Method Development for Identification of Dentin's Strength and Poisson's Ratio

Objective: Ideal dental restoration and further development of dental materials requires structural compatibility of the artificial materials with the tooth part properties. In the present study, we have established a method to determine the compressive strength as well as the Poisson's ratio of human dentin. Methods: Extracted healthy teeth were embedded in resin and sawn in slices. Further embedding and sawing leads to rods and further sawing to cubes (1.6x1.6x1.6mm) of dentin. Exact marking of cubes ensured their allocation to their localization in the intact tooth and allows determination of the influence of anisotropism. For comparison, dental filling composite Grandio Flow (Voco, Cuxhaven, Germany) cubes were prepared the same way. Cubes were tested in popular compression test to determine compressive strength of dentin and in compression test with limited deformation (Fig. 1 a, b) (1mm/min). Poisson's ratio of dentin was determined by simulating compression tests with limited deformation with FEA (Patran/Abaqus). Variation of Poisson's ratio leads to different simulated force-deflection-curves which could be compared with the experimental one. Fig. 1: a) Compression test with deformation b) Compression test with limited deformation Results: Average compression strength of 40 dentin cubes, determined on linear part of force-displacement-curve of popular compression tests, results in 1.9 (±0.12) GPa. Compression strength of Grandio Flow is lower with 1.05 GPa. Variation of Poisson's ratio by FEA for compression test with limited deformation leads to Poisson's ratio 0.15 for dentin. Fig. 2: Force-displacement curve of compression test with deformation for dentin and Grandio Flow Conclusion: A method for preparation of test specimen and a testing method for dentin were established. The combination of both compression tests is appropriate to determine compression strength and Poisson's ratio for dentin. Compression strength for Grandio Flow is lower than for dentin. Anisotropic behavior of dentin could not be observed.