Root canal therapy refers to the process by which a dentist treats the inner aspects of a tooth, specifically that area inside a tooth that is occupied by its "pulp tissue." Most people would probably refer to a tooth's pulp tissue as its "nerve." While a tooth's pulp tissue does contain nerve fiber it is also composed of arteries, veins, lymph vessels, and connective tissue. Where precisely in a tooth is its nerve?
Teeth are hard calcified objects but their inner aspects are not completely solid. Inside every tooth there lies a hollow space which, when a tooth is healthy, contains the tooth's nerve tissue. Dentists use the following terms to refer to various portions of this nerve area
The pulp chamber.
This is a hollow space that lies more or less in the center of the tooth.
The root canals.
Each tooth's nerve enters the tooth, in general, at the very tip of its root(s). From this entry point the nerve then runs through the center of the root in small "root canals" which subsequently join up with the tooth's pulp chamber.
What is the function of a tooth's nerve tissue?
You might think that a tooth's nerve tissue is vitally important to a tooth's health and function, but in reality it's not. A tooth's nerve tissue plays an important role in the growth and development of the tooth, but once the tooth has erupted through the gums and has finished maturing the nerve's only function is sensory (it provides the tooth with the ability to feel hot and cold).
In regards to our normal day to day oral functions the sensory information provided by a single tooth is really quite minimal. Dentists realize that on a practical level it is pretty much academic whether a tooth has a live nerve in it or not. If a tooth's nerve tissue is present and healthy, wonderful. But if a tooth has had its nerve tissue removed during root canal treatment that's fine too, you will never miss it.
What is the purpose of root canal treatment?
You could say that the purpose of root canal treatment is to create an end result where the tissues that surround a tooth's root will maintain a healthy status despite the fact that the tooth's nerve has undergone degenerative changes. Specifically, we mean that the tissues surrounding a tooth's root are not affected by bacterial infection and/or irritating substances leaking from those inner aspects of the tooth originally occupied by the tooth's nerve tissue.
Possibly in more scientific terms, our bodies, as a defense mechanism, will initiate an "inflammation reaction" when irritants (such as those that might seep out of a problematic tooth) have injured or destroyed body tissues. So if we choose to incorporate the term "inflammation" into our description we would say, root canal treatment is the treatment of the inner aspects of a tooth (whose nerve has undergone degenerative changes) so to provide an environment where the tissues surrounding a tooth's root are free of, and will likely to continue to be free of, the presence of inflammation.
How does root canal treatment accomplish this goal?
In a nutshell, the process of root canal treatment first removes (as thoroughly as possible) bacteria, nerve tissue, the organic debris left over from the breakdown of nerve tissue, and bacterial toxins from within the inner aspects of a tooth (the area originally occupied by the tooth's nerve tissue). Each of these items can produce tissue irritants that can cause your body to activate an inflammation reaction.
Subsequently, once this space has been cleansed the second half of root canal treatment involves filling in and sealing up the interior of the tooth. This aspect of the treatment is an attempt to minimize the possibility that bacteria will be able to recolonize the inner aspects of the tooth or that tissue fluids can seep inside the tooth, become stagnant, and subsequently break down. (Either of these situations could produce a state of persistent inflammation in the tissues surrounding the tooth's root.) The seal also contains and encapsulates any debris that could not be fully removed during the cleaning aspect of the root canal treatment process so that it can't leak out and trigger an inflammation reaction.
Why go to all of this trouble?
If you get an infection, say from bacteria entering a cut in your skin, your body will transport white blood cells to and from the area (by way of your blood vessels and lymphatic system) so to combat the bacteria that have caused the infection. In most cases your body will win the battle and kill off the offending bacteria.
The problem with teeth and infections is that once a tooth's nerve tissue has started to degenerate and bacteria have taken up residence in the tooth's nerve area, there is no effective way for white blood cells to get at the bacteria to combat them. The dying nerve's blood and lymphatic vessels used to transport white blood cells will have begun to degenerate too.
The net result of all of this is that the nerve space inside a tooth can provide a nice cozy cave-like location for bacteria to persist because it's a place where your body's defense mechanisms can't get at them effectively. With this scenario, at best your body will only be able to cordon off the infection caused by the bacteria living inside your tooth. At worst, this bacterial infection will overwhelm your body's defense mechanisms and pain and swelling will ensue (an acute tooth abscess).
The idea behind having root canal treatment is that it provides the bulk of the clean up work for your body. It removes bacteria and tissue irritants that are present inside the tooth, especially those in the locations where your body would have the most trouble combating them. As an end result, once root canal treatment has been completed it provides your body with an environment where its mechanisms are able to clear away any residual bacteria and tissue irritants that may still be present, thus allowing complete healing (resolution of the inflammation) to occur.
How do you know when your tooth needs root canal treatment?
It will take an examination by your dentist to determine if root canal treatment is indicated for your tooth. Not only must your dentist determine if the treatment can be an appropriate solution for your situation but also that the overall condition of the tooth in question warrants the time and expense involved.
Here are some situations where root canal therapy might be the proper solution:
- A tooth is currently causing you pain or else has a history of being painful.
- You have noticed the presence of tenderness and/or swelling in your gums near a tooth.
There can be times when you have a tooth that is in need of having root canal treatment but you are unaware of this fact because there has been no swelling or pain associated with the tooth.
A) Problem teeth identified by x-rays.
The nerve tissue inside a tooth can degenerate and die quietly. The death of a tooth's nerve is not always a painful experience. In these instances a tooth's need for root canal treatment can remain undiscovered, even for some years. This is because the virulence of the infection inside the tooth is low and your body's defensive mechanisms, while not being able to clear up the infection totally, are able to keep it in check.
Dentists often discover teeth that need root canal treatment during routine x-ray evaluations. In the most obvious of these cases the dental x-ray will show a dark spot at the tip of the tooth's root. This dark spot indicates that there has been a reduction in the density of the bone surrounding the root's tip. This bone damage has occurred as a result of the infection that is present inside the tooth.
B) A persistent or recurring pimple on your gums.
Sometimes a tooth whose nerve has died will produce a pimple like lesion on a person's gums. The presence and/or size of these pimples (dentists call them fistulous tracts) can come and go. Because they are literally drains for pus from an infected tooth, a person might notice that they discharge a bad taste (the pus). It is possible that a dentist will discover this type of lesion while performing a routine examination, even though the patient hasn't noticed it at all.
