If a tooth is so badly decayed or fractured that it is not possible to place a normal filling, inlay or onlay, it may be necessary to restore the whole of the tooth by placing a crown. Sometimes if a tooth is misshapen because of a developmental abnormality or if it is badly discoloured we may consider a crown to improve the appearance or the tooth. If a tooth has had to have root canal treatment to remove the nerve this can weaken the tooth and it may be necessary to place a crown over the tooth to strengthen and protect it.
What Are Crowns Made Of?
Crowns can be made from various materials. Traditionally crowns on back molar teeth may have been made out of metal but these days alternatives are available which have similar strength but better appearance than metal crowns. Front teeth were usually crowned with porcelain jacket crowns. These have a better appearance but are quite fragile and eventually can form cracks and break similar to the cracks found in a porcelain cup. With the invention of better materials we have three main options for crowns.
What Are The Dental Crowns Options?
Porcelain Fused to Metal or PFM crowns: These are produced in the laboratory using a metal substructure with porcelain fused to the surface to make the crown look more tooth like. These have been in use for years and can give good results. Long-term gum recession around front teeth crowned with PFM crowns can make the metal margin of the crown visible as a dark line. People who clench and grind their teeth may find that the porcelain can chip off of the metal on back teeth.
All Ceramic Crowns: These are a newer type of crown which can be built up in layers by the laboratory giving them a very life like appearance. They are particularly aesthetic on front teeth. They also work on back teeth but may be prone to chipping in people who clench and grind their teeth.
Monolithic Zirconia Crowns. These are extremely strong crowns. They do not have the aesthetics of the all ceramic crowns, although this is improving, but are ideal for people who clench and grind their teeth. These crowns are becoming more and more popular, as clenching/grinding habits are becoming more prominent in patients (let us know if you suffer with the pains associated with TMJ/TMD).
What Is The Dental Crowns Procedure?
The procedure for having a crown is that first the area is numbed up with an injection. If we are restoring an upper tooth the injection is placed in the gum directly over the tooth and left for a few minutes to work. This will numb the tooth and those either side of it. If we are restoring a lower tooth we will quite often need to carry out a different injection known as a dental block. Here the injection is placed behind the back lower tooth and numbs the nerve before it enters the bone. As this bundle of nerves contains the nerves which run to the lips and tongue these will quite often be numb as well.
Once the tooth is numb it will be prepared removing any decay and unsatisfactory old restorations. The tooth may then need to built up with a special core material to give the ideal shape to retain a crown. Once this is completed an impression is taken of both the prepared tooth, using a silicone putty, and the opposing teeth using a minty alginate material. The silicone putty provides a more accurate impression for the laboratory to make the crown and the opposing impression allows the laboratory to check that the bite on the new restoration is correct. Once the impression has been taken a temporary tooth coloured crown will be placed to protect the tooth while the laboratory is making the permanent crown. This appointment will take approximately 1 hour but may vary depending upon the complexity of the preparation and number of teeth prepared.
Approximately 2 weeks later you will return and the tooth will again be numbed. The temporary restoration will be removed and the tooth cleaned. The fit of the crown will be checked and adjusted if necessary. Once satisfied the restoration will be bonded to the tooth using a strong adhesive and the bite checked. You will need to be careful of the area and have a soft diet until the adhesive has fully set which will take a couple of hours. The second appointment should take approximately 30 minutes to complete again depending on the number of teeth being treated.
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The choice of material to be used in each individual case and the pros and cons of each are discussed in detail at the treatment planning stage. This will allow you to make an informed decision for the best option for yourself. If you require a crown or some dental work, please do not hesitate to call us and we will be happy to help.