İki Farklı Led Işık Cihazının Nanohibrid Kompozit Rezinin Mikromekanik Özellikleri Üzerine Etkisi.
Bilge Kütük, Zeynep
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The aim of this in vitro study was to investigate the effects of different curing modes of two LED light curing units from two exposure distances on the micromechanical properties of a nanohybrid composite resin (Kalore/GC). Seventy-two specimens of composite resin with 2 mm thickness (n=6) were cured using two high irradiance LED light curing units (Bluephase 20i/Ivoclar and FlashMax P3/CMS Dental) at 0 and 7 mm exposure distances. The curing conditions were: Grup a: Bluephase 20i – 10 s – High power, Grup b: Bluephase 20i – 15 s – High power, Grup c: Bluephase 20i – 5 s – Turbo, Grup d: Bluephase 20i – 15 s – Soft start, Grup e: FlashMax P3 – 4 mm tip – 3 s, Grup f: FlashMax P3 – without tip – 3 s. The transmitted light power and energy density were evaluated at specimens' bottom in real time during curing, with a radiometer (MARC Resin Calibrator). Vickers hardness (HV) and modulus of elasticity (E) were measured with an automatic universal hardness indenter (Fisherscope H100C) at specimens' top and bottom surfaces after storing 24 hours in distilled water at 37°C. Effects of energy densities, exposure distances and surface conditions were analyzed using One Way Variance Analyze, Tukey and t tests (p=0.05). Different energy densities were observed for all groups according to distance and surface conditions. In all groups, a decrease in intensity and energy density formed in the top and bottom of the composite resin surfaces during the polymerization was determined when the exposure distance was removed from the 0 to 7 mm. The highest hardness (76.61 ± 5.85 N/mm2) and modulus of elasticity (10.42 ± 5.85 GPa) values were observed in the Group b at 0 mm, the lowest hardness (49.41 ± 13.11 N/mm2) and modulus of elasticity (6.63 ± 1.87 GPa) values were observed in the Group e at 7 mm for top surfaces (p<0.05). Increasing the exposure distance was significantly impaired the micromechanical properties of the top and bottom surfaces in the Group e (p<0.05). The light intensities of LED light curing units were higher than the manufacturers' reported. Different light energy densities (0.01 J/cm2 - 23.13 J/cm2) and exposure distances (0-7mm) influenced the micromechanical properties of top and bottom surfaces of a nanohybrid composite. The top and bottom surfaces' micromechanical properties of composite resins were affected by the energy density more than the light intensity of the used light curing units.