For somebody who is missing large amount of tooth structure as a result of tooth decay, congenital disorders, tooth wear or traumatic injures dental crown can be an excellent treatment option.
In this post I would like to discuss the most essential information about dental crowns.
What is a Dental Crown and What are the Indications for Dental Crowns?
A crown is an artificial dental restoration that covers all or major portion of the tooth in the oral cavity. Most common indications for dental crowns include restoration of large amounts of missing tooth structure as a result of (1) tooth decay, (2) tooth wear, (3) dental trauma, and (4)congenital malformations of the teeth. In addition to replacement of missing tooth structure dental crown also restore cosmetic appearance and function, and protect the tooth mechanical, temperature, and chemical stresses.
How does Dental Crown Work?
Dental crown is a shell-like structure in a shape of the tooth. The thickness of dental crown typically ranges from 0.5 to 2.0 mm depending on the material it is made of and desired material properties. Dental crown is permanently secured to the remaining portion of the tooth with a help of a dental adhesive. Once secured to the tooth it functions just like a natural tooth.
Due to the harsh conditions of the oral cavity dental crown is under constant mechanical, chemical, and temperature stresses. In order for it to perform over the long-term, dental crown must be made from materials with adequate strength. The supporting tooth must be free from tooth decay and dental infections. Dental crown also requires to have certain amount of healthy tooth structure or supporting dental filling in order to adhere to the tooth over long-term.
What Types of Dental Materials are Used in Crown Fabrication?
Dental crowns are made from specially formulated ceramics, metal alloys, plastics or combination of metals and ceramics or metals and plastics. The specific material is usually chosen based on the cosmetic requirements of the case, desired strength, and amount of thickness which is required for the restoration.
Ceramic crowns typically provide the best esthetic qualities and are most commonly utilized for the front teeth. One of latest trend is use of crowns made from zirconium ceramics for the back teeth. This type of restorations provide good strength without sacrificing appearance.
Metal Crowns made from gold or other types of dental alloys provide the best strength. They are very strong even when thickness of the material is minimal. Due to their metallic look they are used in the back of the mouth.
Ceramo-metal (also called porcelain fused to metal) crowns is another options where metal provides necessary strength and rigidity for the ceramic materiel thus combining favorable properties of both ceramics and metals. Ceramo-metal crowns can be used in all areas of the mouth.
Plastic (polymer) materials are also used in crown fabrication. Most commonly plastic crowns are used for the provisional restorations. This type of restoration is made for the short to medium duration of time (several weeks to several year).
What are the Steps in the Dental Crown Treatment?
Fabrication of dental crowns is an advanced restorative procedure which involves comprehensive understanding of biology, biomechanics and aesthetics. Complexity of the treatment usually increases when patient requires several restorations or dental crowns are fabricated for the front teeth where they have to be harmonious with the adjacent teeth and patient’s smile and face. Typical process of crown fabrication includes:
(1) Initial evaluation and presentation of treatment options to the patient. As an initial step condition of patient’s mouth and teeth is evaluated and appropriate recommendations and treatment options are discussed.
(2) Diagnostic planning and fabrication of prototype crowns. This step is required in complex cases where there is need to change the shape of the teeth, alter the bite, etc. Typically, analogue or digital models of the patient’s jaws are created and teeth with new improved shape are made in wax or on the computer.
(3) Crown preparation, impression procedure and placement of provisional crown. In this step tooth is prepared to a very specific shape and geometry in order to accept crown restoration. Crowns are fabricated in the dental laboratory or in the dentist’s office on the analogue or virtual model. For the creation of the model dentist makes an impression of the patient’s teeth and jaws. It can be done with an impression material such as dental silicone or with help of a digital scanner. If dental crown is fabricated in the dental office, the procedure can be completed on the same appointment and provisional crown is not necessary. If dental crown is fabricated in the dental laboratory, a dentist will place provisional crown to protect the tooth and allow the tooth to function normally. In a number of situations provisional crowns are placed on the teeth to evaluate appearance, comfort and test function. If this is a case impression procedure is delayed till all requirements of the case are fulfilled.
(4) Fabrication and delivery of the permanent crowns. Crown fabrication is a sophisticated process where a chosen material is formed to achieve specific shape, strength, and appearance. Today’s most common processes in crown fabrication include CAD-CAM, analogue or combination of both. Once completed, crown is evaluated in the mouth and permanently secured to the tooth with a dental adhesive.
In a number of clinical situations patient may also require additional procedures to extend longevity of the tooth and restoration, and improve cosmetic appearance and gum health. Below is a list of procedures which are often performed in conjunction with crown restorations.
What Additional Procedures May Be Required With Dental Crowns?
Core buildup filling (also called foundation filling). A tooth may broken to the point that there is not enough structure to hold the crown. In that case a buildup filling is placed to achieve the desired form of the tooth. If a tooth is broke and has a root canal filling, a dentist may recommend placement of metal or polymer post inside the root canal to support the buildup. Here is a link for a detailed explanation of core build procedure.
Root canal treatment. A tooth may present with infection inside the root canal. If this a case a root canal is disinfected and root canal filling is placed inside the canal.
Crown lengthening surgery. A tooth may be broken to the point that there is minimal or no tooth left to hold the crown and buildup filling. In that case a surgery is perform to expose the necessary amount of the tooth. This type of surgery can also be done for cosmetic purposes in order to improve appearance of the smile.
Orthodontic treatment. In some situations orthodontic treatment (braces) is recommended to improve appearance and extend longevity of the teeth.
What are the Disadvantages of Dental Crown Treatment?
The disadvantages of dental crown treatment include:
- Possibility of complications (see below)
- High cost
- Requires removal of tooth structure (crown restorations require a specific geometry of the tooth and as a result certain amount of tooth structure is irreversibly lost when crown preparation is made)
What are the Most Common Problems/ Complications with This Treatment?
Treatment with crowns carries a low risk of complications. Nevertheless complications do occur. Type of complication usually varies depending on the clinical condition of the tooth. Included is a list of possible complications:
- Temperature and pressure sensitivity after procedure (temporary in nature)
- Crown material fracture
- Crown loosening
- Tooth fracture
- Tooth decay
- Inflammation of root canal tissues which requires root canal treatment
- Allergic reaction to the restorative material
- Chronic gum inflammation around crown-gum interface
What are the Maintenance Requirements for Dental Crowns?
Dental crowns need to be monitored on the periodic basis. Similarly to the natural teeth, teeth with crowns also need to be professionally clean. By doing so, some of the problems can be prevented and if detected, addressed early.
Thank you for reading,
Dr. Alexander Shor