Table 3.
Color Stability Values Converted to National Bureau of Standards (NBS) Unitsa
| Wire Type |
Mean ΔE* (Standard Deviation)b |
NBS Unitsc |
| PEEK alone | 11.47 (0.19) | 10.55 |
| SS wire covered with the PEEK tube | 8.82 (0.4) | 8.11 |
| Nano White | 8.59 (0.38) | 7.90 |
| Ever White | 7.04 (0.15) | 6.47 |
a
PEEK indicates polyether ether ketone; SS, stainless steel.
b
The total color differences (ΔE*) values were calculated according to the formula ΔE* = ([ΔL*]2 + [Δa*]2 + [Δb*]2)1/2, which represents the color difference between VITA A1 and each archwire.
c
NBS units = ΔE* × 0.92. The definitions of color changes quantified by NBS units were used.