General, Oral Hygiene, Pain, Prevention

Cavities under Dental Crowns

Q: Can I get a cavity if my tooth is covered by a cap?

This is a common question. Actually, it’s a good question because people are often surprised to learn that the tooth is still susceptible to the decay process even with a strong crown fitting snugly over it. It is one of the valuable pieces of information that your dentist should pass on to you about your new crown.

A thorough explanation of why you need a crown should also be given. When a dentist recommends that you consider having a crown placed over one or more of your teeth, it is for their protection or to improve their appearance.

Crowns are recommended for teeth if they:

– have a very large filling and it needs to be covered with a crown for added support and strength.

– are weak because they are cracked, broken or worn down

– have cosmetic imperfections

– have undergone root canal treatment

The Destruction Process

What’s important to understand is that even though a crown is very durable, you have to treat it like your natural tooth because it is attached to your own tooth structure underneath. This tooth is still vulnerable to corrosive effects of repeated attacked by highly acids foods and bacterial acids. As acid continually accumulates along the seal between the crown and the tooth, it can soften enough of the tooth to cause a hole into which more bacteria can gather. Eventually it begins to make inroads underneath the crown and farther into the tooth. So, it’s important to understand that it is the tooth, not the crown, that is being destroyed and the cavity can only be cleaned away properly by removing the crown. During the cleaning and repair process, it is virtually impossible to retain the original shape of the underlying tooth and the existing crown will no longer fit this modified tooth precisely enough to protect it from future damage.

Bacterial plaque can accumulate along margin where crown meets tooth

Lifespan of Crowns

Like your tooth, crowns are subject to normal wear and tear and, as mentioned, can be under minded by tooth decay. Crowns generally last anywhere from 5-15 years before they may need to be replaced. However, we have seen crowns last as long as 25 years or more! Full metal ones tend to resist wear and breakage more than all porcelain one or those that are covered in porcelain. Simple chips to the white porcelain covering the crown can sometimes be smoothed by the dentist and in some cases, minor damage and holes due to wear can be covered using white dental filling material. However, all crowns can be compromised by the decay process and usually have to be replaced if it has to be removed. This is why keeping your crown free of plaque and maintaining healthy dental habits are critical to the life of a crown.

As with the care of natural teeth, these 4 habits are the most important factors in caring for your crown:

  1. Space out your meals and reduce, if not entirely eliminate, snacking in between meals.
  2. Brush 3 times/day and floss daily
  3. Eat well balanced, nutritional meals and avoid foods that are high in refined sugars and acids.
  4. See your dentist regularly for professional care.

Regular dental visits are important so that your dentist can monitor the integrity of your crown and the health of the tissues surrounding it.  Your dentist will be extra careful in checking the margin of your crown. Ideally, they would like to be able to detect and repair small issues while keeping your crown in tact before they become more advanced. Regular visits also allow your dental care team to evaluate your home care and advise you as needed.

Early Detection

Monitoring your teeth on a regular basis allows your dentist to assess the health of your teeth and gums. They will check around the margins of your crown to ensure that the area is being kept free of plaque and tartar and that the seal between crown and tooth is still sound. But detecting decay is not always easy. Sometimes there is a cavity growing underneath the crown that goes undetected because there it is showing no clinical evidence of it’s existence and x-rays do not penetrate through metal crowns. A cavity can be growing for a long time before it is caught and can advance to such a stage that the inside of the tooth can turn to mush and the crown loosen without the patient even knowing. At this point, the tooth itself may be at risk and the concern lies in saving the tooth.

Extending the Life of Your Crown

Replacing a crown can be costly in terms of the crown itself and in saving the tooth underneath. The best prevention strategy is to stay one step ahead of tooth decay by practicing good cleaning around where the crown meets the natural tooth at what we call the “margin”. The little time that it takes to clean away destructive bacterial plaque before it has a chance to buildup and become hard to remove is certainly worth the effort to help keep your tooth and surrounding gums healthy for years to come.

Of course, nothing last for ever, but the wise phrase, “An ounce of prevention is worth a pound of cure” is a fitting one when it comes to caring for your crown so it will serve you well for many years.

Yours in Better Dental Health,
The Your Smile Dental Care team
(905) 576-4537 (Oshawa)
(416) 783-3533 (Toronto)
















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