When does a crown make a better choice than a filling?

Crowns vs. Fillings

You may find yourself in a situation where your tooth needs to be rebuilt. And your dentist says that either a dental crown or a filling might be placed. If so, the question that seems to run through many people’s mind is:

• Does choosing crown placement … the repair that costs more Crown Fees than placing a filling Filling Fees … and takes more appointment time (usually two visits vs. just one) … really make a significantly better choice?

That’s the subject of this page.

Below, we examine the crown vs. filling issue from the standpoint of what might make the best choice in terms of creating the most favorable health outlook for your tooth. It explains situations where choosing one approach rather than the other might result in a significant negative event, with fracture being a primary concern.

Not discussed on this page is the subject of comparative restoration longevity. Generally, it’s expected that a dental crown will tend to last longer How long?. But a filling can provide reasonable service too How long?, if placed for appropriate applications like those discussed on this page.

Choosing between dental crown and filling placement. – Factors to consider.

a) Does the tooth require strengthening?

One of the biggest differences between a dental filling and a crown is the greater level of protection that the latter provides.

The way a crown encases its tooth helps to reinforce it.

• Crowns strengthen teeth. – One of the hallmark characteristics of a dental crown is the way that it reinforces and strengthens a tooth. This is due to the way it cups over and encases it (see illustration).

  The crown literally acts as a rigid splint that holds the tooth together. And that means that once one has been placed, the tooth can withstand a greater level of chewing forces without risk of damage.

• Dental fillings don’t offer as much protection. – In comparison, a filling just rests in or on a tooth and generally doesn’t offer any substantial strengthening effect. And as we explain below, in some cases choosing this option may actually place the tooth at greater risk for fracture.

  (Related page: Broken teeth – Repairs and outcomes. Example scenarios.)

Of course, if your tooth doesn’t really require strengthening, then placing a crown is overkill. And in fact, doing so makes a poor choice for your tooth.

Background –

Actually, you can’t have a valid discussion about crowns vs. fillings, without first describing the size of the filling that’s planned.

1) With small fillings, there’s usually no concern about tooth strength.

For small repairs, placing a filling makes the right choice.

With this situation, placing a filling (vs. a crown) is actually the superior choice.

In cases where only a minor amount of repair is needed, placing a crown instead of a filling can actually be detrimental to the tooth. That’s because:

• The aggressive amount of tooth trimming that’s needed for crown placement This much. can stress it. Even to the point where irreversible harm may come to the tooth’s nerve tissue A possible consequence., thus triggering the need for root canal treatment.
• Crowned teeth can be more difficult for a patient to clean (like effectively removing dental plaque from around its gum-line edges), with a primary concern being the development of gum disease and its complications.

Of course, these events don’t occur in all cases. But the potential for them is great enough that placing a crown isn’t justifiable if a simpler type of restoration can satisfy the tooth’s needs.

2) How larger fillings frequently leave a tooth at risk.

Large dental fillings can leave a tooth vulnerable to fracture.

An analogy.

The structural integrity issue we’re discussing here is a little like what you find with an eggshell.

• If you take a raw egg and you want to break it open, it really takes a pretty firm rap. That’s because an eggshell, as an intact unit, is a surprisingly strong object.
• Now, in comparison, say you’ve broken the egg open and the two halves of the empty shell are lying on their sides. In this condition, it’s a simple feat to crush each piece flat.
• That’s because the shell’s structural integrity has been compromised. It’s no longer an intact unit that’s capable of withstanding forces well.

How filling preparation size affects tooth strength.

The numbers shown are the reduction in tooth stiffness (a measure of tooth strength).

That’s why teeth with big fillings can be fragile.

Research evidence.

Our animation illustrates the amount of stiffness reduction associated with the standard outline form of the different classifications of fillings evaluated by the study.

• 1 surface cavity preparation = -20%
  2 surface = -46%
  3 surface = -63%

▲ Section references – Reeh

A filling may create a wedging effect that ultimately cracks its tooth.

b) Fillings can create a wedging effect that leads to tooth fracture.

A major difference between crowns and fillings.

▲ Section references – Rosenstiel

This effect can take place with either large or small fillings. But as discussed above, those teeth that have comparatively larger restorations may already be at comparatively higher risk of fracture, and therefore this issue of greater concern with them.

c) The question isn’t only “if” a filling can be placed.

Don’t confuse the issue of “can a filling be placed” vs. “should one be.”

