Modelagem computacional das hidroxiapatitas

Abstract

The present study is aimed to carry out computerized modeling of hydroxyapatite and some derivatives. This compound in its natural form is a basic component of human bone and, at the same time, in its artificial form, is used as one of the best orthopedic materials. The models were built up for both classical and substituted varieties, in which its constituents have been replaced by the cations and anions with suitable ionic radii. The comparison of a number of modeling softwares presently available shows that in the case of such structural arrangements the HyperChem software with MM+ Force Field may be considered as the best resource. It could be shown that the hydroxyapatite models substituted in cation sites render good approximations to the results obtained using X-ray techniques. Thus, one is capable to fill the gap in structural information for the compounds still unknown of difficult to be synthesized. Radium hydroxyapaptite is a promising example. On the other hand, the modeling of hydroxyapatites substituted in anion sites allowed to elucidate the capacity of arsenic and vanadium as elements to form tetrahedra with close cell parameters. Further, models of tricalcium phosphate structure have been built in order to compare atomic arrangement of both its isomers and their conformers. It can be added, as a general conclusion, that the substitutions in the matrix Me5(TO4)3A where Me - bivalent metal, T - metalloid forming TO4 tetrahedra, and A - OH, F, Cl or Br, is a way to obtain the compositions for orthopedic applications.