Teeth-whitening kits available for retail purchase are demonstrably effective at reducing plaque buildup and returning teeth to their natural shade, but only for periods of about two or three months. They require additional purchases and application. Professional cleaning by dental hygienists, however, can be effective at reducing plaque buildup and improving tooth appearance for six months to a year. Thus, for people looking to improve the appearance of their teeth in the long term, retail teeth-whitening kits should play no part in maintaining dental hygiene.
The argument is most vulnerable to the objection that it fails to
【选项】
distinguish between effective and ineffective dental hygienists
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