C) Exposure of a tooth's nerve.
There can be times when your dentist will find that your needed dental work has resulted in the exposure of your tooth's nerve. The term "exposure" used here simply means that your dentist, while performing your dental work, has literally been able to visualize your tooth's nerve tissue. Sometimes a patient will feel a little prick of pain when the exposure occurs. However, many times a patient is totally unaware of the event.
An exposure can lead to the degeneration of a tooth's nerve tissue. Your dentist may determine that in your situation it is best to go ahead and perform root canal treatment on the tooth now so to avoid possible problems and complications with the tooth later (such as a painful tooth abscess).
D) Teeth which have been traumatized in an accident.
The nerve tissue in teeth which have a history of having been traumatized (such as being bumped in an accident) can deteriorate, thus leading to the need for root canal treatment.
Immediately after the traumatic event the outlook for the nerve's health can be difficult to predict. Sometimes traumatized teeth do quite well, even for many years.
It is always possible however that at some point the health of the tooth's nerve tissue will degenerate and subsequently die (often without symptoms). A tip off that the nerve tissue inside a tooth is undergoing degenerative changes is that the tooth, in comparison to its neighbors, appears darkened.
Will you experience pain during your root canal treatment?
We'd be the first to acknowledge that root canal treatment has a reputation for being painful, but we'd be the last to agree that this reputation is deserved. It seems most likely to us that the majority of derogatory remarks you hear in regards to "having a root canal" almost certainly must have included in them references to the pain and discomfort that the person experienced leading up to receiving treatment.
For the average person and the average case, root canal treatment is a nonevent and not any more uncomfortable than having a filling placed.
If your confidence needs a little bolstering...
You might be surprised to learn that it is possible that even without anesthetic many teeth needing root canal treatment could be drilled on and you would feel no pain what so ever. In fact, it is conceivable that in some isolated cases (those where active infection and inflammation are not complicating factors) the entire root canal treatment process could be completed without any anesthetic or pain. Why? Simply because in these cases the nerve tissue in the tooth has died, and dead nerve tissue cannot transmit pain sensations.
Should you expect that your root canal therapy can be performed without the use of an anesthetic? No, that's not realistic. But if you are unequivocally anticipating that all root canal treatment results in an excruciatingly painful experience then someone has led you astray.
Will your dentist numb up your tooth prior to performing your root canal treatment?
Almost certainly, and especially if you ask them to. Nobody likes a bad time, not you, not your dentist. Just so things go as smoothly as possible and so there are no surprises, most dentists will go ahead and numb up any tooth on which they are performing root canal treatment.
Remember, your dentist is trying to perform treatment that will hopefully last you a lifetime. They need to be able to concentrate on their work and not on how you are reacting to it. By numbing up your tooth both of you will be more at ease and relaxed.
Root canal treatment is a "good thing."
There are many reasons why a person should be eager to begin root canal treatment. In those cases where a person's tooth has been the source of pain or swelling it is the root canal therapy that will initiate the process by which the painful or swollen tooth can be settled down. In some cases just those beginning steps a dentist takes as a part of performing root canal treatment can provide instant relief. Even in those cases where relief is not total the treatment should at least significantly reduce the pain, and also set the stage where the healing process can begin to take place much more rapidly than if root canal treatment had not been initiated.
Even if an episode of pain and swelling has not been experienced, a person should still be eager to initiate their root canal treatment. In the absence of pain and extensive infection the treatment will just go that much more smoothly. You will be relaxed and well rested. Your tooth will respond to the steps of the procedure more predictably. Additionally, any tooth that is in need of treatment, but has not yet received it, is unpredictable. Having your root canal treatment completed sooner rather than later reduces the chances that you will experience a painful tooth flare up (an acute tooth abscess).
What are the individual steps of root canal treatment?
A) Placing a rubber dam around your tooth.
After numbing your tooth but before beginning the actual process of performing the root canal treatment, your dentist will stretch a sheet of rubber around your tooth. Dentists call this sheet of rubber a "rubber dam." It is held in place by a small clamp that grasps your tooth.
The purpose of a rubber dam is as follows. Since one of the fundamental goals of root canal therapy is to clean bacteria out of a tooth, and since saliva does have bacteria in it, the placement of a rubber dam allows the dentist to keep your tooth saliva free so it doesn't get recontaminated with bacteria while your root canal treatment is being performed.
B) Gaining access to the nerve area of the tooth.
As a starting point for the process of performing your root canal treatment your dentist must first gain access to that area inside the tooth where the nerve tissue resides. This is accomplished by using a dental drill and making an access hole that extends down to the pulp chamber of the tooth. On posterior teeth this hole is made on the chewing surface of the tooth. On front teeth the access hole is made on the tooth's backside.
C) Cleaning the tooth out.
The next step of the root canal treatment process is for your dentist to clean out the interior of your tooth (the pulp chamber and all root canals). As we discussed previously, this cleaning process removes any bacteria, toxins, nerve tissue, and related debris that are harbored inside your tooth.
For the most part the cleaning process is accomplished by way of using "root canal files." These objects look like straight pins but on closer inspection you would find that their surface is rough, not smooth. These instruments literally are files and are used as such. Your dentist will work a series of root canal files, each of increasing diameter, up and down in your tooth while simultaneously using a twisting motion. This action will scrape and scrub the sides of the tooth's root canal(s), thus cleaning it out. Additionally, as part of the cleaning process your dentist will wash your tooth out periodically so to help flush away any debris that is present.
The goal is for your dentist to clean the entire length of the tooth's root canal(s), but not beyond. As a means of determining the length of a canal your dentist may place a root canal file in your tooth and then take an x-ray. Once developed the x-ray picture will reveal if the file extends the full length of the canal or not. Alternatively, your dentist may have an electronic device that can make this same determination when it is touched to a file that has been positioned in a canal.
Traditionally the filing action of root canal files has been created by way of the dentist manipulating them with their fingers. There are, however, special dental drills (dental drills are called "handpieces") which can hold and twist these files, and your dentist may choose to use one. As a variation on this same theme, there is yet another type of dental handpiece that produces a cleaning motion by way of holding a root canal file and vibrating it vigorously.
What are the individual steps of root canal treatment? (continued)
D) Placing the root canal filling material.
