Zirconia has grown immensely popular over the years because of its easy-to use, high flexural strength and strong ceramic material. Many patients find the idea of metal-free restorations very appealing. The earliest zirconia restorations had a bone-white appearance that could be challenging to mask with porcelain. Often the opacious nature of the porcelain used to hide the substructure would create a restoration very similar to PFMs. Pre-shaded zirconia overcame part of this problem, but it still couldn’t create such lifelike results as lithium disilicate. The introduction of high translucent zirconia has overcome these difficulties, allowing technicians to create highly aesthetic restorations that meet or surpass patient expectations.
Benefits of Choosing High-Translucent Zirconia
High-translucent zirconia can closely mimic the colour and translucency found in natural teeth. It reflects and absorbs light in a very similar manner to natural tooth structure, while still retaining strength which is what makes zirconia so effective. High-translucent zirconia allows for a wide degree of customization: it has a high strength of 590-720MPa and is available in a range of colours, including effect shades and a fluorescent shade. This material can be used to create monolithic restorations or more traditional layered restorations and is three times stronger than lithium disilicate. High-translucent zirconia requires less occlusal preparation and the thinner wall structure provides higher translucency.
How Is High Translucency Achieved?
The presence of impurities and structural defects can affect translucency. Zirconia’s high degree of translucency is achieved by optimising surface texture to minimise the effects of impurities and structural defects. When zirconia is shaded, its properties for light absorption can be altered due to traces of ions that are incorporated into the zirconia during sintering. These impurities can affect the material’s ability to reflect and transmit light and instead can cause light to be absorbed. When light hits structural defects, it tends to scatter, which reduces translucency.
Often alumina is incorporated into zirconia in order to increase ageing stability, but its refractive index is different to zirconia, which can affect translucency. To overcome this, some zirconia materials do not contain alumina or have minimised the content and have instead chosen to improve its distribution, which helps maintain ageing stability.
Wear Properties of High Translucent Zirconia
Zirconia is a very hard material and some clinicians assume that this material is abrasive to opposing dentition. This isn’t necessarily correct as the abrasive nature of the material is determined by its smoothness. It is possible to avoid excessive abrasion by ensuring zirconia restorations are fabricated with a smooth surface. Sometimes the materials used to veneer zirconia can be more abrasive to enamel. With high translucent zirconia, the strength and wear properties have been found to be very close to earlier zirconia systems. It’s been shown that ageing will not affect the smoothness of the material and its strength is similar to previous generations of zirconia. In comparison, glass ceramics, while being more translucent, have two-thirds less flexural strength when compared to zirconia.
When to Choose High-Translucent Zirconia
High-translucent zirconia is ideal for single anterior and posterior crowns, for bridges up to three units, and for implant crowns. Its use is not always recommended for patients with bruxism. Like all zirconia restorations, high-translucent zirconia is biocompatible, plaque resistant, and a great metal-free alternative to PFMs.
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