White Stuff
One of the goals in dentistry is to make the teeth look nice and natural, maybe even better than natural. So the search for white stuff to restore or replace teeth marches on. In all of recorded history, ivory has been used in various ways, but just like the industrial revolution, all of a sudden there has been an explosion of new products that technology has fostered.
We’re not talking gold, which has been around forever, just the tooth-colored materials and the latest developments, which we think are all that, but in ten years, who knows what we’ll have, unless the government tries to control dentistry, which would discourage any more innovation. Whew, check out that last sentence! I think my grammar teacher would have fainted.
Back in the 1930’s, they figured out how to bond porcelain over the gold and use silicate, or glass cement, to fill the front teeth. Those uses were very limited until after World War II, when they became much more prevalent. Incidentally, the use of plastics for fillings started after the war, and went into another direction. Many generations of improvements have produced the wonderful ceramic filling materials that we enjoy today. But let’s follow the evolution of the more aesthetic porcelain restorations that have attempted to recapture the natural beauty of our teeth.
The early porcelain-fused-to-gold (PFG) crowns were actually pretty nice, but they had two main problems. The porcelain fractured away from the gold frame, and they were super abrasive to the natural teeth. It was like chewing on sandpaper. In no time at all, the natural teeth opposite PFG crowns were worn down to the nerve. The only good solutions were to put PFG crowns on the opposing teeth, or make the biting surface out of gold, which defeated the purpose of using the porcelain.
Then came the porcelain-fused-to-non-precious metal (PFM) crowns. They are less expensive and because of the rigidity of the metal, there are fewer fractures in the porcelain, but they are just as abrasive, they look less natural, and many people are allergic to the metal, which is 62% nickel.
Until 1975, the idea of using porcelain without a metal substrate was unthinkable, because it would break immediately. It gets its strength from being bonded to something. But the advent of tooth bonding and laminated porcelain made it finally possible to make all-porcelain crowns. They were by no means a panacea, because there was still a lot of breakage and they were still too abrasive.
A series of refinements has produced more modern porcelain by using additives that make the traditional feldspar stronger and less abrasive. Ingredients such as Lucite and lithium disilicate have much smaller particle size, giving porcelains those superior qualities as well as a more translucent and natural appearance. These newer blends are categorized as “low fusing”, because they melt at a lower temperature. The old fashioned porcelain is still out there, so whether you get a porcelain-fused-to-metal or an all-porcelain crown or veneer, be sure to insist on a low fusing kind.
Is that all we’ve got? I thought you’d never ask. I saved the best one for last. The hottest thing out now is zirconia. It’s totally nonabrasive and unbreakable! Don’t make the mistake of using the brands that fuse porcelain over the zirconia, because the porcelain still breaks, but the homogenous porcelain-zirconia mixture is better, and pure zirconia is the absolute best. As I was placing one of those in a patient’s mouth, he asked me how durable it would be. I told him in all honesty that if a nuclear bomb went off across the street, all that would be left of him would be that crown.
Esthetically, zirconia is not very translucent, but on the back teeth, where you need the most strength, it looks perfectly natural. On the front teeth, which are not subject to as much stress, we like to use the more translucent types, which are more like your natural enamel, especially if you want to go for that extra bright white that’s so popular now.
Dr. Moulton’s article was published in the Desert Valley Times on
February 2, 2010.
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