A dental crown is a cape made of different materials, covering a tooth that was polished beforehand, to restore the shape, size and improve appearance.
When is a dental crown necessary?
A dental crown is indicated in the following situations:
- To protect a fragile tooth (teeth with bulky fillings of composite or amalgam) from fracturing
- To restore an already broken tooth or a tooth that was badly worn
- To perform a dental bridge in case of missing teeth
- To cover the teeth abnormally shaped or coloured
- To cover a dental implant
- To improve the aesthetic appearance of the front teeth
What types of crowns are available?
Permanent crowns can be made from different alloys (metal crowns), mixed crowns that have a facet of physiognomic material, mixed metal-ceramic crowns (the ceramic material completely covers the metal frame, full ceramic crowns or ceramic crowns on zirconium skeleton.
Metals used for metal crowns include noble alloys (gold, palladium) or non-noble alloys (e.g. nickel or chrome). The benefits this type of crowns are: the sacrifice of tooth structure for the preparation is lower than for other types of crowns, opposite tooth wear is kept to a minimum, withstanding masticatory forces and have a long life. The metallic colour is the main drawback. Metal crowns are a good choice for out-of-sight molars.
Metal-ceramic crowns and full ceramic crowns
Metal-ceramic crowns and full ceramic crowns mimic natural tooth colour best. However natural teeth antagonist to metal ceramic restorations show more wear because the ceramics is very hard. Therefore, this type of restoration is contraindicated in patients with bruxism. Sometimes metal-ceramic crowns cause a dark, purplish line at the gingival margin. Therefore in case of high aesthetic demands in the front area are indicated full ceramic crowns or ceramic crowns on zirconium skeleton. They are also indicated in people who have allergies to metals.
Temporary crowns versus permanent crowns.
Temporary crowns can be made in the dentistry office or dental laboratory, while the permanent crowns are made only in the dental laboratory. Temporary crowns are made of acrylics and can be used as a temporary restoration until a permanent crown is made in the laboratory.
Preparing a tooth for a crown usually requires two visits to the dentist – the first step involves examining and preparing the tooth, the second visit involves placing the permanent crown.
First visit: Examination and preparation of the tooth.
At the first visit in preparation for a crown, the dentist may ask the patient to make a panoramic or retroalveolar radiograph to check the roots of the tooth that will receive the crown and the surrounding bone. If tooth decay is extensive or if there is a risk of infection or injury to the tooth pulp, a root canal treatment can be carried out first.
Before you begin the process of making a crown, the dentist will anesthetize (numb) the tooth and the gum around the tooth. The amount of dental tissue removed depends on the type of crown used (e.g., crowns from metal are thinner and require less sacrifice of tooth structure than full ceramic crowns or metal ceramic crowns. If, on the other hand, a large area of the tooth is missing (due to decay or fractures), the dentist will use different materials to “build” the tooth in order to support the crown.
After preparation of the tooth, the dentist will use a paste or putty to make an imprint of the tooth that will receive the crown. The imprint will include antagonist teeth and the neighbouring teeth, to make sure that the crown will not affect the bite.
Dental prints are sent to a dental laboratory. The duration of dental restoration execution usually lasts one week, two weeks maximum depending on complexity. During this interval it is indicated for the patient to wear a temporary restauration to cover and protect the prepared tooth.
Second visit: Receiving the permanent dental crown.
On the second visit, the dentist will remove the temporary crown and check the shape, colour and bite adjustment in the permanent crown. If everything is acceptable, the new restoration will be cemented provisionally for a trial period, and will subsequently be permanently cemented. Full ceramic crowns and metal-ceramic ones are cemented directly definitively.
How should we protect the temporary crowns?
Since provisional crowns are only a temporary solution until a permanent crown is ready – most dentists suggest some precautions. These include:
- Avoid sticky foods (e.g., chewing gum, caramel), or chewing hard food (raw vegetables)
- Avoid chewing food on the teeth with temporary crown
How long does a dental restoration last?
The average use of dental restorations is 10-15 years. There are a lot of factors that determine the duration of wearing a restoration, such as good hygiene conditions, addictive personal habits (nail biting, breaking the seeds and using teeth to open packaging), bruxism.
Does a restored tooth require special care?
If a tooth is covered by a restoration, it does not mean that it is protected from decay or gum disease. Therefore, it is necessary to follow good oral hygiene practices, including brushing teeth at least twice a day and flossing once a day. Antibacterial mouthwash can also help.