• Pisaisit Chaijareenont, D.D.S.
• Issarawan Boonsiri, B.Sc., D.D.S., Grad. Dip. (Prosthodontics), Cert. in Fixed Prosthodontics

Objective To study the flexural strength of fiber-reinforced resin composites

Materials and methods One hundred forty specimens sized 2 x 2 x 25 mm were divided into 7 groups
(n = 20). The control group was without glass fiber. Four groups contained 10%, 20%, 30% and 40%
by volume domestic glass fiber. One group contained imported glass fiber and the last group contained
polyethylene fiber reinforcement. Each group was divided into 2 sub-groups (n = 10), and then
immersed in distilled water at 37°C for 7 and 30 days respectively. Flexural strength tests were
performed by the universal testing machine (Instron 8874) with a cross-head speed of 1 mm/min.
Statistical analysis was performed by using t-test, one-way ANOVA and Multiple comparisons (α = 0.05).

Results Flexural strength increased in the glass fiber-reinforced groups and decreased in the 30-day
immersion in distilled water groups. The highest flexural strength was found in the 30% by volume
domestic glass fiber-reinforced group. The flexural strength of the 10% by volume domestic glass
fiber-reinforced group was similar to that of the imported glass fiber and polyethylene fiber-reinforced
groups.

Conclusion Appropriate amounts of glass fiber-reinforced could strengthen and lengthen the usage of
the specimens. Longer immersion in distilled water reduced the strength of the specimens.

(CU Dent J. 2011;34:45-54)