thesis
Development and application of imaging techniques for the investigation of dentinal hypersensitivity
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Abstract
The overall aim of this thesis is to examine the underlying physical basis of
dentinal hypersensitivity and to assess methods of treating this cause using
imaging techniques. The scanned probe microscopy (SPM) techniques are then
extended to the study of carbon-based electrode surfaces, as described in the final
chapter.
The use of scanning electrochemical microscopy (SECM), combined with in situ
pressure-time measurements, is described as a means to investigate the flow of
fluid through human and bovine dentine, and the subsequent effect of occlusion
treatments on this flow. Scanning Ion Conductance Microscopy (SICM) is also
introduced as a technique for imaging dentine, with instrument design and
development described, and also calibration of the technique.
Laser scanning confocal microscopy (LSCM) coupled to a constant volume flowpressure
measuring system is introduced as a new technique for the quantitative
measurement of fluid flow across porous materials. 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.
To complement the studies into dentinal hypersensitivity, microscopic
dissolution of bovine enamel is investigated. This chapter describes a novel
approach, based on SECM, to promote the localised dissolution of bovine
enamel, effected by the application of a proton flux to the enamel surface from a
UME positioned within 5 μm of the surface, in aqueous solution. The approach
results in a well-defined “acid challenge” yielding well-defined etch pits that
were characterised using light microscopy and white light interferometry. The
effect of etching in the presence of lactate is considered, as is the effect of
treating the enamel samples with sodium fluoride prior to etching. The approach
described is amenable to mass transport modelling, allowing quantitative
interpretation of etch features.
The techniques developed throughout the thesis are applied to the investigation
of two types of carbon electrodes: boron-doped diamond (BDD) and highly
ordered pyrolytic graphite (HOPG). Heterogeneities in the electroactivity of
these substrates are explored.A scanning micropipet contact method (SMCM) is
described which promises wide-ranging application in imaging and quantifying
electrode activity at high spatial resolution