Ca(H2PO4)2, a crystal structure containing unusual hydrogen bonding

Ab initio computation for solid-state 31P NMR of inorganic phosphates: revisiting X-ray structures

The complete 31P NMR chemical shift tensors for 22 inorganic phosphates obtained from ab initio computation are found to correspond closely to experimentally obtained parameters. Further improvement was found when structures determined by diffraction were geometry optimized. Besides aiding in spectral assignment, the cases where correspondence is significantly improved upon geometry optimization point to the crystal structures requiring correction.

Calcium phosphate cements with strontium halides as radiopacifiers

High radiopacity is required to monitor the delivery and positioning of injectable implants. Inorganic nonsoluble radiopacifiers are typically used in nondegradable bone cements; however, their usefulness in resorbable cements is limited due to their low solubility. Strontium halides, except strontium fluoride, are ionic water-soluble compounds that possess potential as radiopacifiers. In this study, we compare the radiopacity, mechanical properties, composition, and cytotoxicity of radiopaque brushite cements prepared with strontium fluoride (SrF2 ), strontium chloride (SrCl2 ·6H2 O), strontium bromide (SrBr2 ), or strontium iodide (SrI2 ). Brushite cements containing 10 wt % SrCl2 ·6H2 O, SrBr2 , or SrI2 exhibited equal to or higher radiopacity than commercial radiopaque cements. Furthermore, the brushite crystal lattice in cements that contained the ionic radiopacifiers was larger than in unmodified cements and in cements that contained SrF2 , indicating strontium substitution. Despite the fact that the strontium halides increased the solubility of the cements and affected their mechanical properties, calcium phosphate cements containing SrCl2 ·6H2 O, SrBr2 , and SrI2 showed no significant differences in Saos-2 cell viability and proliferation with respect to the control. Strontium halides: SrCl2 ·6H2 O, SrBr2 , and SrI2 may be potential candidates as radiopacifiers in resorbable biomaterials although their in vivo biocompatibility, when incorporated into injectable implants, is yet to be assessed.

Dental research at the National Bureau of Standards: how it changed the practice of dental health service

A history of dental research at the National Bureau of Standards since its inception in 1919 is presented. The initial thrust on dental amalgam by the US Army Dental Corps, the assignment of Dr. William Souder to the project, and subsequent developments are traced. Difficulties in obtaining support for the early stages of the program following World War I are described. The involvement of the American Dental Association in 1928, issuance of the first ADA specification on dental amalgam, and the ultimate ramifications on dental (and medical) standards programs throughout the world are described. Benefits to patients, dentists, and taxpayers from support of the dental research program have been calculated as exceeding the combined budgets of the currently supporting institutions--NBS, ADA, and National Institute of Dental Research.