How long does a dental crown last? What wears it out and when to replace it

How long does a dental crown last?

There is no fixed lifespan. A well made crown on a strong, well looked after tooth can serve a patient for a great many years; another, in a high-risk mouth, may need replacing much sooner. No dentist can therefore promise you a precise duration, but they can tell you what, in your case, works for or against the crown.

In practice, a crown rarely wears out on its own. What limits its service life is usually what happens around it: the tooth that carries it, the margin next to the gum and the forces it receives day and night.

This article looks at those factors and at the signs that a crown should be checked. If yours is loose or has just come off, what to do is explained in our article on a crown that is loose or has fallen out. For a crown on an implant the question is different: see how long a dental implant lasts.

The tooth under the crown: the first factor in longevity

A crown is never stronger than the tooth supporting it. Several features of that tooth carry a lot of weight:

• A living or root-treated tooth. A living tooth keeps its sensitivity, which gives a warning in case of decay or overload. A root-treated tooth gives no warning: leakage can progress painlessly. It is also more prone to fracture when little tooth structure remains.
• The height of sound tooth that the crown wraps around. Dentists call this the ferrule effect: a band of healthy dentine of sufficient height, embraced by the crown, protects the tooth against fracture. A very short tooth, rebuilt mainly with a post and core, is more vulnerable.
• The root and its treatment. A root crack, or an infection returning at the root tip, can mean removing a crown that is itself intact.
• Gum and bone support. If gum disease destroys the bone around the root, the tooth eventually loosens, however good the crown.

Put simply, two identical crowns will not have the same expected service life if one sits on a robust tooth and the other on a tooth that is already badly weakened.

The material and the precision of the crown

The material matters, but not always in the way people think. Each has its own profile:

• Monolithic zirconia is very fracture resistant and rarely chips, which makes it a common choice for molars and for patients who clench.
• Porcelain-layered zirconia looks more natural, but the porcelain layer can chip under heavy loads.
• Lithium disilicate offers lovely translucency and is bonded to the tooth; it suits many situations provided enough thickness is respected.
• Porcelain fused to metal has a long clinical track record; its porcelain can chip, and a grey line may show if the gum recedes.
• Resin crowns are mainly used as temporary or transitional solutions: they wear and stain more quickly.

Beyond the material, precision plays a major role. A tight margin between crown and tooth limits plaque build-up. A crown that is properly adjusted to your bite avoids overload. Digital impressions and computer-aided manufacturing help achieve this precision, but it is the whole chain, from tooth preparation to final adjustment, that makes the difference.

The crown margin: where it all happens

Porcelain does not decay, but the tooth carrying it does. Decay that develops at the edge of a crown, called secondary or recurrent caries, is one of the most common reasons a crown has to be redone.

This risk increases in several situations:

• gum recession exposing the root, which is softer than enamel and more prone to decay;
• a dry mouth, often linked to medication, since saliva naturally protects the teeth;
• frequent sugar intake, including sweet drinks sipped throughout the day;
• insufficient cleaning between the teeth, where the brush cannot reach the crown margin.

Prevention is simple but must be regular: brushing twice a day with a fluoride toothpaste, angling the brush towards the gum, and daily flossing or interdental brushing against the crown. When the decay risk is high, the dentist may recommend a higher fluoride toothpaste or fluoride varnish applications at the practice.

Grinding, knocks and habits: the forces that tire a crown

A crown takes thousands of contacts every day. It is designed for this, but some forces exceed what it can withstand in the long run.

Bruxism, that is clenching or grinding the teeth, often at night and without being aware of it, can cause porcelain chips, cracks in the supporting tooth or debonding. Signs such as jaw pain on waking, worn teeth or a partner mentioning noises at night should be reported. A protective night guard is often suggested; our article on bruxism and teeth grinding explains the options.

Other habits wear crowns out prematurely:

• crunching ice, fruit stones or bones;
• biting nails or chewing pens;
• opening bottles or packaging with your teeth;
• playing contact sports without a mouthguard.

These habits seem harmless, but repeated over time they explain many fractures that appear to happen for no reason.

Signs that a crown should be checked

Some signs justify booking an appointment without waiting for your next check-up:

• a dark line at the gum margin, which may simply be exposed metal, but may also be decay;
• red, swollen or bleeding gum around the crown, while the rest of the mouth is fine;
• pain when chewing, with cold or heat, or discomfort when you clench;
• a bad taste or a localised odour, sometimes a sign of leakage under the crown;
• food that keeps getting stuck between the crown and the neighbouring tooth;
• a chip, a crack or a surface that feels rough to the tongue;
• a feeling of movement, even slight;
• a shade that no longer matches the neighbouring teeth, for example after whitening, since a crown does not whiten.

Be aware that several problems develop without any symptoms, especially on a root-treated tooth. That is why a clinical examination and X-rays at regular check-ups remain essential, even when everything seems fine.

Repair, monitor or replace: the decision at the practice in Agdal

An ageing crown does not necessarily need replacing. Depending on what the examination shows, several approaches are possible:

• Monitor an old crown that is sound, well fitting and free of decay: its age alone is no reason to change it.
• Repair a small porcelain chip by polishing or by adding bonded composite, when the chip is limited and away from high-stress areas.
• Replace the crown in case of decay under the margin, a major fracture, an open margin or chronically irritated gum, sometimes with a new core build-up.
• Reconsider the treatment when the tooth itself can no longer be saved: other replacement options are then discussed.

At German Dental Clinic in Agdal, checking a crown combines a clinical examination with digital X-rays. When a new dental crown is needed, intraoral scanning and in-house milling may be considered depending on the case. If you live in Rabat and one of your crowns is worrying you, you can book an appointment to have it checked.