Post-gel polymerization shrinkage strain evaluation of four light-activated composites using different curing modes

Abstract EN

Background : One of the ways of minimizing polymerization shrinkage of light-activated composites is by applying short pulses of light energy, prepolymerization at low light intensity followed by final cure at high intensity (soft-start polymerization) or a combination of both.

This study investigated the influence of different curing modes on the postgel polymerization shrinkage strain of different light- activated composites.

Materials and methods : This study investigated the Post-Gel Polymerization Shrinkage Strain of two mm thick composite specimens after exposure to different curing modes.

Parameters included six conventional curing modes : Control (C), Pulse Delay I (PDI), Pulse Delay II (PDII), Soft-start (SS), Pulse Cure I (PCI), and Pulse Cure II (PCII) plus three experimental curing modes of higher energy density : Prolonged low-intensity pulse cure mode (PLPC), Prolonged moderate-intensity pulse cure mode (PMPC) and Rapid high-intensity continues cure mode (RHCC) for each of the four different light-activated composite materials (Tetric Ceram, Heliomolar, Herculite XRV and Degufill Mineral).

Results : Statistical analysis of the data by using the one-way analysis of variance revealed that, there was a statistically significant difference for all the polymerization shrinkage strains with the composite type, curing mode and post-curing-time.

Conclusion : Light intensity reduction and elongation of the curing time combined with pulse activation and soft start polymerization (PLPC curing mode) resulted in significantly lower and gradual post-gel polymerization shrinkage strain for all the light-activated composites being tested.