This invention concerns the fabrication of a porcelain dental restoration in a manner which provides the restoration with a UV fluorescence matching that of natural teeth.
The appearance of natural teeth varies with the light source to which the teeth are exposed, showing a fluorescence in the yellow-white to blue-white region of the visible spectrum upon exposure to UV light. It is therefore desirable in the fabrication of porcelain dental restorations such as crowns and bridges to simulate not only the color shade but also the fluorescence characteristics of the remaining natural teeth of a patient.
Past attempts at fabricating dental porcelains with desirable fluorescing characteristics under UV light include the addition of uranium oxide compounds, rare earth elements or complex rare earth elements to the porcelain. The use of uranium oxide compounds is not preferred since the compounds are radioactive and their addition results in a yellowish to yellowish-green fluorescence under UV light, which does not adequately simulate the appearance of natural teeth. Addition of rare earth elements or their complexes produces a suitable white fluorescence; the exact color of this white fluorescence depends upon the rare earth elements present, while its intensity is related to the amounts of both the agent and the color pigment present in the porcelain.
A suitable complex rare earth compound for such purpose is disclosed in U.S. Pat. No. 4,167,417. While this pigment produces the desired UV fluorescence in porcelain dental restorations, a uniform intensity of the fluorescence throughout the restoration has yet to be achieved.
It is therefore a primary objective of the present invention to provide a dental restoration having a UV fluorescence simulating that of natural teeth with a uniform appearance throughout the restoration.