What is dental crown

A crown is an artificial restoration or a covering that fits over the remaining part of a prepared existing tooth, making it strong and giving it the shape of a natural tooth. A crown is sometimes known as a ‘cap’. A dental crown can improve the way a decayed or broken tooth looks and make it stronger and longer lasting. Crowns are usually made from porcelain or a mix of porcelain and metal.

Dental crowns are an ideal way to repair teeth that have been broken, or have been weakened by tooth decay or a very large filling. A crown could be used for a number of other reasons, for example:

• You may have a discolored filling and would like to improve the appearance of the tooth.
• You may have had a root filling and need a crown to protect what is left of the tooth (when too much of the original tooth is missing to hold a filling).
• Dental crowns are also used to protect a weak tooth from breaking, and to cover stained or badly shaped teeth.
• A dental crown may help to hold a bridge or denture firmly in place.

What does a dental crown look like?

Dental crowns can be made of a variety of different materials and new materials are continually being introduced. Some of the most popular options are listed below.

Porcelain bonded to precious metal

• This is what most dental crowns are made from. A precious metal base is made and then porcelain is applied in layers over it.

Porcelain

• These dental crowns are made entirely out of porcelain and are not as strong as bonded crowns. But they can look very natural and are most often used for front teeth.

All-ceramic

• This modern technique offers a metal-free alternative, which can give the strength of a bonded crown and the appearance of a porcelain crown. Therefore it is suitable for use in all areas of the mouth.

Glass

• These dental crowns look very natural and can be used anywhere in the mouth.

Gold-alloy crowns

• Gold is one of the oldest filling materials. Today it is used with other metal alloys to increase its strength, which makes it very hardwearing. These dental crowns are silver or gold in color.

Figure 1. Dental crown

Dental crown replacement procedure

Your dentist will usually prepare the tooth by removing a layer of the outer surface of the tooth. Your dentist will prepare the tooth to the ideal shape for the dental crown. This will involve removing a layer of the outer surface, leaving a strong inner core. The amount of the tooth removed will be the same as the thickness of the crown. That is the dental crown will be the same thickness as the thickness of this removed tooth layer.

Once the tooth is shaped, the dental team will take an impression (mould) of the prepared tooth, one of the opposite jaw and possibly another to show the way you bite together.

The impressions will then be given to a dental technician, along with information about the shade to use and any other information they need to prepare the crown. It can often be matched to the color of your teeth, so it will blend in.

You might be given a temporary crown to get you through until the permanent crown is made.

When your permanent crown is ready, you’ll go back to the dentist and have it fitted using dental cement or adhesive.

How dental crown is fitted

When you and your dentist are happy with the fit and appearance of the new dental crown, it will be fixed in place with special dental cement or adhesive. The cement forms a seal to hold the crown in place.

How long does the treatment take?

You will need to have at least two visits. At the first visit, your dental team will prepare the tooth, take the impressions, make a note of the shade of your tooth, and fit the temporary crown. At the second visit, your dentist will fit the permanent crown. There will usually be about 1 to 2 weeks between appointments.

Does it hurt to have a tooth prepared for a dental crown?

No. You will have a local anaesthetic and the preparation work should feel no different from a filling. If the tooth does not have a nerve, and a post crown is being prepared, then you may not need a local anaesthetic.

Will the dental crown be noticeable?

The crown will be made to match your other teeth as closely as possible. The shade of the surrounding teeth will be recorded, to make sure that the colour looks natural and matches those teeth.

Will the dental crown feel different?

Because the shape of the crown will be slightly different from the shape of your tooth before it was crowned, you may be aware of it at first. Within a few days it should feel fine, and you will not notice it. The crown may need some adjustment if your bite does not feel comfortable, and if this is the case, you should ask your dentist to check and adjust it.

What will dental crown cost?

Costs will vary according to the type of dental crown and the material used. Always get a written estimate and treatment plan before starting any dental treatment.

How do I care for my dental crown?

It is important to keep the crown just as clean as you would your natural teeth. The crown itself cannot decay, but decay can start where the edge of the crown joins the tooth. Brush last thing at night and at least one other time during the day with a fluoride toothpaste, and clean in between your teeth with ‘interdental’ brushes or floss.

How long will the dental crown last?

How long your dental crown lasts depends on how well you look after it. Properly cared for dental crowns should last for many years. Your dental team will be able to tell you how long your dental crown may be expected to last.

What is a temporary dental crown?

A temporary dental crown is a provisional, short-term restoration cemented in place with a soft temporary dental cement until your permanent crown is ready. For best results, temporary crowns should be constructed and cemented immediately after teeth preparation.