Once the tooth has been thoroughly cleaned your dentist can fill in and seal up its interior by way of placing root canal filling material. Sometimes a dentist will want to place the filling material the same day that they have cleaned the tooth out. Other times a dentist might feel that it is best to wait about a week before completing the root canal process. In the latter case your dentist will place a temporary filling in your tooth so to keep contaminates out during the time period between your appointments.
What root canal filling material is used?
The most common root canal filling material being used by dentists now days is a rubber compound called gutta percha. Gutta percha comes in preformed cones that are sized to match the files which have been used to clean out the inside of the tooth.
A root canal sealer (a paste) is usually used in conjunction with gutta percha cones. It is either applied to the cone's surface before the cone is placed into the tooth's root canal, or else applied inside the root canal itself before the gutta percha cone is positioned. Sometimes several cones of gutta percha need to be placed before the interior of the tooth has been filled adequately.
At times a dentist will warm the gutta percha cones (either before or after they are placed into the tooth) so they become softened. This allows the gutta percha to more closely adapt to the precise shape of the interior of the tooth.
As an alternative to the use of preformed cones, sometimes a dentist will place the gutta percha via the use of a gutta percha "gun." This apparatus is somewhat similar to a hot glue gun. It warms a tube of gutta percha so the material is very soft. The gutta percha is then squeezed out into the tooth.
After your dentist has finished the filling and sealing aspect of the root canal process they will place a filling in the access hole they created at the beginning of your treatment. The individual steps of performing the root canal treatment have now been completed.
How long does root canal treatment take?
The total amount of appointment time that will be required for your root canal treatment can hinge on a number of factors. Some of these are:
- Different teeth have differing numbers of root canals, each of which need to be located, cleaned, and sealed. As an example, front teeth typically just have a single root canal while molars often have three or more canals.
- Will your root canal treatment be completed in just one sitting or will the process be broken up into two appointments? At times a dentist will feel it is best to clean out a tooth during an initial visit and then have you return for a second appointment when they will seal up the interior of your tooth. Equally common place, a dentist may feel that it is preferable to perform both tasks during the same appointment.
You will have to ask your dentist what amount of time is needed for your treatment. As a ballpark estimate however, it seems likely that any single appointment will probably last between 30 and 60 minutes.
What should be expected after root canal treatment?
Will there be any pain or discomfort after the root canal treatment?
The hope is that after your root canal treatment you will notice very little discomfort with your tooth. It can be common that for the first day or so after its treatment a tooth might feel a little tender. Whenever you have a question, in all cases, you should feel free to contact your dentist's office just to ensure that what you are experiencing seems to them to be within normal limits.
A tooth's sensitivity can often be minimized by using an over-the-counter analgesic, especially one that also possesses anti-inflammatory properties. Ibuprofen (Advil or Motrin) can be an effective choice for this type of discomfort. Of course you should always read the label, indications, and warnings of any product you anticipate using so to insure that it is an appropriate drug for you.
Should you chew on a tooth that has just had root canal treatment?
Don't look for trouble. It is usually best to exercise caution with a tooth that is undergoing root canal treatment or has just had its treatment completed. Until your dentist tells you otherwise you should minimize chewing on the tooth. Here are some reasons why:
- In those cases where more than one root canal treatment appointment is needed the temporary filling that has been placed in your tooth might come out. If it does, saliva and debris will contaminate the interior of the tooth again. Your dentist will have to spend your next root canal appointment cleaning your tooth out a second time.
- Sometimes, since the tooth receiving the root canal treatment feels so much better, a person is eager to make use of their tooth again. Until your dentist has had a chance to finish rebuilding your tooth it should be considered to be fragile. What a disappointment it would be to spend the time, effort, and money to have root canal treatment performed, only to have the tooth break or crack irreparably before it was fully restored.
What additional dental work is needed for a tooth that has had root canal treatment?
After your tooth's root canal treatment has been completed your dentist will need to discuss with you what additional dental work will be required so to make the tooth fully functional again.
Many times a tooth that has required root canal treatment is one that has a big filling or else has large portions missing due to decay or breakage. These teeth, in this state, are not as sturdy as they once were and for this reason it is commonplace that a dentist will recommend that a tooth that has had root canal treatment should be restored with either a dental crown or else a dental crown in combination with a dental post. Of course your dentist will need to determine what treatment is appropriate in your situation.
The dental restoration that is chosen for rebuilding a tooth that has had root canal treatment provides another function also. It provides a seal protecting the interior of the tooth. This barrier helps to prevent seepage of bacteria and contaminates from the oral cavity into the interior aspects of the tooth. Your dentist will need to advise you as to what they think is best for your situation but, in general, the sooner arrangements can be made to have the permanent dental restoration placed (thus creating the best possible seal) the better.
Placing a post in a tooth that has had root canal treatment.
A "post" is a rod that a dentist has positioned and then cemented in the canal space in a tooth's root. Typically, but not always, dental posts are made out of metal.
Posts are usually only placed in those teeth which have extensive portions of their natural tooth structure missing. Dentists know, in general, that the greater the amount of a tooth that can extend up into the center of the dental crown, the more stable the crown will be. In those cases where a great deal of tooth structure is missing a dentist will "build up" the height of the tooth using dental filling material. A dental post provides a way for the dentist to securely anchor this filling material core to the tooth.
How does a dentist place a post in a tooth?
When placing a post a dentist will first use a drill and remove some of the gutta percha filling material that was placed during the tooth's root canal treatment. They will then cement the post and subsequently place a core of filling material around the post's upper portion, so to increase the overall amount of structure that will extend up into the crown.
Placing a dental crown on a tooth that has had root canal treatment.
Crowns are dental restorations that cup over the portion of a tooth that lies above the gum line. People sometimes refer to dental crowns as "caps." Dental crowns can either be gold or else have a porcelain surface so they look white like a tooth's neighboring teeth.
A dentist will use a dental crown as a means of improving the appearance of a tooth, restoring a broken tooth to its original shape, and/or strengthening a tooth. Additionally, and very importantly, dental crowns create an excellent seal over a tooth. By this we mean that a crown cemented in place provides a barrier that is helpful in preventing bacteria and contaminates from seeping back into those inner aspects of a tooth where the root canal treatment has been performed. After a tooth has had its root canal treatment completed, any or all of these qualities which a crown can provide may be needed.
