September 2018 – Zirconium Metal

Is the Zirconia Full-porcelain Teeth Safe?

Zirconia is an excellent high-tech biological material with good biocompatibility that is superior to various metal alloys, including gold. Zirconia has no irritation or allergic reaction to the gingiva, and is suitable for oral application, avoiding allergic, stimulative, and corrosive reactions of metal in the oral cavity.

Excellent mechanical properties

The zirconia full porcelain dental material has a winding strength greater than 900MPa, so it can also be used to repair the posterior tooth and the all-ceramic bridge with more than 6 units.

Good biocompatibility

In the latest clinical evaluation report of CRAI, a U.S. clinical research association, it was found that the zirconia all-ceramic crown itself had no metal, and the restoration of the zirconia all-ceramic crown could exclude the metal allergic reaction and have good biocompatibility. Therefore, zirconia all-ceramic crowns are superior to various metal alloys in terms of biocompatibility, including gold materials.

Safe non-metallic materials

At present, zirconia is the only mineral in the natural world, which does not contain any metal, and it is safer after medical clean processing.

No obstruction to the X-Ray

If cranial X-ray, CT, and MRI examinations are needed after inserting the zirconia porcelain teeth, the dentures do not need to be removed in the future, because the zirconia porcelain teeth do not have any obstruction to X-ray, so a lot of trouble is avoided.

High intensity and density

Zirconia is widely used, especially in high-precision instruments, such as aviation equipment, because of its ultra-high-strength and density. Among them, the unique resistance to rupture and the strong firmness after rupture can be made into all-ceramic Bridges of more than 6 units, thus solving the problem that all all-ceramic systems cannot be long Bridges. Therefore, they are favored by doctors and patients.

Perfect color

Due to the white color of the base crown of structural ceramics, the neck will not become dark for a period of time after the insert, which solves the extremely difficult problem of the metal crown.

Healthy biomaterials

Zirconia is an excellent high-tech biological material with excellent biocompatibility and no irritation or allergic reactions to the gums. It is very suitable for the mouth.

PFM (porcelain fused to metal) is accepted by most patients for its good strength, but it has its fatal disadvantages. The metal base of low-end porcelain teeth is easy to oxidize and form gray oxides. When scattered and deposited at the edge of the gingiva, the gingiva will turn gray and affect its appearance. At the same time, it has a strong stimulation effect on the gingiva, and some patients may also have gingiva swelling, bleeding, allergy, and other symptoms, which is difficult to meet the clinical requirements. High-end metal porcelain teeth (gold alloy) are expensive without these drawbacks.

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How to tell the Zirconia from Diamonds?

Diamond is the product of adamas finishing, which is the hardest and simplest gemstone in the world. It is a natural crystal with a cubic structure made of carbon. The bigger the diamond, the rarer it is. Diamond often contains 0.05%-0.2% impurity elements, among which N and B are the most important. The pure diamond is colorless and transparent, which presents different colors due to the mixing of trace elements.

Natural diamonds are expensive due to their scarcity, especially the larger ones. However, artificial diamonds (synthetic diamonds) are difficult to achieve large size gemstones. Generally, synthetic diamonds are used in cutting and polishing tools. Therefore, in order to meet the design needs of jewelry and some products, there are usually some substitutes, such as glass, artificial spinel, artificial sapphire, zircon, scheelite, strontium titanate, cubic zirconia and so on. Among them, cubic zirconia is very close to diamond in terms of its optical and hardness properties and is the most common diamond substitute.

The cubic zirconia was first developed by the Soviets, also known as Soviet Stone. Cubic zirconia in cubic crystals is rare in nature and is usually synthesized artificially. Synthetic cubic zirconia is a hard, colorless and optically immaculate crystal, and it has been a replacement for diamonds since 1976 because of its low cost, durability and its resemblance to diamonds. Cubic zirconia is known as a “fake” diamond or CZ diamond. The following is a brief analysis of the difference between diamonds and “fake” diamonds and how they are identified.

