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  • Title: Thermal and mechanical load cycling on microleakage and shear bond strength to dentin.
    Author: Bedran-de-Castro AK, Cardoso PE, Ambrosano GM, Pimenta LA.
    Journal: Oper Dent; 2004; 29(1):42-8. PubMed ID: 14753331.
    Abstract:
    This study evaluated the influence of mechanical and thermal cycling on microleakage at the cervical margins of proximal slot restorations and shear bond strength on flat dentin surfaces. Microleakage Evaluation: One hundred and twenty slot cavity restorations were performed on bovine incisors. The restorations were randomly divided into four groups (n = 30): control (no thermal and mechanical load cycling), thermal cycling (2,000 cycles, 5 degrees C-55 degrees C), mechanical load cycling (50,000-80N) and thermal and load cycling (2,000 5 degrees C-55 degrees C/50,000-80N). The specimens were sealed with acid resistant varnish, leaving a 1-mm window around the cervical margin interface. To detect marginal leakage, a 2% methylene blue buffered solution was used for four hours. The specimens were sectioned longitudinally and qualitatively evaluated by stereomicroscopy (45x) following a ranked score for the dentin cervical margin. The data were analyzed by Kruskal-Wallis test (alpha = 0.05). Shear Bond Strength Evaluation (SBS): Eighty bovine incisors were embedded and polished to obtain a flat standard surface on dentin. The surfaces were restored with Single Bond adhesive system and a resin composite subsequently inserted in a bipartite Teflon matrix. The specimens were randomly divided into the four groups (n = 20) described above for microleakage. Shear bond strengths were measured in a universal testing machine with a crosshead speed of 0.5 mm/minute. The data were analyzed by one way ANOVA test (alpha = 0.05). No statistically significant influence of thermocycling, mechanical load cycling or the combination was observed for both microleakage and shear bond strength.
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