What steps are needed to make a dental crown?
Before a dental crown can be placed the tooth must first be trimmed so it is tapered in shape. This tapered aspect of the tooth will extend up into the dental crown's center and is a very important factor in the crown's stability. After the needed shape has been achieved your dentist will take an impression of the tooth, which in turn is sent to a dental laboratory which will create the crown. Once the dental lab has completed your crown your dentist will cement it in place.
Are there any alternatives to having root canal treatment?
If root canal therapy is indicated for a tooth there really is no alternative treatment other than an extraction. Root canal treatment deals with the inner aspects of a tooth unlike any other dental procedure. If it is required, no other dental work can suffice. If root canal treatment will not be a possibility for a tooth then it should be extracted.
Should you have an extraction rather than root canal treatment?
The cost or simplicity of a tooth extraction might seem attractive in comparison to having root canal treatment performed. But this solution might not be the easiest or least expensive treatment choice in the long run.
When a tooth is missing its neighboring teeth will tend to shift, sometimes significantly. This in turn can have a major impact on your dental health. Even losing a single tooth can lead to problems with your chewing ability or your jaw joint. Teeth that have shifted because of a lost neighboring tooth can be more likely to have dental problems themselves.
So to avoid these complications, in most cases your dentist will probably recommend to you that you have any tooth that has been extracted replaced. Replacing a tooth that has been extracted with an artificial one (using either a dental bridge, removable partial, or implant) can easily cost as much (and usually more) than ideal treatment for your tooth beginning with root canal therapy.
Don't make the decision to have a tooth extracted quickly. Make sure that you and your dentist have discussed and explored all of the benefits and detriments of all of the treatment options that are available to you before you make a decision.
Timing your root canal treatment.
In those cases where root canal therapy is needed it is always best to go ahead and make plans to have the treatment performed sooner rather than later. Sometimes, however, root canal treatment must be delayed because of scheduling conflicts, the need for other dental work, or else financial considerations. Delays such as these can usually be managed, at least to some degree. Often a dentist can perform the initial aspects of root canal treatment, the ones that can make it so your tooth feels better, and then schedule an appointment for you at a later date for the completion of the work.
You should not make a decision to delay root canal treatment unilaterally but instead discuss matters with your dentist. Any tooth that is in need of root canal treatment, but has not yet received it, is not predictable. A tooth could remain asymptomatic for an indefinite period of time or, at the other extreme, could abscess and cause you pain and produce swelling. Even in those cases where a tooth remains asymptomatic, the infection associated with the tooth could cause damage to the bone that surrounds it. Discuss matters with your dentist. Let them explain to you what they would consider a reasonable time frame for the treatment of your tooth.
What are dental crowns?
Crowns are a type of dental restoration which, when cemented into place, fully cup over the portion of a tooth that lies at and above the gum line. In comparison, fillings are dental restorations that fill in or cover over just a portion of a tooth. Since dental crowns encase the entire visible aspect of a tooth, a dental crown in effect becomes the tooth's new outer surface.
Crowns can be made out of porcelain (meaning some sort of dental ceramic), metal (a gold or other metal alloy), or a combination of both. Other terms that are used to refer to dental crowns are "dental caps" and "tooth caps."
Why do teeth need dental crowns?
A dentist might recommend placing a dental crown for a variety of reasons but, in general, most of these reasons will usually fall within one of the following basic categories:
· To restore a tooth to its original shape.
· To strengthen a tooth.
· To improve the cosmetic appearance of a tooth.
How can dental crowns be used to restore a tooth's shape?
Since a dental crown that has been cemented into place essentially becomes the new outer surface for the tooth it is easy to imagine how the placement of a crown can restore a tooth to its original shape. Dental crowns are routinely made for teeth that have broken, worn excessively, or else have had large portions destroyed by tooth decay.
It is conceivable that a dental filling, as an alternative, could be used as a means to restore a tooth's shape. Dental crowns however offer your dentist a big advantage over dental fillings by way of the fact that they are fabricated "away from your mouth." By this we simply mean that dental crowns are fabricated in a dental laboratory (by a dental technician using plaster molds your teeth). Dental fillings, in comparison, are created "in your mouth" by way of your dentist placing the filling material directly upon your tooth.
When a dental crown is made the dental laboratory technician can visualize and examine all aspects of your bite and jaw movements, from a variety of angles, and then sculpt your dental crown so it has the perfect anatomy. In comparison, when a dentist places a dental filling they have far less control over the final outcome of the shape of your tooth because it is often difficult for them to visualize, evaluate, and access to the tooth on which they are working.
How can dental crowns be used to improve the cosmetic appearance of teeth?
Since a dental crown serves to cup over and encase the visible portion of a tooth, any dental crown that has a porcelain surface can be used as a means to idealize the cosmetic appearance of a tooth. Possibly you have heard it rumored (especially in past decades) that certain movie stars have had their teeth "capped." This simply means that the person has obtained their "Hollywood smile" by way of having dental crowns placed.
Actually, getting your teeth "capped" just to improve their cosmetic appearance can at times be a very poor choice. Dental crowns are best utilized as a way to improve the cosmetic appearance of a tooth when the crown simultaneously serves other purposes also, such as restoring a tooth to its original shape (repairing a broken tooth) or strengthening a tooth (covering over a tooth that has a very large filling).
In general, a dental crown probably should not be used as a means to improve the appearance of a tooth if there is any other alternative dental treatment that could equally satisfactorily achieve the same cosmetic results. This is because a dentist must grind a significant portion of a tooth away when a dental crown is made. If a more conservative dental procedure could equally well improve the tooth's appearance, such as a porcelain veneer, dental bonding, or even just teeth whitening, then it is usually best to consider that treatment option first.
The strengthening capability of dental crowns is related to the fact that they cup over and encase the tooth on which they are placed. This means that a crown can act as a splint that binds a tooth together. This is a very important feature of dental crowns and one that makes them a very valuable type of restoration for a dentist to have available to them.
In contrast, dental fillings, especially large ones, can have a weakening effect on the teeth in which they are placed. Dental fillings rely on a tooth's remaining structure to hold and support them. Fillings, in general, don't strengthen a tooth and can't protect a tooth from the forces generated by biting and chewing.
