Mechanical properties of resin composites with filler particles aligned by an electric field.
OBJECTIVE
To explore possible enhancement of the mechanical properties of resin composites by aligning the filler particles.


METHODS
The resin for the composites consisted of urethane dimethacrylate (UDMA) and 1,6-hexanediol dimethacrylate (HDDMA) mixed in the ratio of 90 to 10; the filler was silica-zirconia in two particle sizes, 1.7 microns (P50), which was mixed with the resin in the volume fractions of 29 and 48 vol%, and 0.7 micron (Z100), which was mixed with the resin in the volume fractions of 37 and 57 vol%. Particle alignment was obtained by applying a 60 Hz AC electric field across the composite before the resin was photopolymerized. The stress-strain behavior and the elastic modulus of the hardened composite were measured along the alignment axis in compression.


RESULTS
The elastic moduli of the aligned composites increased by as much as 20%, and the maximum stress sustainable in compression before significant deformation occurred was elevated. An electric field strength of the order of 1 kV mm-1 was required to obtain sufficient alignment.


CONCLUSIONS
Besides conferring a structure to resin composites that is more like that of the natural tooth, particle alignment increased some of the mechanical properties and may have improved durability.
Park
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C
Macromolecular Science and Engineering Center, University of Michigan, Ann Arbor, USA.
Robertson
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D003188:Composite Resins / Q000737:chemistry*; D019245:Compressive Strength; D004548:Elasticity; D004563:Electrochemistry; D006244:Hardness; D008422:Materials Testing; D019563:Mechanics; D008689:Methacrylates / Q000737:chemistry; D008854:Microscopy, Electron; D010316:Particle Size; D011140:Polyurethanes / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D015040:Zirconium / Q000737:chemistry
D003188:Composite Resins; D008689:Methacrylates; D011140:Polyurethanes; C029824:urethane dimethacrylate luting resin; D012822:Silicon Dioxide; D015040:Zirconium; C090921:1,6-hexanediol dimethacrylate; C028541:zirconium oxide