Also called: Dental Crowns, Tooth Crowns
Kenneth Cheng, D.D.S.
A crown is a dental restoration typically made in a dental laboratory that is placed over a natural tooth to replace damaged or unsupported tooth structure. Natural crowns may need to be replaced if they have been damaged by tooth decay, chipping or breaking. Artificial crowns can also be used as part of a bridge or as a restoration over an implant. They are commonly used after root canal treatment because the procedure can make the tooth brittle. A crown will protect the tooth structure from fracture.
Crown restorations range from full crowns that cover the entire natural crown of the tooth (the top surface of the tooth) to three-quarter crowns that leave the front of the tooth exposed (commonly used on front teeth). Crowns may be made of metal alloys (e.g., gold, copper, nickel, chromium), porcelain, porcelain fused to metal, or a type of plastic called composite resin.
The restoration process for a crown is a multistep process, beginning with a dental examinationand x-rays. In many cases, root canal treatment is the first step. A diseased or decayed tooth has its pulp removed from its root canal and replaced with material called gutta percha.
After the initial examination and any preliminary dental work, crowns typically require two or more visits: one to prepare the tooth and take impressions and another to cement the permanent crown to the tooth. Between these visits, the patient wears a temporary crown. There is usually little or no discomfort after a crown has been placed, although some patients may experience some sensitivity to hot and cold. If any additional problems arise, patients should speak with their dentist.
Crowns can closely match the color, shade, shape and length of neighboring teeth and are often difficult to detect as artificial. However, various problems (e.g., chipping, fracture, breaking, loosening, falling out) may require that crowns be replaced. In some of these cases, the crown may be able to be repaired in the mouth or re-cemented, depending on the amount of damage that has occurred.
In general, crowns require the same care as natural teeth. However, it is typically recommended that patients with crowns avoid chewing on extremely hard substances (e.g., nuts, ice), grinding their teeth and biting their fingernails. These activities can damage the crowns or reduce how long they last. Crowns do not protect the teeth from tooth decay, periodontal disease and other common oral concerns. Therefore, diligent dental hygiene remains extremely important.
About dental crowns
A crown is an artificial cap made to cover a natural tooth. The term “crown” can refer to a natural crown (the part of a tooth that is visible in the mouth) or a dental restoration that covers the top part of the tooth.
An artificial crown is a dental prosthesis that covers or replaces the natural crown of a tooth. It typically covers the entire natural crown, on all sides and chewing surfaces. Artificial crowns can be used to cover and strengthen teeth that have been damaged. They may be used to improve the appearance of a tooth that is oddly shaped, badly discolored, or not in proportion with the neighboring teeth. Crowns can be used in cavity restoration when the tooth decay is too widespread for a filling, to restore a broken or cracked tooth, or prevent a tooth from breaking.
Crowns are commonly used as the last step after root canal treatment. Teeth become brittle as a result of this treatment and a crown will prevent further damage to the tooth (e.g., fracture). In these cases, the pulp of the tooth is removed from the root canal and the canal is filled with material such as gutta percha. A post may be placed in the root canal if there is insufficient natural tooth to support a crown. A crown is then typically placed in the area. Crowns can also be used to support a bridge or cover an implant.
Other types of dental restorations include inlays and onlays. These restorations cover smaller portions of the tooth, such as only the top part of the chewing surface. Inlays cover the smallest portion and may be slightly larger than a filling, while onlays cover at least one cusp of a tooth. Because onlays cover the cusps of teeth they offer better structural support. Inlays and onlays are more conservative restorations than crowns because less tooth structure is drilled away to fit.
Multiple visits to a dental office are required to prepare, place and adjust a crown. The crown is constructed in a dental laboratory based on impressions taken by the dentist. The multiple visits and labor crowns require means they usually cost more than simpler restorations, such as fillings.
Crowns require the same dental hygiene (regular brushing and flossing) as natural teeth. Crowns can last many years, depending on the location in the mouth and the level of dental hygiene.
Types and differences of dental crowns
The term “crown” can refer to either the natural crown which is part of a tooth or an artificial crown which is a dental restoration.
