Viscoelastic Behavior of Dental Amalgam *

Measure ments made on dent a l a malgam in tens ion indica te th at a malga m exhib its three types of vi scoelasti c phe nome na: (1) inst antaneous e las ti c s tra in , (2) re ta rded e las ti c st ra in (transie nt c reep), and (3) viscous s train (s teady state c reep). T he co mbina tion of e lasti c plus re ta rded strain can be repre· sent ed by a n eq uation of the form f = A(T + 8 '(J' where A a nd 8 a re fun c ti ons of time but not of the stress, (J . T he viscous s train ra te ca n be represented b y a n equ a tion of the form €v = K(J'" where K a nd m a re constants of the mate ri a l. By a pplying a nonlin ear genera li zation of th e Bolt zma nn s upe rposi ti on principl e to a ge neral eq ua tion descri bing the creep behav ior of a malgam, the results of c reep tests can be d irectl y re la ted to the resu lts of st ress-s train tes ts.