BONE CRYSTAL SIZES - A COMPARISON OF TRANSMISSION ELECTRON-MICROSCOPIC AND X-RAY-DIFFRACTION LINE-WIDTH BROADENING TECHNIQUES

Bone crystals are particularly small and hence estimating their sizes have proved to be difficult and values obtained inconsistent. Here we use rat bone crystals of different ages, as well as different syntheti c carbonate apatite crystals, to compare two methods commonly used for determining bone crystal sizes. One method involves direct measuremen t of crystal lengths and widths, but not thicknesses, from transmissio n electron microscope (TEM) photographs of dispersed crystals. The sec ond method utilizes X-ray diffraction line width broadening to estimat e the average length of crystals. We conclude that line width broadeni ng values tend to reflect crystal coherence lengths rather than the ph ysical dimensions oi the whole crystal. TEM measurements provide relia ble estimates of average crystal lengths and widths and their ranges. Sample preparation procedures, however, cause breakage of the fragile crystals, which probably results in underestimates of in vivo crystal sizes.