Measurement Of Mechanical Properties Of Human Dentin

ObjectivesThis study was designed to determine the mechanical properties of human dentin, and to find out the relationship between the properties and the tubular orientations, whether there are some differences between the dentin of vital teeth and dentin of pulpless teeth that were endodontically treated, and to study the effect of water to mechanical properties of pulpless teeth dentin.MethodsDentin specimens (n=48) were obtained from 30 freshly extracted normal vital human teeth and 18 endodontically treated human pulpless teeth. The vital teeth were grinded to 10 and 20 rectangular specimens according to dentin specimens' longitudinal axes parallel or perpendicular to the tubular directions respectively. The pulpless teeth were grinded to 18 rectangular specimens according to dentin specimens perpendicular to the tubular directions. All the vital teeth specimens and 9 pulpless specimens were immerged in 0.9% sodium chloride solution, and another 9 pulpless specimens were air-dried. After 5 days, their compressive mechanical properties were measured under the hydrated and air-dried conditions with displacement measurement method. All data obtained were analyzed with t tests.ResultsThe elastic moduli, proportional limits and compressive strengths of dentin from vital teeth were 15.77 1.52GPa, 157.07 13.79MPa and 257.67 10.23MPa respectively. They had no relations with tubular directions (p>0.05). The elastic moduli, proportional limits and compressive strengths of dentin from pulpless teeth were 12.08 1.71GPa, 144.30 9.76MPa and 235.26 9.12MPa respectively. The mechanical properties of dentin from vital teeth weresignificantly stronger than the pulpless teeth, there are significant differences between them, (p < 0.05). The mechanical properties of dentin from pulpless teeth did not appear significant differences between hydrated and air-dried conditions (p> 0.05).Conclusions1. In hydrated condition, the elastic moduli, proportional limits and compressive strengths of dentin from vital teeth are 15.77 1.52GPa, 157.07 13.79MPa and 257.67 10.23MPa, respectively.2. This test shows primarily that the mechanical properties of dentin from vital teeth have no evident relations with tubular directions, but it needs to be further studied.3. The mechanical properties of dentin from vital teeth are significantly stronger than of the pulpless teeth, and the results consist with clinic observations.4. The mechanical properties of pulpless teeth dentin do not have significant differences between in the hydrated conditions and in the air-dried conditions. It suggests that water do not significantly affect the mechanical properties of pulpless teeth.