Impedance Spectroscopy of Teeth with and without Approximal Caries Lesions-an in vitro Study

Abstract

Caries diagnosis by the measurement of electrical resistance is hampered by polarization effects when dc or single-low-frequency ac currents are used. Electrical impedance spectroscopy, measuring impedance over a large range of frequencies, will provide more detailed information about the electrical characteristics of teeth. It was the aim of this study (a) to characterize the complex impedance behavior of whole extracted teeth, measured at the approximal surface, and (b) to identify parameters of the complex impedance behavior of the teeth which would be useful in distinguishing between degrees of carious involvement. Thirty-nine extracted premolar teeth with 59 unrestored and undamaged (excepting caries) approximal surfaces were selected. The tooth surfaces were divided into three groups according to their macroscopic appearance: sound (group S, n = 16), white- or brown-spot lesion present (group L, n = 33), or cavitated (group C, n = 10). The teeth were inserted into a jig which allowed for counter-electrode contact via a conducting gel. The working electrode consisted of a carbonated fiber material. Electrical impedance measurements were performed over a maximum range of about 1 MHz to 0.1 Hz. We analyzed electrical impedance data by fitting equivalent circuits. Fit was evaluated numerically and visually. The complex impedance spectra divided naturally into three groups which corresponded almost perfectly with the classifications of S, L, and C. The groups differed most in the dc resistance (R_dc), as calculated from the impedance parameters. Mean Rdc for groups S, L, and C were 68 MΩ, 5.9 MΩ, and 321 kΩ, respectively. These means were significantly different from each other (log-transformed data, ANOVA, p < 0.001; Tukey multiple comparisons, p < 0.001). It is concluded that the in vitro performance of electrical impedance spectroscopy in differentiating among sound, non-cavitated carious, and cavitated approximal tooth surfaces is excellent.

Keywords

dental caries caries diagnosis electrical impedance spectroscopy diagnostic systems

Get full access to this article

View all access options for this article.

References

Bruce PG , Lisowska-Oleksiak A. , Los P. , Vincent CA (1994). Electrochemical impedance spectroscopy at an ultramicroelectrode . J Electroanal Chem 367:279-283.

Friedman J. , Grayson AS (1970). Electrical properties of tooth structure. 23rd ACEMB, Conf. on engineering in medicine and biology, Washington, DC, November 15-19, p. 164.

Hoppenbrouwers PM , Scholberg HP , Borggreven JM (1986). Measurement of the permeability of dental enamel and its variation with depth using an electrochemical method. J Dent Res 65:154-157.

Kumasaki M. (1975). An electric characteristic of the tooth and its equivalent circuit. Part 1. J Osaka Dent Univ 9:9-18.

Levinkind M. , Vandernoot TJ , Elliott JC (1990). Electrochemical impedance characterization of human and bovine enamel. J Dent Res 69:1806-1811.

Levinkind M. , Vandernoot TJ , Elliott JC (1992). Evaluation of smear layers on serial sections of human dentin by means of electrochemical impedance measurements. J Dent Res 71:426-433.

Longbottom C. , Pitts NB , Lawrenson B. (1993). Electronic diagnosis of approximal caries utilizing a metal-coated plastic strip/wedge (abstract). Caries Res 27:207.

Longbottom C. , Huysmans M-C. , Pitts NB , Los P. , Bruce PG (1996). Detection of dental decay and its extent using a.c. impedance spectroscopy. Nature Medicine 2:235-237.

Macdonald JR (1987). Impedance spectroscopy-emphasizing solid materials and systems. New York: Wiley-Interscience .

10.

Macdonald JR , Schoonman J. , Lehner AP (1982). The applicability and power of complex nonlinear least squares for the analysis of impedance and admittance data. J Electroanal Chem 131:77-95.

11.

Matsumoto H. , Fearnhead RW (1980). On the ability to correlate changes in electrical impedance with the formation of subsurface lesions in tooth enamel. J Dent 8:355-361.

12.

Mumford JM (1956). Relationship between the electrical resistance of human teeth and the presence and extent of dental caries. Br Dent J 100:239-244.

13.

Nomura H. , Sakada S. , Itow H. ( 1971). Some observations on electric conductivity of the tooth . Bull Tokyo Dent Coll 12:15-23.

14.

Pieper K. , Visser H. , Hulsmann M. , Wahner M. (1990). Test of an electronic fissure caries detector . Dtsch Zahnärztl Z 45:721-724.

15.

Pincus P. (1951). A new method of examination of molar teeth grooves for the presence of dental caries (abstract). J Physiol 113:13-14.

16.

Pitts NB (1991). The diagnosis of dental caries: 2. The detection of approximal, root surface and recurrent lesions. Dental Update 18:436-442.

17.

Ricketts DN , Kidd EA , Wilson RF (1995). A re-evaluation of electrical resistance measurements for the diagnosis of occlusal caries. [See comments] Br Dent J 178:11-17. Comment in: Br Dent J 178:205.

18.

Rock WP , Kidd Eam (1988). The electronic detection of demineralisation in occlusal fissures. Br Dent J 164:243-247.

19.

Sawada K. , Koike M. , Suda H. , Sunada I. (1986). A new device for detecting dental caries. Quintessence Int 17:373-376.

20.

Scholberg HP , Borggreven JM , Driessens FC (1982). Impedance of dental enamel membranes as a predictor for their permeability. Med Biol Eng Comput 20:578-584.

21.

Scholberg HP , Borggreven JM , Driessens FC (1984). A phenomenological interpretation of the frequency-dependent impedance behaviour of bovine dental enamel. Arch Oral Biol 29:965-970.

22.

Scholberg HP , Borggreven JM , Driessens FC (1987). The analysis of the small-signal ac-response of bovine enamel membranes. Ber Bunsenges Phys Chem 91:129-134.

23.

Verdonschot EH , Bronkhorst EM , Burgersdijk RC , König KG , Schaeken MJ , Truin GJ (1992). Performance of some diagnostic systems in examinations for small occlusal carious lesions. Caries Res 26:59-64.

24.

White GE , Tsamtsouris A. , Williams DL (1978). Early detection of occlusal caries by measuring the electrical resistance of the tooth. J Dent Res 57:195-200.