To compare gloss retention amongst a range of modern micro-filled and nano-filled resin composite materials following simulated toothbrushing.
Methods:
Composite materials were chosen to represent both nano and micro-filled resin composites;
Micro-hybrids: Filtek Z250 [3M], Gradia Direct [GC], Herculite XRV [Kerr], Miris [Coltene Whaledent], Venus [Heraus Kulzer]
Nano-hybrids: Herculite XRV Ultra[Kerr], Tetric Evoceram [Ivoclar]
Eight discs, 12 mm x 2 mm, were produced of each material. The discs were finished and polished following an identical protocol progressively down to a final polish with 3µm diamond polishing paste. Gloss readings were taken using a gloss meter [Sheen Instruments] with a light source at 60º incidence and reflection. Simulated tooth brushing was carried out, using a reciprocal action machine, using a diluted proprietary toothpaste [Colgate Total] as abrasive. A brushing rate of 1.5 Hz and 350g load were applied. Gloss readings were taken at regular intervals with a final reading after 600 minutes (108,000 strokes), rotating each sample following each reading. Statistics were carried out using ANOVA with Tukey's tests. Statistical differences were evaluated to a significance of p<0.05.
Results:
Initial gloss values ranged from 84.8 to 91.7 gloss units (GU).
After 600 minutes, Gradia direct exhibited the least reduction in mean gloss (2.6 GU), significantly less than all of the others except Herculte XRV Ultra (14.1 GU) and Venus (15.9 GU). Filtek Z250 had the highest reduction in gloss (40.6 GU). The time taken for each material to reach a significant reduction in gloss varied from 360 minutes (XRV, Z250, Miris) to 600 minutes (Gradia).
Conclusion:
In this study, the nanohybrid resin composites generally performed well, but not significantly better than the majority of microhybrids, suggesting that other factors such as filler shape and loading, filler material or resin constituents may also contribute to the retention of gloss.