Deformation behavior of the composite “eggshell–polymer plomb” was examined under bending. Hen eggs were taken as a biological material for experiments. It was shown that a viscoelastic polymer coating does not change the type of deformation behavior of the composite, given that the eggshell continued to be brittle despite its mechanical characteristics varying widely for a brittle solid. Joint “polymer plomb–eggshell” never cracked under bending and hence exhibited a high cohesion strength under the stresses applied in these experiments. It seems that the composite “eggshell—polymer plomb” could substitute for the composite “tooth enamel–polymer plomb” under elaboration of novel restorative materials for dentistry, namely, for examination of their mechanical properties, including cohesive strength.