Journal of Dental Research, Vol 71, 1493-1497, Copyright © 1992 by International & American Associations for Dental Research Online Journals
Examination by X-ray photoelectron spectroscopy of the adsorption of chlorhexidine on hydroxyapatite
R. N. Sodhi, H. A. Grad and D. C. Smith
Centre for Biomaterials, University of Toronto, Ontario, Canada.
X-ray photoelectron spectroscopy (XPS) was used for determination of the
effects of chlorhexidine (CHX) solutions (0.2% and 1% solutions of the
digluconate salt) on the elemental composition of hydroxyapatite surfaces.
So that the nature of the adsorbed species after they were washed with
water could be identified, comparisons were made with reference spectra for
CHX obtained from a CHX digluconate film and CHX dichloride powder. The XPS
results clearly indicated the retention of CHX moieties, which could be
ascertained from the spectra by the presence of N and Cl, features unique
to CHX. The spectral envelopes were virtually identical to those obtained
from the reference spectra. High-resolution C 1s spectra also gave support
for the retention of CHX; however, the spectra differed from those of the
CHX digluconate film in that no feature attributable to the C-OH of the
gluconate anion was present, consistent with the view that the CHX cation
remains behind to form an electrostatic bond with the phosphate groups of
the hydroxyapatite. The N:Cl ratio for the washed samples was found to be
higher than that for the reference samples and may be indicative of partial
decomposition of the CHX. Decomposition was also seen to be induced by
x-ray exposure. While the high-resolution spectra presented here do not
directly address the controversy on the mechanism for the anti-plaque
efficacy of CHX, they do provide the necessary basis for the application of
XPS to future in vitro studies on the retention of CHX to dental surfaces.
