Electrical Conductance and Electrode Area on Sound Smooth Enamel in Extracted Teeth

Abstract

Electrical conductance measurements are being used experimentally to diagnose caries. Current equipment, e.g. the electronic caries monitor (ECM), uses a probe to scan occlusal fissures. For full-mouth examination this method is rather time-consuming. A method with which only one measurement is needed for an entire (occlusal) surface would be preferable. However, the enlargement of the area being measured will influence the conductance. It was the purpose of this study to investigate the relationship between the electrical conductance of human teeth and the enamel electrode area, and to compare the range of results of surface measurements with those of the scanning method. Twenty-five sound extracted teeth were selected for the study. The reference electrode of the ECM was connected to the roots. The buccal surface was blotted dry, and a coloured dentifrice was syringed in increments onto the surface. After each increment the surface was photographed together with a metric reference, a conductance measurement was performed by holding the ECM probe tip in the dentifrice, and the ECM reading was recorded. For each tooth between 5 and 10 increments were applied and measured. The photographs were digitised and the electrode areas were calculated. A least squares curve fitting procedure yielded a linear relationship between conductance and electrode area (0.88 ≤ R² ≤ 1.0, mean R² = 0.97). For most teeth the threshold for dentinal caries as used for scanning ECM measurements (ECM reading = 6.00) was reached only when the electrode area exceeded 12 mm2. For 6 teeth this conductance was already reached between 5 and 12 mm². Electrical conductance measurements of the occlusal surfaces of 18 teeth, with electrode areas as projected two-dimensionally of between 5 and 10 mm², showed only 3 measurements above the threshold. None of those 3 came from the group of 6 teeth mentioned before. It was concluded that the relationship between electrical conductance of teeth and electrode area is linear. It was also concluded that when electrical conductance measurements of occlusal surfaces are to be made, the threshold for dentinal caries will probably have to be shifted to a higher conductance level to limit false-positive results.

Intra- and Interexaminer Variability and Validity of Laser Fluorescence and Electrical Resistance Readings on Root Surface Lesions

“…Enlargement of the area being measured using conductive media was suggested to overcome this problem [Huysmans et al, 1995] and could also be considered for assessment of PRCLs in future research. In the present study sites were predefined and marked on digitised images.…”

The Effect of Airflow on Site-Specific Electrical Conductance Measurements Used in the Diagnosis of Pit and Fissure Caries in vitro

“…Similarly, a kappa value of 0.69 was ob tained for readings taken at 10 litres/min and split into di chotomous data according to the cut-off value for the D| level of diagnosis (0.23), and for the D , level of diagnosis (2.27) the kappa value was 0.85. Huysmans et al [1995] have shown that using a curve fitting procedure there is a third power logarithmic relation ship between resistance and ECM readings. The term con ductance has been used to describe the ECM-II scale.…”

In vitro Assessment of Methods of Applying the Electrical Caries Monitor for the Detection of Occlusal Caries

“…The use of a small amount of toothpaste showed a significant correlation with histology for the sample without stain but not for the stained sample. The surface area of the electrical contact is a determinant of the resistance [Huysmans et al, 1995] and applications of inconsistent amounts of toothpaste might result in variable resistance measurements. The application of a small amount of toothpaste to the specific site could control the contact footprint.…”

“…This approach has the advantage that an assessment of the entire surface of the tooth covered by the conducting medium such as toothpaste can be made. However, the surface area of the electrical contact is also a determinant of the resistance [Huysmans et al, 1995] and application of inconsistent amounts of toothpaste might result in variable resistance measurements. In an attempt to overcome this problem a small amount of toothpaste can be applied to a specific area to control the contact footprint.…”