Dental Technology And The Longevity Of Porcelain Veneers Article

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Dental Technology and the Longevity of Porcelain Veneers

If you have been considering porcelain veneers, you probably know all the advantages. You know that they can be used to reshape your smile, to correct discolored teeth, to correct crooked, gapped, or misshapen teeth. You may, however, still have concerns about the longevity of porcelain veneers.

Author: Sara Goldstein

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After all, who would want to spend an average of $11,000 on a dental treatment that will only last a few years. You want assurance that porcelain veneers will last for a long time, and, unfortunately, their name does not convey confidence. To most people, "porcelain" conveys a sense of fragility. It's associated with the jimcrackery in your grandma's china cabinet, the beautiful fragile objects you spent your childhood longing for but never being allowed to touch. However, today ceramics are among the strongest materials available, and porcelain dental restorations are stronger than they have ever been. Because of advances in dental technologies, over 95% of dental veneers last 11 years or more.

Advanced Ceramics

As described above, today's ceramics are not the same as ceramics of the past. In fact, today's ceramics are used in many applications where their strength and durability are tested in the most rugged of conditions. Famously, the space shuttle has depended on heat resistant ceramic tiles for safe re-entry into the earth's atmosphere and was designed to withstand temperatures of up to 2200º F. However, these ceramic tiles are very brittle and would not be suitable for porcelain veneers. (Not even if you used the white ones!)

A better comparison would be the advanced ceramics used to layer composite tank armor. Although steel still does the lion's share of the work in tank armor, ceramic armor is responsible for the incredible advances in protection given to tankers. Most tanks produced by NATO countries, including the Abrams, the Challenger 2, and (unofficially) the "best tank in the world" the Leopard 2 all utilize a ceramic layer in their armor to improve protection. Although the exact composition is classified, the basic ingredient is believed to be alumina (aluminum oxide, more on that later). While this doesn't mean we recommend you should try to stop an armor-piercing round with your porcelain-fused-to-metal dental crown, it does mean you can have some confidence in the toughness of your restorations.

Advances in Porcelain Veneer Technology

So, now that we've established that modern ceramics have some amazing properties, how does this contribute to the longevity of porcelain veneers? The problem with porcelain veneers is not just crafting them, but being able to craft them affordably and consistently on a scale that will allow people to take advantage of the strength and attractiveness of porcelain veneers. The best way to understand the state of the art is to look at previous restorations and their weaknesses.

The first all-ceramic dental restorations were developed in the mid-1960s. These had a porcelain core, reinforced with about 50% alumina, the same stuff that we suspect is part of the advanced tank armor. These restorations had a thin layer of feldspathic porcelain on the exterior to give them the appearance of natural enamel. Unfortunately, these restorations had a problem: shrinkage. Although generally predictable, shrinkage of the restoration during firing meant that the fit was sometimes very poor.

Shrinkage was corrected by the addition of magnesium oxide to the material and the use of injection molding. Unfortunately, although these ceramic restorations always resulted in a great fit, they had reduced strength. The failure rate for these restorations was up to 21% at three years! Clearly, this is unacceptable.

Another possible solution was the use of slip cast restorations using porous alumina core material infiltrated by liquid glass. This gave great strength, but, unfortunately, was a highly opaque material that was aesthetically inferior.

Another advanced manufacturing technique to create high-strength restorations was the sintering technique. In this process, powder is fired to create the restoration. A drawback is that this results in microporosities in the restoration, which are weak points that can lead to systematic failure.

Castable glass systems have been investigated for use in porcelain restorations. These castable ceramics have the same problem with shrinkage as the original cast systems. And the first of these castable glass systems had failure rates of up to 36%! Others were better, but still had very high failure rates.

Heat-pressing was originally developed as a way to counteract shrinkage during casting. When the material is cast under pressure, it better maintains the shape of the mold. It also allows the restorations to be created more quickly without additional treatment. And heat-pressing makes it possible to infuse the ceramic matrix with a plastic material that reduces brittle failure of the restorations. The plastic of choice for most dental restorations is leucite, an extremely durable plastic.

One clinical trial of dental crowns made of this material showed a failure rate of only 1.3% at three years! Additional clinical studies have established that the survival rate for this type of restoration is about 95% at eleven years. To put this in terms of your restoration: if you get 12 porcelain veneers (six on top and six below), there is a 2/3 chance that all of your veneers will be intact at eleven years.

Now that's longevity!

If you live in the San Diego area and want to learn more about porcelain veneers, you can visit the website of cosmetic dentist Dr. Mary A. Walsh-Cole.

About Author

Dr. Mary A. Walsh-Cole offers cosmetic dentistry to patients in San Diego, Encinitas and Carlsbad.

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Dental Technology and the Longevity of Porcelain Veneers