The mechanical properties of dental composites were improved by porous diatomite and nano-sized silica (OX-50) used as co-fillers. The resin composites, filled with silanized OX-50 and silanized diatomite (40:60 wt/wt), presented the best flexural strength (133.1 MPa), elastic modulus (9.5 GPa) and Vickers microhardness (104.0 HV). Besides these, TiO 2 nanoparticles were introduced to tune the dental resin composites colours which were valued by the CIE-Lab system. The colour parameters (L n ,

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... n , b n ) showed that the colour changes of resin composites could be perceived obviously, when 300-400 nm TiO 2 particles were introduced as fillers. The resin composite, filled with 0.5 wt% TiO 2 , exhibited both clear discolouration (DE n ¼ 3.22) and high mechanical strength. Using scanning electron microscope (SEM) equipped with an energy dispersive X-ray (EDX), the titanium elemental mapping results indicated that the TiO 2 particles were distributed evenly in the prepared dental composites.