Space-cutting model of hydroxyapatite

The possibility of substitution of trace elements such as Mg2+, Sr2+ and Ba2+ into the columnar Ca2+ positions of hydroxyapatite was examined by computer graphics with a personal computer and a space-cutting method. Data on the structural coordinates of the hydroxyapatite were put into a protein graphics program in Angstrom units. The connection of each element, with front and rear, was displayed by the shade-line erasing method, and the solidity of the image was expressed by the degree of lightness from the light source. The space-cutting model was obtained by selecting the cutting plane with three atoms in the crystal. Rotating the graphics freely around the X, Y and Z axes gives a view from any direction. The computer graphics suggested visually how the lattice dimensions expand with Sr2+ and Ba2+ substitution and contract with Mg2+ substitution.