown.
How soon does the permanent restoration need to be placed?
Your dentist will make a recommendation about the time frame that is appropriate for placing your tooth's final restoration (dental crown or filling). The term "as soon as is reasonably convenient" (meaning not an emergency but definitely a priority), might be considered applicable.
In general, the temporary restoration that has been placed is just that. It can't be relied upon to provide a significant strengthening effect for the tooth. Additionally, the seal created by this temporary restoration will not be as lasting as that provided by the placement of a permanent dental restoration.
Can a tooth's existing crown continue to be used after root canal therapy?
Some teeth will already have a crown in place before their need for root canal treatment is discovered. And in some instances, it might be possible to make use of this pre-existing restoration. We discuss this subject here: Can a tooth's existing crown be used after its root canal therapy is finished?