If only a small amount of tooth decay is present then it's usually no problem for a dentist to make a repair for a patient by way of placing a dental filling. In these cases there will still be a substantial amount of healthy tooth structure remaining after the decay has been removed and the filling has been put in place.
On the other hand, repairing a large cavity often requires the removal of so much tooth structure that the overall strength of the tooth is reduced, in some cases greatly. This is because the tooth is no longer as intact as it once was, its structural integrity has been compromised.
Of course it's not exactly the same thing but... the structural integrity aspect of a tooth is a little like an egg. If you take a raw egg and you want to break it open..., well it really takes a pretty firm rap. That's because an egg shell, in that specific shape, is really a surprisingly strong object.
Now, in comparison, say you have broken the egg open and the two halves of the empty shell are lying on their sides. It's fairly simple to crush each piece of the shell now. Its structural integrity has been compromised. The shell is no longer in the shape it was meant to be so to be able to withstand forces. Teeth are somewhat the same in the sense that once a large portion of the tooth is missing (because it has broken, decayed, or has been drilled away) it is simply no longer as sound.
What constitutes a big dental filling?
Well of course this is the $64,000 question, and it's more or less what you are relying on your dentist to advise you about. It's your dentist's obligation and responsibility to provide you with opinions, information, and options concerning how best to restore your teeth.
Really, any filling which is greater than about a third of the width of its tooth overall could be considered to be a filling large enough that the strength of the tooth has been compromised and the tooth is now a good candidate for the placement of a dental crown. Some dentists are even more conservative in their opinion and feel that if a filling is greater than about one third of the distance between a tooth's cusp tips, the tooth should have a dental crown placed.
Take a look at the animation to the right. Each of the dental fillings shown could be considered to be "large." In each illustration an arrow(s) points to that portion(s) of the tooth which would be expected to be most prone to cracking or breaking off.
What size are the dental fillings in your teeth?
Possibly by now you have already been to the mirror so you can judge the size of the dental fillings in your teeth. Did you see any "large" ones? Now, ask yourself how long those big fillings have been in place. What was your answer? Two years, five years, longer? So what's the deal? If teeth with big fillings are so weakened, why haven't parts of these teeth already fractured off?
Of course the answer is that no dentist can know for certain which teeth will develop problems and which teeth won't. No doubt if your dentist could see into the future they wouldn't be spending their time practicing dentistry. Dentists do have however, both from their dental training and clinical experience, an idea of which teeth are more at risk for breaking than others and they have an obligation to report this information to you.
Clearly not every tooth with a "large" filling will break. Many people get many years of service out of these "large" restorations. Additionally, not every tooth that does crack or break will be especially problematic to repair. What your dentist is trying to relate to you however when they suggest that a dental crown should be placed instead of a filling is that they believe a crown will produce the most predictable successful outcome for your tooth, in the long run.
The relationship between dental crowns and root canal treatment.
Some people seem to equate a tooth's need for a dental crown with the need for root canal treatment for that same tooth also. While both of these dental treatments may be required they are entirely separate procedures and, most certainly, not every tooth which has a dental crown placed on it needs root canal treatment.
The relationship between dental crowns and root canal treatment is similar in nature to that between automobile bodywork (dental crown treatment) and under the hood work (root canal treatment). If you are in an accident (tooth breakage) you will need bodywork (the dental crown). If the accident has been especially severe and your radiator has been damaged, then you will need under the hood work also (root canal treatment), but it depends on the specific nature of the accident.
What are the consequences of not protecting a tooth with a dental crown?
It's impossible to know precisely what the future holds for a tooth that seems to be a candidate for a dental crown. Here are some of the possible scenarios that might develop for the tooth, ranging from benign to somewhat painful.
[ A red asterisk "*" Indicates a potentially significant problem which the placement of a dental crown could have prevented.]
A) The tooth will experience no problems.
When a dentist suggests that a dental filling should not be placed but instead the tooth should have the protection of a dental crown they are no doubt basing their recommendation on their years of dental training and clinical experience.
As you might guess, some teeth that seem to require the protection of a dental crown never experience any problems at all. No dentist can know precisely what set of occurrences will transpire with a tooth. They are simply advising you as to what they consider to be the most predictable treatment in regards to the long-term health of your tooth.
B)The tooth will crack.
One possible outcome for a tooth that is in need of the protection of a dental crown is that it will crack. Unlike cracks in bones, the cracks in teeth do not repair themselves or heal over. Once a crack has formed it can, and often will, increase in size over time due to repeated exposure to heavy biting forces.
Those teeth that do crack can do so in the following fashions:
1) Teeth that have cracked but no piece has broken off or has become mobile. The tooth produces no pain or discomfort.
In many cases unless a portion of your tooth has broken off you may not be aware that a crack has formed. This is because many cracks are difficult, if not impossible, to visualize and not all cracks in teeth (seen or unseen) are significant enough to produce symptoms.
Probably the greatest threat associated with this status is that this condition may be the prelude to a more serious scenario. While clearly not all cracks will unequivocally lead to problems, the presence of a crack can suggest that a fracture, cracked tooth symptoms, or a problem with the tooth's nerve may develop in the future.
2)*Teeth that have cracked and no piece has broken off or has become mobile. The tooth does produce some pain or discomfort.
Cracked teeth can be sensitive. Biting pressure can separate the portions of the tooth associated with each side of the crack and as a result trigger a painful response.
The classic sign of a cracked tooth is that there is a sudden sharp pain from the tooth when you bite down. The pain then subsides immediately once you have released your biting pressure. The pain may not be produced every time you close. Sometimes it takes biting (or biting on something) at just the right angle to trigger the response.
While cracks in teeth do not heal, cracked tooth symptoms can subside. If you anticipate that you do have a tooth that has cracked you should let your dentist evaluate it and make a treatment recommendation. They may determine that your tooth requires little or no treatment, or that a dental crown should be placed. In the most extreme cases they may determine that root canal treatment is required before the dental crown can be placed.
3) Teeth which crack and as a result have a portion that breaks off or becomes mobile.
A tooth can crack and result in a situation where a piece of it comes off. The piece that has separated can break away cleanly or, if the fractured portion is still attached to the gums, the piece will be mobile yet stay in place somewhat.
As you might anticipate, the amount of pain or discomfort associated with a tooth that has broken can vary widely depending on the specifics of the situation. Sometimes these teeth:
· are totally asymptomatic.
