The relationship between Shore hardness of elastomeric dental materials and Youngʹs modulus

Objectives ss of elastomers can be directly related to Youngʹs modulus, a relationship that was investigated in detail by Gent in a paper in 1958. The aim of this study was to test this relationship for 13 dental elastomers (12 silicone and 1 polyether) using the equation derived by Gent and one from BS 903 (1950) that accounts for departures at low values. s ntal elastomers were subjected to tensile testing and Shore A scale hardness measurements. Youngʹs moduli were calculated from the hardness values using the Gent equation and the BS 903 equation. These calculated values were then compared with values derived experimentally from the tensile tests. s ss values were in the range 30.2 (±0.5)–62.9 (±0.8) with the corresponding calculated modulus values in the range 1.1–4.1 MPa and 0.9–4.3 MPa for the Gent and modified equations, respectively. Youngʹs modulus values derived from the tensile data were in the range 0.8 (±0.3)–4.1 (±0.3) MPa, showing good agreement with those calculated from the hardness values. Providing viscoelastic creep is minimal during the duration of the test, there is a reasonably well-defined relationship between Shore hardness and Youngʹs modulus in the hardness range studied. icance , non-destructive hardness measurements can be used to determine Youngʹs modulus values. Such values are needed in any calculations of stress distributions in soft lining materials, e.g. by FEA.