Evaluation of demineralized dentin contraction by stereo measurements using environmental and conventional scanning electron microscopy

Numerous investigations of etched human dentin are performed using scanning electron microscopy (SEM). Usually specimens are fractured and cross sections of etched layers with underlying unaffected dentin are observed. Results from this study showed that the edge of the etched layer contracted and became curved after fracture of wet specimens and that tensile stresses were developed in this layer by acid etching. The degree of contraction was determined utilizing profiles of the specimen edges obtained with the help of stereo measurements. Fixation in glutaraldehyde decreased the contraction in wet specimens prepared for environmental scanning electron microscopy (ESEM). Fixation also decreased shrinkage of the demineralized layer due to gradual desiccation in the ESEM during observation. For conventional SEM, the contraction was minimized if specimens of etched and fixed dentin were fractured in the dry condition after dehydration.