• Calheiros, Fernanda C.
• Braga, Roberto R.
• Daronch, Márcia

Abstract

<p>Objective: Verify the influence of radiant exposure (H) on composite degree of conversion (DC) and mechanical properties. Methods: Composite was photoactivated with 3, 6, 12, 24, or 48 J/cm². Properties were measured after 48-h dry storage at room temperature. DC was determined on the flat surfaces of 6 mm x 2 mm disk-shaped specimens using FTIR. Flexural strength (FS) and modulus (FM) were accessed by three-point bending. Knoop microhardness number (KHN) was measured on fragments of FS specimens. Data were analyzed by one-way ANOVA/Tukey test, Student's t-test, and regression analysis. Results: DC/top between 6 and 12 J/cm² and between 24 and 48 J/cm² were not statistically different. No differences between DC/top and bottom were detected. DC/bottom, FM, and KHN/top showed significant differences among all H levels. FS did not vary between 12 and 24 J/cm² and between 24 and 48 J/cm². KHN/bottom at 3 and 6 J/cm² was similar. KHN between top and bottom was different up to 12 J/cm². Regression analyses having H as independent variable showed a plateau region above 24 J/cm². KHN increased exponentially (top) or linearly (bottom) with DC. FS and FM increased almost linearly with DC/bottom up to 55% conversion. Conclusions: DC and mechanical properties increased with radiant exposure. Variables leveled off at high H levels.</p>

Topics

• surface
• strength
• composite
• flexural strength