Ultrathinning Dental Porcelain for Transmitted Light Microscopy

A technique for ultrathinning brittle materials, originally developed at Battelle Pacific Northwest Labs for examination of lunar materials, has been successfully adapted for the preparation of dental porcelain specimens. A commercial dental porcelain and “Component No. 1” of the Weinstein et al. patent were ultrathinned using this technique. Each material was examined in the unfired powder form, after one firing, and after five firings. The sections were typically from 2 to 6 μm thick. The ultrathinned specimens were then examined using transmitted light microscopy. Identical areas of fired porcelain specimens were also examined by reflected light microscopy, scanning electron microscopy, and transmitted light microscopy of ultrathinned specimens in order to compare the three techniques. The porcelain powder and each frit were analyzed by x-ray diffractometry (XRD). Leucite (K2O·Al2O3·4SiO2) was detected by XRD in the commercial porcelain and the Component No. 1 frit. Optical micrographs of the ultrathinned specimens revealed a second phase within the glassy frit particles of the commercial porcelain and the Component No. 1 material. No phase changes between unfired and fired specimens were detected by XRD. This success in ultrathinning dental porcelains provides a significant improvement in the ability to resolve the constituent phases of these materials relative to standard petrographic techniques and a useful addition to the techniques available for microstructural examination of dental porcelain.