Dental crowns are prosthetic teeth designed by a dentist and usually created by a lab technician (or more recently, a CAD-CAM machine). They can be either metal like gold or platinum, porcelain fused to metal (PFM), or all porcelain/ceramic. All ceramic restorations are typically not as strong as those with metal substructures and can cause increased wear of the opposing teeth. Dental crowns are usually needed under the following circumstances:
- When there is not enough good tooth structure to support an amalgam or dental composite filling. These materials are carved to shape by the dentist and as such, have limited strength.
- When a tooth contains more filling than tooth
- When there is extensive damage to the tooth from decay
- If a tooth has fractures or has undergone a root canal procedure
- Each of these circumstances places a tooth at risk for cracks and fractures. A fixed dental crown would provide the support, structure and strength that is needed for the tooth. A dental crown offers customization of tooth over a damaged tooth.
The process of a dental crown involves preparing a tooth by first reducing its tooth structure (size) in order to accommodate a crown. Because the process involves removing tooth structure, this is an irreversible procedure. If the dental crown will be made using gold material, only a minimum amount is taken off of the tooth because gold is fairly thin. If the fixed crown will be made using a porcelain material, more tooth structure is shaved off.
The following contains very specific steps on the process of a dental crown procedure.
- An index is taken of the tooth using impression material. An index is taken to use as a guide for reducing the tooth and/or as a matrix for creation of a temporary crown.
- Using a dental handpiece or laser, decay is removed from the tooth. If the tooth is heavily damaged, the dentist may restore the height of the tooth with a dental filling material in order to obtain greater surface contact between the crown and the prepared tooth. This will create a greater strength of bond between the prepared tooth and the crown.
- Again using the dental handpiece, the dentist begins to remove some tooth structure and core to allow sufficient thickness of crown material to cover the damaged tooth. Different materials need different thickness. Gold generally requires the least amount of thickness for strength, porcelain the most.
- The dentist then prepares the margins of the crown preparation. The margins involve the joining of the natural tooth and the crown. This margin must be on healthy tooth structure the entire way around; the crown may never end on the core.
- The dentist takes an impression of the teeth and records how the teeth meet. The dentist chooses the shade, and writes a prescription for the dental lab technician to follow. If the shade is difficult to match, the dentist may refer the patient for a custom shade match by a ceramicist, after the temporary crown has been placed.
- A temporary crown is made by the dentist and placed over the prepared tooth. A temporary crown protects the site area while the crown is being fabricated by the dental laboratory. Some systems exist to manufacture these temporaries partially ahead of time, but a custom-made temporary generally has a better fit.
Because a temporary crown is cemented with temporary cement, they can and often do come loose, even if treated with care. Please refer to the dental emergency page to learn what to do when a temporary crown falls out.
- The models of the teeth are sent to the dental laboratory where the technician makes the crown according to the prescription. The technician will try to make a shape that fits the shape of other teeth in the mouth, paying close attention to the fit of the teeth during chewing and biting. Any high spots, even if they are a fraction of a millimeter too high, can cause the tooth to become extremely sore, or can damage the dental crown or opposing teeth.
- The finished crown is returned to the dentist for fitting. The temporary crown is removed and usually using a dental explorer, the fit of the final crown is checked. Dental crowns require extremely precise fits, (under 100 micrometers or so), to be acceptable, some materials such as gold can produce fits within 10 or 20 micrometers). The crown's cosmetic appearance is also checked during this visit.
- If all is well, the final crown is cemented over the damaged tooth using a luting cement. A luting cement is a dental cement agent which is made up of a moldable substance used to seal a space or to cement two components. In this case, the two components are the newly made crown to the tooth structure. The tooth has been restored to a good strength and function.
A temporary crown may feel a little rough and sensitive to hot and cold because it does not touch the gum area. It is adjusted to fit your bite and then cemented with temporary cement for easy removal later.
- While wearing a temporary crown, it is extremely important to follow care. You should do the following:
- avoid chewing for at least ½ hour after the placement to allow for the temporary cement to set.
- Keep the site of the temporary crown clean to maintain tissue compatibility.
- Avoid eating curry it may turn the temporary crown bright yellow or orange.
- Be careful about chewing toffees, gum, grainy rolls and tough steak in this area. I would avoid these foods altogether until your permanent crown is in place.
- Brush at least twice a day using a soft toothbrush and toothpaste with fluoride. Be sure to brush carefully around the temporary and take extra care to thoroughly clean this area.
- You should use a proxy brush to clean around the area after every meal.
- Floss very carefully around this area at least once a day.
- Use an alcohol free, antibacterial mouth rinse once to twice a day.
If you smoke cigarettes or cigars, you should know that smoking can also stain the temporary crown. In addition, it is important to keep your dental appointments during the process of getting a fixed crown. The condition of this area can change before treatment is completed. This will result in the permanent crown/bridge not fitting and requiring either a lot of adjustments and chair time, or having to do the process again.