Effect of Polishing and Simulated Tooth Brushing on Composite Surfaces

Objectives: Evaluate the effect of four polishing systems on surface roughness and gloss, plus the impact of tooth brushing on the polished surfaces of two composite resins with spherical filler particles and a control.

Methods: Two nanohybrid composite materials with spherical filler particles, Kerr Harmonize (KH) and TPH Spectra ST (SST), and one microhybrid composite control, TPH Spectra (SP) were prepared (14mm-X-2mm discs) using an aluminum mold (n=120). Samples were finished with 600-grit wet silicon carbide paper to establish a baseline surface. Polishing of samples was performed with Green/Brown metal polishers (GB), Spiral SofLex (SS), DiaComp Feather Lite (DCFL), or Enhance Pogo (EP) polishing systems (n=10/group). Surface roughness (Sa) and gloss were measured at baseline and after polishing using a three-dimensional laser measuring microscope and a glossmeter. Similar measurements were made following tooth brushing with a slurry containing 170g Colgate Total toothpaste in 500ml RO water with an Oral B Indicator brush (200g dead weight, 10,000 cycles) to simulate the effect of wear.

Results: Sa value ranges after polishing were: KH, 0.14 with GB to 0.32 with EP; SST, 0.14 with DCFL to 0.22 with EP; SP, 0.15 with DCFL to 0.28 with EP. After brushing the same samples, the ranges were: KH. 0.11 with GB to 0.15 with EP; SST, 0.14 with GB to 0.21 with SS; SP, 0.14 with DCFL to 0.27 with SS. Gloss measurements showed lower values for EP and GB and higher values for DCFL and SS, both after polishing and after tooth brushing. There was only a moderate negative correlation between roughness and gloss (r = -0.48).

Conclusions: Simulated-brushing increased surface roughness and decreased gloss for all materials polished with EP, while other combinations either decreased or stayed the same. There was a moderate negative correlation between surface roughness and gloss.