Solid state spatially resolved H-1 and F-19 nuclear magnetic resonance spectroscopy of dental materials by stray-field imaging

As part of a program to evaluate the use of stray-field magnetic resonance microimaging (STRAFI) in dental materials research spatially resolved nucle ar magnetic resonance (NMR) for solid dental cements has been investigated. By applying a quadrature echo pulse sequence to a specimen positioned in t he stray-field of a NMR spectrometer superconducting magnet the magnetic re sonance within a thin slice was obtained. The specimen was stepped through the field in 500 mu m increments to record H-1 and F-19 profiles and T-2 va lues at each point. The specimens were fully cured cylinders made from four types of restorative material (glass ionomer, resin modified glass ionomer , compomer, composite). The values for H-1 T-2 varied with material type an d reflected the nature of the matrix structure. For all materials containin g F-19 in the glass two values were calculated for F-19 T-2, one short and one long. These were relatively invariant. Solid state magic angle spinning (MAS)-NMR showed that they came from the glass. This suggests that a propo rtion of the element is relatively mobile (in a glass phase) and the remain der is more tightly bound (in a compound dispersed in the glass). This demo nstration, that NMR microimaging of both H-1 and F-19 in solid dental cemen ts is possible, opens up exciting new possibilities for investigating the d istribution of these elements (in particular fluorine) in solid dental mate rials. (C) 1999 Kluwer Academic Publishers.