Objective To study the influence of surface protection on the surface hardness of glass ionomer cement, discuss the most suitable surface protection material for the clinical application. Methods Three types of glass ionomer cement were selected as the research objects, namely KetacTM Molar Easymix, GC Fuji Ⅱ LC, KetacTM N100. 30 disc-shaped samples of each material were randomly divided into three groups: Control group, vaseline coated group, GLUMA Comfort Bond coated group. The surface protection materials were applied after initial setting reaction. The specimens were immersed in artificial saliva, at 37 ℃. Micro-hardness tester was used to test the micro-hardness of the samples at 1 h, 24 h, 1 week, 1 month. In each specimen five indentations were done and the average micro-hardness values were recoarded. The statistical analysis was performed using the SPSS 13.0 statistical package. The measurement data were analyzed by t test. Results It was found that, for GC Fuji Ⅱ LC, there was no statistical difference among the micro-hardness value of the samples under three different surface protection materials. While for KetacTM Molar Easymix, the micro-hardness value of the vaseline coated group was higher than that of control group at the 24 h point. The micro-hardness value of vaseline coated KetacTM N100 group was higher than that of the GLUMA Comfort Bond coated group at 24 h point. Conclusion The compact protective film formed by the adhesive resin as a protective agent on the mateial surface is not conducive to the curing action of the material, while vaseline can be used as surface protective agent to enhance the long-term hardness of the material.
