Electrical impedance related to experimental induced changes of human skin and oral mucosa
Author: Nicander, Ingrid
Date: 1998-09-07
Location: Föreläsningssal 1, plan 4, Odontologiska klinikerna, Alfred Nobels allé 8, Huddinge
Time: 9.00
Abstract
There is a need for an objective and non-invasive method for assessing
reactions in the human skin and oral mucosa, particularly for weak
reactions. During the past few decades, several methods of measuring
irritant responses have indeed been developed for the skin and to some
extent also for the oral mucosa. The focus of this thesis is upon a new
measurement system based on electrical impedance, which reflects
structural and chemical changes in living tissues. The system is an
improvement over earlier impedance techniques, and measures magnitude and
phase of impedance in the frequency range 1 kHz to 1 MHz at 5 depth
settings. From the raw data, four indices are calculated, representing
most of the information in compressed form, and also reducing
inter-individual and inter-site variation by normalisation.
The method has been used to study skin irritation induced by various
concentration of sodium lauryl sulphate (SLS). Results have been compared
with visual scoring as well as with those of other bioengineering
techniques - transepidermal water loss (TEWL), electrical capacitance
moist measurements (ECM), and laser Doppler flowmetry (LDF).The results
show that electrical impedance is at least as sensitive as other
bioengineering techniques, and more sensitive than visual scoring. The
later was confirmed in a study using low concentration of SLS, which
demonstrated that the electrical impedance method is a delicate technique
for detecting responses induced by SLS, when these are weak enough to be
macroscopically negative. Furthermore, a good correlation was found
between the severity of the changes observed visually, the
histopathological alterations, and changes in the four electrical
impedance indices. We have also found the method to be highly sensitive
for detection of changes in the lipid content in the stratum comeum.
Other irritants producing different types of histological skin responses
have been shown to create their own distinctive impedance index patterns.
Furthermore, the reduced data sets in the form of the four impedance
indices contain sufficient information for classifying different
responses of the skin, although additional information may be extracted
from the complete spectrum.
The impedance technique, can also be used in the oral mucosa, and has
been shown capable of detecting mucosal responses induced by SLS in the
invisible or barely visible range.
Since different anatomical regions display typical baseline values for
the skin as well as the oral mucosa it is important to use contra lateral
reference sites from the same anatomical location or even better to
follow a site over a period of time before and after exposure to a test
agent. If references are not available, e.g. in situations where the
entire skin or mocosa is affected, established baseline values for
different sites in the skin and the oral cavity may be substituted. Such
values have now been provided for both the skin and the oral mucosa.
The electrical impedance technique seems to be a powerful tool for
quantification and classification of reactions in both the skin and the
oral mucosa.
Issue date: 1998-08-17
Publication year: 1998
ISBN: 91-628-3097-X
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