engleski

Real-time transmittance measurements for assessment of polymerization kinetics of composite materials

Objective: To investigate polymerization kinetics of experimental composite materials based on amorphous calcium phosphate (ACP) using real-time transmittance measurements. Materials and methods: Light-curable experimental composite materials were prepared by blending methacrylate resin (67% Bis-EMA, 23% TEGDMA, 10% HEMA) with ACP, barium glass (Ba) and silica (Si) fillers using a dual asymmetric centrifugal mixer. Three ACP-based materials and one control material were prepared (numbers refer to the mass ratio of a certain component): ACP40, ACP40-Ba5Si5, ACP40-Ba9Si1 and Ba40Si10. Tetric EvoCeram was used as a commercial control. Samples in Teflon rings (n=5, diameter= 6 mm, height=2 mm) were sandwiched between glass plates (h=1 mm). During the curing (LED, 30 s, irradiance of 1200 mW/cm2), transmittance was measured at wavelength of 468 nm and time resolution of 20 s-1. Transmittance changes were plotted as a function of time and the initial part of transmittance curve was approximated by a straight line. The obtained slope was assessed as a measure of polymerization rate. Results: The initial part of transmittance curves shows a linear rise lasting for 17-19 seconds for ACP-composites and 7 seconds for Ba40Si10. Mean slope values for materials ACP40, ACP40-Ba5Si5, ACP40-Ba9Si1 and Ba40Si10 were 4.1, 4.6, 4.5 and 7.1 (%/s), respectively. Transmittance curve of the commercial control resembled an exponential shape, with no detectable linear part. Conclusion: A distinct shape of transmittance curves of experimental materials suggests a nearly-constant reaction rate throughout a rather long period of polymerization. This may retard the development of polymerization shrinkage stress, but also impair mechanical properties. The study was supported by CSF programme (08/31).

polymerization kinetics, light transmittance

nije evidentirano