Im sure there are dental records, but when you have a missing relative you want to obtain them ASAP so that they are available when needed, rather than try to track them down when remains are found. Of course, if he wore dentures, the same would apply I imagine.
Im not sure how it works either, but whoever was involved in giving info to NAMUS would have known to request both dental and DNA for speed of identifying remains. That should have been explained to the family. I cant imagine why they wouldnt comply. In fact, WS may have suggested it to the family friend posting on the first thread.
ETA: They set up the NamUs profile very quickly in February. In March and April I commented that it was a very weak profile and needed more information and photos added, including the Lands End Photo. I believe the friend was still around in March, so Im not sure why those things werent added.
http://www.websleuths.com/forums/search.php?searchid=7966922