A new method to measure the polymerization shrinkage kinetics of light cured composites

Abstract

This study was undertaken to develop a new measurement method to determine the initial dynamic volumetric shrinkage of composite resins during polymerization, and to investigate the effect of curing light intensity on the polymerization shrinkage kinetics. The instrument was basically an electromagnetic balance that was constructed with a force transducer using a position sensitive photo detector (PSPD) and a negative feedback servo amplifier. The volumetric change of composites during polymerization was detected continuously as a buoyancy change in distilled water by means of the Archimedes' principle. Using this new instrument, the dynamic patterns of the polymerization shrinkage of seven commercial composite resins were measured. The polymerization shrinkage of the composites was 1.92 approximately 4.05 volume %. The shrinkage of a packable composite was the lowest, and that of a flowable composite was the highest. The maximum rate of polymerization shrinkage increased with increasing light intensity but the peak shrinkage rate time decreased with increasing light intensity. A strong positive relationship was observed between the square root of the light intensity and the maximum shrinkage rate. The shrinkage rate per unit time, dVol%/dt, showed that the instrument can be a valuable research method for investigating the polymerization reaction kinetics. This new shrinkage-measuring instrument has some advantages that it was insensitive to temperature changes and could measure the dynamic volumetric shrinkage in real time without complicated processes. Therefore, it can be used to characterize the shrinkage kinetics in a wide range of commercial and experimental visible-light-cure materials in relation to their composition and chemistry.

Silorane- and high filled-based"low-shrinkage" resin composites: shrinkage, flexural strength and modulus

“…1 Shrinkage is caused by an exchange of van der Waals spaces for shorter covalent bond spaces when monomer molecules are converted into a polymer network. 2 The resulting composite shrinkage of 2%-5% 3,4 generates stress at the dentin/adhesive interface, 5,6 causing cusp deflection 7,8 or de-bonding, marginal staining, enamel cracking, and/or post-operative sensitivity. 9 Many strategies have been proposed to reduce the shrinkage stress created during the polymerization of RCs into the prepared tooth cavity.…”

Optimizing light-cured composite through variations in camphorquinone and butylhydroxytoluene concentrations

“…7,8 Manipulation of the initiator system concentrations has been previously reported as a valid method for modulating polymerization shrinkage stress rate and magnitude. 9 In this study, we hypothesized that different CQ and BHT combinations can modify the curing and mechanical properties of light-cure resin composite based on their effects on the viscoelastic behavior of the composite during curing, which is directly related to their polymerization shrinkage stress.…”

Analysis Methods Regarding the Polymerization Properties of Composite Resins

“…17 Ayrıca örnek hazırlama aşaması zor olan civa dilatometrede akış-kan kompozitler gibi düşük viskoziteye sahip materyallerde ölçüm yapılamayacağı bildirilmiş-tir. 13 …”