Laser scanning confocal microscopy coupled with hydraulic permeability measurements for elucidating fluid flow across porous materials: application to human dentine.

Laser scanning confocal microscopy (LSCM) coupled to a constant volume flow-pressure measuring system is introduced as a new technique for the quantitative measurement of fluid flow across porous materials. Such processes are ubiquitous from the life sciences to materials science and the methodology herein could find widespread application. The methodology has been applied to the detection of fluid flow through human dentine, in-vitro, and in the assessment of occlusion actives. Dentine is a calcareous material sandwiched between the pulp and enamel in the tooth structure that contains tubules which traverse dentine in the pulp to enamel direction. The tubules become patent during enamel erosion or gum recession, leading to dentinal hypersensitivity. Understanding the nature of fluid flow is important, as a pressure gradient exists across dentine in-vivo and this has implications for the development of suitable treatments. The methodology described herein firstly allows a ready assessment of the general efficacy of treatments via hydraulic permeability measurements. Second, LSCM images allow the nature of the flow process and the mode of action of the treatments to be revealed at high spatial resolution. For the particular case of dentine, we demonstrate how the method allows candidate treatments to be compared and assessed.