The effect of time of trimming on the surface finish of anterior composite resins.

Abstract

This in vitro study investigates whether the surface smoothness of a finished composite resin is a function of the time at which it is trimmed. Five materials were studied. Visiodispers (VIS) is a sintered microfine, the remainder were hybrid formulations: Miradapt (MIR), Command Ultrafine (COM) and two experimental formulations-'EXP (2)' and 'EXP (15)'-with larger filler particles. All except MIR were photo-activated. Samples were placed and cured in holes machined in Perspex rods, ensuring excess of material and moulded to shape with cellulose acetate matrix strip. The strips were removed immediately after light curing and after 5 min in the case of MIR. Sample groups were finished after the following intervals: 10, 15, 30, 45s, 1, 2, 3, 4, 5 min, dry, and after 1 and 7 days in 37 degrees C water. The finishing procedure used plain-cut tungsten-carbide burs and coarse, medium and fine finishing discs, which were applied for standardized times, directions and pressures. Surface roughness was assessed visually and with a surface profilling instrument. COM and VIS materials significantly improved in surface finish when the procedure was delayed for 7 days. However, EXP (2), EXP (15) and MIR surface finishes were independent of finishing time. This may result from a rapid attainment of optimum surface hardness, whereas with COM and VIS incomplete curing leads to smearing of resins and filler across the surface.