The effect of adding hydroxyapatite on the flexural strength of glass ionomer cement.

This present study investigated the effects of the addition of hydroxyapatite (HA) on the flexural strength and microstructure of conventional GIC, and its effect on the cement's initial flexural strength at different storage conditions. Specimens were fabricated by mixing HA in whisker or granule form into commercially prepared GIC, and these were subjected to a three-point bending test and SEM observations. Some specimens were stored in different conditions from dry to wet for 15 minutes to an hour prior to testing. When compared to the control, specimens with 16-25% HA whiskers added at P/L 1.75 showed a significant increase in the flexural strength (p < 0.05), and as well with 19% HA whiskers at P/L 1.75 (p < 0.001) and 2.33 (p < 0.05). A significant increase was also noted for those with 8-25% HA granules added at P/L's 1.75 (p < 0.05), 2.5 (p < 0.05) and 3.60 (p < 0.01). The addition of HA hastens the development of early (15 min, 1 hour) flexural strength of GIC in moist or wet conditions. These results indicate that the addition of HA, regardless of form, improve the flexural and microstructural properties of GIC.