To determine buffering capacity of glass ionomer cement materials, disks (n=3) of diameter 13 mm × 1 mm thick were immersed in 10 ml of lactic acid solution (pH 4.0) and incubated at 37℃ from 24 hours to 28 days. Measurements of pH (pH/ion meter; Orion 8102BNUWP, Thermo Fisher Scientific) and ions (ICP-AES; ICPS-8000, Shimadzu Co.) in solution were performed. As results, pH was raised to a range of 5.3 to 6.4 in all samples after 24 hours. Significant amounts of elements (Al, Ca, Na, P, Si and Sr) were determined. The pH increase was in correlated with the any of released ions.