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 treated 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.

 

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.

After its endodontic therapy, this tooth will require a crown.

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

  • 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 suggests 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.

Section references - Eliyas

Coronal leakage - Bacteria seeping past a dental filling.

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

2) The tooth will require a proper seal.

If contaminants 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.

Section references - Eliyas

b) More involved cases.

In comparison to teeth that are 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.

(If enough of the tooth's original tooth structure is missing, a dental post and core may be required before crown placement.)

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.

 
Picture of filling placed in anterior tooth after root canal treatment.

Conservative access openings in front teeth may only require filling placement.

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

  • Placing a dental crown has increasingly become considered to be the appropriate "standard of care" for endodontically treated molars (see next section).

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

  • For other teeth, especially relatively intact front ones (incisors and canines), and even possibly premolars, the decision to place a dental filling may make a perfectly appropriate choice.
Choosing between the two.

Just to recap, the decision here is basically one of judging if the needs of sealing the tooth (to protect the integrity of its root canal work) can be met by a filling over the long-term.

Issues involved include the quality of seal it creates and its anticipated service performance (strength, durability, longevity). Of course, the restoration must also meet the needs of the tooth in terms of helping to prevent catastrophic failure (i.e. tooth fracture).

Pros and cons.

The advantage of utilizing a filling is that it avoids subjecting the tooth to the aggressiveness of crown placement. This includes much more extensive tooth structure reduction and greater cost. Also important to consider, crown placement still involves duration-of-service factors.

The decision between the two typically boils down to the extent of original tooth structure that still remains (is the tooth still structurally intact) and the degree of wear and tear and level of force the restoration is expected to be subjected to (can it be expected to provide predictable service).

Obviously, your decision will almost always be based on the advice of your dentist. But it's these types of issues and factors that they should have considered, and be able to provide an explanation to you about. There is no cookie-cutter best choice that applies to all cases.

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 a6 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%.

Section references - Aquilino, Nagasiri, Lynch

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.

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.

 

 
 
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 Page references sources: 

Aquilino S, et al. Relationship between crown placement and the survival of endodontically treated teeth.

Eliyas S, et al. Restoration of the root canal treated tooth.

Lynch C, et al. The influence of coronal restoration type on the survival of endodontically treated teeth.

Nagasiri R, et al. Long-term survival of endodontically treated molars without crown coverage: A restrospective cohort study.

All reference sources for topic Root Canals.

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.

Composite filling in root canalled tooth one year before crown?

I need to have a root canal in a molar tooth, since there is a cavity under the old silver filling on the chewing surface. From two other root canalled molars I know the tooth needs a crown and that it takes some time for the lab to create the crown. But I don’t have the time waiting for that, as I am expatriated to Asia very soon. Therefore I will ask my dentist to prepare a regular composite filling in my root canalled molar tooth, hoping that such a filling will last a year or so (as a temporary one-year solution), then I will have the crown once I return from Asia. Is that a suitable solution for a root canalled molar? Don’t know if one year is too long to wait for a crown on a weakened root canalled molar tooth even though it has a composite filling or whether it will break during that year. Alternative is to get a crown while I am in Asia

Flemming

In regard to the timing of the crown placement, we'll defer to your dentist's opinion. There is no question that a 1 year delay in placing the crown isn't usually ideal. But for some teeth (possibly even a molar) some type of conventional filling might provide an adequate final restoration. Just ask your dentist what they would do for their own tooth (wait until you return, or have the crown placed in Asia).

In regard to making a go of a dental filling. The quality of the coronal seal of the restoration can be improved by the dentist extending the filling down into the opening of each of the canals just a few millimeters.

(Here's a link to a paper that discusses exactly that, and mentions that dental composite creates the superior seal as compared to other restorative materials. But also mentions that all groups showed some leakage, so that might be your answer right there.
An assessment of coronal leakage of permanent filling materials in endodontically treated teeth: An in vitro study.)

In regard to filling placement and protecting a potentially fragile tooth, your dentist would probably make the occlusion on the tooth as passive as possible (meaning it doesn't get much pressure when you bite down or slide your teeth around when touching). And then of course, you would want to favor the tooth as much as possible.

While it would mean utilizing a different dentist, same-day crown placement is a possibility in some dental offices. Probably the most durable type of crown they would have to offer is (monolithic) IPS e.max. You might ask your dentist about suggestions with this option.

And finally, if you'll Google "best dental schools in the world" (and consider that a proxy for the type of dentistry practiced in that country), several seem to be in Asia.

Thanks a lot for a very

Thanks a lot for a very informative and detailed answer. I had my root canal done yesterday. My dentist was clearly in his opinion that I should have the crown very soon and that 1 year delay is far too long. But he accepted my wish and made a composite filling (don’t know if he extended it down the canals as you mention). But he shaped the tooth/filling so it will not have the hard pressure for chewing and of course I will try to favor the tooth as well. He also mentioned that dentists should be quite good in Asia, so maybe I should consider have the crown while staying there.

Restoration After Root Canal

I had a root canal performed on my #2 molar. I would be OK with only a filling as the tooth is not visible and the repair would be less expensive than a crown.

* Comment notes.

Ramond

The issue isn't about appearance. Instead it's (always) about how well the restoration seals the tooth (so to prevent coronal leakage) and possibly a restoration is needed that can strengthen your tooth.

If you haven't already, you should read this page about final restorations for root canalled teeth. (Make sure to read the statistics section.)

Possibly just placing a filling is satisfactory for your situation. But only your dentist can advise you on this issue.

* Comments marked with an asterisk, along with their associated replies, have either been edited for brevity/clarity, or have been moved to a page that's better aligned with their subject matter, or both. If relocated, the comment and its replies retain their original datestamps, which may affect the chronology of the page's comments section.


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