<prompt> Amalgam exhibits a Poissons ratio of0.30.50.61  <response>: Most rigid materials, such as enamel, dentin, amalgam, and dental composite, exhibit a Poissons ratio of about 0.3. Brittle substances such as hard gold alloys and dental amalgam show little permanent reduction in cross section during a tensile test.More ductile materials such as soft gold alloys, which are high in gold content, show a higher degree of reduction in cross-sectional area and higher Poissons ratios. Rubber has a Poissons ratio of nearly 0.5. Cork exhibits little lateral expansion under compression and has a Poissons ratio close to 0. This property has made cork a common material for sealing wine bottles.Ref:Craigs Restorative Dentistry ed 14th pg 36 