Mechanical Properties of Novel Short Zirconia Fibre Reinforced Composites

Objectives: The purpose of this study was to evaluate and compare the fracture toughness, Vickers-hardness and compressive strength of fibre reinforced composites (FRC) loaded with various percentages of short zirconia fibres.
Methods: Novel silane system with 1.0-vol% (3-acryloxypropyl)trimethoxysilane + 0.5-vol% bis-1,2-(triethoxysilyl)ethane in 90-vol% ethanol (pH=4.0) was used to silanize zirconia fibres (diameter: 3-8-mm, length 50-250-mm). Next, various amounts (1-wt%, 3-wt%, and 5-wt%) of silanized zirconia fibres were mixed with resin matrix (78.4wt%-bis-GMA/19.6-wt%-MMA/1wt%-CEMA/1wt%-CQ). Resin matrix without any fibre was served as control. These resin composites were then poured and light-cured (Elipar 2500, 3M-ESPE) into various moulds for different mechanical tests: Notchless triangular prism (NTP) fracture toughness (6-mm×6-mm×6-mm×12-mm), Vickers-hardness indentation (25-mm×2-mm×2-mm) and compressive strength tests (10-mm×2-mm×2-mm). Six test specimens from each group was stored in either ambient (room temperature, 1-day) or water (37°C, 7-day). SEM and EDX were taken at the silanized fibres, and fracture sites after fracture toughness test. The data were statistically analyzed with 1-way ANOVA and Bonferroni post hoc test (a=0.05).
Results: The novel silane system could effectively coat zirconia fibres. Only the experimental FRC group with 3-wt% zirconia fibres raised the fracture toughness (116.55 MPa mm^1/2) after water storage, which is a statistically higher (p<0.05, ANOVA) than other groups. 1-wt% FRC group in dry condition showed a statistically higher Vickers-hardness than other groups (p<0.05). However, compressive strength of experimental groups had no significant difference (p>0.05).
Conclusions: Reinforcement of FRCs with short zirconia fibres might improve the mechanical properties.