A temporary crown will be made so that you can use the tooth while you wait for the permanent crown to be made. A temporary crown may be more noticeable but is only temporary.

Main functions of temporary dental crown

• Partially restores aesthetics by disguising the prepared teeth to some degree. This is especially important if teeth are located in visible parts of the mouth.
• Protects the prepared teeth (for example from temperature variations) and prevents damage to the periodontal tissues (gums).
• Partially restores the chewing function.

Features of temporary dental crown

Temporary crowns are usually constructed from plastic-like materials (acrylic) or composite resins. These crowns don’t need any metal frame because they have a short life-span.

It is possible to manufacture temporary crowns from stainless steel or aluminium. Usually, these types are prefabricated.

If fabricated from acrylic resins or composite, temporary crowns have a close color to the adjacent teeth and low resistance to chewing. There is no need for a high resistance because they stay in place only for a short time.

How are temporary crowns manufactured?

There are two ways to manufacture a temporary crown:

1. Direct method

The temporary crown material is shaped by the dentist to form a tooth shape. For this operation, the dentist uses a specific crown kit. The crown kit contains prefabricated crown forms for incisors, canines, premolars and molars.

These crown forms are manufactured from various materials: polycarbonate, acrylic, transparent plastic and sometimes aluminium.

Technique

• After tooth preparation, the dentist selects from the kit a crown form that best fits the prepared tooth.
• The crown form is adjusted on the prepared tooth.
• The temporary crown material is placed inside the crown. Usually, this material is supplied together with the crown kit.
• The material has several shades and a relatively short curing time.
• The crown form with the temporary material inside is repositioned on the prepared tooth. The temporary crown is shaped between the inside walls of the crown form and the outside walls of the prepared tooth.
• After temporary material sets, the crown is removed from the tooth and the temporary material (which by now is hardened) is removed from the crown form. Further adjustments can be made if necessary.
• The temporary crown is adjusted to fit in the bite. At the end, the final polish is performed.
• The crown is cemented in place with a soft temporary cement. This allows for easy removal when fitting the definitive restoration.

2. Indirect method

This method involves the dental laboratory. The crown is manufactured by the dental technician and sent to the dental office for temporary cementation.

Technique

• After teeth preparation, the dentist makes a dental impression. It is possible to make an additional impression for the temporary crown but more often the same impression is used. The impression is sent to the dental lab.
• The technician pours fluid gypsum inside the impression to create the dental cast. Then, according to the instructions received from the practice, the dental technician constructs the temporary crown on the dental cast.
• The crown can be constructed using various techniques some of them similar to the direct method described above (but performed by the dental technician on the dental cast). The materials used are dental acrylic or composite.
• After modelling is over, the crown is placed in specific processing units for polymerization. At the end, the technician polishes the crown for a smooth surface. The whole process takes 1-2 hours, so the temporary crown can be fixed during the same day.

Other temporary restorations

Besides temporary crowns, other types of temporary restorations can be manufactured.

• Temporary bridges: indicated in cases with extended restorations but they are rarely used. Usually, in such situations, temporary crowns are constructed on all abutment teeth. If aesthetic demands are high and it is estimated that the restoration will require a longer time to completion, provisional removable dentures are preferred.
• Provisional removable dentures: are constructed when large restorations require a long period of execution. For example, in case of dental implants the time that is needed may be up to 6 months.

After the medical examination, the dentist will consult with the patient to determine the exact type of temporary restoration that will be manufactured.

What is a post dental crown?

In root-filled teeth it may be necessary to insert a post into the tooth root before placing a crown. A post gives support and helps the crown to stay in place. The surface of the tooth may be removed down to the level of the gum.

A post can be made of prefabricated stainless steel which the dentist can fit directly into the root canal. Or a custom-made post can be constructed by a dental technician to accurately fit the shape of the prepared root canal. The post is placed into the root canal and cemented in position, ready for the crown to be attached.

Are there any alternatives to post dental crowns for root-filled teeth?

If a root-filled tooth is not completely broken down, it may be possible for your dentist to build it up again using filling material. This ‘core’ is then prepared in the same way as a natural tooth and the impressions are taken.

What are the benefits and risks of a dental crown procedure

Dental crowns are a way of protecting your teeth that are weak or have been broken. Dental crowns also help improve the appearance of your teeth that are irregularly shaped or stained. Dental crowns can last many years if they are cared for properly.

But sometimes dental crowns break or fall off. This might be because the cement doesn’t hold, or it might be because the tooth under the crown has decayed.

Alternatives to dental crowns

There are alternatives to dental crowns. If you want to improve discolouration, then veneers – which are thin layers fixed onto the front surface of a tooth – might be an option. If your tooth is chipped, your dentist may also try to rebuild your tooth structure using filling material.