Effect of fiber direction on the polymerization shrinkage of fiber-reinforced composites

Article information

Restor Dent Endod. 2009;34(4):364-370

Publication date (electronic) : 2009 July 31

doi : https://doi.org/10.5395/JKACD.2009.34.4.364

Department of Conservative Dentistry, School of Dentistry, Seoul National University, Korea.

Corresponding Author: In-Bog Lee. Department of Conservative Dentistry, School of Dentistry, Seoul National University, 275-1 Yeongeon-Dong, Jongno-Gu, Seoul, 110-768, Korea. Tel: 82-2-2072-3953, Fax: 82-2-2072-3859, inboglee@snu.ac.kr

Received 2009 May 11; Revised 2009 May 31; Accepted 2009 June 25.

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.

Keywords: fiber-reinforced composite; longitudinal direction; transversal direction; polymerization shrinkage; strain gage; linear variable differential transformer

References

1. Giachetti L, Scaminaci Russo D, Bambi C, Grandini R. A review of polymerization shrinkage stress: current techniques for posterior direct resin restorations. J Contemp Dent Pract 2006. 779–88.

2. Vallittu PK, Lassila VP, Lappalainen R. Acrylic resin-fiber composite-Part I: The effect of fiber concentration on fracture resistance. J Prosthet Dent 1994. 71607–612.

3. Vallittu PK. Acrylic resin-fiber composite--Part II: The effect of polymerization shrinkage of polymethyl methacrylate applied to fiber roving on transverse strength. J Prosthet Dent 1994. 71613–617.

4. Goldberg AJ, Burstone CJ. The use of continuous fiber reinforcement in dentistry. Dent Mater 1992. 8197–202.

5. Butterworth C, Ellakwa AE, Shortall A. Fibre-reinforced composites in restorative dentistry. Dent Update 2003. 30300–306.

6. Dyer SR, Lassila LV, Jokinen M, Vallittu PK. Effect of cross-sectional design on the modulus of elasticity and toughness of fiber-reinforced composite materials. J Prosthet Dent 2005. 94219–226.

7. Tezvergil A, Lassila LV, Vallittu PK. The effect of fiber orientation on the polymerization shrinkage strain of fiber-reinforced composites. Dent Mater 2006. 22610–616.

8. Sakaguchi RL, Versluis A, Douglas WH. Analysis of strain gage method for measurement of post-gel shrinkage in resin composites. Dent Mater 1997. 13233–239.

9. Versluis A, Tantbirojn D, Douglas WH. Distribution of transient properties during polymerization of a light-initiated restorative composite. Dent Mater 2004. 20543–553.

10. Lassila LV, Vallittu PK. The effect of fiber position and polymerization condition on the flexural properties of fiber-reinforced composite. J Contemp Dent Pract 2004. 514–26.

11. Lee IB, Cho BH, Son HH, Um CM, Lim BS. The effect of consistency, specimen geometry and adhesion on the axial polymerization shrinkage measurement of light cured composites. Dent Mater 2006. 221071–1079.

12. Sakaguchi RL, Wiltbank BD, Shah NC. Critical configuration analysis of four methods for measuring polymerization shrinkage strain of composites. Dent Mater 2004. 20388–396.

Article information Continued

Figure 1

a) 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.

Figure 2

Electric 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).

Figure 3

Experimental setup for the measurement of axial linear shrinkage using an LVDT probe.

Figure 4

a) Representative curves of radial shrinkage strains for composite specimens as a function of time.

b) Post-gel shrinkage strains for four groups.

Figure 5

SEM photomicrographs showing the cross-section of composite specimens.

a) Some voids were observed between fibers. The arrows show fiber bundles (F).

b) There was an intimate contact between the strain gage and composite. The arrow shows the strain gage (SG).

Table 1

Post-gel radial shrinkage strain measured using a strain gage for composite specimens at 600 s.

^*Superscript letters mean statistically significant difference.