WHAT IS A CROWN (also called a CAP) and WHAT IS THE DENTAL CROWN PROCEDURE?
The dental crown procedure is usually done in two appointments, the preparation appointment, then the seating appointment. There are also machines like, Cerec, which can make the crown within 1-2 hours, and have everything done in one appointment.
The first appointment of the dental crown procedure is the preparation. The tooth is reduced on all 4 sides plus the top in order to make room for the crown. This is also when any decay is removed and filled accordingly.
CROWN BUILD UP:
After the decay is removed, the tooth usually has lost a substantial amount of tooth structure and is in an odd shape. A crown build up is similar to a filling, where by the tooth is built up back to attain the most ideal form or shape to support the crown.
The dentist will take an impression, or mold, of the tooth which is normally sent to an off site dental lab. The lab uses this mold to make an identical model of your tooth, onto which the crown is fabricated.
Many offices are now using intra-oral scanners, which take images of your teeth and are then used by a computer to design your crown.
THE TEMPORARY CROWN:
The last step in the dental crown procedure is to make a temporary crown, which is made, then cemented with temporary cement onto your tooth, which will stay on for 2-3 weeks until the final crown is seated (at the second appointment). The temporary crown helps to decrease sensitivity, protect it from fracture, and helps to keep the space between the adjacent teeth. It is important to not chew anything hard, sticky, or chewy on your temporary crown. It is also important to be careful when flossing around a temporary crown. If it comes off, if you have an appointment to have the real crown put in soon and the tooth doesn't bother you, you can leave it off. If it is sensitive, is an esthetic concern, or want it replaced, call your dental office and they should be able to recement or remake it for you.
If you are having the crown done in a single visit, you shouldn't need a temporary crown.
A shade is then selected so the lab knows what color to make the crown. Depending on what the tooth looks like, your dentist can request combinations of shades or even have you go directly to the lab (if they use a local lab) to have a custom shade made.
Below is a shade guide that shows various shades that your dentist may select.
The second appointment of the dental crown procedure involves seating the
crown. This normally does not require anesthetic. The temporary crown is removed and the final crown is fitted onto the
tooth. This normally involves some adjustments, and then the crown is cemented
onto the tooth.
The crown will be made on a model in a LAB (this is the reason for the 2 appointments).
Some dental offices have CAD/CAM, OR CEREC milling machines, in which
case your dental crown procedure can be done in a single visit. This is not
available in the majority of dental offices at this time, although the
technology points towards this in the future.
CEREC: Cerec crowns, made by Sirona, is one type of dental crown procedure that can be made in a single visit. After the tooth is prepared, instead of taking an impression, and special intraoral camera is used to take photos of the prepared and surrounding teeth. Special software is used which helps design the crown, it is milled right at the dental office, and then fitted and cemented in all on the same day.
Cerec machines can also be used to make inlays, onlays, and bridges.
There are a few other intraoral cameras that are available, and in the near future it is possible that this will become the standard of care when making crowns, rather than taking impressions.
SO WHY ARE TEETH CROWNED?
Teeth are crowned for a number of reasons... most often being because of INSUFFICIENT TOOTH STRUCTURE.
When a tooth BREAKS, IF there is not enough tooth structure to SUPPORT A FILLING, you may need a crown.
HOW MUCH TOOTH IS NOT ENOUGH?
In POSTERIOR teeth (in the back), if part of it fractures, a crown would be the next logical step. Large fillings can sometimes be placed, but if the tooth has fractured once already, most likely if you put a larger filling in a tooth, it will fracture again.
WHY ELSE are teeth crowned?
Many dentists will have you believe that teeth NEED to be crowned to PREVENT fracture. This IS TRUE in BACK TEETH that have had ROOT CANALS done.
If you have had a root canal on a back tooth, you definitely need to have it crowned. After a root canal, the tooth is kind of like a dead branch. It's going to break, we just don't know when. A crown is done to help prevent that from happening.
Large amalgam fillings can cause fractures in teeth over time. More and more dental offices are equipped with intraoral cameras (cameras which take pictures of your teeth from inside your mouth), and it is very common to see fracture lines on teeth with large amalgams.
Once the dentist can detect the fracture with his or her instruments, it is likely that that tooth will fracture at some point. Doing the dental crown procedure can prevent that from happening.
Yes, crowns are expensive, but if it is not done and the tooth fractures, it is possible that that tooth may be lost, or need to be root canaled , or even extracted . Both of which would be much more expensive than that single crown.
Patients who have bad PERIODONTAL DISEASE may not be the ideal situation for the dental crown procedure, but if the tooth is going to break without one, just be aware that your tooth is compromised so the long term prognosis is decreased.
If you CLENCH OR GRIND YOUR TEETH , you are more likely to FRACTURE teeth. So crowns MAY BE necessary.
IS IT POSSIBLE TO PREDICT WHICH TEETH WILL FRACTURE AND WHEN?
Unfortunately not, but if there are existing fractures in a tooth, it is like playing Russian Roulette with your teeth.
WHAT ARE CROWNS MADE OF?
CROWNS can be GOLD, PORCELAIN or other tooth colored material, or PORCELAIN FUSED TO GOLD/METAL (PFM/PFG).
The hardness of gold is very close to natural tooth hardness, therefore it does not wear against the opposing tooth. PORCELAIN is much harder than natural tooth structure, therefore can wear down the opposing tooth/teeth. Gold crowns also require less reduction of tooth structure during the dental crown procedure, which in general is better for the longevity of the tooth.
WHY NOT GOLD?
ESTHETICS. In the current day of everyone wanting whiter teeth and looking more natural, gold is esthetically less acceptable, unless it is in the back of your mouth.
PORCELAIN vs PORCELAIN FUSED TO METAL?
Like gold, the metal hardness is closer to that of natural tooth structure, so part of the tooth can be PORCELAIN (for esthetics) and part of it can be metal/gold (part that hits the opposing tooth). The metal is normally an alloy of gold, with the amount of gold and other metals varying depending on the type of crown.
Because of the metal substructure, the esthetics of PFM crowns can be close to your natural tooth, but not normally as good as the following 2 options.
These are all very strong/esthetic crowns like PFM crowns, except the metal substructure is primarily cubic zirconia, which has a white appearance rather than a silver or gold appearance. This allows for much better esthetics and the materials nowadays are very strong and fine for posterior teeth.
There are several tooth colored crowns including the ones listed above that are stronger than porcelain but offer similar esthetics.
WHY 100% PORCELAIN?
ESTHETICS. Full porcelain crowns look very good and natural, but they do not tend to hold up too well in the posterior region. In the anterior region, if they are not subjected to too much force, they should be ok.
As mentioned in the gold crown section, when porcelain crowns are done, the preparation phase of the dental crown procedure requires more tooth structure to be removed in order to make room for the porcelain on porcelain crowns.
With the materials available today, crowns can be made to look virtually identical to natural teeth in all areas of the mouth.
CROWN FAILURES, ISSUES
After a crown is placed, the tooth still needs to be flossed and brushed, because it is still possible to get cavities under a crown.
There are other issues that can arise after crown placement of the dental crown procedure.
In general, there are 3 ways to replace your missing teeth.