Rheological properties of dental resin cements during polymerization

Abstract

Purpose. The purpose of this study was to observe the change of viscoelastic properties of dental resin cements during polymerization. Materials and Methods. Six commercially available resin cement materials (Clearfil SA luting, Panavia F 2.0, Zirconite, Variolink N, RelyX Unicem clicker, RelyX U200) were investigated in this study. A dynamic oscillation-time sweep test was performed with AR1500 stress controlled rheometer at 32oC. The changes in shear storage modulus (G), shear loss modulus (G), loss tangent (tan δ) and displacement were measured for twenty minutes and repeated three times for each material. The data were analyzed using one-way ANOVA and Tukeys post hoc test (α=0.05). Results. After mixing, all materials demonstrated an increase in G with time, reaching the plateau in the end. RelyX U200 demonstrated the highest G value, while RelyX Unicem (clicker type) and Variolink N demonstrated the lowest G value at the end of experimental time. Tan δ was maintained at some level and reached the zero at the starting point where G began to increase. The tan δ and displacement of the tested materials showed similar pattern in the graph within change of time. The displacement of all 6 materials approached to zero within 6 minutes. Except Variolink N, initial setting time of the other five resin cement materials was less than 6 minutes. Conclusion. Each dental resin cement showed differences in rheological properties and handling characteristics. Compared to other resin cements used in this study, RelyX U200 maintained plastic property for a longer period of time. When it completed the curing process, RelyX U200 had the highest stiffness. It is convenient for clinicians to cement multiple units of dental prostheses simultaneously.