A: 6.5 grams of Xylitol each day has been shown to eliminate harmful bacteria in about 5 weeks. ...
And what other bacteria does it kill off? Since they're recommending it in pill form, it seems highly unlikely it's just affecting "bad" mouth bacteria.
Still - "consuming x grams" != "keep a ratio of X in mouth at least Y minutes per day". If consumption is what matters, how does it work?
I don't think it's that Xylitol kills off bacteria, just that it makes it more inhospitable. To be fair, it should still be cause for worry; while some bacteria do cause acid production that can lead to tooth decay, other bacteria are part of our immune system. There is little reason to suspect that a mouth inhospitable to bad bacteria would still allow the good bacteria to thrive.
edit: here it is http://www.ncbi.nlm.nih.gov/pubmed/783060
The suggestions are interesting, and I might look into them more carefully, but it has seriously tripped my they're-using-overly-religious-reasoning alarm.