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BIOCERAMICS

30,000 years of ceramics!

Did you know that the oldest ceramic piece ever discovered is the Venus of Dolní Věstonice which has been dated to approximately 30,000 years ago! Most incredibly, scientists have discovered the fingerprint of a young child on the piece

​Ceramics is ultimately a catch-all term for the process of taking inorganic materials like clays, silicates, and other more sophisticated oxides, and heating them up through very high temperatures into a new solid form. This firing process sinks energy into the atomic structures of the materials which allows them to form new bonds, creating a much stronger lattice structure. Take a look at the picture below. On the left if the powdered form of Zirconium Oxide (ZrO2). Through the firing process, the powder was transformed into the crucibles you see on the right. We chose to use Zirconium Oxide here as the base material since that is what we use in the dental field and our implants, but the same ideas with any of the materials we listed earlier.

ZrO2 powder.JPG

Fired at
2700˚C   /  4892˚F

ZrO2 crucibles.JPG

What are Ceramics in General?

Zirconium Oxide
ZrO2

Zirconia Crucibles
ZrO2

What are Bioceramics Then?

Bioceramics is simply one specific form of ceramics, sort of like how a Saint Bernard is just one type of dog. Ceramics can be formed from many different materials, but not all of them play nice with your body over the long term. On the other hand, bioceramics interact with the body where appropriate, and don't interact where we don't want them to. The key here is the concept of biocompatibility. This office only uses the most biocompatible materials, which is why we use Zirconia implants. And, we want you to understand why Zirconia is the most biocompatible material, thus this whole page. So to summarize a bit, bioceramics are the most biocompatible material being used in dental implants, which is why we use them. More specifically, the zirconia ceramic is materially inert and will not release any ions into your body like a titanium implant can. Also, there is no need for a special coating on the implant post as the Zirconia promotes bone growth all by itself.

So What is the Difference Between Zirconium, Zirconia, and Zircon

First thing, all of these names sound really similar, so it's certainly a bit confusing. We describe them below in increasing complexity, from a singular atom to is mineral form. We've even included pictures to help clear things up!

  • Zirconium: Zirconium is simply an element like you've seen on the Periodic Element Tables back in chemistry class. Zr is the symbol for Zirconium. Zirconium easily combines with other elements to create more sophisticated molecules with wildly different properties.

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  • Zirconia: Zirconia, or more specifically Zirconium Oxide (ZrO2) is the molecule that makes up the ceramics that we use in the dental field. You can see from the diagram that the ceramic matrix is made of only two elements: Zirconium (Zr) and two Oxygen molecules (O2). You can actually see from the diagram how the arrangement of the two atoms creates an incredibly strong molecular arrangement. It is one of the strongest ceramic molecules in existence.

  • Zircon: Zircon is technically called zirconium (IV) silicate (ZrSiO4). Zircon is actually a mineral that can be mined for either zircon flour or as a semi-precious gemstone. Zircon gemstones come in so many different colors because of the open lattice work of the zircon matrix allows for a wide array of other elements to be trapped, thus causing color diferentials.

ZrO2 Crystaline Lattice.JPG
Zircon Model.png

Why Zirconium is a Metal, but Zirconia is Not

Zirconium, just the element Zirconium, is what is termed a transition metal, just like Titanium.  The definition of a transition metal is rather complicated; but, the gist is that there is an electron, or electrons, missing from the inner orbital d shell (think of the shells like layers of different clouds around a core). For yours and our purposes, the difference between metals and transition metals is not that much different as it relates to dentistry other than transition metals can more easily form oxides like Zirconia. Zirconia is actually called Zirconium Oxide (ZrO2). The oxide is the O2 part; but, that ends up being the most important part since the O2 is what completely changes the nature of the material. 

Does the Oxide (O2) Part of Zirconia Make that Much Difference?

Capital 'Y' followed by a lower case 'es'. One of the great parts of chemistry is how small differences in chemical compounds can completely and fundamentally transform the nature of a compound, from how it looks to how reactive it is. My favorite lesson from Chemistry class regarding this was about the chemical called carvone. There are two versions of carvone. There is R-Carvone (R stands for right-handed), and S-Carvone (S stands for sinistral, or left-handed). Below are the two versions of Carvone. You can see that they are exact mirror images of each other, but they have very different traits. R-Carvone is what gives us spearmint flavor; S-Carvone is what gives us dill and caraway seed flavors. ​

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R-Carvone

and 

S-Carvone

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The point of this example is to show you that even when a compound has the exact same structure but differs only in orientation, the effects can be very different. So what happens when completely new elements are added together? First, Below is what pure elemental zirconium and titanium look like.