Dentists are humans just like anyone else. And sometimes an aspect of the treatment options they offer has to do with trying to satisfy their patient’s wishes (with cost issues often being the primary factor when crowns are involved).

Know what you’re getting.

Just because they feel they can anchor some type of filling to replace your tooth’s missing parts, you still need to ask them what they expect the results to be.

Should the restoration be considered to be a “permanent” fix? Or instead, just an interim solution, with a crown hopefully placed before any further harm occurs?

Even the latter approach doesn’t necessarily make a bad plan. But if that’s the situation, you should be fully aware of it.

What constitutes a ‘big’ dental filling? When should a crown be placed instead?

As mentioned above, and discussed further below, a big part of determining when a crown is indicated for a tooth instead of a filling has to do with the size the filling would need to have.

That’s because when larger amounts of tooth structure are missing, the tooth is typically in greater need of reinforcement (a function that crowns, as opposed to fillings, excel in providing).

Of course, deciding when a filling seems “too big” (to provide needed strength or predictable service) is really only something your dentist’s evaluation can determine. During this process, here are some of the issues they will consider.

Intercuspal distance = Cusp tip to cusp tip.

Fillings greater than 1/3 the distance between cusp tips tends to significantly weaken a tooth.

Crowns vs. fillings – Common guidelines.

• A study by Larson determined that fillings that take up just 1/3rd of the “intercuspal distance” of a tooth (see picture) reduce the tooth’s resistance to fracture by more than one half.
• Geurtsen stated that a tooth’s risk for fracture increased substantially as its filling approached 50% of its intercuspal distance. This paper’s recommendation was that fillings, composites (white) or amalgam (silver), should not exceed 1/3 to 1/4 this distance.

Your mileage may vary.

Not all dentists are as conservative with their recommendations as suggested by the guidelines above. And from a practical standpoint, many teeth with “larger” fillings do just fine, even over the long term. (A quick look in your mouth may confirm this.)

▲ Section references – Larson, Geurtsen

These are all “big” dental fillings.

The arrows indicate the most fragile portions of the tooth.

Examples of “large” fillings.

Generally speaking, they’re the cusp that the filling encroaches on the most. (Cusps that don’t meet the requirements stated in the general rules above.)

Not all teeth with large fillings are problematic.

Possibly by now you’ve already been to the mirror so you can judge the size of the dental fillings in your mouth. Did you see any “large” ones?

Now, ask yourself, how long have those big fillings been in place? What’s your answer? Two years, five years, longer? If so, what’s the deal? If teeth with large fillings are so weak, why haven’t parts of yours already fractured off? Don’t these teeth need dental crowns, immediately?

What do experts say?

We found a section in the dental treatment planning textbook authored by Stefanac that discusses this type of scenario at length.

It goes as far as to state that diagnosing the need of a dental crown for a tooth that has a large filling that has provided acceptable service for some years and has no obvious deficiencies “is one of the most common opportunities for overtreatment in dentistry.”

When should replacement be considered?

The book suggests that basic reasons for intervening include: a defect in the filling, the identification of tooth decay or a fracture line in the tooth, and pain on biting. And states that short of the presence of one or more of these symptoms, making a compelling case for crown placement can be difficult.

Of course as it should, the book expounds on more detailed scenarios and considerations that could be factors that tip the scale in favor of one treatment approach over the other. But the salient point we took away was that the act of crown placement can have unintended consequences, and as such a decision to place one must be based on a reasonable justification.

(We’ll also state that we noticed that there’s an added implication here that large fillings (at least those that survive an initial number of years) can make a reasonable choice for teeth.)

What to do?

Obviously, with this subject there are no cut and dried answers. The hope is, base on both their knowledge and clinical experience, that your dentist has the ability to formulate an educated opinion about which of your teeth have a true need for a crown.

▲ Section references – Stefanac

Don’t overlook that prevention is really the key.

As this page has discussed, in many, many cases the debate between placing a filling or a crown simply boils down to how much tooth structure has been lost. And that suggests that a person’s potential for requiring a crown can be reduced if steps are taken to help to keep tooth damage to a minimum.

Of course, in many cases you’ll have no control over this factor at all. But there actually are some habits and lifestyle choices that do increase a person’s risk for tooth damage, and therefore crown placement. If you’d like to learn more, read this page: 8 things you can do to reduce your chances of ever needing a dental crown. Proactive steps.

Comments.

This section contains comments submitted in previous years. Many have been edited so to limit their scope to subjects discussed on this page.