Chemical Activators on Fluorescence of Dental Ceramics

Under exposure to ultraviolet, natural teeth emit a light blue fluorescence which also enhances the whiteness and brightness of teeth in daylight. Different chemical activators are added in commercial dental ceramics to present the fluorescence which can act as natural teeth in color and intensity under exposure of sunlight or artificial ultraviolet illumination.

Objectives: To investigate which chemical elements play the most important roles for fluorescence in the commercial dental ceramics, and to measure the change of fluorescence intensity by increasing the proportion of chemical activators within commercial dental ceramics.

Methods: 5 commercial ceramic systems ( Procera AllCeram, Cercon Zirconia, IPS Empress II, Noritake Ex-3 and Shofu Vintage ) were chosen as test samples. 1 ~ 2 g enamel powders of A1 shade of each system were examined with the Inductively Coupled Plasma-Mass Spectrometer (ICP-MS) to detect key chemical elements for fluorescence. The possible chemical activators were added into the commercial ceramic powders with the different proportion, and then ceramic disks were fabricated according to the manufacturers' instructions of firing procedures. The excitation and the emission spectrum of ceramic disks were recorded by using the spectrofluorometer.

Results: The result of ICP-MS suggested that Cerium(Ce) and Yttrium (Y) were the main chemical elements related to fluorescence in commercial dental ceramics. However, concentrations of these two elements in 5 tested ceramic systems were not strongly related to the measured fluorescence intensity. By adding more Ce or Y in ceramic powders showed higher fluorescence intensity under ultraviolet illumination.

Conclusion: Among rare earth oxides, Cerium (Ce) and Yttrium (Y) were two of the most important chemical activators on fluorescence of commercial porcelains. However, specific formulae and firing procedures of each ceramic system may also have influence on fluorescence. Changing the proportion of chemical activators can affect the fluorescence intensity of dental ceramics.