engleski

Curing kinetics of the experimental composite materials based on amorphous calcium phosphate investigated by impedance spectroscopy

Aim: To investigate the applicability of impedance spectroscopy as a new method for monitoring photopolymerization kinetics of the experimental composites based on amorphous calcium phosphate (ACP). Materials and methods: Light-curing 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. Materials were applied in quartz rings 4 mm in diameter and 4 mm in height and both ring openings were covered by brass electrodes of the impedance analyzer. During the curing (LED, intensity of 1090 mW/cm2), the complex impedance was monitored at 2 V and 1 kHz, with time resolution of 5 measurements per second. Changes in the electrical resistivity were presented graphically and appropriate part of the curve was approximated by a straight line. The obtained slope and a constant τ represent a measure of reaction rate. Results: Mean slope values for materials ACP40, ACP40-Ba5Si5, ACP40-Ba9Si1 and Ba40Si10 were 9.2, 16.1, 7.5, 20.8 (106 Ωcm/s), respectively. Mean values of τ were 44.6, 38.3, 40.3 and 40.3 (s), respectively. Relative standard deviation for slope and τ was under 9% and 5%, respectively. Conclusion: Single frequency impedance measurements enable monitoring curing kinetics in real time. The observed differences in reaction rate parameters reflect the differences in filler composition. The study was supported by CSF programme (08/31).

impedance spectroscopy, electrical properties, dental composites

nije evidentirano