· are sharp or rough and therefore irritating to the person's tongue or cheek.
· have an increased sensitivity to hot and cold stimuli.
· are painful to biting pressure.
· are spontaneously painful.
Here are some of the scenarios that often present themselves as a result of a tooth fracture:
a) The tooth breaks in a fashion that is easily repaired.
It's not always a catastrophic event when a tooth breaks and, in fact, in most cases it usually it isn't. Any tooth, however, that has broken should always be inspected by your dentist so they can make a treatment recommendation. A stitch in time really can save nine when it comes to broken teeth.
It is conceivable that such a small portion of the tooth has fractured off that it only requires some minor smoothing. At the other extreme you may find that your dentist recommends the placement of a dental crown. Especially in those cases where a large portion of your tooth is missing, take the obvious hint that your tooth is trying to give you. Let your dentist make a crown for your tooth.
b)*The tooth breaks, but it requires other types of dental work before the dental crown can be made.
More serious tooth fractures will require more involved dental treatment to repair them.
The tooth fractures, periodontal surgery (gum surgery) is required.
If that segment of the tooth that has broken off comprises a portion of the tooth's root a type of gum surgery termed "crown lengthening" may be needed before a dental crown can be placed. This is because the edge of a dental crown cannot extend too far underneath the gum line or else it will impair the health of the gum tissue around the tooth.
The tooth fractures, root canal treatment is required.
Deep tooth cracks or extensive tooth breakage can compromise the health of a tooth's nerve. In these cases your dentist cannot simply place a dental crown on the tooth. They must first perform root canal treatment so to remedy the problem with the tooth's nerve, then the dental crown can be placed.
c)*The tooth breaks in a fashion in which it cannot be repaired.
Surprisingly, even teeth that have broken off flat with the gum line can usually be rebuilt. If a crack or break involves a large portion of the root portion of the tooth however (the portion way down underneath the gum line), your dentist may find that no dental treatment will be able to adequately repair the tooth and therefore the tooth must be extracted.
It typically takes two separate appointments for a dentist to make a dental crown for a tooth:
I) The initial dental crown appointment.
A) Your dentist will numb your tooth.
Before the process of making your dental crown is begun your dentist will anesthetize (numb) both your tooth and the gum tissue which lies around it.
B) Your dentist will shape your tooth.
In order to have adequate strength and, in the case of porcelain type crowns, proper aesthetics, a dental crown must possess a certain minimal thickness. Your tooth in turn must be reduced by this same amount so once the crown is cemented into place on your tooth will not be oversized. In most cases the minimal crown thickness that is required will lie on the order of about two millimeters or so, which is just a little more than a sixteenth of an inch.
In those areas where a portion of your tooth has already broken off your dentist may find that they have very little tooth reduction to perform. As a part of the trimming process your dentist also will ensure that any decay that is present has been removed from your tooth.
Besides reducing your tooth so it is smaller in size your dentist must also shape your tooth in a specific fashion. A tooth receiving a dental crown must be slightly tapered in form so the crown will slip over and onto the tooth.
The greater the amount of tooth structure that extends up into the interior of a dental crown the more stable the crown will be. There can be times when so much of a tooth has broken off that a dentist will feel that they must "build up" a tooth with filling material first (make the tooth taller) before they do the final shaping for the crown.
C) Your dentist will make an impression of your tooth.
Once your tooth has been shaped appropriately your dentist will need to make a copy of it by way of taking an impression. Your crown will then in turn be made from this impression. There are two scenarios by which this impression taking process can take place:
1) Most dentists will take an impression of your tooth using a putty-like material simply called "impression material." This impression will then be sent to a dental laboratory that will in turn use it to create a plaster cast. A dental technician will fabricate your crown so it fits accurately on the plaster cast. Since the cast is a precise representation of your teeth the crown will fit on your tooth also.
Depending on the arrangements your dentist has made with the dental technician, the amount of time required to fabricate dental crowns usually lies on the order of two weeks or so.
2) Your dentist might have a dental ceramic milling machine in their office. These machines are attached to a camera that can take an impression of your tooth optically. From this image the machine can subsequently design your dental crown and then create it by milling down a block of dental ceramic ("porcelain"), all in a matter of some minutes. The obvious advantage of this technique is that a tooth can be shaped and its dental crown cemented into place, all in one visit.
If your dentist does not utilize a ceramic milling machine it can be for good reason. Milling machines can only be used to fabricate all ceramic ("porcelain") crowns. Your dentist may feel that the physical properties and/or the aesthetics of this type of crown are not appropriate for your situation.
D) A temporary dental crown will be made for your tooth.
In those cases where your dental crown will be created by a dental laboratory you will have to wait the two to three weeks required for your crown to be fabricated. During this time period your tooth will be covered over by a temporary dental crown that your dentist has made. The temporary crown, which is typically made from plastic or else a thin shell of metal, will be cemented into place over your tooth. (Information regarding temporary crowns.)
E) Your dentist will select the proper shade of porcelain needed for your dental crown.
If your crown will have a porcelain surface your dentist will need to determine what shade of porcelain most closely matches your tooth's neighboring teeth. Usually a dentist will have a series of small, tooth shaped pieces of dental porcelain (each of a different color) which are collectively termed a "shade guide." Your dentist will select various porcelain samples from this shade guide and hold them in the area your new crown will occupy, until they find the one that most closely matches the color of your tooth's neighboring teeth.
II) Your second dental crown appointment.
Cementing your permanent crown in place.
At that point in time when the fabrication of your crown has been completed your dentist will proceed with the process of cementing it on your tooth. First your dentist will insure that your tooth is numb. Then, if a temporary crown has been placed, your dentist will remove it.
Before your dentist can cement your new dental crown into place they will first need to evaluate the way it fits on your tooth. To do so, your dentist will place the crown on your tooth, inspect its fit (possibly by way of using dental floss, feeling it with a dental tool, or asking you to gently bite down), remove the crown and adjust it, repeatedly, until they are satisfied. Additionally, and especially in those cases where the dental crown will hold a prominent position in your smile, your dentist will need to evaluate (and probably ask your opinion about) the crown's overall shape and color.
Once you and your dentist both agree that all seems right with your new crown it can be cemented. First your dentist will place dental cement inside your crown and then they will seat the crown on your tooth. After a few moments, so to allow the cement to set somewhat, your dentist will use a dental tool and scrape away any excess cement that has extruded from underneath the edges of your crown. The placement of the crown is now complete.