The natural crown of a tooth may be defined in two ways:
- Anatomical crown. The part of the tooth covered by enamel, which may be above or below the gumline.
- Clinical crown. The portion of the tooth visible inside the mouth and not covered by soft or hard tissue.
Different types of artificial crowns include:
- Full crown. An artificial crown that covers the entire natural crown.
- Jacket crown. A thin crown that covers large areas of the natural crown in the front teeth. It may not be strong enough for use in the back teeth, which endure greater levels of chewing stress and pressure.
- Dowel crown. A full crown that is anchored by a dowel pin that extends into the root canal of a tooth that has undergone a root canal treatment.
- Three-quarter crown. A crown that covers all of a natural crown except the front surface of the tooth, which remains natural for aesthetic purposes.
- Abutment crown. An artificial crown used to support a bridge or cover an implant.
Artificial crowns may also be classified by their materials:
- Gold alloys. Composed of a combination of gold, copper and other metals. These materials are strong and highly resistant to tarnishing, corrosion, fracture and wear. These materials do not tend to require as much removal of the underlying natural tooth material as other crown materials. They are compatible with the nearby teeth and are well tolerated by patients. However, many patients find the metallic gold color displeasing for teeth that are visible when talking, smiling or laughing.
- Base metal alloys. Composed of a combination of base metals (e.g., nickel, chromium). These materials have strength and resistance qualities similar to gold alloys. However, they have a metallic silver color that many patients do not like. They may also cause an allergic sensitivity or initial discomfort with hot and cold in some patients.
- Porcelain. May be composed of porcelain, ceramics or glasslike materials. These materials have a color and translucency that closely matches natural teeth. They are also highly resistant to wear. However, they may be prone to fracture and can wear down nearby teeth if the porcelain surface becomes rough. They may also require the removal of a larger amount of natural tooth than metal alloy crowns to support enough porcelain to produce a strong crown.
- Porcelain fused to metal (PFM). Composed of a porcelain crown bonded to a metal base. This combination is strong and durable and highly resistant to wear. However, it can wear down nearby teeth if the porcelain surface becomes rough. It may also cause an allergic sensitivity or initial discomfort with hot and cold in some patients. In addition, it may require the removal of a larger amount of natural tooth than metal alloy crowns to support the combined metal and porcelain.
- Composite resin. Composed of a type of composite plastic similar to the material used in tooth-colored fillings. This material tends to be relatively inexpensive and looks like natural teeth. However, it may stain more readily than porcelain and is not as strong or durable as porcelain.
Before the dental crown procedure
Before a crown can be placed, patients need to see a dentist for a dental examination to determine what type of crown is right for them. The dentist may also evaluate the patient’s medical and dental history. In some cases, a root canal treatment may be necessary due to extensive tooth decay. This treatment may also be needed if the tooth has to be reduced to such an extent that the tooth’s pulp may be injured or risk infection.
If there is not enough natural tooth structure to support the crown, a foundation may need to be built up, frequently around a pin or a post. Pins are thin shafts, typically made of metal, that are inserted into a hole that has been drilled into the tooth. They are becoming less common due to advances in adhesive dental materials that now allow weaker or smaller teeth to support crowns. Posts are thicker rods, frequently made of metal, that are inserted into the root canal of a tooth that has undergone root canal treatment.
After the initial examination and any preliminary dental work, crowns typically require two or more visits: one to prepare the tooth and make impressions and another to cement the crown to the tooth. The tooth that will support a crown must first be prepared by reducing its size to make room for the crown. Surrounding teeth may also require some adjustments so the crown will fit.
During and after the dental crown procedure
After the tooth is prepared, the dentist takes an impression of the prepared tooth and nearby teeth. A medicated thread or cord may be used to separate the gum from the tooth, allowing a more accurate impression. The impression will be sent to the dental laboratory, where it will be used to make the crown. The dentist then places a temporary crown, which the patient will wear until the permanent crown is placed. Temporary crowns may be prefabricated or made from resin in the dental office. They do not last long, but keep the prepared tooth safe until the permanent crown is available.
