Dental crowns — All you need to know

Crowns, sometimes called caps, are fixed prosthetic devices that completely cover a tooth. They are cemented onto existing teeth or implants. They restore the normal shape and appearance of teeth.

When do I need a crown for my tooth?

1. Extensively decayed tooth

A large cavity severely damages and weakens the tooth. Large fillings on such a weak tooth increases the risk of the tooth breaking. There may also not be enough of the tooth left to allow a filling. Crowns are often needed in such cases.

2. Root canal treated tooth

A root canal treatment removes the dental pulp which nourishes the tooth. Completely cutting off the nourishment to the tooth makes it brittle and vulnerable to fractures in areas of high pressure during chewing. To withstand these pressures and for optimum function, your dentist will usually advise crown for the tooth. Crowns may not be recommended when a large part of the tooth is still retained, and/or the tooth is not located in areas of high pressure.

3. Surveyed crown

If a tooth intended as a support (abutment tooth) for a removable partial denture does not meet the criteria of size or feature, it may be restored with a crown. Such a crown, which makes the support tooth more favourable, is called a surveyed crown.

4. Dental implant

Implant is an artificial ‘root’ (post), usually made of titanium, placed into the upper or lower jaw bone. Once the post is placed and properly integrated into the bone, a crown is cemented over it to provide a tooth-like shape and structure.

5. Improve smile

A crown may be used to make a cosmetic modification to aesthetically improve your smile.

Prefabricated and custom made crowns – what are they?

Prefabricated crowns are made of plastic or stainless steel, and are used as a temporary measure until a permanent crown is made. Stainless steel crowns are commonly used on primary teeth in children.

Custom made crowns are made to order in a laboratory. They match your teeth and fit over the prepared existing natural teeth.

How many visits to the dentist do I need to make?

Most crowns require two visits to the dentist. During your first visit the dentist will prepare or file down the tooth to make room for the crown. Using a rubber-like material, impression (copy) of the tooth is then taken and sent to the lab. A temporary crown is placed over the prepared tooth while your permanent crown is made in the lab.

A crown can be made and placed in a single visit with CAD/CAM technology. The digital picture of the prepared tooth is converted into a 3D image on the computer screen. The design data is sent from the computer to a separate milling machine which makes the desired crown from a block of porcelain. Your dentist then bonds the crown to the prepared tooth during the same visit.

What are the types of dental crowns available?

Crowns can be made from metal, porcelain fused to metal, resin, or ceramic (porcelain) materials.

Metal crowns

Metals used to prepare crowns include gold alloy, palladium alloys or a base-metal alloy (nickel or chromium).

Advantages:

• Less tooth structure needs to be removed
• Stronger, and are better choices for back teeth
• Last the longest in terms of chipping, breaking or wearing off
• Do not wear down opposing teeth

Disadvantages:

• Metal crowns are unsightly. Hence they can’t be used for teeth in the front.

Composite resin crowns

Advantages:

• Less expensive than other crown types
• Same colour as natural teeth
• Don’t chip as easily as porcelain crowns

Disadvantages:

• Stain more easily
• Wear quickly over time
• More prone to fractures

Ceramic (porcelain) crowns

Advantages:

• Excellent aesthetics
• Restores natural appearance of the tooth
• More resistant to staining than resin

Disadvantages:

• Brittle, hence not recommended for posterior (back) teeth fillings
• Can chip easily
• Are more abrasive and cause excessive wear on opposing teeth

Porcelain-fused-to-metal dental crowns

A coating of porcelain is fused over a metal shell.

Advantages:

• Stronger than composite and porcelain crowns
• Look most like normal teeth; next only to all-ceramic crowns

Disadvantage:

• Underlying metal can show up as a dark line at the gum line
• Wear down opposing teeth more than all-metal crowns
• Porcelain part can chip or break

How long do crowns last? What could go wrong with my dental crown?

Permanent crowns can have a long life if you take good care of them. Depending on the amount of wear and tear the crown is exposed to, it can last for 5 and 15 years on an average. Tooth-coloured crowns may need to be replaced over time if the shade (colour) of the crown does not match that of the surrounding teeth.  With time, gum recession around the crown may also make the crown unsightly.

Sensitivity

Sensitivity is not uncommon after a crown is placed on a vital tooth. You may experience some sensitivity to heat and cold which should gradually decrease with time. Experiencing pain or sensitivity when you bite down indicates that the crown is placed higher on the tooth. Receding gums around the crown can also cause sensitivity. Consult your dentist if the sensitivity lingers on or increases, you experience sharp pain in the tooth or you notice swelling in the gums around the crown.

Chipping

Porcelain crowns can sometimes chip. A small chip can be repaired by smoothening and reshaping the remaining crown. If the chip is large enough the crown may need to be replaced with an entirely new one.

Loose fitting

Washing out of cement from under the crown can cause it to become loose and fall out. After evaluating, your dentist may re-cement it in place or recommend a new one.

Decay beneath the crown

Sometimes the crown can fail due to decay under it. An ill-fitting crown on a vital tooth allows bacteria to seep in and cause decay along the edges in the remaining tooth structure. Timely detection of decay and replacement of crown can reduce the amount of destruction of tooth.  The old crown needs to be removed and a new crown fixed after removing the decay.

Originally published on www.healthsite.com