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 surface on treatment with sodium hypochlorite (NaOCl), a known deproteinating agent. In addition, sequential treatment with both acid and NaOCl are characterized. Modifications are evaluated using photoacoustic FTIR (PA-FTIRS), a surface-sensitive spectroscopy. Spectra of NaOCl-treated dentin samples show a slow and heterogeneous removal of its organic phase, leaving calcium hydroxyapatite and carbonate apatite unchanged. Spectra of this deproteinated surface resemble those of apatites synthesized at low temperatures and having very high-surface areas. A combined sequential 2-min treatment of dentin with both maleic acid and NaOCl indicates that this treatment can produce a surface region which is neither significantly demineralized nor deproteinated. This sequential treatment can be used to remove the smear layer and restore the dentin surface to its natural composition.