The processing times of zirconia have more than significantly shortened in recent years, especially when it comes to the fabrication of crowns and small, three-unit bridges. New technologies and materials can significantly reduce sintering cycles from up to 12 hours to less than one hour to 20 minutes. The processing of zirconias differs significantly depending on the generation of raw materials used. Whereas some materials can be easily sintered at high speed (definition of high-speed sintering: sintering cycle < 1h) (Fig. 1), this is not possible or only to a limited extent with other raw materials from most zirconia raw material suppliers. The zirconias which belong to the class of 5Y-TZP zirconias (3rd generation) do not develop their translucent properties as desired due to the short, intensive energy input and clearly remain too opaque (Fig. 2).
In close cooperation with our long-standing partner Tosoh (Fig. 3), we have succeeded in realizing the desired requirements for the 5Y-TZP material in terms of strength and high-speed sintering capability. Through targeted changes in the composition together with further powder modifications in terms of lower grain growth and complete pore healing, an existing raw material (Zpex Smile.m , Tosoh) could be significantly further optimized as a result, thus creating the basis for a meaningful further development in the area of multi-generation blanks.
An additional plus in strength of over 200 MPa and consistent translucency properties regardless of the respective sintering protocol (conventional / high speed) provide the final basis for an uncompromising zirconia material for dental applications. Zolid Bion, with its significantly increased translucency in the cutting area and an average strength of 1100 MPA ± 150 MPA (DIN EN ISO 6872 3-point flexural test) over the entire cross-section (Fig. 4), thus retains its consistently high translucency even after sintering for only 45 minutes. Numerous studies have further proven that the high-speed process has no negative impact on material properties.
Ceramill Therm DRS high-speed sintering furnaces were provided to cooperation partner Tosoh during the development process, thereby enabling the new generations of raw materials to be tested and validated directly. Due to the option of open programming of the machines, suitable sintering cycle parameters could be derived for the modified zirconia raw materials and translated into successful results. As a consequence, the new Zolid Bion zirconia is already perfectly matched to the sintering process in the Ceramill Therm DRS (Fig. 5).