Yes, it is possible to use knitting yarn as a way of flossing. One of the things to keep in mind is that only synthtic yarn is recommended. Other types of yarn such as wool, can damage the gums. It can be used around and in between bridges, teeth with wide spacing, and teeth with exposed roots.
References:
(1) Redirect Notice. (n.d.). Google. Retrieved December 9, 2011, from http://www.google.com/imgres?um=1&hl=en&biw=1280&bih=705&tbm=isch&tbnid=XCT3zTYdPf2hCM:&imgrefurl=http://
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