Gallium Release From Experimental Dental Composites Containing Gallium-Doped Bioactive Glass

Objectives: To test the gallium release from experimental antibacterial dental composites containing gallium-doped bioactive glass and antibacterial monomers.
Methods: Method: The Ga-bioglass (Na2O-SiO2-CaO-P2O5-Ga2O3) was synthesized using a sol-gel method. The control composite was formulated with 29% commercial dental monomers (BisGMA:EBPAGMA:HDDMA = 4:4:2), 1% photoinitiators, and 70% commercial F-releasing glass filler (SCHOTT AG, Germany). Experimental composites were formulated by replacing part of the filler contents in the control with 10%, 20%, 25%, and 30% Ga-bioglass, and 5% synthesized antimicrobial monomers C16DC2 or DD11 (compositions shown in Table 1). The disc specimens of the composites (10.5 mm dia., 2.1 mm thick, n=5) were light-cured, polished, and immersed in 5 mL of acetate buffer (pH=5.5) and DI water (pH=7.0), respectively. The solutions were withdrawn every day and replaced by fresh solutions. Each sample solution was mixed (1:1) with an acetate buffer (pH=4) containing 5 mM hexadecylpyridinium chloride and 1 mM carminic acid, let stand for 2h, and tested for gallium concentration using a Lambda 35 UV-Vis spectrophotometer (Perkin Elmer). The standard calibration curve was made by a serial gallium nitrate standard solutions (10^-6M-10^-4M) under the same conditions. The data were analyzed using ANOVA and Tukey HSD test (a=0.05).
Results: As shown in Table 1, gallum release increased with Ga-bioglass content, higher release at pH7 than pH5.5, and increased by additional antimicrobial monomers.
Conclusions: Dental composites containing gallium-doped bioactive glass can release significant amount of gallium and thus have antibacterial activity.