Characterization of the kinetic behavior of resin modified glass-ionomer cements by DSC, TMA and ultrasonic wave propagation

In this study the isothermal kinetic behavior of two resin modified glass i onomer cements (RMGIC) and a dental composite have been compared by differe ntial scanning calorimetry (DSC) and thermo-mechanical analysis (TMA). The simultaneous evolution of the multiple reactions occurring in RMGIC has bee n analyzed not only by DSC and TMA but also by ultrasonic wave propagation using the pulse-echo technique. The propagation of ultrasonic waves, acting as a dynamic mechanical deformation at high frequencies, is proportional t o the longitudinal bulk moduli of the material and may be used to measure t he changes of mechanical properties induced by a chemical reaction as occur s in RMGIC. TMA and ultrasonic analysis have been used to monitor the acid- base reaction of RMGIC in dark conditions. Moreover an RMGIC presenting a d ouble reactive mechanism in dark conditions, a thermally activated radical polymerization and an acid-base reaction are studied using these experiment al techniques. Finally DSC and TMA results obtained during photopolymerizat ion of an RMGIC and of a dental composite have been compared. (C) 2001 Kluw er Academic Publishers.