A photoacoustic FTIRS study of the chemical modifications of human dentin surfaces: II. Deproteination

This work focuses on the chemical alterations occurring on the dentin surfa ce on treatment with sodium hypochlorite (NaOCl), a known deproteinating ag ent. In addition, sequential treatment with both acid and NaOCl are charact erized. Modifications are evaluated using photoacoustic FTIR (PA-FTIRS), a surface-sensitive spectroscopy. Spectra of NaOCl-treated dentin samples sho w a slow and heterogeneous removal of its organic phase, leaving calcium hy droxyapatite and carbonate apatite unchanged. Spectra of this deproteinated surface resemble those of apatites synthesized at low temperatures and hav ing very high-surface areas. A combined sequential 2-min treatment of denti n with both maleic acid and NaOCl indicates that this treatment can produce a surface region which is neither significantly demineralized nor deprotei nated. This sequential treatment can be used to remove the smear layer and restore the dentin surface to its natural composition. (C) 2001 Elsevier Sc ience Ltd. All rights reserved.