The creep of dental amalgam

Abstract

In this paper experiments were described on the steady-state creep rate of six dental amalgams and its dependence on applied stress and deformation temperature. It was found that both the experimental results reported in this article and the experiments reported in literature could be described satisfactorily by equation (2) $$\begin{array}{}\text{(2)}& \dot{\mathit{ϵ}}={\mathit{K}}_2{\mathrm{(}\mathit{\sigma }-{\mathit{\sigma }}_0\mathrm{)}}^{2}exp\mathrm{(}-\mathit{U}\mathrm{/}\mathit{k}\mathit{T}\mathrm{)}.\end{array}$$ In this equation $\dot{\mathit{ϵ}}$ is the steady-state creep rate, σ is the applied stress, ${\mathit{\sigma }}_0$ is an internal stress component, U is the activation energy, T is the temperature (K), K ₂ is a constant and k is the Boltzmann constant. No differences could be detected between the mean values of the activation energies of the six amalgams, the overall mean being 108.5 kJ/K mole. Furthermore, ${\mathit{b}}^{\prime }={[{\mathit{K}}_{2}exp\mathrm{(}-\mathit{U}\mathrm{/}295.5\mathit{k}\mathrm{)}]}^{-\frac{1}{2}}$ was found to be independent of the mercury content (i.e. the quantities of the low melting phases γ ₁ and γ ₂). Within the experimental error b′ was found to be independent of the ratio of the volume fractions of the γ ₁ and γ ₂ phase. It was concluded that the most probable phase which determines the value of b′ is the γ ₁ phase.