Effect of Glass Fibre Reinforcement on Flexural Strength of Composites

Objectives: Loss of anterior teeth requires quick functional and aesthetic repair. Composites have been used extensively for this, but their biggest drawback is their low fracture resistance. The objective of this study was to measure the flexural strength of two composites, reinforced with woven glass fibre net. The null hypothesis tested was that fibre reinforcement would not increase flexural strength of composites. Methods: Four groups of specimens (n=10) were prepared from dental composites for three-point bend flexural testing (ISO 4049:88). For the first group Filtek Flow and Filtek Z250 were used. A thin layer of Filtek Flow was placed in the mould. The fibre net, EverSTICK, was cut into strips and imbedded into the uncured resin. The composite was then cured for 10 s. The mould was then filled with Filtek Z250 and polymerised. Specimens for Group two were prepared similarly as for Group one, using Esthet-X flow and Esthet-X. Group three was prepared with the same materials as for Group one, but no fibres were included. Likewise, specimens for Group four were prepared as for Group two, but without the fibres. Groups three and four served as the controls. Testing was performed using an Instron testing machine at a crosshead speed of 0,5mm/min and a load cell of 5kN. The mean and standard deviations for each test group were calculated using one-way analysis of variance (ANOVA) and post-hoc Tukey paired group comparison tests at 95% confidence level. Results: It was found that fibre reinforcement significantly (p<0,001) increased the flexural strength of both composites. Conclusions: In this experiment, the addition of a single layer of a woven glass fibre increased the flexural strength of the composites by ± 30%. Thus, it can be speculated that multiple layers may increase flexural strength even more.