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    Bond strength of resin composite to light activated bleached enamel
    (Wolters Kluwer Medknow Publications, 2016) Yavuz, Tevfik; Özyılmaz, Özgün Yusuf; Öztürk, Atiye Nilgün; Aykent, Filiz
    Objectives: This study evaluated the microtensile bond strength (mu TBS) of a resin composite bonded to bleached enamel as a function of bleaching conditions. Materials and Methods: The whiteness hydrogen peroxide (HP) bleaching agent containing 35% HP was applied to the central incisors' facial enamel surface and irradiated as follows: No treatment (G1; control); no light (G2); light-emitting diode, the 40s (G3); diode laser, the 20s (G4); and neodymium: yttrium aluminum garnet laser, 20s (G5). A Variolink II resin composite structure was then built up incrementally on the surface. The teeth were sectioned into three 1.2 mm x 1.2 mm wide "I"-shaped sections. The specimens were then subjected to microtensile testing at a crosshead speed of 1 mm/min. Data were analyzed using one-way ANOVA (alpha = 0.05) followed by the Tukey Honestly Significant Difference post-hoc test. The fractured surfaces were observed with a stereomicroscope at x 100 magnification. Results: One-way ANOVA revealed no statistical differences among the groups (P > 0.05). No differences appeared between the groups bonded 14 days after bleaching (P > 0.05). Mean mu TBS values (MPa) were as follows: 22.05 +/- 5.01 (G1); 19.6 +/- 5.6 (G2); 19.3 +/- 5.4 (G3); 20.08 +/- 2.08 (G4); and 18.1 +/- 4.8 (G5). Many adhesive failures occurred at the bleached and irradiated enamel surfaces. Conclusion: The various irradiation treatments following the application of the whiteness HP bleaching agent to enamel did not significantly reduce the mu TBS within a 14-day period.
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    Temperature rises during tooth bleaching with different light-curing units
    (Taylor & Francis Ltd, 2015) Özyılmaz, Özgün Yusuf; Yavuz, Tevfik; Sarı, Tuğrul; Aykent, Filiz; Öztürk, Atiye Nilgün
    The aim of this study was to evaluate the influence of three different light-curing units on the temperature rise induced in the pulpal cavity, when bleached with 35% hydrogen peroxide (HP). Forty extracted maxillary central incisors were randomly divided into four groups according to photoactivation procedure (n=10). Whiteness HP (WHP) bleaching agent which contains 35% HP bleach was placed on the facial tooth surface and no photoactivation device was used (control); an blue light-emitting diode (LED, 40s), a diode laser (4W, Continous mode, 20s), and Nd:YAG laser (4W, 60Hz frequency, 20s). Temperature rise in the pulpal chamber was measured with a J-type thermocouple wire that was connected to a data logger before and immediately after each 20-40s application. One tooth of each group was selected for scanning electron microscope analysis. Data were analyzed using one-way ANOVA followed by the Games Howell post hoc test at a preset alpha of 0.05. One-way ANOVA revealed that there was a significant difference among the light-curing units (p<0.05) and between control group and light-curing units (p<0.05). The Nd:YAG induced significantly, which resulted in higher temperature increase than other light-curing units (10.7 degrees C). The LED unit produced the lowest temperature changes (3.2 degrees C) among the light-curing units. The presence of the bleaching gel did not cause a temperature increase in control group (0 degrees C). The results suggested that using light-curing units caused temperature changes in the intrapulpal cavity during tooth bleaching. The use of LED will be more safer for pulpal health when assisted with WHP bleaching gel.