In vitro analysis of 'smear layer' on human dentine using ac-impedance spectroscopy.
OBJECTIVE
To analyse smear layers on human dentine using ac-impedance spectroscopy.


METHODS
Dentine samples were prepared from extracted, sound, third molars. Impedance measurements were carried out on dentine samples before and after etching. After measuring, samples were examined under scanning electron microscope (SEM) to correlate electrical measurements with structure.


RESULTS
Marked differences in impedance before and after etching were demonstrated. SEM investigation showed that a smear layer overlies dentine surfaces before etching, but completely disappeared after etching, leaving open dentinal tubules.


CONCLUSIONS
The clinical removal of smear layers is still subjective. This objective method, based on combined ac-impedance and admittance measurement in vitro, has the potential to allow development of standardised techniques and if developed further may be of use in vivo.
Restorative Department, Dental Institute, University of Leeds, Leeds LS2 9JT, UK.
Aziza H
AH
Eldarrat
Alec S
AS
High
Girish M
GM
Kale
D000134:Acid Etching, Dental; D000328:Adult; D003804:Dentin / Q000737:chemistry / Q000648:ultrastructure*; D017097:Electric Impedance; D006801:Humans; D008855:Microscopy, Electron, Scanning; D016369:Smear Layer; D013057:Spectrum Analysis