What precautions should be taken with a temporary dental crown?
Here are some things to know about temporary dental crowns, including some of the types of precautions dentists often recommend their patients take during that time when their temporary crown is in place.
Temporary dental crowns are held in place by "temporary" cement.
Temporary dental crowns are usually cemented into place using "temporary" cement so they can be removed easily at the time of your next dental appointment. Because this cement is not as strong as other types of dental cement, your dentist will probably suggest to you that you take some precautions so not to dislodge your temporary crown. Some of the types of precautions your dentist might suggest are listed below. You will simply need to ask your dentist if any of these precautions (or any other precautions not listed here) are important and relevant to your specific situation.
Minimize the usage of the side of your mouth that has the temporary crown.
There's no need to look for trouble, give the temporary dental crown some consideration when eating. As much as possible, shift the bulk of your chewing activities to other areas.
Keep sticky foods away from the temporary dental crown.
Anything sticky (caramel, chewing gum, etc...) has the potential to grab onto the temporary crown and pull it off its tooth.
Avoid chewing hard foods with the temporary dental crown.
Chewing exceptionally hard foods, such as raw vegetables (carrots), can dislodge or break a temporary dental crown.
Brushing and flossing suggestions for temporary dental crowns.
A tooth with a temporary dental crown can usually be brushed and flossed in normal fashion, with the following consideration. After flossing it may be best to remove the dental floss by way of letting loose of one end and then pulling it out to the side. Pulling the floss back out in normal fashion might snag the temporary crown and pull it off its tooth.
What to do if a temporary dental crown comes off.
If your temporary dental crown does happen to come loose you should contact your dentist's office so they can provide you with specific instructions and also make arrangements for you to come in and have it recemented.
In regards to that time period before you get back to your dentist's office to have the temporary crown recemented, your dentist might suggest that you simply place the temporary crown right back on your tooth. Doing so can protect the tooth somewhat from irritating stimuli such as hot or cold liquids. Wearing the temporary crown will also hold the tooth in place and keep it from shifting position (an important factor in how well or how easily your permanent dental crown can be fitted). Report to your dentist if you find that the bite on your temporary crown seems incorrect when you place back on your tooth. If this is the situation you find your dentist will probably prefer that you leave the temporary crown off.
If your uncemented temporary dental crown doesn't seem to stay in place very well your dentist might suggest that you fill it with toothpaste, Vaseline, or else denture adhesive before you place it over your tooth (this technique should only be used for a few days). Of course your dentist will no doubt advise you that you will need to be careful with your temporary crown until it is recemented. So you don't end up swallowing or biting on it unexpectedly, your dentist will probably suggest that your temporary crown should be removed when you sleep and eat. Anytime your temporary crown is not in your mouth you should keep it wet. Put it in a glass of water or close it up in a baggie with a moist piece of paper towel.
Pain and discomfort while your temporary dental crown is in place.
If you notice any pain or discomfort with your tooth it's best that you let your dentist know so they can evaluate your symptoms. Here are some of the types of problems that can occur:
A) The tooth has increased thermal sensitivity.
It is within normal limits that a person will notice some increased sensitivity to both hot and cold foods and beverages during that time during which their temporary dental crown is in place. This can be related to the fact that the edges of the temporary dental crown cover over the tooth less precisely than a permanent dental crown's edges will, thus providing a space by the gum line where these thermal irritants can get at your tooth. Just to play it safe however, in this situation go ahead and contact your dentist's office, report your symptoms, and let them make a determination.
B) The gums around your tooth hurt.
It might be expected that the gum tissue around a tooth that has been prepared for a dental crown will be tender for a day or so. Since the edge of most crowns end at or below the gum line your dentist will have to perform dental work in this area. It is very easy for a person's gums to get roughed up during the crown making process. As a solution a dentist will often suggest that rinsing with warm salt water up to three times a day may speed up the healing of this gum tissue. However, in all cases, if something seems amiss you should feel free to report to your dentist and let them evaluate your situation.
C) The bite on your temporary dental crown seems incorrect.
After your numbness wears off you may find that when you bite down your temporary crown touches its opposing tooth before its neighboring teeth do. When this situation exists your dentist will probably be very eager to adjust the bite of your temporary crown. Don't expect this situation to take care of itself or improve with time. Allowing this condition to persist can seriously aggravate or even compromise the nerve in a tooth.
D) Discomfort with your tooth.
It is not out of the ordinary that a tooth might feel a little aggravated after having been shaped for a dental crown. If you do notice discomfort go ahead and let your dentist know so they can evaluate your symptoms. As a solution for minor reversible conditions, a dentist will often suggest that their patients take an anti-inflammatory analgesic (such as ibuprofen or aspirin) so to help their tooth settle down. (You will need to read and evaluate the directions and precautions that accompany these products so that you know that their usage is appropriate for you.)
What problems might be experienced with a permanent dental crown?
People can and do experience problems with those teeth on which a dental crown has been placed. No doubt it is both your and your dentist's hope that once your dental crown has been completed that your tooth will be just fine. Unfortunately, life sometimes runs contrary to our wishes.
Here are some of the types of complications people can experience. They can range from very minor and commonplace in nature to serious and disappointing. In all cases, if you experience a problem you should let your dentist know, sooner rather than later, so they can evaluate your symptoms and make a treatment recommendation.
A) The tooth has sensitivity to both hot and cold stimuli.
It's not uncommon that after a dental crown has been cemented into place that a person notices that their tooth has sensitivity to both hot and cold foods and beverages. Typically the location of this sensitivity is at the edge of the crown, by the gum line.
In some cases a dentist might have a very simple solution for this problem. The remedy might be as easy as using a tube of one of those toothpastes marketed as a treatment for "sensitive teeth" (the active ingredient in these products is usually potassium nitrate). However, rather than make an incorrect treatment decision yourself, let your dentist know you are having a problem so they can evaluate your situation and make a recommendation.
B) The bite of the dental crown seems off.
Your dentist will have evaluated the way your dental crown touches against your other teeth when you bite down during that visit when they cemented your dental crown in place. Even so, you may find, especially after your numbness has worn off, that some aspect of your crown's shape is not quite right. Possibly when you bite down you feel your crowned tooth makes contact first, or maybe as you slide your teeth from side to side you can feel some aspect of the crown which seems too prominent.
