Amalgam exhibits a Poisson’s ratio of
Most rigid materials, such as enamel, dentin, amalgam, and dental composite, exhibit a Poisson’s 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 Poisson’s ratios. 
Rubber has a Poisson’s ratio of nearly 0.5. 
Cork exhibits little lateral expansion under compression and has a Poisson’s ratio close to 0. 
This property has made cork a common material for sealing wine bottles.
Ref:Craig’s Restorative Dentistry ed 14th pg 36
0.3
0.5
0.6
1