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Abstract
The aim of this study was to evaluate the effect of fiber direction on the polymerization shrinkage of fiber-reinforced composite. The disc-shaped flowable composite specimens (d = 10 mm, h = 2 mm, Aeliteflo A2, Bisco, Inc., IL, USA) with or without glass fiber bundle (X-80821P Glass Fiber, Bisco, Inc., IL, USA) inside were prepared, and the longitudinal and transversal polymerization shrinkage of the specimens on radial plane were measured with strain gages (Linear S-series 350ω, CAS, Seoul, Korea). In order to measure the free polymerization shrinkage of the flowable composite itself, the disc-shaped specimens (d = 7 mm, h = 1 mm) without fiber were prepared, and the axial shrinkage was measured with an LVDT (linear variable differential transformer) displacement sensor. The cross-section of the polymerized specimens was observed with a scanning electron microscope to examine the arrangement of the fiber bundle in composite. The mean polymerization shrinkage value of each specimen group was analyzed with ANOVA and Scheffe post-hoc test (α=0.05).
The radial polymerization shrinkage of fiber-reinforced composite was decreased in the longitudinal direction of fiber, but increased in the transversal direction of fiber (p<0.05). We can conclude that the polymerization shrinkage of fiber-reinforced composite splint or restoratives is dependent on the direction of fiber.
Figures and Tables
 | Figure 1a) Experimental setup for the measurement of radial linear shrinkage using a strain gage.
b) Definition of directions on a disc shaped specimen in the measurement.
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 | Figure 2Electric circuit design for the strain measurement (Vo: output voltage, Va: voltage between two fixed resistances, Vb: voltage between two strain gages, Vs: input voltage, R: fixed resistance, ΔR: resistance difference, SG: strain gage).
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 | Figure 4a) Representative curves of radial shrinkage strains for composite specimens as a function of time.
b) Post-gel shrinkage strains for four groups.
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