Abstract
The aim : to study in laboratory conditions the microhardness of a glass-fiber-reinforced photocomposite under different modes of light exposure at different times. Materials and methods . The microhardness of the everX Posterior, GC glass-fiber-reinforced photocomposite was investigated on 60 samples using a PMT-3 microhardness meter on three sample surfaces within 1 hour, 1 day and 7 days after polymerization. Samples of a cylindrical shape with a height of 3 mm of group 1 were irradiated with the light flux of a photopolymerizer in the soft start mode, samples of group 2 were polymerized with light of constant high intensity 1400 mW/cm 2 . Research results . After 1 hour, the microhardness on the surface closest to the LED was 87.34±1.21 kgf/mm 2 in samples of group 1, 102.0±0.94 kgf/mm 2 (p<0.05) in group 2, and 70.98±1.23 kgf/mm 2 (the lowest indicator) and 90.65±1.12 kgf/mm 2 (p<0.05). After 1 day, on the nearest surface, the microhardness increased in the samples of group 1 to 97.03±1.25 kgf/mm 2 , group 2 – to 114.61±1.13 kgf/mm 2 (p<0.05), on the most distant - up to 75.95±1.11 kgf/mm 2 and 99.83±1.24 kgf/mm 2 (p<0.05), respectively. At 7 days, the indicators on the first surface in group 1 were 104.64±1.23 kgf/mm 2 , in 2 – 123.35±1.15 kgf/mm 2 (p<0.05), on the other surface – 80.25±1.48 kgf/mm 2 and 107.53±0.92 kgf/mm 2 (p<0.05). The growth of microhardness on these surfaces for the entire period was 16.5 % and 11.6 % in the samples of group 1, and 17.3 % and 15.7 % in group 2. Conclusions. The light flux of constant high intensity provides statistically significantly (p <0.05) higher microhardness indices of the glass-fiber reinforced photocomposite on all surfaces of the samples than the light exposure in the “soft start” mode. In the direct restoration of teeth, it is necessary to reduce the thickness of the photocomposite layer for soft start polymerization
Highlights
Dental restoration technologies, which have made it possible to restore the anatomical shape and aesthetic properties of carious teeth, are constantly being improved and optimized
The dynamics of microhardness on the most distant surfaces of samples 1 and 2 groups again showed a more significant relative to the initial values on these surfaces increase in samples of groups 2, the microhardness of the material of these samples increased (p
On surfaces A, which were closest to the light source, in samples of group 1 microhardness within 7 days increased by 16.5 % compared to baseline, i. e. that which was determined 1 hour after light exposure, in samples of group 2 the indicator increased at 17.3 %
Summary
Dental restoration technologies, which have made it possible to restore the anatomical shape and aesthetic properties of carious teeth, are constantly being improved and optimized. The risk of cracks in direct photocomposite restorations is especially significant in large cavities located in the lateral teeth, with no vertical walls or after endodontic treatment It is in such cases that the use of fiberglass-reinforced photocomposite is shown, but it is necessary to ensure its full hardening and the acquisition of certain strength characteristics, which depend on the duration of the recovery. It is well known that the specific light energy significantly affects the achievement of any photocomposite material a certain level of hardening, hardening continues for some time after light exposure, stretching for several days [8] During this time, the physical and mechanical characteristics of the photocomposite improve, in particular, the microhardness, the indicators of which can give an idea of the degree of polymerization of the material. It is advisable to study the microhardness of the photocomposite material, reinforced with fiberglass, which hardens under light exposure in different modes, with tracking of its parameters over time
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