What's the difference between a cap and a crown?

I was forced to have a root canal on one of my molar teeth because of an abscess. The dentist advised me that it's very easy for the filling to break down. He said I should cap my tooth.

What's the difference between a cap and a crown?

Actually, there is no difference whatsoever between dental caps and crowns.

A dental crown is a "cap" that looks exactly like your tooth, only it's placed above your tooth.

It's meant to cover your old tooth to restore its original shape and size, or even enforce its strength. Some people use caps to make the tooth look better.

The crown is cemented into place and fully covers the entire visible portion of your old tooth at and above your gum line.

Why do people have crowns in the first place? In my case, it's because the dentist told me that he's afraid my root canal filling will break down.

Yes, in your case, it's to strengthen the tooth so that you won't have to have another filling if and when the tooth wears down.

These are the usual reasons why a crown may be needed:

1. To protect a tooth that has weakened, usually from dental decay. This prevents it from breaking.

2. To hold together parts of a tooth that has been cracked or broken. For example, by biting on something hard, like a bone, or from being punched in the mouth.

3. To hold together a tooth that has been extremely worn down. For example, in the case of older people after years of chewing.

4. To support a tooth with a huge filling when there is no longer enough enamel or dentin left. For example, when you have had a root canal that involves coring out the entire pulp and centre of your tooth.

5. To hold a dental bridge in place.

6. To cover an ugly or extremely odd-shaped tooth. This is completely for cosmetic purposes. A lot of people who like to have nice smiles get caps for their front teeth.

7. To cover a severely discoloured tooth. For example, if you have been smoking cigarettes, chewing tobacco or drinking a lot of coffee or cola drinks.

8. To cover a dental implant.

Shave off existing tooth?

OK, I'm getting ready to have a crown, but my dentist says he has to shave my existing tooth off first. I'm scared! My tooth is already bad enough as it is. Isn't shaving it off going to make it worse?

This is exactly what will happen when you go for a crown.

There will be two visits to the dentist required. In the first visit, your dentist will examine your tooth. He may or may not take some X-rays to check where the roots of your tooth are in context to the surrounding jawbone.

The X-ray usually involves him giving you a film encased in something that you have to bite down hard on, and then him taking the X-ray from outside your cheek.

This step is usually a little uncomfortable as the edges of the film can dig into your gums.

Then your dentist will give you a mild injection to numb the area surrounding your tooth.

He then files your tooth down along its chewing surface and also the sides. He has to do this to make room for the crown.

The amount of tooth he files away (or shaves, if you like to call it that) will depend on the type of crown you chose.

After reshaping your tooth, he will ask you to bite down hard on an impression paste or putty for three minutes.

He is basically making an impression of the teeth above as well. That way, he is ensuring that when the real crown comes, you will have the correct bite.

He then sends you home, while the impressions are sent to a dental lab, where your crown will be manufactured.

It is only during the second visit that your new crown will be fitted into place. And yes, this requires anaesthetic as well.


What types of crowns are available?

What types of crowns are available?

There are permanent crowns and temporary crowns.

Temporary crowns are, as the name suggests, crowns that the dentist puts on your tooth while awaiting the two to three weeks for the dental lab to manufacture your permanent crown.

Permanent crowns can be made from:

1. Metal - this can include gold or gold alloys, or even a base metal alloy like nickel or chromium.

Metal crowns are thinner and stronger, and less tooth material needs to be removed during the filing process to accommodate a metal crown. They also rarely chip or break.

Unfortunately, they may leak after a while, and they do not look nice cosmetically because they retain their metallic colour.

These days, semi-precious metals are used in order to prevent leakage. This is called a "noble alloy", and consists of a mixture of gold, nickel and chromium. Many different types of amalgams exist.

2. All ceramic or all porcelain crowns - these actually match your tooth colour. But they are not as strong as metal crowns and may wear down faster.

These are usually used for front teeth.

3. Porcelain-fused-to-metal - a mixture of both. Still not as strong as pure metal.

Dr YLM graduated as a medical doctor, and has been writing for many years on various subjects such as medicine, health advice, computers and entertainment. For further information, e-mail starhealth@thestar.com.my. T

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