Chemically conditioned dentin: a comparison of conventional and environmental scanning electron microscopy findings

The purpose of this study was to compare the structure of acid-conditioned dentin in its wet and dry state.

Using conventional and environmental scanning electron microscopy, conditioned dentin was examined in a wet, air-dried and critical point-dried state. Six different treatments were used including citric, maleic, nitric, oxalic and phosphoric acids in their commercial formulations and applied in accordance with manufacturer's instructions.

Loss of moisture from acid-conditioned dentin through simple air drying and drying under controlled conditions of environmental scanning microscopy resulted in morphological alteration of the fibrous, collagenous structure. Critical point drying preserved the fibrous integrity of the outer mineral-depleted zone. This observation was true for all the acids used.

While the ultrastructure of dentinal collagen may be chemically stabilized or relatively unaltered by acid conditioning, it is nonetheless subject to morphological degradation and collapse during water loss. Only critical point drying can control the interfacial stress accompanying water transport and loss at the fiber boundary. Confirming previous observations, this study supports the concept of maintaining the moist state of dentin and the morphological integrity of the collagen so as to facilitate optimal resin infiltration in the bonding procedure.