1.   More serious stains might require sanding, refinishing and rewaxing.

2.   Stains require repainting.

3.   Stubborn stains may require a stronger cleaning agent.

4.   The dentist should also ask about exposures that might account for the staining, since different stains may require different techniques.

n. + require >>共 1117
law 13.33%
rule 3.41%
bill 2.73%
plan 1.63%
regulation 1.59%
state 1.57%
agreement 1.50%
government 1.31%
job 1.25%
measure 1.18%
stain 0.03%
stain + v. >>共 94
be 36.96%
peel 4.30%
remain 3.72%
come 2.87%
go 2.58%
cover 2.58%
have 2.29%
appear 2.01%
spread 2.01%
disappear 1.43%
require 1.15%
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