Difference in hardness

Natural diamonds have a Mohs hardness of 10 and are difficult to process, and the cubic zirconia has a Mohs hardness of 8.5 to 9.0, while quartz sand is 7 and stainless steel is only 5.5. Therefore, the treatment of gem-level cubic zirconia can meet the requirements of daily use and is easier to process.

Differences in dispersion

The dispersion of cubic zirconia was 0.060, which is higher than that of diamond, so cubic zirconia looks more brilliant than diamonds.

The index of refraction

Cubic zirconia has a refractive index of 2.176, which is slightly lower than diamond’s 2.417. Depending on the refractive index, cubic zirconia cuts slightly differently from a diamond, which can be seen under a magnifying glass.

Color

Completely colorless diamonds are very rare, and usually, they are pale yellow. However, the cubic zirconia can be made into diamonds of the highest grade, or D-grade color. A variety of trace elements can also be added to the cubic zirconia to render it in different colors to meet customers’ demand for colored gems.

The crystals of different colors can be obtained by adding different metal oxides to the raw materials. For example, cerium: yellow, orange, red; chromium: green; neodymium: purple; erbium: pink; titanium: golden brown.

Specific gravity

Cubic zirconia is 1.7 times heavier than a diamond, so they can be distinguished by differences in specific gravity, but can only be used to separate unencrusted gems.

The heat-transfer capability

The thermal conductivity of cubic zirconia and diamond are two extremes. Cubic zirconia is a good insulator and can be used as an insulator for jet engines, while diamond is one of the best heat conducting bodies, its heat-conducting ability surpasses copper.

Stanford Advanced Materials supplies high-quality zirconia products to meet our customers’ R&D and production needs. Please visit http://www.samaterials.com for more information.

How is the Zirconia Ceramic Made?

As the most important type of advanced ceramics, zirconia ceramic material is an important basic material for the development of the modern high-tech industry. Zirconia is widely used in the market, and its specific applications include the solid fuel cell, automobile exhaust treatment, dental materials, ceramic cutting tools, and zirconia fiber core plug.

However, as mobile 5G era approaches at any time, zirconia ceramics become the hot spot of the industry again due to its characteristics such as warm feeling, anti-scratch and wear resistance, no signal shielding, and excellent heat dissipation performance.

Zirconia is insoluble in water, sulfuric acid, hydrochloric acid, and nitric acid. It is slightly soluble in hydrofluoric acid and concentrated sulfuric acid when heated. Pure zirconia is an insulator at room temperature. Adding a stabilizer can increase its conductivity and show ionic conductivity at high temperatures. There are three crystal types of zirconia. The crystal parameters and the schematic diagram of the structure of the three crystal types are shown below.

Zirconia ceramics have high hardness, wear resistance, high-temperature thermal stability and impact resistance. The preparation of high-performance zirconia ceramics depends on high-quality zirconia powder and optimized sintering process parameters.

Preparation of high-quality zirconia powder

The preparation methods of high-quality zirconia powder mainly include the physical method and the chemical method. The physical methods include high-temperature spray pyrolysis, spray induction coupled plasma pyrolysis and freeze-drying; chemical methods include gas phase, liquid phase, and solid-phase method. Among them, the liquid phase synthesis method has high efficiency, fine powder particle quality, and simple equipment, so it has been widely used.

The sintering method

Sintering process parameters include sintering temperature, sintering pressure and sintering time. Ceramic materials with very different microstructures and properties can be obtained when the same ceramic materials adopt different sintering processes. At present, the sintering process of zirconia ceramics at home and abroad has pressureless sintering, hot pressing sintering, hot isostatic sintering, and discharge plasma sintering. Pressureless sintering, also known as traditional atmospheric sintering, is the sintering of a prefabricated ceramic body under atmospheric pressure and high-temperature conditions; hot press sintering is a sintering method for applying axial pressure to the powder in the mold; spark plasma sintering (SPS), also known as plasma-activated sintering, is a new rapid sintering technology.

Stanford Advanced Materials supplies high-quality zirconia powder and related products to meet our customers’ R&D and production needs. Please visit http://www.samaterials.com for more information.