This type of problem is usually an easy fix for your dentist, they simply need to buff your dental crown down so its shape is more in harmony with your bite. Don't expect this type of problem to take care of itself because it won't. In fact, if this condition is not remedied promptly it can lead to serious consequences related to the health of the nerve in your tooth.
C) Other difficulties with dental crowns.
The same events and circumstances that have led to the need for your dental crown (a broken or cracked tooth, a large cavity, etc...) can have a detrimental effect on other aspects of your tooth's health. Possibly your tooth was asymptomatic initially and now that the crowning process has been begun (or completed) problems seem to have popped up. While this set of circumstances is disappointing, it is not an indication that all was well with your tooth initially. It simply suggests that the full extent of the tooth's problems could not be identified beforehand.
Sometimes after dental crown treatment has been begun or completed a problem with the tooth's nerve becomes apparent and subsequently root canal treatment is needed. Some teeth are cracked seriously enough that even a crown cannot hold the tooth together sufficiently. These are not circumstances your dentist can predict with certainty, they can't see the future and know all outcomes. If you have found that a problem has developed, or has persisted, after your dental crown has been placed simply report to your dentist, sooner rather than later, so they can evaluate your current situation and suggest a treatment solution.
D) What to do if a dental crown comes off.
If your dental crown comes off contact your dentist's office promptly so they can provide you with specific instructions and make an appointment for you where they will evaluate your situation and then, if possible (and it very often is), recement the crown on your tooth.
During that time which exists before your dental appointment your dentist may suggest that you simply place the crown back on your tooth. The idea here is that wearing the crown will protect your tooth from irritating stimuli such as hot or cold liquids. Placing the crown on your tooth will also keep the tooth from shifting. (A tooth without its crown can shift in position so much that a dentist may not find it possible to recement the crown but instead will have to make you a new one.)
Sometimes when a person places a dislodged crown back on their tooth they will find that the crown's bite seems to be off. This condition must be reported to their dentist so a revised recommendation can be made. Usually in this instance a dentist will feel that is best just to leave the crown off, but that is for them to decide.
If your dental crown doesn't seem to stay in place very well your dentist might suggest that you fill it with toothpaste, Vaseline, or else denture adhesive before you place it on your tooth (this technique should only be used for a few days). Of course your dentist will probably also tell you that you will need to be careful with your crown until it can be recemented. So you don't end up swallowing or biting on your crown unexpectedly, your dentist will probably suggest that you remove your temporary crown when you sleep and eat.
What type of dental crown ("cap") should you have made?
Dental crowns (also known as "dental caps" or "tooth caps") can be made from metal (gold or other metal alloys), ceramic materials (such as porcelain), or a combination of both. The information on this page explains some of the advantages and disadvantages of each of these various types of dental crowns, but in general you should rely on your dentist's judgment and advice as to which of these types of crowns would be most appropriate for your situation.
All metal dental crowns. / "Gold" dental crowns.
Some dental crowns are made entirely of metal. The classic metal dental crown is one made of gold, or more precisely a gold alloy. Over the decades a variety of different metal alloys have been used in making dental crowns. Some of these metals are silver in color rather than yellow like gold.
Having a gold dental crown made can be an excellent choice. Here are some reasons why:
1. Because of its physical properties, dentists find gold to be a very workable metal. This characteristic helps a dentist to be able to achieve a very precise fit with the crown.
2. Since they are metal through and through, gold crowns withstand biting and chewing forces well. They will not chip. It would be uncharacteristic for a gold crown to break. Of all of the types of dental crowns, gold crowns probably have the greatest potential for lasting the longest.
3. Although they are very strong, the wear rate of a gold crown is about the same as tooth enamel. This means that a gold dental crown won't create excessive wear on the teeth it opposes (the teeth it bites against).
Metal dental crowns are usually placed on those teeth that are not overly visible when a person smiles (i.e., molars). If you are considering a gold crown take our advice on this point, before you give your dentist the go ahead on making the crown check with your spouse first. They're the one who will be looking at your smile and your new dental crown the most.
Dental crowns that will show prominently when you smile are usually made of porcelain (dental ceramic) or else will have a veneer of porcelain on their surface (i.e., porcelain-fused-to-metal crowns), so they have a white color like the rest of your teeth.
All-porcelain dental crowns.
Some dental crowns are fabricated in a manner where their full thickness is porcelain (dental ceramic). These crowns can possess a translucency that makes them the most cosmetically pleasing of all of the different types of dental crowns.
Although they can be very life like in appearance, the overall strength of all-porcelain dental crowns is less than other types of crowns. While they can be a good choice for front teeth, due to the hefty chewing and biting forces that humans can generate, all-porcelain dental crowns may not be the best choice for back teeth. Your dentist's judgement will be required on this point.
Porcelain-fused-to-metal dental crowns.
Porcelain-fused-to-metal dental crowns are somewhat of a hybrid between metal crowns and porcelain crowns. When they are made the dental technician first makes a shell of metal that fits over the tooth. A veneering of porcelain is then fused over this metal (in a high heat oven), giving the crown a white tooth-like appearance. Depending on the requirements of your situation, these crowns are sometimes made where the porcelain veneer only covers those aspects of the crown that is readily visible (meaning the other portions of the crown have a metal surface). In other cases these crowns are pretty much fully surfaced with porcelain.
Porcelain-fused-to-metal dental crowns can be a good choice for either front or back teeth. These crowns are strong enough to withstand heavy biting pressures and at the same time can have an excellent cosmetic appearance. There are some disadvantages associated with porcelain-fused-to-metal crowns however (which no doubt your dentist will try to minimize as much as is possible). They are:
1. While the cosmetic appearance of these crowns can be excellent, they often are not as pleasing aesthetically as all-porcelain dental crowns.
2. The crown's porcelain can chip or break off.
3. The porcelain surface of the crown can create wear (sometimes this wear is significant) on those teeth that it bites against.
4. The metal that lies underneath a crown's porcelain layer can sometimes be visualized as a dark line found right at the crown's edge. A dentist will usually try to position this dark edge just underneath the tooth's gum line but if a person's gums recede this dark line can show, thus spoiling the crown's appearance.
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:
1) 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.
2) 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.
