Objectives: To develop a method for calculating the compliance of interfaces using the finite-element method (FEM).
Methods: A dentin rod (Ε=15GPa; ν=0.31) of known compliance (0.0666μm/N) bonded (‘glue contact') to a resin-composite rod (Ε=21GPa; ν=0.24) was simulated by FEM. The materials were considered linear, homogeneous, elastic and isotropic. Their ends were fixed in Z axis direction. A 1% volumetric shrinkage was simulated for the resin-composite using thermal analogy. The ratio of the ‘displacement' mean values and the ‘contact normal force' sum (both in Z direction and also in magnitude) at interfacial dentin nodes was compared to the calculated analytical compliance.
Results: The ratio calculated by FEM was 0,0652μm/N. The small difference in comparison to the analytical one (0.0666μm/N) is attributed at the completeness of the constitutive model, which considers the Poisson's ratio, not included in analytical calculations. For more accurate representations of the phenomenon, the use of the displacement-magnitude is recommended, as loading by isotropic contraction produces also transversal deformations. The same FEM parameters could be applied for calculating the real compliance of any interface of complex structures.
Conclusion: The method was validated for the compliance calculation of complex structures subjected to shrinkage loading.(supported by FAPESP: process 2006/00186-3)