Reducing composite restoration polymerization shrinkage stress through resin modified glass-ionomer based adhesives

Background: The aim of this study was to determine whether employing resin modified glass-ionomer based adhesives can reduce polymerization contraction stress generated at the interface of restorative composite adhesive systems. Methods: Five resin based adhesives (G Bond, Optibond-All-in-One, Optibond-Solo, Optibond-XTR and Scotchbond-Universal) and two resin modified glass-ionomer based adhesives (Riva Bond-LC, Fuji Bond-LC) were analysed. Each adhesive was applied to bond restorative composite Filtek-Z250 to opposing acrylic rods secured within a universal testing machine. Stress developed at the interface of each adhesive-restorative composite system (n = 5) was calculated at 5-minute intervals over 6 hours. Results: The resin based adhesive-restorative composite systems (RBA-RCS) demonstrated similar interface stress profiles over 6 hours; initial rapid contraction stress development (0-300 seconds) followed by continued contraction stress development = 0.02MPa/s (300 seconds -6 hours). The interface stress profile of the resin modified glass-ionomer based adhesive-restorative composite systems (RMGIBA-RCS) differed substantially to the RBA-RCS in several ways. Firstly, during 0-300 seconds the rate of contraction stress development at the interface of the RMGIBA-RCS was significantly (p < 0.05) lower than at the interface of the RBA-RCS. Secondly, at 300 seconds and 6 hours the interface contraction stress magnitude of the RMGIBA-RCS was significantly (p < 0.05) lower than the stress of all assessed RBA-RCS. Thirdly, from 300 seconds to 6 hours both the magnitude and rate of interface stress of the RMGIBA-RCS continued to decline over the 6 hours from the 300 seconds peak. Conclusions: The use of resin modified glass-ionomer based adhesives can significantly reduce the magnitude and rate of polymerization contraction stress developed at the interface of adhesive-restorative composite systems.