A dental crown is a tooth-shaped "cap" that is placed over a tooth -- to cover the tooth to restore its shape and size, strength, and improve its appearance. The crowns, when cemented into place, fully encase the entire visible portion of a tooth that lies at and above the gum line.
Dental Crown is Needed...
- To protect a weak tooth from breaking
- To hold together parts of a cracked tooth
- To restore a broken or severely worn down tooth
- To cover and support a tooth with a large filling when there isn’t a lot of tooth left
- To cover misshapened or severely discolored teeth
- To cover a dental implant
Types of Crowns
Permanent crowns can be made from all metal, porcelain-fused-to-metal, all resin, or all ceramic.
- Metals used in crowns include gold alloy, other alloys (for example, palladium) or a base-metal alloy (for example, nickel or chromium). Compared with other crown types, less tooth structure needs to be removed with metal crowns, and tooth wear to opposing teeth is kept to a minimum. Metal crowns withstand biting and chewing forces well and probably last the longest in terms of wear down. Also, metal crowns rarely chip or break. The metallic color is the main drawback. Metal crowns are a good choice for out-of-sight molars.
- Porcelain-fused-to-metal dental crowns can be color matched to your adjacent teeth (unlike the metallic crowns). However, more wearing to the opposing teeth occurs with this crown type compared with metal or resin crowns. The crown’s porcelain portion can also chip or break off. Next to all-ceramic crowns, porcelain-fused-to-metal crowns look most like normal teeth.
- All-ceramic or all-porcelain dental crowns provide the best natural color match than any other crown type. However, they are not as strong as porcelain-fused-to-metal crowns. All-ceramic crowns are a good choice for front teeth. There are new materials available now that make all porcelain crowns an acceptable treatment option for posterior teeth. This material is called Zirconia. Zirconia crowns can look beautiful and very natural. Zirconia is an extra tough ceramic material, and it can be made extra thin. They have no metal in them, and can be made translucent or opaque, depending on the demands of the situation. If they are bonded onto the teeth, and not just cemented with conventional dental cement, they won’t show a dark line at the gumline years later, the way porcelain fused to metal crowns do.
- Temporary versus permanent. Temporary crowns can be made in your dentist’s office whereas permanent crowns are made in a dental laboratory. Temporary crowns are made of acrylic or stainless steel and can be used as a temporary restoration until a permanent crown is constructed by the dental laboratory.
The temporary crown acts as a “blanket” for the tooth, insulating it from hot and cold foods and drinks. The temporary crown is also needed to help maintain the appearance of the tooth while the permanent crown is being made. A trimmed tooth can be unattractive without the temporary, especially if the tooth is near the front of the mouth. Finally, and perhaps most importantly, the temporary crown holds the position of the tooth while the permanent crown is being finished.
Steps Involved in Preparing a Tooth for a Crown
Preparing a tooth for a crown usually requires two visits to the dentist — the first step involves examining and preparing the tooth, the second visit involves placement of the permanent crown.
First Visit: Examining and preparing the tooth.
Before the first visit in preparation for a crown, I may take a few X-rays to check the roots of the tooth receiving the crown and surrounding bone. If the tooth has extensive decay or if there is a risk of infection or injury to the tooth’s pulp, a root canal treatment may first be performed. If too much of the tooth structure is damaged, it might have to be replaced with dental implant.Before the process of making your crown is begun, I will anesthetize (numb) your tooth and the gum tissue around the tooth. Next, the tooth receiving the crown is filed down along the chewing surface and sides to make room for the crown. The amount removed depends on the type of crown used (for instance, all-metal crowns are thinner, requiring less tooth structure removal than all-porcelain or porcelain-fused-to-metal ones).After reshaping the tooth, I will use impression paste or putty to make an impression of the tooth to receive the crown.The impressions are sent to a dental laboratory where the crown will be manufactured. The crown is fabricated in 2 weeks.During this first office visit a temporary crown will be fabricated to cover and protect the prepared tooth while the crown is being made. Temporary crowns are held in place using a temporary cement.
Second Visit: Receiving the permanent dental crown.
At your second visit, I will remove your temporary crown and check the fit and color of the permanent crown. If everything is acceptable, a local anesthetic will be used to numb the tooth and the new crown is permanently cemented in place.Before the crown is permanently cemented, make sure that you approve the fit and the color of the crown, because once permanently cemented, the changes can not be made.
Potential Problems With a Dental Crown
- Discomfort or sensitivity. Your newly crowned tooth may be sensitive immediately after the procedure as the anesthesia begins to wear off. If the tooth that has been crowned still has a nerve in it, you may experience some heat and cold sensitivity.
- Chipped crown. Crowns made of all porcelain can sometimes chip. If the chip is small, a composite resin can be used to repair the chip with the crown remaining in your mouth. If the chipping is extensive, the crown may need to be replaced.
- Loose crown. Sometimes the cement washes out from under the crown. Not only does this allow the crown to become loose, it allows bacteria to leak in and cause decay to the tooth that remains. If your crown feels loose, contact your dentist’s office.
- Dark line on crowned tooth next to the gum line. A dark line next to the gum line of your crowned tooth is normal, particularly if you have a porcelain-fused-to-metal crown. This dark line is simply the metal of the crown showing through.
Life of a Crown
On average, dental crowns last between 5 and 15 years. The life span of a crown depends on the amount of “wear and tear” the crown is exposed to, how well you follow good oral hygiene practices, and your personal mouth-related habits (you should avoid such habits as grinding or clenching your teeth, chewing ice, biting your fingernails, and using your teeth to open packaging).
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