Polishing performance of multiple-use silicone rubber-based polishing instruments with and without...

To evaluate the effect of the multiple-use of a three-step rubber-based polishing system on the polishing performance with and without a disinfection/sterilization protocol with prolonged disinfection (overnight).

The three-step polishing system Astropol was applied under standardized contact pressure of 2 N on 320 grit pre-roughened flat composite specimens of Tetric EvoCeram for 10 seconds (F and P disc) and 30 seconds (HP disc) respectively. After each polishing step, the surface gloss and roughness were measured with a glossmeter and an optical sensor (FRT MicroProf), respectively. Material loss of the composite specimens and polishing instruments were measured after each step with a high precision digital scale. For all four variables (surface gloss, surface roughness, composite loss, loss of rubber material) the mean percentage of change compared to the reference was calculated.

Already after the first use, the instruments which were used without disinfection or sterilization demonstrated a statistically significantly reduced polishing performance in all polishing steps compared to the reference (new polishing system) (t-test, P < 0.05). In addition, this loss in performance further increased with the second and third re-use. Especially the third component (Astropol HP) was affected by performance loss. By contrast, the multiple-use of the instruments which were subjected to prolonged disinfection did not result in a reduced polishing performance. For the P disc, a statistically significant improvement of the polishing performance could be observed throughout almost all multiple-use sessions (ANOVA, P < 0.05). The improved polishing performance was, however, accompanied by an increased loss of the silicone rubber material of the P and F polishing discs; the HP discs were not affected by this loss. Furthermore, particles of the rubber material also adhered to the composite. The polishing performance of the discs which were only subjected to the sterilization process was not statistically significantly different to the polishing performance of the control group in terms of surface roughness; but the surface gloss was worse than that of the control group. No loss of rubber material or adherence to the composite was observed in this group.