Influence of inorganic fraction on polymerization stress development in composites

Objectives . Polymerization stress in dental composites remains a concern in restorative dentistry. The objective of this study was to evaluate the influence of inorganic fraction ( F i ) on polymerization stress ( σ pol ) and its determinants: volumetric shrinkage (VS), elastic modulus ( E ) and degree of conversion (DC).

Materials and methods . Eight experimental composites were produced with equal parts of BisGMA and TEGDMA (mol%) and 2 μm average size barium glass in concentrations of 25, 30, 35, 40, 45, 50, 55 and 60 vol%. σ pol was obtained in a universal testing machine by inserting the composite (1 mm thick) between acrylic rods (5 mm in diameter). VS was determined using a water pycnometer. E was determined in three-point bending. DC was measured by FT-Raman. Data were obtained 15 min into polymerization and were analyzed by one-way ANOVA and Tukey’s test ( α = 0.05). Specimens were photoactivated with quartz–tungsten–halogen light curing unit, reaching a radiant exposure of 18 J/cm 2 (570 mW/cm 2 × 32 s).

Results . The table shows the mean ± standard deviation of σ pol. VS, E and DC.

Inorganic fraction (vol%) Polymerization stress (MPa) Elastic modulus (GPa) Volumetric shrinkage (%) Degree of conversion (%)
25 5.8 ± 0.4 a 1.6 ± 0.2 f 3.3 ± 0.6 a 53.0 ± 3.1 a
30 5.3 ± 0.4 ab 1.8 ± 0.2 ef 3.2 ± 0.6 ab 56.1 ± 1.6 a
35 5.4 ± 0.2 ab 2.3 ± 0.2 de 3.1 ± 0.6 ab 53.7 ± 2.8 a
40 4.8 ± 0.4 bcd 2.7 ± 0.3 cd 2.8 ± 0.5 abc 54.5 ± 3.1 a
45 5.0 ± 0.1 bc 3.1 ± 0.4 c 2.9 ± 0.4 ab 55.7 ± 0.8 a
50 4.5 ± 0.3 cd 4.3 ± 0.6 b 2.7 ± 0.5 abc 57.6 ± 3.6 a
55 4.4 ± 0.3 d 4.3 ± 0.5 b 2.4 ± 0.3 bc 51.1 ± 0.3 a
60 3.9 ± 0.2 e 5.9 ± 0.9 a 2.1 ± 0.3 c 51.8 ± 1.1 a
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Nov 30, 2017 | Posted by in Dental Materials | Comments Off on Influence of inorganic fraction on polymerization stress development in composites
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