Zirconia is more suitable for high-value restorations, which is the standard for most patients who require anterior restorations. The latter undoubtedly provides a more compatible color foundation for standard tooth color accumulation, especially standard layering. When white zirconia is used, zirconia is very suitable for producing the desired aesthetic effect. The white neutral matrix of zirconia makes the applied color appear very pure and real. The zirconia core or frame lacks fluorescence and must be replaced with a thin lining or frame modifier coating to provide natural fluorescence inside the restoration. The lining/modifier can also be dyed with a fluorescent initial dye alone.
When clinicians specify A2 chromaticity, as done in the case report later in this article, the laboratory needs to adjust the basic chromaticity in a different way from traditional porcelain layering. When making A2 chromaticity, the basic chromaticity should be at least the color effect of A3. For the zirconia frame, it should be a warm color, because the dentin-colored frame material will become brighter every time it is fired. The result is that the layered restoration without enhanced chromaticity appears too light in the patient's mouth.
The white, non-chromatic enhanced zirconia restoration also has a similar appearance. The lack of chromaticity and fluorescence on the frame will cause the appearance to be too bright and too white/grey. The original zirconia layering system compensated for this unwelcome addition and standardized the layering procedure for laboratory technicians.
Evaluating the optimal firing of AL/ZR ceramics is not so simple. Incorrect firing usually results in incorrect shading in AL/ZR restorations. The combustion temperature of most furnaces is 20°～30°C lower, especially in the temperature combustion range of zirconium ceramics. All these ceramics, especially AL/ZR, will react at low firing temperatures, but the transparency and color effects are slightly limited. On the other hand, a slightly higher firing cycle will not cause any problems, and actually supports color and transparency effects. The firing stability of ceramics is very good, so in most furnaces, it is recommended to increase the final temperature by 10° to 30°C for best results.
When using white zirconia restorations, incorrectly constructed or layered frames are another reason for aesthetic failure. Generally speaking, the size of the frame should be the same as the circumference of all frames, and should be made of lightweight zirconia material. If the frame size is different, the color around the smaller frame will be different, and it will appear dark or too dark or too thick.
