Dental crowns are a restorative treatment that cover damaged, chipped, or discolored teeth. They encase the tooth and protect it from bacteria, acids, sugars, starch, and hot or cold foods and beverages.
They are typically used after a root canal or to repair broken teeth. The dentist reshapes the tooth, removes any diseased tissue, and makes impressions to fit the crown.
Porcelain
The most commonly used type of dental crown, porcelain crowns are a great option for patients with cosmetic concerns who want their smile to look as natural as possible. These crowns can make crooked teeth appear longer and symmetrical, for instance, or mask dark spots on the gum line.
Before a porcelain crown can be applied, the tooth needs to be shaped and filed down in order to create a stable foundation that will support it once it is cemented. This is done by numbing the tooth and surrounding area and filing down its chewing surface as well as the sides. This is also a good opportunity for the dentist to take a bite-wing radiograph (also known as a periapical) of the tooth, which will be used to help determine whether or not the crown should be placed on this particular tooth.
Porcelain crowns are fabricated in two layers, with a metal alloy core being built up using standard dental materials and then a lifelike outer layer of feldspathic porcelain being added to the top. This porcelain can be bonded directly to the underlying tooth (which allows its translucent properties to transmit the underlying tooth colour) or it can be layered over a pre-built core, like in the case of PFM or VMK crowns.
Zirconia
Zirconia is a relatively new material for dental crowns, but it offers many benefits. It’s strong, durable, and very aesthetic. It also has a translucency, meaning that it will look more natural than other types of crowns.
Zirconium oxide is naturally white, so this type of dental crown looks the most like your natural teeth. It can be shaped into any tooth shape, and it will blend in perfectly with the rest of your smile. This makes it a good choice for crowns on back teeth that are not visible.
The strength of zirconia is comparable to that of porcelain-fused-to-metal (PFM) crowns, but it has a much better aesthetic. It can be used in either solid or layered form. Solid zirconia is suitable for anterior crowns, while layered zirconia is best for posterior crowns.
Solid zirconia structures can be milled using CAD/CAM technology in one of two ways. The first technique produces a milled structure that has no structural shrinkage. This method is less costly than the second technique but may produce burs that produce flaws in the final structure. The second technique lays down a pre-sintered block of zirconia and then uses CAD/CAM technology to sculpt the final crown, eliminating the potential for distortion that can negatively affect mechanical reliability.
Metal Alloys
Metal alloys, which can include gold, platinum, chromium and nickel, are the most common crown materials. They are strong and withstand biting and chewing forces well. However, their visible metallic color and high cost are the main drawbacks. Therefore, they are best used on out-of-sight molars.
The best metal crowns are fabricated with noble alloys that contain at least 25 percent of precious metals. These alloys have higher biocompatibility ratings than non-noble alloys, which are made from base metals such as nickel. Therefore, they are less likely to cause allergic reactions in patients.
Dental porcelain fused to metal (PFM) crowns have a layer of feldspathic porcelain on top of the metal substructure. This enables them to blend in with the surrounding tooth, but they are not as strong as porcelain or ceramic crowns. Consequently, PFM crowns can sometimes crack or break. They also cause the teeth they bite against to wear down faster than other types of crowns. Additionally, they can sometimes impact a dark line next to the gum of the crowned tooth.
Resin
Resin crowns are typically less expensive than metal or porcelain-fused-to-metal crowns and can last three to five years on average. These restorations are most often used as temporary crowns while the patient waits for a permanent restoration to be made.
Dental resins are tooth-colored and therefore blend in with the natural teeth. They are often used for minor cosmetic modifications like closing gaps or reshaping teeth. They can also be used as a filling material when the tooth is too damaged to support a large filling.
Dental alloys are made from a combination of different pure metals. This creates a metal that has better physical properties than the pure metals alone. Some popular alloys are gold, platinum, silver and copper. The advantages of dental alloys are that they are easier for lab technicians and dentists to work with than the pure metals and they have a lower melting point so they can be cast thinner. They are often used for molars and back teeth because of their durability and strength. The disadvantage is that they are metallic in appearance and can cause accelerated wear on the opposing teeth.
All Ceramic
The newest all-ceramic crowns are made from very thin and light lithium disilicate. They are extremely long-lasting and have excellent aesthetics. IPS Empress, which is a leucite-reinforced pressable porcelain, was one of the first of these to be launched into the market. The current leader in this type of all-ceramic crown is IPS E –Max, which uses a zirconia core but is layered with standard transparent porcelain to build up the visible parts of the crown. This gives a more lifelike result and allows the crown to withstand biting pressures.
Traditional ceramic crowns are usually fused to metal copings, which require the enamel of adjacent teeth to be removed before fitting. This can cause them to wear away faster than the natural tooth underneath.
Our dentists have invested in the latest digital scanning technology (E4D) that allows them to prepare, manufacture and place all-ceramic crowns in a single appointment. This can save you time, stress and the inconvenience of having to come back for multiple appointments. However, because of the complexity and precision of their fabrication, all-ceramic dental crowns are generally more expensive than other types of dental restorations.