Spreading of oligomers on polymers

The successful repair of a composite restoration may depend on the ability of a repair composite to spread on the restoration to be repaired. The purpose of this study was to measure the spreading of four oligomers on their polymers. The oligomers were: ethoxylated bisphenol A dimethacrylate (EB), BisGMA/3EDMA:70/30 (ED), BisGMA-Nupol (NU), and urethane dimethacrylate (UD). Polymer strips were made from these oligomers by light-curing. Spreading was calculated from measurements of the contact angle of the oligomers on the polymers, the surface tension of the oligomers, and the viscosity of the oligomers. In this model system, values of spreading of EB, ED, UD, and NU on oligomer ED were: 2.8, 1.4, 0.24, and 0.0009 cm/s, respectively. The spreading by oligomers EB, ED, and UD on polymer ED was slightly higher than that on polymer UD.