The structure and microstructure of dental porcelain in relationship to the firing conditions.

A scanning electron microscope and heating microscope are used to visualize the microstructure of dental porcelain during fabrication and demonstrate the relationships of the porcelain firing conditions to the translucency and hue of the completed restoration. The firing cycle, temperature, rate of temperature rise, holding time, and cooling time influence the distribution of the sintering, glass, and crystal phases in the microstructure of the porcelain. Observing the changes of fritted porcelain and opacifiers as they progress through the firing cycle demonstrates how the quality of the final ceramic restoration is largely dependent on the firing conditions chosen.

Hippocampal mossy fiber distribution and long-term potentiation in two inbred mouse strains.

We studied long-term potentiation in the inbred mouse strains DBA/2 and C3H/He known to be different in both hippocampal mossy fiber distribution and several aspects of learning. Tetanic stimulation of mossy fibers resulted in a significantly stronger increase of the population spike amplitude in the CA3 pyramidal cell layer of C3H mice. This result suggests that the extent of the CA3 hippocampal mossy fiber projection correlates with synaptic efficacy in mice.