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Home --> Prosthetic Dentistry --> Porcelain Crowns
What is a Porcelain Crown?

A dental crown is a tooth-shaped "cap" that is placed over a tooth -- covering the tooth to restore its shape and size, strength, and/or to improve its appearance. The crowns, when cemented into place, fully encase the entire visible portion of a tooth that lies at and above the gum line.

A dental crown may be needed in any of the following situations:

To protect a weak tooth (for instance, from decay) from breaking or to hold together parts of a cracked tooth
To restore an already broken tooth or a tooth that has been severely worn down
To cover and support a tooth with a large filling when there isn’t a lot of tooth left
To hold a dental bridge in place
To cover misshaped or severely discolored teeth
To cover a dental implant

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All Porcelain Crowns

The most beautiful crown for a tooth is, without question, All Porcelain or all-ceramic. With Porcelain Fused to Metal crowns, there has to be an opaque layer put over the metal to block out its color. This makes it impossible to have a translucent restoration that mimics the translucency of natural teeth. Only with pure porcelain or pure ceramic can you have such translucency.

To define some terminology, porcelain is a particular type of ceramic that is built by stacking and firing. When we say ceramic, we include porcelain - porcelain is a type of ceramic.

When there is not enough tooth structure left, or the chewing demands in the mouth are too great for veneers, a stronger, more extensive restoration is needed. Here we need porcelain jacket crowns. Porcelain jackets are pure porcelain crowns placed on a fully prepared tooth. They are the most life-like of all full crown type restorations. The technique initially consists of preparing the teeth. Next, an impression is taken and then sent to the dental lab where the porcelain jacket is fabricated. Finally, they are placed in the patient's mouth and permanently cemented onto the teeth.

All Porcelain dental crowns provide the best natural color match of all crown types and may be more suitable for people with metal allergies. However, they are not as strong as Porcelain Fused to Metal crowns and they wear down opposing teeth a little more than metal or resin crowns. All Porcelain crowns are a good choice for front teeth.

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 Porcelain Fused to Metal Crowns

Porcelain Fused to Metal crowns are a cross between all metal crowns and All Porcelain crowns. A veneer of porcelain is then fused over this metal, giving the crown a white tooth-like appearance.

Once the decay has been removed, your dentist will prepare the space for the filling by cleaning the cavity of bacteria and debris. If the decay is near the root, your dentist may first put in a liner made of glass ionomer, composite resin, or other material to protect the nerve. Generally, after the filling is in, your dentist will finish and polish it. Depending on the requirements of your situation, these crowns are sometimes made where the porcelain veneer only covers those aspects of the crown that are readily visible.

Porcelain Fused to Metal crowns can be a good choice for either front or back teeth. These crowns are strong enough to withstand heavy biting pressures and at the same time can have an excellent cosmetic appearance.

When biting pressure is too great for porcelain jackets or gaps from missing teeth must be filled in, metal alloy must be placed under the porcelain for strength. This is the Porcelain Fused to Metal crown technique. More tooth structure is removed to accommodate both metal and porcelain. Once an impression is taken, a metal coping is made on the prepared tooth. This is then covered with porcelain. Porcelain Fused to Metall crowns do not have the translucency of pure porcelain crowns. Therefore, aesthetics may be slightly compromised in some situations. However, a talented ceramist with experience in custom staining can usually overcome these limitations, thereby creating life like restorations. When teeth are loose due to periodontal bone loss, this technique is used. Here the crowns are splinted together by joining the metal substructure of the crowns so they are tied together like a small fence in the mouth.

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Porcelain Fused to Metal dental crowns can be color-matched to your adjacent teeth (unlike the metallic crowns). However, more wearing to the opposing teeth occurs with this crown type compared with metal or resin crowns. The crown’s porcelain portion can also chip or break off. Next to all-ceramic crowns, Porcelain Fused to Metal crowns look most like normal teeth. However, sometimes the metal underlying the crown’s porcelain can show through as a dark line, especially at the gum line and even more so if your gums recede. These crowns can be a good choice for front or back teeth.
Comparison of All Porcelain Crowns to Porcelain Fused to Metal Crowns

All Porcelain is generally not as strong as Porcelain Fused to Metal. It has to be bonded to the tooth in order to have adequate strength for oral function. The bonding technique is very demanding and is not fully taught in dental schools. We recommend that you only have an expert cosmetic dentist place this type of crown.
With Porcelain Fused to Metal, the porcelain has to be opaque in order to block out the appearance of the metal underneath. They all also eventually develop an unsightly dark line at the margin where the edge of the crown meets the tooth.
Some of the all-ceramic systems that have an inner ceramic core with an outer layer of porcelain baked on require more tooth reduction. Grinding away more of the tooth is often not desirable.
Some of the ceramic materials that are very tough and fracture resistant are also quite abrasive against the opposing teeth. Of the crowns listed above, the Empress is the kindest to the teeth it chews against.

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 What Steps Are Involved in Preparing a Tooth For a Crown?

Preparing a tooth for a crown usually requires two visits. The first step involves examining and preparing the tooth, and the second visit involves placement of the permanent crown.

Examining and preparing the tooth. At the first visit, your dentist may take a few x-rays to check the roots of the tooth that is receiving the crown and surrounding bone. If the tooth has extensive 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 your crown is begun, your dentist will anesthetize your tooth and the gum tissue around the tooth. Next, the tooth receiving the crown is filed down along the chewing surface and sides to make room for the crown. The amount removed depends on the type of crown used (for instance, all-metal crowns are thinner, requiring less tooth structure removal than All Porcelain or Porcelain Fused to Metal ones). If, on the other hand, a large area of the tooth is missing (because decay or damage), your dentist will use filling material to "build up" the tooth enough to support the crown.
After reshaping the tooth, your dentist will use impression paste or putty to make an impression of the tooth. Impressions of the teeth above and below the tooth to receive the dental crown will also be made to make sure that the crown will not affect your bite.
The impressions are sent to a dental laboratory where the crown will be manufactured. The crown is usually returned to your dentist’s office in 2 to 3 weeks. If your crown is made of porcelain, your dentist will also select the shade that most closely matches the color of the neighboring teeth. During this first office visit, your dentist will make a temporary crown 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 a temporary cement.
Receiving the permanent dental crown. At your second visit, your dentist will remove your temporary crown and check the fit and color of the permanent crown. If everything is acceptable, a local anesthetic will be used to numb the tooth and the new crown is permanently cemented in place.

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