Mechanical properties of glass ionomers under static and dynamic loading

Objectives. This study evaluated the mechanical properties under static and cyclic loading conditions of various types of glass ionomers used for bases and core build-ups under restorations. Methods. Compressive strength and three-point flexural strength of two different glass ionomers and two metal-reinforced glass ionomers were determined 1 d after the start of mixing. The flexural fatigue resistance of these materials was measured in the load range of 650 g to 1050 g using a three-point bending machine, and fractured surfaces of the specimens were examined using SEM. Results. All the glass ionomers exhibited similar compressive and flexural strengths. The results analyzed by Cox's proportional hazard model demonstrated that the admired-type metal-reinforced glass ionomer had the highest fatigue resistance, while the water-hardening glass ionomer had the lowest fatigue resistance among the materials examined (p<0.05). Significance. There was no significant improvement in the static mechanical properties from incorporating metal particles into the glass ionomers. However, the addition of metal particles as in the admired-type metal-reinforced glass ionomer produced a material with increased fatigue resistance.