http://www.snopes.com/cokelore/tooth.asp suggests that submerging teeth in any acidic substance (e.g. orange juice) will soften and eventually dissolve them. Since this does not adequately replicate conditions in the mouth, it would not be useful to determine how such substances affect enamel.
I don't see how "not adequately replicating mouth conditions" leads to "would not be useful to determine effect on enamel".
Yes, there will be significant differences between drinking Coke and soaking a tooth in Coke overnight. But that doesn't mean it won't provide a useful basis for comparison! Possibly even more useful than the arbitrary formula the author and dentist in the article came up with.
>But that doesn't mean it won't provide a useful basis for comparison!
Why bother? There are plenty of people out there who've been drinking coke for decades. All you need to do is compare their dental health to people who don't.
Perhaps a week is too much time.