JENA, Germany: Researchers at the Otto-Schott-Institute for Glass Chemistry in Jena, Germany, have produced a new kind of glass-ceramic with a nanocrystalline structure, which could be well suited to use in dentistry. The material’s strength is five times higher than that of comparable denture ceramics.

The hardest substance in the human body is moved by its strongest muscles: when we bite into an apple, enormous strengths are at work on the surface of our teeth. “What the natural tooth enamel has to endure also goes for dentures, inlays or bridges. After all, these are worn as much as healthy teeth,” said glass chemist Prof. Christian Rüssel, who developed the material together with his team.

The ceramic materials used thus far have not been suitable for bridges because they are mostly not of sufficient strength. Glass-ceramics are distinguished by their enormous strength based on magnesium, aluminium, and silicon oxide. “We achieve a strength five times higher than with comparable denture ceramics available today,” Rüssel explained.

The Jena glass chemists have been working on high-strength ceramics for a while, but so far only for utilisation in other fields, for instance as the basis of new efficient computer hard drives. “In combination with new optical characteristics, an additional field of application is opening up for these materials in dentistry,” Rüssel is convinced.

In order to be used for dentures, materials must be optically similar to natural teeth. The correct colour shade is also important. “The enamel is partly translucent, which the ceramic is also supposed to be,” Rüssel said.

To achieve these characteristics, the new glass-ceramic is produced according to an exact temperature scheme. First, the basic materials are melted at about 1,590°C, then cooled down and finely cut up. Subsequently, the glass is melted and cooled down again. Finally, nanocrystals are generated by controlled heating to about 1,000°C. “This procedure determines the crystallisation crucial for the strength of the product,” Rüssel explained. However, this is a fine line technically because a too strongly crystallised material disperses the light, becomes opaque and looks like plaster. The secret of the Jena glass-ceramic lies in the consistently small size of its nanocrystals. The size of these is generally 100 nanometres at most. “They are too small to strongly disperse light and therefore the ceramic looks translucent, like a natural tooth,” Rüssel said.

“The material is translucent, extremely strong and easy to colour. Furthermore, it is chemically highly resistant. A disadvantage could be that it is harder than the natural tooth,” Rüssel told Dental Tribune Online. “The production costs for glass-ceramics will probably only make up a negligibly small amount of the patient’s cost”.

According to the chemist, there has been a lot of positive feedback, especially from the dental industry. However, a great deal of development must still be done before the new glass-ceramic can be used for dentures. “The whole palette of common teeth colours must be available. Therefore, the material needs to be advanced in terms of shade,” Rüssel told Dental Tribune Online. The study was published in the February issue of the Journal of Biomedical Materials Research.

The study was published in the February issue of the Journal of Biomedical Materials Research.