The ultrastructure of human dental enamel heat-treated in the temperature range 200 degrees C to 600 degrees C.

Abstract

Heating enamel in the temperature range 200 degrees C to 600 degrees C resulted in poor crystal packing due to void formation, permanent change in the sign of its birefringence (from negative to positive) in some areas, and an altered crystal morphology. Transmission electron microscopy of enamel heated in the temperature range 200 degrees C to 400 degrees C revealed that the distinction between the positively birefringent regions and the negatively birefringent regions (which were present up to 350 degrees C and occasionally up to 400 degrees C) at the tooth's surface was due to the greater volume of intra- and inter-crystalline voids within the positively birefringent regions. There was a ..