Tooth crowns in general add a good deal of strength to weakened or worn teeth. It can improve both the appearance and function of injured or damaged teeth. They cover and protect the entire surface area of the tooth, eliminating pain and restoring strength.
Depending on your habits and the condition of your gums, there can be some drawbacks. Your cosmetic dentist will advise which is best for you given many factors, including how important appearance is to you. The following are the advantages and disadvantages of the most common crown types.
Advantage: The preparation of a tooth for a gold crown is the simplest and least complicated preparation as there is minimal tooth structure removal with as much as possible of the healthy tooth structure remaining untouched. While porcelain is hard by comparison, it may cause wear on opposing teeth over the years where gold is not as likely to do so. Gold is also easier to fit to the area where the tooth and crown meet for a better fit. Gold is also a healthier environment for the gum tissue.
Disadvantage: The biggest disadvantage to gold crowns is the cosmetic aspect, unless it is being used in the back of your mouth
All Porcelain Crowns
Advantage: Porcelain crowns or new reinforced resin are considered to be the most aesthetically pleasing, as it is so easily matched in color to the surrounding teeth.
Disadvantage: The thickness of the porcelain required for pleasing aesthetics also requires that more tooth structure needs to be removed. It is more difficult for your cosmetic dentist to get an ideal fit where your gum meets the crown. Gingival inflammation appears to be more common with porcelain crowns than gold crowns. All-porcelain crowns require a higher skill level from your dentist and lab.
Today, there are dental crowns available that do not require a metal substructure and are made of only porcelain. Depending on the specific type, they get their strength either from the bond to the remaining tooth structure or from a dense tooth colored substructure. Since there is no metal, these types of dental crowns allow more light to pass through, which enables them to have more depth and vitality, much like natural teeth. So why isn’t this type of crown used all the time? The main reason is that they are not as strong as crowns with a metal substructure. So, if a person grinds their teeth, these crowns have a greater risk of fracture. Another reason why an all-ceramic dental crown cannot be used in all situations is if the underlying tooth structure itself is dark. Very dark teeth are difficult to mask with these types of crowns because of their translucency. In these instances, the dark color may show through the crown. So, for situations where a lot of force will be placed on the teeth (such as grinding habits) or if a tooth is really dark, a well-made porcelain crown with a metal substructure may be a better restoration.
Porcelain Dental Crowns With a Metal Substructure
Traditionally, crowns are made of two materials:
- porcelain, which gives it the tooth-colored appearance
- metal substructure, which gives the crown its strength
Generally, it is this type of crown that can appear opaque. The reason for this is that while porcelain is very translucent and lets light travel easily through it, no light can pass through the underlying metal. In order to prevent the metal color from showing through the porcelain, which would make the crown seem dark or gray, the metal has to be “masked out” with an opaquing material. It is this masking or opaquing that can affect the final appearance, giving rise to the opaque or lifeless look.
Porcelain Fused-to-Metal Crowns
Advantage: Porcelain fused-to-metal crowns have a very natural appearance.
Disadvantage: They have a metal substructure and require an opaque below the porcelain. This can make the translucency of natural teeth difficult to replicate. Occasionally a darker line will be visible at the edge of the crown, near to your gum when it recedes with age.
The most common complaint associated with crowns is that they look “opaque,” “lifeless,” and “fake” compared to natural teeth. Do you need an extreme makeover to solve the problem? No!
The appearance of a crown is affected by many factors, but ultimately, the final result is determined by how the crown reacts with light. Natural teeth have a high degree of translucency, which means a certain amount of light passes through the tooth. The result of this is that the tooth appears to have depth and vitality.
How long can dental crowns last?
It would be reasonable to expect that a dental crown could last between five and fifteen years. Most likely a crown which did only last five years would be somewhat of a disappointment to your dentist
It’s probably their hope that any crown they make for you will last ten years or longer. Depending on the environment and forces the crown is exposed to (chewing, biting, accidental trauma, tooth grinding) and how well you keep the tooth to which it is cemented free of dental plaque, a crown can last somewhat indefinitely. Especially one positioned where its cosmetic appearance is not much of a concern.
Why do dental crowns need to be replaced?
There can be a variety of reasons why a dental crown might need to be replaced. Some of them are:
A) Tooth decay has formed at the edge of the crown.