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Elemental Zirconium

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Elemental Titanium

Now let's add two Oxygen (O2) atoms to each element and see what we get. See Below:

ZrO2 powder.png

Zirconium Oxide

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Titanium Oxide

Now that is completely different! What was clearly a metal has been transformed into a white powder, and all it took was two oxygen atoms. Specifically, what is created is a zirconium oxide ZrO2 (Zirconia) powder and a titanium oxide (Titania) powder. From there, with enough heat and pressure, these oxides can be transformed into their ceramic forms. 

Why is Ceramic Zirconia Better than Ceramic Titania for Dental Implants?

Looks can be deceiving. Just because those two powders look alike does not mean they have anything in common. In its ceramic form, pure Zirconia is well known as being one of the strongest ceramics in the world. Titania is not. In fact, Titania is used almost exclusively as a whitening pigment for ceramic glazes. What is really crazy is that the powdered form of Titania is used as a whitening element in things like powdered sugar donuts and paint. But, ceramic Titania has nowhere near the stability and tensile strength needed to withstand the biting and chewing actions even though it is strong enough to be used on ceramic plates and other dishware. Ceramic Titania is simply not strong enough on its own. We will talk about how the non-ceramic form of Titania is used on Titanium implants shortly though.

​Ultimately, Zirconia is the only choice. As a bioceramic, Zirconia stimulates the bone grown we need to integrate the implant into the jaw. We call those processes osseointegration and biointegration. Titania also promotes those processes, it just isn’t strong enough on its own to work as an implant.

Why is Ceramic Zirconia Better than Ceramic Titania for Dental Implants?

Titanium implants use Titanium Alloys and Titanium Oxide Coatings

Titanium implants are not made of just elemental Titanium. For a Titanium implant to integrate properly, the Titanium core of the implant must be coated with some form of compound. This compound is then what actually comes into contact with the bone and soft tissues during integration. That compound has been made or formed of Titania (See Above). Titania in this instance can be formed through simply oxidizing the outer layer of Titanium instead of making a ceramic overlay. It is more efficient to do it this way and probably more resilient to damage as a thin ceramic layer would be fairly easy to chip off.

That sounds all well and good, but what happens if there is damage to the outer layer of the Titanium implant? It is not hard to imagine how easy it is to damage the outer layer given that you have to literally screw the implant into the jaw bone. It is even more likely to occur when you realize that the implant manufacturers have to prepare the implant surface so that is rough. This ‘roughness’ is important to give the bone and tissue something to grab onto during the integration process. Too smooth and there is nothing for the bone to attach to; too rough and the frictional forces due to torquing the implant in the bone can sheer off the oxidation layer. Since most Titanium implant manufacturers don't care about Titanium being shorn off, the surface is considerably prepped.

Issues and Side-Effects with Titanium Implants

Titanium is fairly corrosive free, but not entirely and some people can have allergic reactions. One thing our office sees frequently in patients with titanium implants where the bone around the implant has simply dissolved away. That decay is called osteonecrosis.

So Quick Question. What is Cubic Zirconia Then?

Chemistry is fun! So this is yet another form of Zirconia! Cubic Zirconia has a bit of a bad rap since you have the entire multi-billion dollar diamond industry doing everything they can to try and convince you to pay thousands of dollars for a gemstone.

Regardless, Cubic Zirconia has a slightly different chemical makeup versus our Zirconia implants, and it is heated for a bit longer during the crystallization stage. And, if you're still wondering why Cubic Zirconia isn't used in implants, it's as hard as our implants, but it's more brittle and the biting action would ultimately cause cracking. Cubic Zirconia is meant to be sparkly, not withstand a biting force.

Though both ceramics and metals have similar uses, especially in households, these two materials are very different. Below are some of the major ways in which Ceramics and Metals are different:

  • Electrical conductivity. Electrical conductivity refers to a material’s ability to carry electric current. Metals have high electrical conductivity, while ceramics are poor conductors of electricity. Ceramics are good insulators.

  • Thermal conductivity. Thermal conductivity refers to a material’s ability to conduct heat. For example, metals are good heat conductors and will therefore transfer heat. On the other hand, ceramics are poor heat conductors. 

  • Corrosion. Corrosion is the process of destroying, damaging, or weakening slowly by chemical action. Corrosion is a problem for metals, while ceramics are corrosion-resistant.

  • Workability. Metals are malleable and ductile, meaning that they can quickly be hammered into shape without breaking. On the other hand, ceramic is hard and breaks easily when subjected to stress.

  • Tensile strength. Tensile strength is a material’s ability to withstand a pulling force. The tensile strength of metals is high and will therefore not break when subjected to tensile force. Dental ceramics are almost never subject to a pulling force. Ceramics are good at the compression force of eating, especially the advanced ceramics used in our dental implants.

  • Plasticity. Plasticity is the ability to be easily shaped. For example, metals can easily be shaped or molded, while ceramic can only be made into shapes through molds.

Summary, What Is the Difference Between Metals and Ceramics