Do I Really Need A Crown?
Darren Gardner DDS- Provo Dentist
Our teeth take a beating! And some people are harder on their teeth than others (clenching, grinding, chewing ice, popcorn kernals, hard candy, nuts, etc.) After years of use, teeth begin to crack and break- especially if they were previously weakened by large cavities.
Tooth previously weakened with a large filling has fractured
Fillings do not strengthen teeth! If a tooth has a filling that is deep and wide, the surrounding tooth structure is weak and will give way after years of chewing stress. Fractured or fracturing teeth should be strengthened with a restoration that makes the tooth stronger. Crowns will strengthen teeth, but many times they are done unnecessarily.
There is a better alternative to crowns: an onlay. Experts have been telling us for years that dentists are doing too many crowns. Preparing a tooth for a crown means stripping the tooth of all the outer enamel, 360 degrees around the tooth, and 1 mm underneath the gum to hide the junction where the crown and the tooth meet. It is aggressive and removes a lot of healthy tooth structure which cannot be put back.
An onlay, on the other hand, removes only the weak parts of the tooth and saves the rest. If you had a finger that needed to be removed to keep the rest of your hand healthy, would you go to a doctor that wanted to cut your hand off? Probably not! Most of the time a tooth is being crowned for the first time, an onlay should be done instead.
Teeth Prepared for full crowns are ground down to stubs
Comparison of the amount of tooth removed for a full crown compared to an onlay
Even though dentists themselves know that doing an onlay is healthier for the tooth than doing a crown, most of them are still doing crowns! In a recent article by Gordon Christensen, a world renown expert on dentistry that lives here in Provo, he said that of the about 38 million lab restorations that were placed nationwide in 2011, only 5% were onlays. Only 5%! ! !
As a minimally invasive dentist, about 90% of the lab restorations I do are onlays or 3/4 crowns. While there are a few situations where a full crown is better than an onlay, almost all of the crowns I do are to replace an old crown that has failed.
Why are most dentists still doing crowns when they know onlays are better for the tooth? Gordon Christensen's answer: because crowns are easier and dentists don't want to change their routine. Preparing a tooth for a crown is basically the same for every tooth. Preparing a tooth for an onlay utilizes a custom design for each tooth in which the dentist evaluates the existing tooth structure and designs a restoration that will strengthen the weak parts of the tooth without removing the strong parts of the tooth. It is a procedure that isn't being taught in most dental schools because of the extra skill that is involved.
Tooth prepared for an onlay and the finished result
Note the contrast between a crown and the tooth after gum recession. The results are very unnatural.
Here are the advantages of onlays over crowns according to Gordon Christensen*:
- Gums recede around crowns in only a few years exposing the ugly line between the crown and the tooth
- Onlays look more natural. They blend into the existing tooth structure so the line between the onlay and the tooth is invisible.
- Onlays eliminate unnecessary removal of healthy tooth structure
- A tooth covered with an onlay is stronger than a virgin tooth (a tooth that has never been weakened by decay, fractures, or fillings)
Other advantages:
- Less root canals: Teeth that are prepared for crowns are more likely to need root canal treatment because more of the tooth is being taken away, which is more traumatic to the tooth pulp.
- Onlays are absolutely the best restoration for teeth that are too weak for a filling in young people: Crowns done on teenagers and young adults in their early twenties are more likely to cause root canal treatment. The pulps are very large and a crown prep gets very close to the nerve. Gum recession will also happen naturally which will expose the ugly line at the base of the crown very quickly in young people.
- Teeth last longer: A tooth that is treated conservatively with an onlay can have more replacement restorations and a longer life than a tooth that has been crowned because there is more tooth structure to work with. Each time a restoration is replaced, more tooth structure is removed; and when there isn't enough tooth to restore, it must be extracted. A crowned tooth will reach that point sooner than an onlayed tooth.
- Healthier gums: The gums are healthier around an onlay because the gums remain undisturbed against the natural tooth. There isn't a crown margin buried under the gums to trap bacteria and cause inflammation.
Now that you are educated about the advantages of onlays versus crowns, next time a dentist tells you that you need a crown, get a second opinion!
* "The case for onlays versus tooth-colored crowns" Gordon Christensen, DDS, MSD, PhD JADA October 2012 page 1141.