A dental crown, also referred to as a fixed prosthodontic or “cap” is a cast (metal) or porcelain restoration that is cemented into place to become a permanent part of the dental arch. Dental crowns provide valued support to the remaining teeth and prevent drifting of the occlusion (bite) in instances where missing teeth are present. Think of a crown as a protective covering over any damaged or chipped surfaces on the natural tooth.
• Severe tooth decay – Tooth decay that has gone untreated can structurally weaken the teeth, requiring reinforcement with crowns. When decay is removed, sometimes the pulp or nerves can also be exposed. If this is the case, glass ionomer cement and composite resin can be used to build up the area before placing the crown. This will reduce any sensitivity of the tooth.
• Tooth trauma – Crowns can be used to preserve teeth that have become fractured or cracked due to trauma.
• Dental implants – Crowns are fitted over dental implants to restore missing teeth.
• Incisal wear – caused by bruxism. Preservation of the crown will require the use of a mouthguard.
• Dental bridges – Another use for crowns is to hold a three unit bridge in place on abutment teeth. This will help to stabilize the adjacent teeth by affixing the bridge on either side of the pontic crown which is the center crown.
• Aesthetic Correction – Crowns can be used to straighten a misaligned smile. A crooked or misshaped tooth can be crowned and fixed without need for braces. This is an invasive treatment approach if the deformed teeth are otherwise healthy.
• Root canal therapy – Teeth that have undergone endodontic treatment are fragile and prone to breakage. A crown will add strength to that tooth and protect it from fracturing.
A contraindication for a crown would be the presence of periodontal disease or excessive mobility of other teeth. Otherwise, crowns are an ideal choice unless less invasive treatment is available. For instance, a dental onlay might be preferred for treating a large carie (cavity) such that healthy parts of the tooth are preserved. Not all dentists offer this type of treatment but it is worth seeking out for minimized tooth trauma.
The cost of a dental crown is typically $1,000 and upwards. The cost is dependent on where you receive treatment, the type of crown your get, and whether you have insurance coverage. Some dentists will agree to work out a payment schedule to help with the cost.
There are several type of crowns available that are appropriate for a wide array of circumstances. Some of the factors that influence crown selection include aesthetic considerations, occlusal (biting) forces present in the area being treated, and the patient’s budget.
Porcelain Fused to Metal (PFM)
Full crowns cover the entire tooth surface. On posterior (back) teeth they are usually made of porcelain over high noble metal (such as gold). The addition of a metal substrate provides for a more stable biting surface with less chance of any breakage. These are called PFM crowns or Porcelain fused to metal crowns.
All Porcelain Crowns
A crown can also be made of solid porcelain or of solid metal with no porcelain such as gold. An all-porcelain crown is usually used for anterior (front) teeth as it gives a more translucent, natural tooth appearance. If a PFM crown is used on the anterior teeth, there is a risk of metal allergy which manifests as a dark outline at the top of the crown on the gingival gum surface. This effect is not aesthetically pleasing and does not occur with all porcelain crowns.
Partial Crowns and Others
Partial crowns cover three sides of the tooth surface. During a partial crown preparation, retention grooves are made on both the mesial and distal sides of the tooth. These grooves help to hold the seated crown into place. There are also resin crowns and 7/8 crowns. Despite all these choices, patients opt for a PFM crown in the large majority of cases.
During your first visit for a crown, expect to have impressions of your tooth and the upper and lower arches taken and also a bite registration. Usually there are also x-rays taken and an exam to help decide the best course of treatment. At this point local anesthetic is administered. The shape of the natural tooth is reduced using a diamond stone and any caries are removed. Sometimes the dentist will use a laser in place of a drill to remove any decay. This is a fairly new technique that is growing in popularity amongst patients. Talk to your dentist to see if you are a candidate.
If a traditional drill is used, at this point the finishing burr is used to prepare the shoulder or circumference around the crown. The next step in the procedure is gingival retraction followed by another impression. At this point a shade color for the new crown is determined. Next, a temporary crown is then created and placed and the patient sent home.
On your second visit the temporary crown is removed and the new crown is tried on. If all goes well and the color matches and the fit is ideal, it is then cemented into place. As the cement dries the excess along the margins is cleaned away by the dental assistant with an explorer. A bite registration is now taken and any adjustments are made. This is usually done with articulating carbon paper that will indicate any high spots. These are then polished away and once the bite feels right the patient is dismissed.
Crowns will last for many years even as long as 40 and some for a lifetime. With a well fitting crown, you should be able to brush and floss your teeth as usual. Regular dental checkups are essential for keeping crowns in working order.