Adult human enamel. II. An electron microscopic study of the effect of grinding.

Abstract

A study in the electron microscope was carried out to determine if the broadening of X-ray diffraction patterns was related to crystal fragmentation or strain resulting from the preparative technique. All enamel samples, collected either by grinding with high- or low-speed diamond stones or by carbide burs, contained large amounts of finely-divided enamel, a relatively large number of scattered individual crystals and relatively few particles (usually 5 μ, the larger particles predominating. Annealing bone crystallites increased their size appreciably but they remained undamaged despite prolonged grinding in the ball mill. There was no evidence to suggest a plane of preferred cleavage in enamel; the composite nature and crystal morphology may be responsible, therefore, for the severe fragmentation observed. Crystallite fragmentation is probably responsible for the line-broadening observed in the X-ray diffraction pattern, although strain may also be a contributing factor.