One of the most challenging problems in restorative dentistry is polymerization shrinkage and low strength due to theirinferior mechanical properties. The introduction of resin material Bisphenol A glycidyl methacrylate, or Bis-GMA, haschanged its chemical structure dramatically, to overcome the problem of shrinkage, thermal expansion, and low strength to someextent. The introduction of nanotechnology led to the discovery of nano-filler particles. Hybrid composites were developed bycombining inorganic glass fillers of various sizes to provide better strength and smooth finish. Nanocomposites are composedof two or more materials that include a matrix material and nanoscale particles. The properties are improved drastically byreducing the size of fillers based on nanotechnology. The properties of nanocomposites (good translucency, contouring andsurface finish) are excellent and can restore lost or damaged dental tissues. In addition, such materials should have bioactive andbiocompatible properties at the interface between the material and tissue to prevent micro-leakage and ingress of bacteria. Thecomposite resins consist of three basic phases - the organic phase (matrix), the dispersed phase (filler) and the interfacial phase(coupling agent). The resin matrix is a mixture of methacrylate/acrylate monomers. During the application the monomers ofresin matrix are polymerized to crosslinked polymer structure by free radical nonlinear polymerization process. In order toachieve a strong covalent interaction in between the organic matrix and inorganic fillers, coupling agents are used. The couplingagents tend to promote bonding or adhesion between the filler particles and matrix and helping in the transfer of load andstresses. A commonly used coupling agent is gamma methacryloxy propyl trimethoxysilane (MTPS). One side of the couplingagent tends to bond with hydroxyl groups of silica particles and other is copolymerized with polymer matrix.A study of the modification of dental nanocomposites with nanosized fillers is presented. TiO2 has good antibacterialproperties that depend on the surface of the material and decrease in size of the nanoparticles. It is not toxic so it was selected asan additive to the dental nanocomposite material. The principal aim of this study was to synthesize dental nanocomposites withdifferent sizes, treated, nano-TiO2 fillers in resin matrix for potential application in posterior restoration and to evaluate theirmechanical properties. The incorporation of TiO2 (titania) nanoparticles, via a silane chemical bond, to the dental acrylic resinmatrix shows an increase in the wear resistance, flexural strength and surface hardness properties of the dental nanocomposites.For comparison, a commercially available dental resin was reinforced with untreated and treated nano-TiO2 particles withvarious sizes.