Effects of Storage Media on the Flexural Strength of GIC

Method: The FS of commercial glass ionomer (Fuji Equia Fil, GC) was measured using a method based on ISO9917-2:1998. Specimens (n=10 per group) were prepared in split moulds (2x2x25mm), compressed and light-cured according to manufacturers' instructions, stored at 37^oC (100% RH) for 24 hours. Samples of Group 1 were allowed to set without coat application and in the Group 2 samples were coated (Equia Coat, GC) and light cured for 20s (Bluephase G2, IvoclarVivadent). Three different media (distilled water, artificial saliva and vaseline) were used to store 10 samples from each group (total of 60 samples). Each specimen was tested using an Universal testing machine at 1 mm/min crosshead speed and loaded to fracture using a 3-point bending test (l=20mm), with 1kN load cell. Data were analysed by ANOVA and Tukey HSD post hoc test p<0.05.

Result: FS of glass ionomer cement samples stored in distilled water (21.8 MPa) was significantly lower than FS of samples stored in artificial saliva (37.4 MPa) and Vaseline (40.1 MPa). Results obtained in artificial saliva displayed significantly lower FS values than samples stored in vaseline. The highest values were obtained in group treated with Coat and stored in Vaseline (78.7 MPa). There is no significant difference between coated and no coated samples stored in distilled water and between coated and no coated samples stored in artificial saliva.

Conclusion: Results showed that current ISO standard proposed for storage media (distilled water) is inappropriate due to high amount of ion leakage in the water affecting material properties.