This study focused on some mechanical properties such as the transverse strength, the maximal deflection, and the modulus of elasticity of resin reinforced with two different types of agents-treated and with untreated glass fibre, and without fibre. A Teflon mould was used to prepare six groups of specimens. Two different types of chemical modification agents, hydroxyethyl-methacrylate (HEMA)-monomer and air atmosphere were applied to create hydrophilic surfaces on the glass fibres. The flow rate was kept at two different levels, 25 and 60 mL min(-1). The discharge powers of the surface treatment process were 15 or 20 W. The fibres were exposed to glow discharge conditions for the periods of 10 or 15 min. Without fibre specimens were the control group. The provisional resin was same in all groups. All the specimens were subjected to transverse testing with a cross-head speed of 5 mm min(-1). The three-point load test was used to record the load of the fracture for each specimens. The Kruskal-Wallis analysis of variance was used to compare the transverse strength, the maximal deflection and the modulus of elasticity. The differences in the transverse strength and the maximal deflection between the six groups were found statistically significant but the modulus of elasticity was not statistically significant. The transverse strength of HEMA-monomer (group A) was shown the highest value (66.3 MPa). For without-fibre group, the value was 52.9 MPa. This difference was statistically significant when the Mann - Whitney U-test was used for comparing. Repairing or remaking provisional restorations can be a time-consuming endeavour. The added strength of the polymethyl methacrylate with the fibre can reduce clinical failures of provisional fixed partial dentures. The surface treatment process was increased the transverse strength and the maximal deflection. The clinical implication of chemical modification agents-coated fibres is reduced incidence of fixed provisional restoration failure.