|
|
|
How a Dental Crown is Made?
The tooth is prepared, or shaped by the dental drill. Enamel and some dentin is shaved from around the sides of the tooth and the top of the tooth resulting in a very specific shape. The patient will usually be anesthetized with local anesthetic ("novacaine") for this.
A temporary cap of plastic or metal is made to fit the tooth, so that the tooth will be covered between visits.
An impression is taken of the tooth with a small tray of rubber or silicone-like material. Steps 1-3 can frequently be accomplished in one visit.
The impression will go to a dental lab where it is poured. The crown is made to fit the poured model. This usually takes 1-3 weeks.
The patient returns to the dental office. The temporary cap is removed and the permanent cap is placed. It should be a tight fit on the tooth and cement is used to place it. The bite is adjusted.
The making of the crown at the lab is beyond the scope of this site. I can state that the basic ceramo-gold crown is made by placing and carving wax on the poured model of your tooth and it is cast in the lost-wax method. Porcelain is baked on the metal substructure. This is like having jewelry custom made for you, with alloys that are carefully tested and manufactured and a lab person who has the skill to dip a paintbrush in porcelain power and water, bake it in a tiny and very hot oven, and make it look like a tooth. This is not a small undertaking and it is custom work; it adds to the fee you pay your dentist.
The quality of the crown depends on the dentists skill and the skill of the dental lab technician. The under-casting can be made of precious or non-precious metals.. Dentists have a responsibility to choose a good quality lab tech and alloy for your crown.
The Immediate Crown-Making Machine
Some dentists boast that they have CAD CAM crown making machines on-site. Instead of being made of an understructure of metal with porcelain baked on the outside, the entire crown is milled out of a block of porcelain. After the tooth is prepared, photos are taken by a computer. The data is entered into the milling machine which produces the crown.
These computer-made crowns are not appropriate for all situations., especially where the edges of a crown must tuck far under the gum (Where a good photo cannot be obtained.) Also, the machines are expensive and the dentist must do enough crowns to make the purchase pay for itself.
I prefer the porcelain-fused to gold method since the margins can be made thinner and stronger. Also, I do not want the pressure of having to do a certain number of crowns each month to make my payment for this expensive machine. If the crow quality were better that the traditional crown, it might be worth the expense. It isn't.
|
|
|
|
|
