What is a PFM dental crown?
May 27, 2015
Porcelain fused metal dental crowns, or PFMs as they are commonly referred to, consist of a layer of metal alloy at the base topped by porcelain. These are among the popular choices for dental restorations such as crowns or bridges. Within this category of crowns, further choice still exists catering to the budget and requirements of the patient.
PFM Crown Types
PFMs are classified according to the metal alloys being used. These are:
High noble: Also known as precious, these consist of about 60 percent of gold or palladium or platinum. No porcelain fused metal crown can be made of pure gold as it is too soft to work with. Though this is the most expensive PFM, it is also the most reliable as far as durability is concerned.
Noble: Also referred to as semi-precious, these have a lower content of precious metals like gold and platinum. Generally, it will be about 40 percent. This helps to bring the cost down while still maintaining a good level of strength.
Base: Also described as non precious, these have approximately 20 to 25 percent of precious metal material while the rest is mainly nickel, chromium and others. This is the strongest metal alloy, but some people experience inflammation in the gums because of the metals used in it. However, any negative effect is localized only to the immediate area. In general, there are no systemic reactions or impact on general health. In some cases, there may be an allergic reaction to the material being used.
Pros and Cons of Porcelain Fused Metal Dental Crown
The metal foundation adds strength and durability as compared to porcelain only crowns. Therefore they are ideal for the back teeth where there is heavy chewing force. This metal and ceramic combination is also considered to be next best to porcelain for natural looking restorations. This makes it appropriate for the front teeth too. In rare cases, the porcelain top can get damaged, but this can be repaired and does not affect the innate stability of the restoration. This is because the metal base continues to support the structure. Normally, this is the preferred choice in case of extensive destruction of the tooth structure resulting from deep caries or even previously failed restorations. However, it requires excessive tooth reduction and may not be suitable for young patients with large pulp chambers.
Introduction of newer methods in the construction of these crowns has minimized the chances of the black line that becomes visible in porcelain fused metal crowns. This has taken away the biggest concern as far as the aesthetic aspect is concerned. Additionally, careful matching and staining can get good aesthetic results which are comparable to an all ceramic restoration. It is therefore still the preferred option though other crown materials may have gained use.
A porcelain fused metal crown requires at least two sittings with the dentist. In the first visit, the tooth is prepared for restoration and a dental impression is taken and sent to the laboratory for the casting of the crown. The crown is fixed in place at the second visit.
What is a VMK dental crown?
The VMK abbreviation stands for veneered metal crown. Basically, both VMK and PFM crown mean the same thing - a porcelain fused to metal dental crown. The last letter of the abbreviation VMK comes from the German word 'Krone' which means a crown.
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