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), scan ning electron microscopy (SEM), confocal laser scanning microscopy (CL SM) and secondary ion mass spectroscopy (SIMS). MR measurements reveal ed that NaOCl caused a tissue contraction not related to water loss bu t to removal of organic substance(s), resulting in reductions of the l esion depth and mineral loss values by 15% and 42%, respectively. CLSM observations on wet dentin showed that the dentinal tubules underneat h the surface are clearly observable and not deformed substantially by the NaOCl, except near the outermost surface. This indicates the impo rtance of wet as well as of dried (high vacuum) observations. SEM micr ographs (high vacuum) showed definite changes in the outer dentin surf ace 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 i ncrease of chlorine (Cl) content in the entire lesion due to the NaOCl , indicating deep penetration of the original OCl ions. The results su ggest that the 2-min treatment of demineralized dentin by NaOCl soluti ons removes and/or changes part of the dentin matrix in nearly the who le lesion. As a consequence the mineral is somewhat redistributed, the outermost surface of a few mu m is changed, but the main dentin struc ture and element composition are still intact. These findings indicate that NaOCl treatments are of interest in remineralization and hyper-r emineralization studies of dentin.