Glass–ceramic filler particles containing various amounts of fluoroapatite–mullite crystalline phases were synthesised using SiO2–Al2O3–P2O5–CaF2–CaO system as the base glass formulation. Different additives were used to promote crystallisation in this system. Composite samples were prepared by incorporating the silane treated glass–ceramic particles into the BisGMA/TEGDMA (60 : 40 mass ratio) epoxy matrix. Structural and microstructural characterisations were conducted using Fourier transform infrared spectroscopy, X-ray diffractometry and scanning electron microscopy (SEM). The mechanical properties of the light cured samples were examined by measuring flexural and diametral tensile strength, as well as conducting Vickers microhardness test. Results obtained in this study showed strong dependence of the flexural strength on the composition of the filler particles. Diametral tensile strength and microhardness values demonstrated lesser sensitivity to the filler composition. Microstructural examination of the samples by SEM revealed particle pull-out, debonding and crack deflection as the major energy consuming mechanisms in the fracture process.

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