While doing some online research I came across the Dine Mini Macro Flash, which appears to be some sort of SB-400 conversion to provide closeup ring-type TTL for recent Nikon bodies. Haven't tried it myself yet, but it does seem like an interesting variant, even if it is a bit pricey. Dine has been selling to dentists for as long as I can remember--my childhood dentist had one of their early units.