engleski

Shrinkage Evaluation Of Composite Polymerized With LED Units Using Laser Interferometry

Composite materials shrink during polymerization regardless of curing unit or polymerization program used. However, different polymerization programs lead to different shrinkage percentage. The aim of this study was to evaluate linear polymerization shrinkage for five composite materials polymerized with different curing modes of two LED curing units. Bluephase C5 (500 mW/cm2, 20 seconds) and Bluephase C8 (high power mode - 800 mW/cm2, 20 seconds polymerization and soft start mode - 650 mW/cm2 for the first 5 seconds, then 800 mW/cm2 for the next 15 seconds), (both curing units Vivadent, Schaan, Liechtenstein) were used for composite resin photopolymerization. Polymerization shrinkage was recorded during each second of polymerization process using laser interferometry. The results were analyzed by ANOVA and Tukey post hoc test was used for finding siginficance levels. The highest shrinkage values were obtained in the case of composite polymerization using high polymerization mode of Bluephase C8 curing unit (0.61% for Tetric EvoCeram A1 and A3 and 0.69% for Artemis A2) while the lowest results were observed the soft-start mode of Bluephase C8 LED (0.48% for Artemis A2, 0.41% for Tetric Ceram A3, and 0.35% for TetricEvoCeram A3.5) and Bluephase C5 curing unit were used (0.40% for Tetric Ceram A1 and 0.44% for TetricEvoCeram A3.5). Artemis A2 showed maximal overall sample dimension change, regardless of the light curing source used. The initial expansion was recorded for all composite resins and curing modes during the first 4 – 9 seconds of illumination. Negative consequences of polymerization shrinkage and temperature rise can be diminished by applying polymerization program with lower initial light intensity which prolongs the pre-gel phase of polymerization process.

polymerization shrinkage; initial expansion; LED units; curing mode; composite

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