General Dentistry

Tooth Decay

Tooth decay is one of the most common infectious diseases known to man. (Only the common cold is more prevalent.) Decay or caries occurs when the teeth are attacked by acid, which is introduced to the mouth in one of two ways: 1) Through the consumption of foods or acidic drinks like soda pop, fruit juice, etc. or 2) Through the breakdown of the sugars and starches in our diet by the naturally occurring bacteria in our mouths.

For most people, cavities develop due to excessive ingestion of sugary foods and candy, as well as soda pop. This causes the localized acid load in the mouth too increase to such a high level (pH < 5.5) that the acid literally rots a hole in the tooth. Excessive consumption of carbonated beverages like colas can be especially bad for the teeth, because they contain both acid and sugar.

To avoid cavities, and still enjoy a sweet or carbonated beverage, simply brush and floss immediately after eating or drinking these. This removes the sugars and acids and stops the decay process from progressing.

However, for some of us, the decay process has already occurred, necessitating a filling or perhaps a crown.

Fillings

If the cavity is small, fillings are an appropriate restorative option. By small, we mean that the old filling (if present) and decay must take up less than 50% of the tooth (above the gum line). If the cavity takes up more than 50% of the tooth, then a crown or cap is necessary.

Fillings are commonly differentiated by their color, either silver (grayish) or white (tooth-colored). Silver fillings or amalgams are made up of an alloy comprised primarily of silver, tin, copper and mercury. Amalgams have been around for over 150 years are extremely durable and work extremely well. However, cosmetic concerns have resulted in these being phased out in favor of the more esthetically pleasing tooth-colored fillings.

Silver fillings also have a major disadvantage: They contain mercury, which is quite hazardous to the environment (because of this, some countries in Europe have banned silver fillings). However, for the vast majority of the population (>99%), silver fillings are considered to be safe in the mouth. The issue is more an environmental one: factories that process mercury generate waste that is extremely toxic to wildlife, especially birds.

Modern dental offices have therefore largely moved to tooth colored fillings and are doing fewer and fewer silver fillings. Tooth colored fillings are comprised of either composite resin or glass/resin ionomers. Composite resin fillings are more common since they can stand up to heavy chewing pressures and not break. Ionomers are better suited for non-load bearing situations—cavities between the teeth, for example.

Tooth colored fillings look great, but do have the disadvantage of costing slightly more. The white filling material usually costs more than amalgam and typically takes longer to place in the tooth (resulting in a higher fee from the dentist).

And be aware that some (not all) dental insurance companies view silver amalgam as “good enough” and only have one payment amount for a particular type of filling—regardless of whether it is silver or white. This results in the patient having to pay a slightly higher “out-of-pocket” for white fillings than for silver. If your dental insurance downgrades the fee for white fillings down to that for silver, be sure to voice your concerns to the person in human resources that buys your insurance.

Crowns and Caps

When the decay and old filling (if present) take up more than 50% of the upper portion of the tooth, a crown or cap is necessary— there is not enough tooth left to structurally support a filling.

A crown necessitates a two-visit procedure for the patient (unlike fillings which are a single visit procedure). Two visits are necessary with crowns, since the new tooth top (or crown) is fabricated by an outside dental laboratory (though a few dentists do have in an in-house lab). The outside dental laboratory takes about 1.5-2.0 weeks to fabricate the crown out of porcelain or gold, after which the patient needs to return to the dentist to have this placed.

In the crown procedure, the dentist removes the decay from the tooth and then places a temporary plastic crown. The patient wears this temporary for about 2 weeks—the time it takes for the lab to fabricate the permanent crown—and then returns to have the temporary popped out and the permanent crown cemented in.

The temporary crown should feel just fine during this two week period. And for the majority, this is the case. However, if the crowned tooth is sensitive, you need to contact your dentist. With deep decay, a bit of sensitivity can occur and the dull pain should be controlled with Ibuprofen (Advil). If the temporary is sensitive only after eating, you may need a quick adjustment of the bite. And if the crowned tooth if sensitive to hot/cold and percussion (or tapping), you may need to be evaluated for a root canal.

Crowns are usually differentiated by the material they are made of:

Porcelain fused to metal

A metal under-layer with esthetic white colored porcelain over the metal. Can look slightly more opaque than all porcelain crowns, but has high strength making it the preferred choice for molar crowns. However, esthetics and advances in materials technology may eventually result in the replacement of porcelain fused to metal with porcelain over zirconia.

Porcelain over Zirconia

Zirconia is a ceramic that boasts superior esthetics to metal, since it can be made white colored and semi-translucent, resulting in a superior cosmetic result (compared to metal). Common brands of zirconia include 3M’s Lava and Nobel Biocare’s Procera. Lava is a bit more translucent than Procera, so is preferred by some cosmetic dentists.

All Porcelain

All porcelain restorations are indicated for the front teeth that show when we smile. Feldspathic (layered) porcelain gives the best esthetics and is used in almost all Mitchell Dental Spa cosmetic and veneer cases. Empress pressed ceramic is another material commonly used, but Empress is cast rather than layered. This necessitates having to apply the final color of the restoration to the surface of the crown or veneer. With feldspathic porcelain, one achieves a much greater depth of color and naturalness, since the color is layered in deep within the crown.

Gold

Gold crowns are non-esthetic, but have a much longer lifetime than porcelain (gold has a bit of give to it, while porcelain has little, resulting in longer-lasting restorations in the case of gold). The use of gold is declining, though, as most patients desire a more natural looking white colored restoration. However, if you want longevity, or have a problem with clenching / grinding (TMD), gold can be a great way to go.

The Impact of the Dental Laboratory on Crown Quality

The dental laboratory can have a tremendous impact on the look and longevity of a crown or veneer, so we at the Downtown Dentistry only advocate the use of the very best labs. Crowns, depending on the skill of the dental lab, can look exactly like a tooth in shape and color. Or, on the other hand, they can resemble a distorted, monochromatic cube. In addition, labs have a tremendous impact on the fit of a crown, which is critical. Tightly fitting crowns, with no open margins, will be resistant to decay-causing bacteria and therefore last longer. A poorly fitting crown is extremely prone to premature failure (as little as 1/10 the lifetime, relative to a good fitting crown).

Buildups (An Adjunct Procedure to a Crown)

Sometimes the tooth is so compromised, due to cracks, breakage, or decay, that retention to what is left of the tooth, can become an issue. In these cases, a buildup under the crown is indicated to provide a solid foundation for the crown to sit on. This is a separate and additional procedure to the crown and is highly recommended when necessary, since it can dramatically increase the lifetime of the crown (since the fit and retention are enhanced).

Bridges

Bridges or implants are suggested when a patient is missing a tooth. A crown (or crowns) is placed on each side of the area missing a tooth (or teeth) and then a tooth top (or pontic) is suspended over the area that is absent the tooth (or teeth). The pontic is then attached to the adjacent crowns, forming a bridge.

A bridge can be somewhat less expensive than an implant and is indicated when the adjacent teeth are already compromised, due to decay or large restorations present. An implant is preferable if the adjacent teeth do not require any dental work.