Crowns

What are dental crowns?

Dental crowns, sometimes called "dental caps" or "caps," are restorations that cover and encase the tooth on which they are cemented. We use crowns when we need to rebuild root-canal treated, broken or decayed teeth, strengthen teeth, or improve the cosmetic appearance of a tooth. When cemented into place, crowns fully cover the tooth. 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.

What are crowns made from?

Crowns can be made out of porcelain (or some sort of dental ceramic), metal (a gold or other metal alloy), or a combination of both. There are many materials to choose from and we work both with our patients and with our laboratory partners on each case to make decisions on which material to use.

Porcelain to Gold Crowns	Full Cast Gold Crowns	All Ceramic Crowns

Gold Crowns

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. Because of its physical properties, we are able to achieve a very precise fit with the crown.Since they are metal through and through, gold crowns withstand biting and chewing forces well. They will not chip or break. Of all of the types of dental crowns, gold crowns probably have the greatest potential for lasting the longest. 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 chews against.

All-porcelain 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.

Porcelain-fused-to-metal Crowns.

Porcelain-fused-to-metal dental crowns are 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 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). While the cosmetic appearance of these crowns can be excellent, they often are not as pleasing aesthetically as all-porcelain dental crowns. The crown's porcelain can chip or break off from the metal substructure and the porcelain surface of the crown can create wear on those teeth that it bites against.

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. We will usually try to position this dark edge just underneath the tooth's gum line but if your gums recede this dark line can show, thus spoiling the crown's appearance.

Why do teeth need crowns?

We 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 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.

Dental crowns have a big advantage over dental fillings by way of the fact that they are fabricated "away from your mouth." 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". When a 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 we place a dental filling we have far less control over the final outcome of the shape of your tooth because it is often difficult to visualize and access the tooth on which we are working.

How can dental crowns be used to improve the cosmetic appearance of teeth?

Since a crown encases 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 having 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 we must grind a significant portion of a tooth away to fit a crown. 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.

How can dental crowns strengthen teeth?

The strengthening capability of dental crowns is related to the fact that they completely cover 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.

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 to make a repair. 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.

What constitutes a big dental filling?

Well of course this is the $64,000 question. It's our 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.

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 can't know for certain which teeth will develop problems and which teeth won't. If we could, we wouldn't be practicing dentistry. We do have an idea of which teeth are more at risk for breaking than others andwe 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 we are trying to relate to you however when we suggest that a dental crown should be placed instead of a filling is that we believe a crown will produce the most predictable successful outcome for your tooth, in the long run.

What is the relationship between dental crowns and root canal treatment?

Some people equate a tooth's need for a crown with the need for root canal treatment for that same tooth. While both of these dental treatments may be required they are entirely separate procedures. Not every tooth which has a 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 (crown treatment) and under the hood work (root canal treatment). If you are in an accident (tooth breakage or cavities) 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.

What can happen if my tooth cracks?

	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 are significant enough to produce symptoms. This condition may be the prelude to a more serious scenario. While 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. On the other hand, 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 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 us evaluate it. We may determine that your tooth requires little or no treatment, or that a crown should be placed. In the most extreme cases we may determine that root canal treatment is required before the dental crown can be placed.
	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. Other times, they may be sharp or rough and therefore irritating to the person's tongue or cheek, have an increased sensitivity to hot and cold stimuli and are painful to biting pressure. 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. 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.
	More serious tooth fractures will require more involved dental treatment to repair them. 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. Deep tooth cracks or extensive tooth breakage can compromise the health of a tooth's nerve. In these cases we cannot simply place a dental crown on the tooth. We must first perform root canal treatment so to remedy the problem with the tooth's nerve, then the dental crown can be placed.
	Sometimes a tooth breaks or is damaged by caries 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. We can often use root canal, crown lengthening and crowns to great effect but we must always keep our eyes on the final results that we want. The more procedures required, the less predictable the final outcome usually becomes. More importantly, these procedures are expensive and, if we choose them, we want them to work for a long time. If a crack or break involves a large portion of the root portion of the tooth (the portion way down underneath the gum line), we may find that no dental treatment will be able to adequately repair the tooth. Other times, cavities may extend down beyond the level of the bone and too far for crown lengthening to be effective. In these cases, the tooth must be extracted and we must begin to look at ways to replace it. A dental implant is often the best solution in these cases.

