Assertion: fluoride's level | /r/HasProperty | 4.5-10 ppm
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Source sentences:
text: In the same article, water fluoridation within the acceptable levels of 0.7-1.3 ppm has been shown to beneficial to dental hygiene, with dental fluorosis and skeletal fluorosis only occurring at much higher levels (4.5-10 ppm for dental, and approximately 10 times higher than that for skeletal).