ABSTRACT
BACKGROUND: Most of studies on the mechanical properties of modified glass ionomer cement mainly focus on the compression and bending experiments, but there are few reports on the stress relaxation and creep experiments of glass ionomer cement after adding strontium hydroxyapatite. OBJECTIVE: To compare the stress relaxation and creep characteristics of traditional glass ionomer cement, composite resin enamel adhesive and modified glass ionomer cement. METHODS: Strontium doped hydroxyapatite was added into glass ionomer cement according to the mass ratio of 15%, and then the modified glass ionomer cement was prepared. Samples of modified glass ionomer cement, composite resin enamel adhesive and traditional glass ionomer cement were maded. Ten samples from each group were taken for stress relaxation test and another 10 samples for creep test. RESULTS AND CONCLUSION: (1) At 7 200 s in the stress relaxation test, the stress in the traditional group was decreased by 1.18 MPa, decreased by 1.39 MPa in the composite group, and decreased by 1.38 MPa in the modified group. The decreased value in the traditional group was significantly less than that in the composite and modified groups (P 0.05). (2) At 7 200 s in the creep test, the stress in the traditional group was increased by 0.24%, increased by 0.33% in the composite group, and increased by 0.32% in the modified group. The increased value in the traditional group was significantly less than that in the composite and modified groups (P 0.05). (3) The viscoelastic properties of glass ionomer cement are improved by compounding 15% strontium-doped hydroxyapatite with glass ionomer cement. The increase of viscoelasticity is beneficial to the adhesion and bulk bond strength of glass ionomer cement.