The stresses generated during the light curing of resin composites and the effect of the stress relaxation after the polymerization has been investigated using a micro-strain technique. Three different classes of composites were tested: traditional composites, condensable composites and flow composites. For each material six samples were light cured with an halogen light at constant power (500 mW/ cm2) and six samples were light cured in two steps with a plasma source light: the first step at medium power and the second at high power. A composite sample was positioned on an aluminum plate; a strain gauge positioned under the aluminum plate measured the deformation of the plate during light curing and the effect of strain relaxation in the following time. Maximum interfacial stress was evaluated by using mathematical model of simply supported beam. The strain and stress relaxation time was evaluated by long time strain measurement and model fitting. The experimental results show that the plasma cure induces a lower shrinkage stress than the halogen cure and the relaxation time of the condensable materials were shorter than the traditional ones.
Comparison of different light source in shrinkage stress phenomena
AMATO, Massimo;
2003-01-01
Abstract
The stresses generated during the light curing of resin composites and the effect of the stress relaxation after the polymerization has been investigated using a micro-strain technique. Three different classes of composites were tested: traditional composites, condensable composites and flow composites. For each material six samples were light cured with an halogen light at constant power (500 mW/ cm2) and six samples were light cured in two steps with a plasma source light: the first step at medium power and the second at high power. A composite sample was positioned on an aluminum plate; a strain gauge positioned under the aluminum plate measured the deformation of the plate during light curing and the effect of strain relaxation in the following time. Maximum interfacial stress was evaluated by using mathematical model of simply supported beam. The strain and stress relaxation time was evaluated by long time strain measurement and model fitting. The experimental results show that the plasma cure induces a lower shrinkage stress than the halogen cure and the relaxation time of the condensable materials were shorter than the traditional ones.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
