Rebuilding your tooth after its root canal treatment.

- Dental crowns vs. fillings. Which makes the best choice? - success rates | How soon does a final restoration need to be placed?

Crown or
filling?

Link to crown vs. filling section.

Advantages
of crowns.

Link to research about placing a crown after endodontic treatment section.

Every tooth will need a final restoration.

After a tooth's root canal therapy has been completed, it will require some type of permanent dental restoration.

This page discusses the different options you have in deciding how your tooth is rebuilt (crown vs. filling), and details that need to be considered when selecting between them.

Considerations:

You may also be interested in these additional topics about rebuilding root canalled teeth:


A) A crown or a filling after root canal - Which makes the best choice?

For the most part, the two basic options that you have for restoring an endodontically treated tooth are the placement of a dental crown or else a filling.

Here are some of the issues that need to be considered when choosing between the two.

An access cavity tends to weaken a tooth.

Teeth that have had treatment may require strengthening.

1) The tooth may need strengthening.

Teeth that have had root canal therapy can be fragile, possibly significantly so. Here are some reasons why:

Weakening has occurred during their treatment.

When performing root canal therapy, the dentist must create an access cavity (opening) in the tooth through which its work will be performed (see picture). And creating this hole tends to weaken the tooth.

  • When a conservative opening can be made in a virgin tooth (one that did not have a previous dental restoration), the reduction in tooth stiffness that results may just be on the order of 5% or so. (Eliyas)
  • But with many cases, like when the tooth's individual root canals have been difficult to locate, the dentist may need to remove a comparatively greater amount of internal tooth structure, to the point where the tooth may become significantly hollowed out.
After its endodontic therapy, this tooth will require a crown.

This tooth is very hollowed out and should have a dental crown placed.

Previous damage.

Teeth that end up requiring root canal treatment have often already experienced some type of significant event, and as a result are already in a weakened state.

  • It's common that treated teeth have previously suffered levels of trauma that have resulted in crack formation or outright fracture. The loss of tooth structure due to the effects of advanced tooth decay can significantly weaken a tooth.
  • When repairs are made, it's been found that the need for a filling on the chewing surface of a back tooth tends to reduce its stiffness on the order of 20%.

    Larger fillings, like those whose extension is such that they touch neighboring teeth, have been found to result in an over 60% reduction. (Eliyas)

Changes in tooth dentin.

The flexural strength of dentin (the hard, calcified tissue that makes up the bulk of a tooth) is likely reduced by the various chemical agents frequently used during the cleaning phase of root canal therapy (Eliyas).

Each of the above suggest that by the time its root canal treatment has been completed a tooth may be at substantial risk for fracture, even when exposed to normal chewing forces.

If so, a dentist will frequently recommend that a crown should be placed. Dental crowns provide a strengthening effect that can help to prevent fracture.

 Reference: 

Coronal leakage - Bacteria seeping past a dental filling.

If contaminates re-enter a tooth, its completed treatment will fail.

2) The tooth will require a proper seal.

If contaminates from the mouth find a way to seep past a tooth's dental restoration (a phenomenon termed "coronal leakage"), its root canal treatment can fail.

A dental crown, more than any other type of restoration, can help to predictably prevent this type of event. (Use the link above for a more detailed explanation.)

3) Restoration longevity / durability is an important factor.

The final restoration that a dentist places must be one they feel can provide lasting service. The specific physical properties that the restoration needs, however, will vary on a case-by-case basis.

Examples.

a) Relatively intact teeth.

It's possible that a tooth that ...

  1. Just has a conservative access cavity ...
  2. And no other history of significant tooth structure loss (such as a previous cavity, filling or breakage)

... might be successfully restored with just the placement of a dental filling.

This approach may be best suited for front teeth (incisors and canines) where the direction of force applied is typically non-axial.

With back teeth (premolars and especially molars), forces are more commonly directed straight down (axially) and for this reason providing for tooth reinforcement (like that created by crown placement) may make the more prudent choice. (Eliyas - linked above.)

b) More involved cases.

In comparison to teeth still in relatively pristine condition. those with large fillings or extensive decay, or teeth that fractured prior to their receiving root canal treatment, are probably best restored with a dental crown. (A dental post and core may be required too.)

This approach may be needed for either front or back teeth. Crown placement is especially appropriate for molars, a type of tooth that must be able to withstand heavy chewing forces.

What type of final restoration makes the right choice for your tooth?

  • Increasingly, placing a dental crown on an endodontically treated molar has become the "standard of care" in dentistry (see below).
  • For other teeth, especially relatively intact front ones and even possibly premolars, the placement of a dental filling may be perfectly satisfactory.

Related page: Can a tooth's existing crown be used after its root canal therapy is finished?

B) Dental research confirms the benefit of dental crowns.

An x-ray showing completed endodontic therapy and a dental crown.

X-ray showing a tooth's completed treatment and dental crown.

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 track record of 400 endodontically treated teeth and found that those that were not crowned 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 teeth for a three year period following the completion of their root canal 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%.

 

Learn about the different types of dental crowns.

Click image to jump to topic Dental Crowns.


C) 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 phrase "as soon as is reasonably convenient" (meaning not an emergency but definitely a priority), often applies to this situation.

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Why the rush?

In general, the temporary restoration that has been placed is just that. Here's why:

  • It can't be relied upon to provide adequate protection or strengthening for the tooth over the long term, thus leaving it at risk for fracture.
  • When compared to a permanent restoration, the seal that a temporary creates isn't as lasting, thus placing the tooth at risk for recontamination.
 

Last revision/review: 11/16/2018 - Minor revision. References added.

 
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Comments

Is crown necessary?

My tooth that's just had root canal had a filling in it for years and it did just fine. My dentist said we should now place a crown. Is that really necessary? It's a big added expense. I'd rather have another filling placed.

Heather

We're not going to have enough information about your tooth and situation to know what's needed. Your dentist is in a position to have an idea, and evidently they think that crown placement makes the best plan.

There are two important factors that you should keep in mind:
1) The restoration that's placed needs to be able to create a seal that prevents bacteria and such from seeping back into the interior of your tooth (see coronal leakage link above). Crowns are very good at preventing this.
2) Your tooth probably isn't as strong and fracture resistant as it was previously. (For example, it's been substantially hollowed out during your root canal treatment.)

It's not so much that a filling can't provide a seal and serve as a strong restoration, it's just that crowns do this so much more reliably and predictably. Evidence of this is found in the studies mentioned above. Teeth that have had crowns placed after their root canal treatment tend to have a higher survival rate.

That doesn't mean that all teeth require a crown. It in part depends on how much tooth structure has been lost. In your case, we're assuming that the filling that existed previously was somewhat sizable (a repair large or involved enough that root canal treatment was ultimately needed).

If instead the hole in the tooth is just a small one (and really only your dentist would be able to make this judgment), a filling might suffice just fine.

Ideally the crown (or whatever permanent restoration is chosen) would be placed promptly after the completion of your tooth's endodontic work. If finances or such make that difficult, bring the issue up with your dentist and see if they can offer any solutions/alternative plans (payment plan, placing the crown as soon as your next insurance cycle allows, etc...). Good luck.


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