Kinetic setting of a resin modified glass ionomer cement

Objective: To determine the effect of time and light exposure timing on the flexural strength of a RMGIC within the first hour of setting, whilst at the same time, studying the timing of both reactions that occur: acid-base and polymerization. Methods: Twelve rectangular specimens of Fuji Ortho LC (25x2x2mm) for each of the nine groups were fractured using a 3-point bending test. Groups differ from the light time exposure (5 to 30 seconds) and from the time frame of fracture (10minutes, 30 minutes and 1 hour). Infra Red investigation (FTIR) was carried out to give an accurate characterization of the light catalysed polymerisation and polyacid neutralisation rates within the first hour from setting in function of time light exposure. Results: The time factor increases flexural strength values from 10 minutes to one hour. A dual dose of light-cured, with a primary flash dose following, 30 minutes later, by the complementary light dose enables to obtain flexion strength values and a similar elastic behavior for the Fuji Ortho LC at 30 minutes that at 1 hour when is entirely light cured initially. Conclusion: The interest resides in the possibility to work at 30 minutes from initial setting, when using Fuji Ortho LC, instead off waiting one hour as arch wires are typically placed whilst bonding appointment, when light-cured resins or cements might not have been completely polymerised.