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Degree of conversion and mechanical properties of a BisGMA:TEGDMA composite as a function of the applied radiant exposure.

Author information

1
Department of Biomaterials and Oral Biochemistry, School of Dentistry, University of São Paulo, São Paulo, Brazil.

Abstract

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/cm(2). 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/cm(2) and between 24 and 48 J/cm(2) 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/cm(2) and between 24 and 48 J/cm(2). KHN/bottom at 3 and 6 J/cm(2) was similar. KHN between top and bottom was different up to 12 J/cm(2). Regression analyses having H as independent variable showed a plateau region above 24 J/cm(2). 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.

PMID:
17635039
DOI:
10.1002/jbm.b.30897
[Indexed for MEDLINE]

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