⦁ Porcelain Fused to Metal Crowns and Bridges
Porcelain fused to metal crowns
Porcelain fused to metal crowns are more affordable than all ceramic crowns. Even though they are not as aesthetic as porcelain crowns they are still a good candidate for back teeth restoration. Read this article to find out what the advantages and disadvantages of PFM crowns are.
Porcelain fused to metal crowns (or PFM crowns) can be referred to as full-cast crowns which has porcelain fused on most or all parts of the tooth. They are a hybrid between porcelain and metal crowns. The entire crown has a metal layer underlying and porcelain / ceramic on top of it.
The metal framework is thin, strong, and perfectly fits the prepared teeth. It’s a combination of different types of alloys which are designed such that they bond very well with the porcelain. Metal alloys with a high melting temperature are used to fuse porcelain to the surface and preventing the metal from melting. This ensures the porcelain to bond without changing its color.
When the tooth is prepared for such crowns, a large part of the tooth tissue gets removed making space for porcelain as well as the metal.
A porcelain veneer is fused over the metal shell. The porcelain layer is 1.5 mm to 2 mm thick depending on the area of your tooth. The porcelain layer is tough, withstands the chewing forces very well, and looks like your natural teeth.
Porcelain fused to metal crown
Porcelain fused to metal crown
Porcelain crowns are the most preferred crowns as they easily match the color of the adjacent teeth better than the metallic crowns. However, they cause more damage to the opposite teeth than the resin and metal crowns. Some cases show that the porcelain portion of the crown can also break or chip off from the teeth.
In receding gums, such crowns are not suitable as the porcelain can start showing distinctively. They are best suited for the back and front teeth.
Types of porcelain fused to metal crowns
The metal framework is a combination of different types of alloys. The type of framework is one of the factors which decides the price of your porcelain fused to metal crown.
1. Porcelain fused to base metal alloys
As the name suggests, here the framework uses a combination of base metals which are popular in dentistry. However, some of you may have an allergy to few of the base metals such as nickel. Opting for noble metal crowns helps you avoid allergy.
2. Porcelain fused to titanium alloys
Titanium alloys have the properties of noble metals such as gold.
As they have superior properties they are useful for implants and other dental prostheses. Your dentist builds a crown on it and it feels like your natural teeth.
Porcelain fused to titanium alloys carry better properties than base metal alloys but gold alloys carry even better properties.
3. Porcelain fused to gold alloys
Gold alloys offer the best properties, carry the highest strength, durability, and cause no allergy.
Though the name says gold, a gold alloy is a combination of gold, platinum, silver, palladium, copper, and tin. The first four metals in a gold alloy are known as noble metals as they have superior properties. The last two metals are known as base metals. The higher the amount of noble metals present in a gold alloy, the higher is the price and better are the properties.
Generally, dental gold alloys carry 16 karat gold; thus, gold restorations used in dentistry also carry a resale value. The composition of gold alloys varies based on the use. PFM crowns, gold inlays, and gold crowns / bridges carry a different composition based on the properties needed.
If you are using a gold alloy under PFM, most of the times, gold is 40% of the crown, other precious metals such as platinum, silver, and palladium are 20%, and base metals make 40% of the crown. We call this type of PFM crown as the porcelain fused to high noble metal crown.
Sometimes your crown may be having more than 25% of noble metals and the rest is base metals. We call this as porcelain fused to noble metal crown.
The base metal crowns may also have some amount of noble metals in them.
Talk to your dentist and opt for the crown that best suits your needs.
Gold does not corrode, does not cause allergy, bonds very well with your tooth, and is longer lasting. A major advantage of a gold base is even if we prepare a thinner crown to preserve your natural tooth structure, gold carries the same properties. Thickness doesn’t decide the strength for gold. You can skip the black gum line if you use a gold alloy for PFM crowns.
Advantages of porcelain fused to metal crowns
They are strong and durable
We have been using PFM crowns for more than 35 years. In fact, many are replacing their all porcelain crowns with PFMs these days. The reason being the underlying metal makes your crown stronger and more stable. The metal enhances the bonding to the tooth.
They look like your natural teeth
You have a variety of shades to choose from to make it look like your other teeth. A unique property of porcelain is, it is translucent, and it helps to mimic your natural teeth. (Translucency is the phenomenon wherein the light partially passes through the object. Your natural teeth have some amount of translucency.)
They have a very high rate of success in the long run.
The best part of these crowns is the stability and strength which is unmatched to any other restorations available today.
These are best for patients looking for natural look and durability.
PFM is a preferred choice when bridges for the long run are required and night grinding is a problem. Since these crowns are a combination of porcelain and metal they are accepted worldwide and well known for the treatment they cater. They are trusted not only by the patients but also by the doctors all over the globe.
You lose a lot of your tooth structure
As PFMs have a metal base underneath, your dentist needs to trim a large part of your tooth to fit them well. Natural is always the best. The more natural tooth structure you have in your mouth, the better is your oral health. However, if you opt for a gold base underneath, your dentist can save more of your tooth.
May cause gingivitis
PFM crowns increase the chances of gingivitis more than the other crown types. However, a gold base is great on your gums, as your body tolerates it well.
(Gingivitis is the inflammation of gums. Redness, swelling, pain, and bleeding are the signs of gingivitis.)
May harm your opposing teeth
When you chew, your teeth in both your jaws, come in a contact. Porcelain tends to wear out the opposing teeth in the long run.
They don’t give you a perfect smile
PFM crowns restore your looks but other crowns such as all-ceramic crowns give you a better smile. Over a period of time, the gum line of PFM crowns gets darker. A grey line appears there which is visible when you smile. This is more true when your gums start going down due to the ageing process.
PFMs are not suitable for someone who has receding gums / gums which have gone towards your bone. The latest technology allows your dentist to opt for a porcelain butt joint margin. This makes sure you don’t see a black gum line even when your gums recede.
May chip off
The porcelain from the PFM crowns can chip off when you bite on very hard foods.
These crowns may be heavy on your pocket especially when you opt for a metal which is a combination of precious metals. However, it guarantees better quality. As these crowns stay longer in your mouth, they can save you on the repeat charges; thus, they are beneficial in the long run.
Last few years have seen a lot of advancement in the field of porcelain fused to metal crowns. Patients with all porcelain crowns are getting theirs replaced with these ones. The latest type of Captek crowns have also done away with the black line that becomes visible around the patients gum line. These crowns have been the commonest option for dentists as well as for patients for over 35 years.
Preparation of PMF crowns
The process of preparing the porcelain fused to metal crown is like that of other crowns. Your dentist examines your mouth, gives anesthesia, prepares your tooth, takes an impression, and designs a crown. Your dentist ensures that the porcelain fuses to the metal which melts at a higher temperature for making your PFM crowns; thus, PFM crowns don’t melt in your mouth or change their fittings when you have hot or very hot foods. This property of metals used for making the crown also ensures that porcelain keeps its natural color when we fuse it to the metals while making PFM crowns.
The porcelain layer too has variations, either it can be:
Full veneer: It covers all the surfaces of your tooth or
Partial veneer: It covers only the front surface or the visible surface of your tooth. Here the rest of the surface that covers your tooth is metallic.
Tips to maintain your porcelain fused to metal crowns well
Avoid biting very hard foods with your PFM crowns. The porcelain layer may chip off. No matter how good porcelain is, it’s not as good as your natural teeth.
Remember to brush twice a day, floss every day, and clean your tongue regularly to keep your mouth healthy.