Hardness of Resin-Modified Bioactive Glass Ionomer Cement

Use of bioactive bonding agents in orthodontics would be beneficial in helping to prevent white spot lesions from developing in patients with poor oral hygiene.

OBJECTIVE: This study evaluated the Vickers hardness values of resin-modified bioactive glass ionomer cements (RM-BGIC) containing various amounts of bioactive glass (BAG).

METHODS: Bioactive glass (BAG) (75%SiO₂, 21%CaO, and 4%P₂O₅) was synthesized by a sol-gel method, sieved and ground to ~2.0 µm using a micronizer (Sturtevant Inc. Hanover, MA). It was mixed with Fuji ORTHO LC powder in volume ratios of 1:0 (100% Fuji control), 1:3 and 1:1. The powders were mixed with standard Fuji liquid, were placed into cylindrical molds (5x2mm), and pressed between two glass slides. Each disc was light cured individually for 60 seconds per side. Discs were stored in deionized water for 24 hours prior to testing. Vickers hardness indentations were made with a 100g weight (20 seconds), and five separate indentations on each disc (N=5) were measured under 50X magnification. Data were analyzed with ANOVA/Tukey. Statistical significance was set at P < .05.

RESULTS: The mean hardness values were 11.08±4.78 and 21.20±4.63 for the experimental groups containing BAG in 1:3 and 1:1 volume fractions, respectively. The mean value for the control group was 62.24±2.64. Experimental groups had significantly lower hardness values than the control group. (P < .05).

CONCLUSION: Our results suggest that the novel bioactive RMGI may exhibit different mechanical properties than the control group. Further studies are needed to evaluate the effect of the decreased hardness values on the strength of the bioactive glass containing RMGI cement.

ACKNOWLEDGEMENT: Funded by the A.D. Williams Trust.