Dental crown

What are they used for?

Crowns are used in cosmetic dentistry to cover teeth that are damaged, broken, devitalized (pulpless tooth) or severely decayed and whose structure would not be strong enough to support a new filling or a dental veneer. Crowns can solidify and embellish these teeth, especially when several of their surfaces have to be rebuilt. The artificial crown can be seen as some kind of a cap that is cemented over a natural tooth.

They are appropriate if it is still possible to save the damaged tooth, when the dental pulp is unharmed and when a root canal can be considered. The tooth root must still be viable in order to proceed with the installation of a crown.

It is sometimes necessary to make and install a post that is anchored in the tooth root before we can install a crown. A post is also required when the natural tooth structure is destroyed after a root canal, as it is the only way to ensure a good support for the crown.

Just like dental veneers, artificial crowns can also fix several minor dental imperfections. They are used in several cases:

The restoration of decayed or broken teeth: crowns have the ability to cover completely a damaged tooth, unlike the veneers that cover only the front of a tooth.
The replacement of teeth that have changed colour over time, of devitalized teeth (after a root canal treatment), of teeth with important fillings or deformed teeth;
The improvement of the smile appearance by correcting the colour, shape and function of teeth.

Artificial dental crowns are part of the family of fixed partial dentures.

Benefits of crowns

They provide functions and look that are similar to those of natural teeth.
They are as durable and strong as natural teeth, which helps to restore the pleasures of almost normal chewing.
They are cemented permanently in the mouth, unlike partial or complete dentures. Because they are fixed, they are more stable than other types of prostheses.

Types of crowns

There are 3 types of frequently used dental crowns, according to their separate manufacturing methods:

Porcelain-fused-to-metal crowns;
All-ceramic or all-porcelain crowns;
All-resin crowns.

The gold crown still exists, although it is rarely used today. It is mostly installed on out-of-sight molars. However, it is very resistant and tooth wear to opposing teeth is kept to a minimum.

Porcelain-fused-to-metal crowns

This type of dental crown is made of a metal alloy substructure topped by a porcelain (ceramic) prosthesis.

Its main disadvantage is that with time, the metal underlying the crown’s porcelain can show through as a dark line, especially at the gum line, especially if your gums recede.

However, it offers several advantages, such as high strength and durability, in addition to minimizing wear to opposing teeth. It is very often used in difficult conditions when other crown making techniques cannot be used. In addition, it is often less expensive than other types of crowns.

Placement of the crown

The installation of a porcelain-fused-to-metal crown typically requires several steps performed in at least two appointments.

During the first visit, the dentist prepares the tooth that will receive the crown. The natural tooth receiving the crown is filed down. The procedure is performed under local anesthesia.
Impressions of the tooth to replace are then taken to create a plaster cast that will help the prosthetist or the dentist to fabricate the crown in the laboratory. At this stage, it is possible to install a temporary crown, often made of acrylic, during the making of the final crown.
Together, the dentist and the prosthetist ensure that the final crown will match perfectly the remaining natural dentition by considering several parameters, including the colour and shape of adjacent teeth. The prosthetist or dentist first fabricates a metal structure that will be then covered with thin layers of ceramics.
When the crown is ready, often within a few days, another appointment is needed to cement the final crown onto the tooth.

All-ceramic crowns

As the name suggests, an all-ceramic crown is an artificial crown built on a ceramic substructure instead of a metal one.

Because ceramic really looks like natural dental enamel (translucent), its main advantage is its aesthetic aspect. Ceramic is also a fully biocompatible material, which means that the all-ceramic crown blends perfectly with the natural tooth.

On the other hand, the all-ceramic crown is contraindicated in cases of important malocclusion and abnormal contact between upper and lower teeth, as well as for certain types of teeth. Indeed, the ceramic is less resistant than metal and can break or become damaged from repeated contact with other teeth.

The installation of an all-ceramic crown requires the same steps as for the porcelain-fused-to-metal crown except that no metal substructure is made.

With the CEREC technology, it is now possible to make porcelain crowns in one appointment. They are then designed by a computer and produced directly at the dental office.

Disadvantages of crowns

The aesthetic results depend mainly on the material used to make the crown. Some materials are more expensive than others, which can represent a substantial investment of money for the patient.
The crowns are irreversible treatments because the damaged tooth must be filed down to reduce its size in order to create space for the crown.

Contraindications

In the presence of cavities or gum disease, these issues must be solved before considering to install crowns.
In the presence of bruxism (teeth grinding or clenching), crowns may be damaged or even break, depending on the material they are made of. Crowns can even cause damage to healthy teeth if they are made from a material that is harder than tooth enamel.