Comparison of light transmittance and color changes between polyurethane and copolyester retainer materials after staining and destaining

Table 1 Criteria of the National Bureu of Standards (NBS) units. Note that a value above 3 is considered of clinical significance in the study

NBS nits	Critical Remarks of Color Differences
0-0.5	Trace	Extremely slight change
0.5-1.0	Slight	Slight change
1.5-3.0	Noticeable	Perceivable
3.0–6.0	Appreciable	Marked change
6.0–12.0	Much	Extremeley marked change
12.0 or more	Very much	Change to orther color

ISSN: 1472-6831