Abstract
To study the influence of fast high-intensity (3-s) and conventional (20-s) light curing protocols on certain physical properties including light-transmission and surface wear of two nano-hybrid composite resins (Tetric PowerFill and Essentia U) specifically designed for both curing protocols. According to ISO standards, the following properties were investigated: flexural properties, fracture toughness and water sorption/solubility. FTIR-spectrometry was used to calculate the double bond conversion (DC%). A wear test using a chewing simulator was performed with 15,000 chewing cycles. A tensilometer was used to measure the shrinkage stress. Light transmission through various thicknesses (1, 2, 3 and 4 mm) of composite resins was quantified. The Vickers indenter was utilized for evaluating surface microhardness (VH) at the top and the bottom sides. Scanning electron microscopy was utilized to investigate the microstructure of each composite resin. The light curing protocol did not show a significant (p > 0.05) effect on the mechanical properties of tested composite resins and differences were material-dependent. Shrinkage stress, DC% and VH of both composite resins significantly increased with the conventional 20 s light curing protocol (p < 0.05). Light curing conventional composite resin with the fast high-intensity (3-s) curing protocol resulted in inferior results for some important material properties.
Highlights
In this study, we aimed to investigate the impact of fast high-intensity (3 s) and conventional (20 s) light curing protocols on certain physical characteristics including light transmission and surface wear in two nano-hybrid composite resins (Tetric PowerFill and Essentia U), designed for both curing protocols
Tetric PowerFill is intended for a fast high-intensity light curing protocol (3 s) and Essentia is designed for conventional light curing protocol (20 s)
The differenceThe difference between each tested property of the material after being cured with either between each tested property of the material after being cured with the recommended or the non-recommended light curing protocol is shown in the bar graph either the recommended or the non-recommended light curing protocol is shown in the result of each test (Figure 1)
Summary
Dental practitioners are always searching for an effective method to handle their clinical procedures involving quick-set materials and reduced practical steps to decrease total time and costs. This trend or wish of shortening the restorative procedure time leads to competition between dental manufacturers to develop faster restorative techniques with shorter practical steps and light curing time. This requires dentists to improve their knowledge of the new materials/equipment and their safe practical applications [3,4,5]
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