While a dental crown cannot decay the tooth on which the crown is cemented certainly can. If dental plaque is allowed to accumulate on a tooth in the region where the crown and tooth meet, a cavity can start.
While there can be a lot of variables with this type of situation, the worst case scenario for your dental crown is that in order for your dentist to be able to get at and remove the decay the crown will need to be taken off and replaced with a new one.
B) The dental crown has become worn excessively.
Dental crowns are not necessarily significantly more resistant to wear than your own natural teeth, nor is it in your best interest that they should be. The ideal dental crown would be one made out of a material that has the same wear characteristics as tooth enamel. This way neither the dental crown nor your teeth would wear the other excessively.
Dental crowns can wear out, especially in those cases where a person has a habit of clenching and grinding their teeth. A dentist will sometimes detect a small hole on the chewing surface of a dental crown in that area where it makes contact with an opposing tooth (meaning a tooth that touches on the crown when you bite). Since the seal of the crown has now been lost your dentist will probably recommend that a new crown should be made, before that point in time when dental plaque has seeped in underneath the crown and has been able to start a cavity.
C) The dental crown has broken.
Dental crowns can break, or more precisely the porcelain component of a dental crown can fracture. Some dental crowns are made in a fashion where their full thickness is porcelain (all ceramic dental crowns). If this is the case then if the crown breaks it will most likely have broken all of the way through, thus compromising the seal of the crown and necessitating its replacement. Even with a less catastrophic fracture it seems likely that the esthetics or function of the crown could be compromised, thus providing a reason why the crown should be replaced.
Anther type of ceramic dental crown is of the “porcelain-fused-to-metal” variety. When this type of crown is fabricated the dental technician first makes a thin metal shell that fully covers over the tooth, a layer of porcelain is then fused to this metal so to give the crown a tooth-like appearance. In cases where a porcelain-fused-to-metal crown has broken it is almost certainly the layer of porcelain that has fractured off, usually revealing the metal that lies underneath (which is often grey in appearance). While the function and esthetics of the crown may have been compromised, the crown’s seal over the tooth has probably not been affected.
Since the seriousness of a dental crown fracture can vary greatly, any crown which has broken should be evaluated by your dentist. Some minor damage might not be of much concern, and possibly remedied by smoothing off the area of the fracture with a dental drill. In other cases the crown will need to be replaced. Only your dentist can make this treatment determination, and only after they have had an opportunity to evaluate your specific situation.
D) The esthetics of the crown have become objectionable.
Some dental crowns are replaced because, from a cosmetic standpoint, their appearance is no longer pleasing. Two situations where the cosmetic aspects of a dental crown can change with time are:
E) The dental crown’s edge has become visible and it has a grey appearance.
As time passes the gum line of a tooth on which a dental crown has been placed will sometimes recede. This is especially likely in those cases where diligent brushing and flossing have not been practiced. If enough recession takes place the edge of the dental crown, which was originally tucked out of sight just under the gum line, will become visible. Many times this edge of the crown will have a grey appearance.
Inherent to porcelain-fused-to-metal dental crowns (related to their construction) is the fact that the very edge of these crowns will typically show some darkness (a hint of the grey metal that lies underneath the porcelain). If enough gum recession occurs this dark edge will become visible, thus spoiling the cosmetic appearance of the crown.
An all-porcelain dental crown does not have the same inherent edge darkness that a porcelain-fused-to-metal crown does. Gum recession can, however, reveal that portion of the tooth that lies beyond the edge of an all-porcelain crown (the tooth’s root surface). Usually the coloration of this part of the tooth is darker (possibly even significantly) than the color of the dental crown, thus spoiling the overall cosmetic appearance of the tooth.
F) The color of the dental crown no longer matches its neighboring teeth.
Also related to the cosmetic appearance of a dental crown, there can be times when, as years have elapsed, the color of the crown no longer closely matches the shade of its neighboring teeth. In these cases it is not the color of the porcelain crown that has changed but instead the neighboring teeth have stained and darkened.
There can be two solutions for this situation. The dental crown can be replaced with a new one that more closely matches the current color of its neighboring teeth. Another solution could be to use a teeth whitening process so to attempt to return the neighboring teeth to the color they were when the dental crown was originally placed.