Assertion: electric toothbrush's bristle | /r/MadeOf | cheaper material
Facets:
Source sentences:
text: Bristles make contact with the tooth, and a bristle made of cheaper material will wear down quickly and become too sharp, scratching the enamel.
text: Quality of bristles: Bristles make contact with the tooth; a bristle made of cheaper material will wear down quickly and become too sharp, scratching the enamel.