Penetration of glutaric dialdehyde into human dentine as measured by changes in dentine microhardness and dentine dimensions.

Microhardness indentation lengths were measured on human dentine sections unfixed and fixed with glutaric dialdehyde (GDA) at pH 7. Fixed dentine was found to be softer than unfixed dentine. Indentation length increased by approximately 10% after fixation in a buffered 5% GDA solution at pH 7. Using this effect the variation of indentation length in the direction of the penetrating GDA as a function of fixation time was measured. Describing the penetration in the mineralized matrix as diffusion in a plane sheet, a diffusion coefficient of 0.5.10(-12); m2/s was calculated. Dimensional changes of the dentine due to fixation were also measured. Dentine was found to expand in both the direction parallel (approximately 0.4%) and perpendicular (approximately 2%) to the tubules.