The effects of a sodium hypochlorite treatment on demineralized root dentin.

The effects of a 10% NaOCl treatment for 2 min on demineralized human root dentin were investigated by means of: microradiography (MR), scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) and secondary ion mass spectroscopy (SIMS). MR measurements revealed that NaOCl caused a tissue contraction not related to water loss but to removal of organic substance(s), resulting in reductions of the lesion depth and mineral loss values by 15% and 42%, respectively. CLSM observations on wet dentin showed that the dentinal tubules underneath the surface are clearly observable and not deformed substantially by the NaOCl, except near the outermost surface. This indicates the importance of wet as well as of dried (high vacuum) observations. SEM micrographs (high vacuum) showed definite changes in the outer dentin surface structure; 85% of the originally open dentinal tubules were closed after NaOCl treatment. No marked changes were observed in the dentin ultrastructure inside lesions, as shown by SEM on fractured surfaces. SIMS data, pertaining to samples in high vacuum, showed a remarkable increase of chlorine (Cl) content in the entire lesion due to the NaOCl, indicating deep penetration of the original OC1 ions. The results suggest that the 2-min treatment of demineralized dentin by NaOCl solutions removes and/or changes part of the dentin matrix in nearly the whole lesion. As a consequence the mineral is somewhat redistributed, the outermost surface of a few mu m is changed, but the main dentin structure and element composition are still intact. These findings indicate that NaOCl treatments are of interest in remineralization and hyper-remineralization studies of dentin.