Surface Properties of Resin Composites and CAD/CAM Blocks After Simulated Toothbrushing

Four resin composites with different filler particle size (Gracefil Flo [GFF, 0.7 μm], Gracefil LoFlo [GFL, 0.25 μm], Gracefil ZeroFlo [GFZ, 0.15 μm], and Gracefil Putty [GFP, 0.3 μm]), two CAD/CAM resin composite blocks with different filler particle size (Cerasmart 300 [CS3, 0.7 μm] and Cerasmart Prime [CSP, 0.3 μm], GC), and one CAD/CAM lithium disilicate glass-ceramic block (Initial LiSi Block [ILS], GC) as a control were evaluated. Twenty slab-shaped specimens were obtained from each material. Ten specimens were subjected to 80,000 toothbrushing strokes and measured for surface gloss (Gloss Unit, GU), surface roughness (Ra, μm), and color (L*, a*, and b* values) before toothbrushing and at every 20,000 strokes. Color differences (ΔL*, Δa*, Δb*, and ΔE₀₀) before and after toothbrushing were calculated. After 80,000 strokes, abraded surfaces were observed using scanning electron microscopy. The other 10 specimens were measured for Vickers microhardness (VHN).

Results

After 80,000 toothbrushing strokes, the mean GU ranged from 60.43 to 16.12 (the highest for ILS and lowest for GFL), and the mean Ra ranged from 0.079 to 4.085 (the lowest for ILS and highest for GFL). At all measuring stages, the calculated ΔE₀₀ values ranged from 0.31 to 0.92 for all materials. The mean VHN ranged from 632.34 to 39.08 (the highest for ILS and lowest for GFZ). The resin composite containing the largest filler particle (GFF) showed significantly lower Ra and higher VHN than other resin composites (GFL, GFZ, and GFP). The CAD/CAM resin composite block containing a smaller filler particle (CSP) retained significantly higher GU than that containing a larger filler particle (CS3). A negative correlation between GU and Ra was detected.

Conclusions

Based on the findings, toothbrush abrasion induced a decrease in GU and an increase in Ra for all resin-based materials tested. Resin-based materials with larger filler size tended to show lower Ra, while resin-based materials with smaller filler size tended to show a smaller reduction in GU. These were more pronounced for light-cure resin composites than for resin composite blocks for CAD/CAM.

Figure 1.

Scatterplot showing a correlation between average surface gloss (Gloss Unit, GU) and average surface roughness (Ra, μm) of tested materials after 20,000-80,000 toothbrushing strokes. Here, a significant negative correlation is observed.

Figure 2.

Scanning electron microscopy images of each tested material at magnifications of 100×, 1000×, and 10,000× after 80,000 strokes of toothbrushing. Abbreviations: Direct resin composites: GFF (Gracefil Flo), GFL (Gracefil LoFlo), GFZ (Gracefil ZeroFlo), and GFP (Gracefil Putty); CAD/CAM resin composite blocks: CS3 (Cerasmart 300) and CSP (Cerasmart Prime); CAD/CAM glass–ceramic block: ILS (Initial LiSi Block).

Figure 3.

Scanning electron microscopy image showing the size and shape of the dentifrice particles (1000×).

Figure 4.

Bar graph showing mean (SD) values of the Vickers Hardness Number (VHN) of tested materials. *Indicates no significant difference (p≥0.05). Abbreviations: Direct resin composites: GFF (Gracefil Flo), GFL (Gracefil LoFlo), GFZ (Gracefil ZeroFlo), and GFP (Gracefil Putty); CAD/CAM resin composite blocks: CS3 (Cerasmart 300) and CSP (Cerasmart Prime); CAD/CAM glass-ceramic block: ILS (Initial LiSi Block.)

Contributor Notes

*Corresponding author: 1-8 Hamaura-cho, Chuo-ku, Niigata, 951-8580, Japan; e-mail: collagen@ngt.ndu.ac.jp

Accepted: 30 Apr 2023