Stress relaxation properties of human dentin

Objectives. This study compared the stress relaxation properties of moist and air-dried human dentin to determine if air drying modifies this mechanical property. Methods. Cylindrical dentin specimens, prepared from human canine and maxillary incisor teeth, were subjected to a controlled compressive stress applied at a constant strain rate to a predetermined maximum value, and the stress relaxation response recorded. Groups of moist and air-dried specimens were tested at both low and high stress. After a period of 1 wk, the incisor specimens were retested. Results. The dentin exhibited a linear stress relaxation with the logarithm of time. Air-dried dentin consistently demonstrated a decreased stress relaxation. When subjected to a second high load, the air-dried dentin displayed significantly slower stress relaxation. Air-dried incisor dentin was found to be significantly stiffer than air-dried canine dentin. Significance. These data suggest that the stress relaxation properties of human dentin are modified by air drying and by previous exposure to a constant compressive strain.