Procedures

Crowns

The process

When you have invasive dental procedures like crowns done, the dentist will review your health history. If you have replacement joints (e.g. total knee, hip, etc.), you may be pre-medicated with antibiotics for the procedure. If you have certain types of heart murmurs or replacement heart valves, you may also need to take an antibiotic pre-medication prior to the procedure.

If you are anxious about dental procedures, your dentist may recommend sedating you for the procedure. There are several methods of relaxing patients for dental treatment, including oral anti-anxiety pills like Valium®; inhaled anti-anxiety medication like nitrous oxide; and intravenous anti-anxiety medication, such as Versed®. Your dental plan may not pay benefits toward sedation.
Learn more: Procedures › General anesthesia/sedation

The following describes the typical crown preparation and laboratory process in detail. Your procedure may vary a bit from the procedure described.

Anesthetic—The tooth to be crowned is usually anesthetized by injecting local anesthetic around the nerve(s) that supply sensation to the tooth. Discomfort from the injection can be minimized by use of a topical numbing gel for a minute or two prior to the injection.
Learn more: Procedures › Local anesthetic

Pre-impression—Frequently, a preliminary impression (or "mold") is made of the teeth before they are altered. The material used most for crown impressions is polyvinyl siloxane, a dimensionally stable and extremely accurate elastomer (meaning it's "stretchy", but returns to the shape it takes when it cures after a minute or two). Other materials may be used. The impression can be used to make a temporary crown for the tooth while the final crown is being made in a laboratory, a process that can take a couple of weeks.

Shade Matching—If the tooth is to be crowned with a tooth-colored crown, a shade matching guide will be used to determine the shade of your natural teeth. The shade should be matched in natural lighting, also called "full spectrum" lighting. Fluorescent lights can make teeth appear blue to grey; Incandescent lights can make them appear too yellow. Dental porcelains and resins available today can produce a stunningly precise match for the shade and optical properties of your natural tooth enamel, allowing a single crown to be made that matches your teeth nearly imperceptibly.

Isolation—The tooth is isolated from mouth structures like the tongue and cheeks to prevent injuries from instrumentation used to prepare the tooth. An isolation barrier known as a "rubber dam" or "dental dam" is frequently used, but there are other retraction devices in use. Some dentists may simply use cotton rolls and cheek shields.
Learn more: Glossary › Rubber dam

Core Prep—The tooth is prepared by removing old restorative materials (if necessary), removing any decay, and (if necessary) filling in any deep holes or missing corners of the tooth. It may be necessary to place small metal (normally titanium) pins in the tooth to rebuild the portion of the tooth that will be crowned. The dentist may use any of a variety of filling materials to rebuild the tooth, including composite resin, glass ionomer, and silver amalgam.

Core buildups are considered a separate billable procedure from crowns. A distinction is made between buildups that involve all or a substantial portion of the core of the tooth, and those that require only a small amount of filling material in the core to build out a minor chip. You should discuss with your dentist in advance whether a complete core build-up is going to be required or not to avoid unexpected costs.
Learn more about core buildups: Procedures › Fillings & core buildups

Crown Prep—The outer surface of the tooth is reduced in all dimensions (biting surface and sides) by 0.75mm to 3mm to make room for the crown that will be placed on the tooth. The walls of the preparation are tapered to allow the crown to be slipped down over the tooth. A ledge is created around the circumference of the tooth against which the crown will be tightly sealed.

Impression of Prep—An impression of the prepared tooth and the teeth that bite against it is made, taking care to gently reflect the gum tissue away from the prepared tooth. Often, the dentist will place "retraction cord" in the trough between the gums and prepared tooth prior to making the impression. The cord will be removed after the impression is made.

Temporary Crown—The impression that was made prior to preparing the tooth can now be used to make a temporary crown. This is done by filling the pre-impression with a gooey tooth-colored resin material, having the consistency of thick syrup, and placing it over the prepared tooth. The resin material will gel in about a minute, and the impression can be removed from the mouth. The space between the prepared tooth and the unprepared tooth is now filled with temporary filling material, which completely hardens in another minute or two. Once hardened, the temporary crown will be trimmed to proper fit, polished, and cemented onto the tooth with temporary cement.
Learn more: Symptom checker › Crown loose, temporary

Labwork and Final Crown Seat—Although some dentists now have computer-controlled milling machines for making ceramic crowns in their offices, a more common scenario is that the crown would be made in a dental prosthetics laboratory. Essentially, the labwork involves the following:

• Cast Fabrication—The impression of the prepared tooth and the teeth that oppose it is poured with lab plaster and allowed to harden.
• Articulation—The casts of the teeth are assembled into a hinged jaw simulation device known as an "articulator" in their proper bite relationship.
  Learn more: Glossary › Articulator
• Die Preparation and Fabrication of a Wax Pattern—The cast of the prepared tooth (the "working die") is inspected closely for undercuts and any other irregularities. The technician will create a crown from wax using sculpture techniques. This wax pattern will be used in any of a variety of ways to produce the final crown, depending on whether the crown is to be made of ceramic, metal, or a combination of those.
• Production of the Actual Crown—Depending on which type of crown is to be fabricated, the crown may be cast from a variety of metal alloys, pressed from ceramic, or made of ceramic fused to the metal alloy.
• Finishing—Depending on which type of crown is made, it may require metal finishing and polishing or other staining and glazing procedures to make the tooth match the patient's natural teeth as closely as possible.

Delivery of Final Crown—When your final crown is ready, a second visit is necessary to remove the temporary crown and replace it with the permanent crown. About half of the time, a patient will ask to be anesthetized for the second visit, to avoid any discomfort associated with removing the temporary crown and cleaning the temporary cement from the prepared tooth. Teeth which have been endodontically treated (i.e. root canal) generally do not need to be anesthetized for the delivery of a permanent crown, although many dentists prefer the patient to be numb for the crown preparation due to the potential for discomfort associated with soft tissue management (gum retraction, etc.).

Adjust and Polish—The "occlusion" (i.e. functional biting relationship) of the crown may need to be adjusted slightly, and the crown repolished. This should take just a minute or two under normal circumstances.