Journal of Dentistry
Volume 38, Issue 2 , Pages 138-148, February 2010

Monitoring bacterial-demineralization of human dentine by electrochemical impedance spectroscopy

  • Zhang Xu

      Affiliations

    • Department of Restorative Dentistry, Faculty of Dentistry, National University of Singapore, 5 Lower Kent Ridge Road, 119074 Singapore, Singapore
    • ,
  • Koon Gee Neoh

      Affiliations

    • Department of Chemical & Biomolecular Engineering, National University of Singapore, Kent Ridge 119260, Singapore
    • ,
  • Bennett Amaechi

      Affiliations

    • Department of Community Dentistry, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA
    • ,
  • Anil Kishen

      Affiliations

    • Discipline of Endodontics, Faculty of Dentistry, University of Toronto, 124 Edward Street, Toronto, ON, Canada
    • Corresponding Author InformationCorresponding author.

Received 28 May 2009; received in revised form 21 September 2009; accepted 27 September 2009. published online 05 October 2009.

Abstract 

Objective

The purpose of this study was two-fold: (1) to monitor bacterial biofilm formation and bacteria-induced demineralization of dentine in situ by using electrochemical impedance spectrum (EIS); (2) to examine the relationship between EIS findings and changes in the chemical composition and ultrastructure of dentine during bacteria-induced demineralization.

Methods

In this study, dentine demineralization was induced by Streptococcus mutans (ATCC 25175) in the presence of sucrose in culture medium and was monitored using two EIS measurement systems (Type A with a working electrode and Type B without a working electrode). Scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) were employed to examine the morphology, element contents and crystallinity of hydroxyapatite (HAP) on the dentine surface. Transverse microradiography (TMR) was used to characterize the lesion depth and degree of mineral loss during demineralization.

Results

The resistance of the bulk dentine (Rd) and the apparent resistance of dentine (Ra) measured from the Type A and Type B EIS systems, respectively, decreased gradually with demineralization. The resistance of the biofilm formed on dentine surface was determined by fitting the EIS data with equivalent circuits. The presence of biofilm slightly increased Ra of dentine before demineralization. However, the electrochemical behavior of biofilm did not affect the decreasing impedance of dentine with demineralization. The SEM, EDX, XRD and TMR results demonstrated that the surface and bulk dentine gradually became more porous due to the loss of minerals during demineralization, which in turn resulted in the decrease in Rd and Ra values obtained from EIS systems.

Conclusions

This investigation highlighted EIS as a potential technique to monitor biofilm formation and bacterial-induced demineralization in situ.

Keywords: Electrochemical impedance spectroscopy (EIS), Bacterial-induced demineralization, Dentine

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PII: S0300-5712(09)00230-9

doi:10.1016/j.jdent.2009.09.013

Journal of Dentistry
Volume 38, Issue 2 , Pages 138-148, February 2010

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