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The tooth is reduced by a certain amount 360 degrees around the tooth so that the "cap" or crown fits over the tooth. The amount of reduction depends on the material.
In some cases, a technology called cerec, can be used. This allows the crown to be made in one appointment with no temporaries or impressions.
First, let's talk about what got your tooth to the point of needing the crown. Again we go back to the partnership you have with your dentist in maintaining your oral health. When the decay gets so extensive that a filling cannot be supported by the remaining healthy tooth structure, then we need to place a crown. We can stay away from the need for a crown by brushing and flossing well every day and keeping up with our regular re-care exams. This isn't to say that crowns are caused by gross neglect but it is our desire to keep these down to a minimum. Crowns are sometimes used to repair a trauma causing a broken tooth. Also they can be used to place a bridge that replaces a missing tooth.
A crown preparation is to make the tooth a miniature copy of what it was before. The tooth is polished down in such a way to remove enough tooth structure to replace it with porcelain and metal or sometimes just porcelain. The thickness has to be two millimeters or thicker in order to be strong enough to withstand the forces of chewing.
Esthetics is another part of the design of a crown. When you look at the tooth the appearance should blend into the appearance of the other teeth. The color is very integral in having a crown not look like a crown. There is an entire art in the value and hue and chroma that enables these little works of art to blend into the other teeth.
The shape of the crown is also very important in the appearance and performance of a crown. If the contour of the tooth is not correct then it will create a food impaction area. If it doesn't contact the adjacent tooth well enough, it will also create gum irritation.
The tooth must be prepared properly in order for the technician to make a crown properly.
No matter how well your crown is placed it becomes a different cleaning problem. It will add an area that potentially can retain plaque that you didn't have there before. Proper flossing and brushing will become crucial issues in lengthening the life of your crown. And of course re-care appointments with your dentist is very important.
First the tooth and or adjacent teeth will be numbed with a local anesthetic. Then using the hand piece or drill the dentist will reduce the size of the tooth in all directions. This will provide two things. The first is the space needed by the laboratory to make the actual crown or "cap" that will cover the tooth.
The second is the shape needed to help retain or hold the crown on the tooth. The prepared tooth must have a specific shape and height in order to help hold the crown in place. Once the tooth is prepared an impression or mold will be made of the tooth and the teeth next to it as well as the teeth opposing it. These impressions or molds will be poured or cast in stone forming models. In addition the dentist will take what is known as a bite registration which allows the laboratory, which makes the crown, to interdigitate the two models. A temporary crown (usually made from acrylic) will be placed on the tooth while the laboratory is making the permanent crown.
At the lab a ceramist will then use materials (gold, gold alloys, porcelain) to make a crown in the proper dimensions and colors for that specific patient based on the models provided. The crown is returned with the models to the dentist. The dentist will remove the temporary crown, and then seat the permanent crown and verify its fit. The crown must seat fully, have no gaps, match in color to other teeth, and must feel proper to biting. If necessary minor adjustments can and may be made by the dentist.
Once the dentist and patient are satisfied with the result, the dentist will use a cement to place the crown. Proper hygiene still must be maintained as a crowned tooth can still develop a cavity. While it is the strongest most durable restoration a dentist can provide to a patient, nothing is stronger than a perfectly healthy tooth.
The dentist will remove a layer of the tooth from all surfaces and then take an impression. This will be sent to a laboratory where a crown will be created.
This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.