A dental crown also called “cap” or “cover” is a custom designed helmet like material used to cover a damaged or decayed tooth to protect it from further damage. Crowns can also be used to cover a discolored or misshapen tooth.  A tooth that treated with crown feels looks and works very much like a natural tooth.  The crown, when cemented on tooth, it covers the entire visible part of a tooth that lies above the gum line.

helmet like tooth shaped strtucture on tooth

Why Is a Dental Crown Needed?

Treatment of dental crown is used commonly for the following reasons.

(1) Strengthening teeth.

Sometimes in treatment of badly carious tooth, large portion of tooth structure is damaged and it is restored by large restoration, leaving unsupported and insufficient original structure, which is more prone to fracture, to hold artificial filling material, require crown placement to cover and support a tooth to withstand heavy chewing forces and retain filling material to fail. After root canal infection, tooth lost the nutritional supply and became brittle. That’s why after root canal treatment most of tooth require crown to strengthen against heavy chewing forces.

dental crown prevent fracture of extensively restored tooth

(2) Restoring teeth to their original shape and function
Crown is used to rebuild the original shape and function of tooth which is broken or decayed. It also used to restore a tooth that has been severely worn down.

(3) Improving the appearance of teeth.
When a dental crown is cemented over tooth, it becomes the new outer surface of a tooth. By this benefit we can cosmetically modify color, shape and even alignment of tooth. We can change the badly shaped or severely discolored teeth by making crown over teeth.

Types of dental crowns

There are three types of dental crowns. Full metal, Porcelain-fused-to-metal (PFM) and all-ceramic.

Clink link to know more details about various types of crowns 

 (1)   MetalFree All-Ceramic or All-Porcelain

 (2)   Porcelain-Fused-to-Metal (PFM) 

 (3)   Full Metal

Factors to determine type of crown:

♦  There are a number of factors that need to be considered when making this determination, which type of crown is most suitable for you according to your need.
♦  Esthetics - color match and appearance
♦  Function - chewing and biting accuracy
♦  Tissue compatibility- the contour of the prosthesis must allow the surrounding tissue to conform to a natural, healthy position.
♦  Cost factors – Full metal crown is cheaper while all-ceramic is most costly.
♦  Skill of dentist – Preparation of tooth for PFM and all-ceramic crown is highly precise work. The skill of dentist definitely impact on durability, cosmetic appearance of crown and health of adjacent tooth and gums.

Procedure for Crown and Bridge Treatment

Preparing a tooth for a crown and bridge (A bridge is two or more capped teeth connected together with one or more false teeth in between the capped teeth) are same.
It usually requires two visits to the dentist -- the first step involves examining and preparing the tooth, the second visit involves placement of the permanent crown.

First Visit: Examining and Preparing the Tooth

At the first visit in preparation for a crown, X-ray may be taken to check the roots of the tooth receiving the crown and surrounding bone. If the tooth has decay or if there is a risk of infection or injury to the tooth's pulp, a root canal treatment may first be performed.
Before the process of making a crown begins, we will anesthetize the tooth and the gum tissue around the tooth (in case of vital tooth). Next, the tooth receiving the crown is reshaped along the chewing surface and sides to make room for the crown. The amount removed depends on the type of crown fabricated (for example, full metal crowns are thinner and require less tooth structure removal than all-porcelain or porcelain-fused-to-metal ones). If, in case of a large area of the tooth is missing (due to decay or damage), we will use post & core or filling material to build up the tooth to support the crown. After reshaping the tooth, we will use a paste or putty to make an impression of the teeth to copy tooth. Impressions of the teeth opposite jaw will also be made to make sure that the crown will not affect your bite.
The impressions are sent to a dental lab where the crown will be manufactured. The crown is usually returned in one week. If the crown is made of porcelain, we will also select the shade and that most closely matches the color of the neighboring teeth and photographed. After that temporary crown is placed to cover and protect the prepared tooth while the crown is being made. Temporary crowns usually are made of acrylic and are held in place using weak temporary cement.

Second Visit: Cementation of Permanent Dental Crown.

At the second visit, temporary crown is removed and check the color and fit both on the tooth and the way it touches neighboring and opposing teeth. After making any needed adjustments and if everything is ok then the new crown is permanently cemented in place.