Crowns are generally made in dental laboratories and may take several weeks. After the crown arrives, the dentist removes the temporary crown and checks the fit of the permanent crown. The dentist makes any necessary adjustments (e.g., polishing, glaze) and temporarily cements the crown onto the prepared tooth. The dentist also ensures that the patient’s bite is correct with the new crown. If the crown is comfortable and satisfactory to the patient, the crown will be permanently cemented. This may occur at a later date.
There is usually little or no discomfort after a crown has been placed, although some patients may experience some sensitivity to hot and cold. In some crowns (e.g., porcelain fused to metal crowns), a dark line may be visible along the gumline. This is a small, visible portion of the metal base of the crown. It is not noticeable in most cases.
If any additional problems arise, such as pain or sensitivity when biting down, patients are advised to speak with their dentist. Some issues can be fixed in the dental office in a single visit. Others may require replacement of the crown.
The multistep process of preparing a tooth for a crown and having the crown placed may take weeks. Researchers are investigating new techniques that may help to reduce this time, allowing dentists to place crowns much sooner after the tooth has been prepared.
Potential risks and benefits of dental crowns
Crowns have a natural look and feel that many patients consider superior to bridges and other forms of dental restoration. They can closely match the color, shade, shape and length of neighboring teeth and are often difficult to detect as artificial. They are generally considered affordable and are usually covered by insurance.
Crowns also have drawbacks. Many problems may require the crowns be replaced. Crowns may chip, fracture or break. Sometimes, chips or fractures can be repaired with composite resin without removing the crown. However, in many cases, the crown must be removed and a new crown placed.
In some cases, the porcelain part of a porcelain fused to metal crown may detach from the metal. It may come apart cleanly, or parts of the porcelain may remain attached to the metal. In some cases, these crowns can be bonded back together. However, they often must be replaced.
Tooth decay can still occur in the underlying tooth. Poor placement of the crown may allow food to get under the crown, or the cement may partially wear or wash out, making the crown loose and unstable. Patients should continue daily dental hygiene (brushing and flossing) and monitor any unusual changes around the crown. To avoid tooth decay, it is important to see a dentist as quickly as possible when a crown becomes loose. The crown can often be re-cemented before any damage to the tooth itself occurs. If the tooth does become damaged, the crown will no longer fit properly and a new crown will need to be made.
Occasionally, a crown may become loose and fall out entirely. It is important to see a dentist as soon as possible to ensure that the crown and tooth are not damaged. If either becomes damaged, the crown will no longer fit properly and a new crown will need to be made.
Finally, changes in the material of a crown (e.g., discoloration, wear) or changes in the surrounding teeth (e.g., whitening attempts) may cause a crown to become unattractive. Patients may wish to have such crowns replaced.
Lifestyle considerations with dental crowns
In general, crowns require the same care as natural teeth. However, it is typically recommended that patients with crowns avoid chewing on extremely hard substances (e.g., nuts, ice), grinding their teeth and biting their fingernails. These activities can damage the crowns and reduce durability.
Crowns can last many years. According to the Academy of General Dentistry, crowns tend to last for around five to eight years. However, diligently cared for crowns can last many decades.
It is important for all patients, whether or not they have artificial crowns, to see a dentist regularly for a dental examination and cleaning. Diligent dental hygiene is also extremely important. Crowns do not protect the teeth from tooth decay, periodontal disease and other common oral concerns. While patients with crowns are not generally required to do anything that is not recommended for natural teeth as well, they may be advised to pay particular attention to the area of the tooth by the gumline. This is where plaque and decay may get under the crown and damage the underlying natural tooth.
Questions for your doctor regarding dental crowns
Preparing questions in advance can help patients to have more meaningful discussions with their dentist regarding their treatment options. Patients may wish to ask their doctor the following crown-related questions:
- Why do I need to get a crown?
- What type of crown is right for me?
- How closely will my crown match my natural teeth?
- Will I need to have a root canal treatment or any other preliminary dental work?
- How much of my natural tooth needs to be removed?
- How long will I need to wear a temporary crown?
- Should I make any modifications to my regular dental hygiene habits?
- After the crown is placed, how frequently should I come in for dental appointments?
- How long is my crown expected to last?
- Is this procedure covered by my insurance policy?