What steps are involved when dental crowns are made?

It typically takes two separate appointments for a dentist to make a dental crown for a tooth:

Appointment One:

	We will numb your tooth and the gum tissue which lies around it. We will then shape your tooth for a crown.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 we may find that they have very little tooth reduction to perform. As a part of the trimming process we will ensure that any decay that is present has been removed from your tooth. Besides reducing your tooth so it is smaller in size we 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 we must "build up" a tooth with filling material first (make the tooth taller) before they do the final shaping for the crown. Once your tooth has been shaped appropriately we 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. You will usually 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. The temporary crown, which is typically made from plastic or else a thin shell of metal, will be cemented into place over your tooth. If your crown will have a porcelain surface we will need to determine what shade of porcelain most closely matches your tooth's neighboring teeth. We have a series of small, tooth shaped pieces of dental porcelain (each of a different color) which are collectively termed a "shade guide." We select various porcelain samples from this shade guide and hold them in the area your new crown will occupy, until we find the one that most closely matches the color of your tooth's neighboring teeth.

Appointment Two:

When the fabrication of your crown has been completed we will proceed with the process of cementing it on your tooth. First, if a temporary crown has been placed, we will remove it. Before we can cement your new dental crown into place we will first need to evaluate the way it fits on your tooth. To do so, we 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, we will need to evaluate (and probably ask your opinion about) the crown's overall shape and color. Once we both agree that all seems right with your new crown it can be cemented. First we will place dental cement inside your crown and then we will seat the crown on your tooth. After a few moments, to allow the cement to set somewhat, we 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 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 our 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 us know, sooner rather than later, so we can evaluate your symptoms and make a treatment recommendation.

1. 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 we might have a very simple solution for this problem. The remedy might be as easy as using a tube of sensitivity toothpaste or prescription fluoride.
2. The bite of the dental crown seems off. We 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. We simply need to buff your dental crown down so its shape is more in harmony with your bite.
3. 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.
4. 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 we can predict with certainty.
5. If a dental crown comes off contact us promptly so we can recement the crown on your tooth. A tooth without its crown for too long can shift in position so much that we may not find it possible to recement the crown but instead will have to make you a new one.

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 us. It's our hope that any crown we 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) a crown can be a solid, long-lasting investment. The biggest factor is how well you keep the tooth to which it is cemented free of dental plaque. We have seen many 'average' crowns last 20 years or more because they have been well maintained. by the same token, we have also seen some very well made crowns that needed to be replaced because they simply were not kept clean.

Why do dental crowns need to be replaced?

• Tooth decay has formed at the edge of the crown. While a 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 crown is that in order for us to be able to get at and remove the decay the crown will need to be taken off and replaced with a new one.
• The crown has become worn excessively. Dental crowns can wear out, especially when a person has a habit of clenching and grinding their teeth. Sometimes a small hole forms on the chewing surface of a dental crown in that area where it makes contact with an opposing tooth. Since the seal of the crown has now been lost we may recommend that a new crown should be made, before dental plaque has seeped in underneath to start a cavity.
• Dental crowns can break, or more precisely the porcelain component of a dental crown can fracture. If an all ceramic 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. 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. While the function and esthetics of the crown may have been compromised, the crown's seal over the tooth has probably not been affected. 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 may need to be replaced.
• Some dental crowns are replaced because, from a cosmetic standpoint, their appearance is no longer pleasing. As time passes the gum line of a tooth on which a 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 crown, which was originally tucked out of sight just under the gum line, 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. 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.

Root Canals and crowns are expensive and time-consuming. Can't I just have it pulled?

This seemingly simplest and cheapest solution can be the worst and most expensive choice in the long run. When a tooth is extracted its neighboring teeth will have a tendency to shift, sometimes significantly. The resulting misalignment of your teeth can, in turn, have a major impact on your dental health. Even the removal of a single tooth can lead to problems associated with chewing ability, jaw joint problems, or create a situation that can predispose any teeth that have shifted to developing problems in the future. So to avoid these complications,we recommend to you that you replace teeth that has been extracted. Replacing a tooth that has been extracted with an artificial one will all most certainly cost more than the alternative treatment plan of not having the tooth extracted and instead rebuilding it with a crown.