The effect of length and concentration of glass fibers on the mechanical properties of an injection- and a compression-molded denture base polymer

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Abstract

Statement of problem

Fiber-reinforcement has been used to overcome the mechanical limitations of denture base polymers. One major difficulty in the use of fiber reinforcement has been the addition of fibers during conventional processing methods.

Purpose

This study evaluated the effect of various lengths and concentrations of chopped E-glass fiber-reinforcement on the transverse strength, modulus of elasticity, and impact strength of injection and compression-molded polymethyl methacrylate based denture base polymer.

Material and methods

Test specimens (n=10) of 4-, 6-, and 8-mm fiber length and 1%, 3%, and 5% weight fiber concentrations were prepared with either an injection or a compression-molded processing method. Denture base polymer specimens without any fiber reinforcement were used as control for both processing methods. Transverse strength test specimens (65 × 10 × 2.5 mm) were stored in water bath at 37°C for 2 weeks. The transverse strength (MPa) and modulus of elasticity (GPa) was measured with the 3-point bending test. Impact strength (kJ/m2) test specimens (60 × 7.5 × 4 mm) were tested with the Charpy-type pendulum impact test setup. The data were analyzed with multifactorial analysis of variance and Tukey post hoc tests (α=.05).

Results

Injection-molded fiber-reinforced groups showed significantly higher transversal strength, elastic modulus, and impact strength compared with compression-molded groups (P < .001). In the injection-molded groups, fiber concentration increased all mechanical properties tested (P < .05), but fiber length only increased transverse strength and modulus of elasticity (P < .05). In the compression molded groups, fiber concentration affected modulus of elasticity and impact strength significantly (P < .05), but fiber length did not show any significant effect on the mechanical properties tested (P > .05).

Conclusion

The transverse strength, elastic modulus and impact strength of injection-molded denture base polymer increased significantly with the use of chopped E-glass fibers, whereas the effect was not significant with the compression-molded polymer.

Section snippets

Material and methods

Twenty test groups, each containing 10 specimens were used for transverse strength, modulus of elasticity, and impact strength tests. Control groups, without any fiber reinforcement (n=10 per test), were prepared for both compression and injection molding (Table I).

Results

The mean values and SEs of the transverse strength, modulus of elasticity, and impact strength tests are shown in Fig. 1, Fig. 2, Fig. 3, respectively, and the mean subsets for Tukey analysis are shown in all 3 figures. The results of 3-factor ANOVA showed that processing method and fiber volume had a significant effect (P < .05) on transverse strength (Table II), modulus of elasticity (Table III), and impact strength (Table IV), whereas fiber length showed a significant effect on transverse

Discussion

This study compared the transverse strength, modulus of elasticity, and impact strength of chopped E-glass fiber-reinforced injection or compression molded denture base polymer with various lengths and concentrations. For the chopped fiber-reinforced composites, the fibers are oriented randomly in the matrix, which has a continuous phase. Fiber reinforcement is only effective if the stress can be transferred from the polymer matrix to the fiber.39, 45 This is achieved if the fibers have a

Conclusions

Within the limitations of this in vitro study, it was demonstrated that 6-mm chopped glass fibers with 5% fiber in combination with the injection-molding technique can result in a significant increase in the transverse strength, elastic modulus, and impact strength of the denture base polymer.

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  • Cited by (0)

    The material used for this study was bought by the Cumhuriyet University Research Funding, funding of the Finnish Technology Agency (TEKES) and CIMO Fellowship Grant.

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