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[Effects of dental cements on the stress distribution in amalgam-restored teeth].

OBJECTIVE
To evaluate the effects of 5 kinds of base materials on the stress distribution and deflection in amalgam- restored teeth.


METHODS
A computerized two-dimensional finite-element of the tooth model first molar was established. Various dental cements with a thickness of 0.5 mm and amalgam restorations with thickness of 2 mm in the prepared cavity were simulated and subjected to microhardness test (load=45 kg). The stresses and deflections along the cavity wall interface were analyzed by finite-element method.


RESULTS
High stress and deflection occurred mainly at the line angle of the cavity, this could be magnified by using cements with lower elasticity modulus. The maximum compressive stress at the line angle induced by common ZOE or Ca(HO)(2) was increased 3.3 times or 2 times and deflections increased by 40% and 25% respectively that by Zinc phosphate and glass ionomer.


CONCLUSION
Modulus elasticity of cement plays an important role in affecting the fracture strength of the amalgam restored tooth. The lower the elasticity modulus, the higher the stresses and deflections induced in the dentine. From the point of mechanical property, zinc phosphate is one of the best dental cements.