When we are planning your cosmetic dentistry procedure like a full mouth rejuvenation, we will probably choose ceramic restorations. But that doesn’t necessarily make the decision much easier. One of the great advances in cosmetic dentistry technology has been the explosion of advanced ceramics that are available to us. So when it comes time to make a decision about your restorations, we will have to decide from among all the amazing options we have.
Usually, that means managing the tradeoff between translucency (the ability to let light and color through) and strength.
Why Translucency Matters
Hopefully, it’s clear why we want stronger materials for your restorations. Until we have good restoration materials that can flex like your natural teeth, strength is the best solution we have to prevent cracking and chipping. So, in general, higher strength is better for your restorations.
But you might not understand why translucency matters. Actually, it’s simple. Your enamel is translucent, so we want to use a restoration material that is translucent, too, especially when we’re placing porcelain veneers on your front teeth. That allows your teeth to look natural, including the ability for dentin to show through, creating a gradient that makes your restorations indistinguishable from your natural teeth.
Of course, sometimes we don’t want too much translucency. If you have a tooth that is discolored from within (perhaps by trauma), we don’t want too much translucency. Instead, we want to conceal the discoloration with an opaque material that imitates translucency. It looks like it’s translucent, but it’s actually keeping you from seeing what’s inside. A neat trick that’s not easy, but we can do it.
Translucency Diminishes as Strength Increases
It’s an unfortunate tradeoff that as we develop ceramics that are stronger and stronger, they become less translucent. It kind of makes sense–the structure has to be denser, so it let’s less light through.
For proof, look at this study that used consistent size pieces of ceramic and compared the translucency. The most translucent material was Vita VM9, an updated version of traditional feldspathic ceramics. Vita VM9 has a flexural strength of about 100 Megapascals (MPa), about 14,500 pounds per square inch (psi). Incidentally, traditional feldspathic ceramics–the kind you might have gotten if you had veneers 10 or 20 years ago–had a flexural strength of about 60-70 MPa. A material with moderate translucency is e.Max, a lithium disilicate glass ceramic. e.Max has a flexural strength of 400 MPa, about 58,000 psi. The least translucent material tested here was Lava, a kind of zirconia ceramic. Zirconia ceramics have a flexural strength between 900 and 1100 MPa–up to nearly 160,000 psi! This approaches the strength of titanium that we use for dental implants!
Juggling Translucency and Strength
Of course, there are lots of ways we can play with materials to get the combination of properties we want. As materials get stronger, we can use thinner sections, which will increase the translucency. As this study shows, it’s possible to get zirconia sections that have translucency similar to that of lithium disilicate.
Another potential solution is to use a translucent ceramic on top of a zirconia core, similar to a porcelain-fused to metal crown, and with similar problems.
You may not need a restoration as strong as you think. If you’ve had teeth and restorations break in the past, it’s likely due to an imbalanced bite. A neuromuscular dentist can help balance your bite to minimize the force that your restorations have to stand up to.
Find a Dentist You Can Trust
Is your head spinning from all these numbers and options? Don’t worry–this is not a decision you have to make. It’s your dentist’s decision. All you have to do is decide on the dentist. Find a dentist you can trust to make the right decision and let them make the hard call about what ceramic is right for you.