See I would think that having business knowledge would be more helpful there (MBA, running a small business) instead of having a DDS. You don't really need to know all the basic science knowledge or all the procedural knowledge to give advice in the business sense. I think that practice owners should be restricted to dentists, but I don't think that you need the nitty gritty science knowledge to give advice on business models. You'd probably know all you need to know from actually working in the field with dental practices instead of going through 4 years of dental school. Dental school doesn't teach you how to run a practice. It teaches you dentistry. Maybe the DDS/JD would help you relate to dentists more since you're one of them, but it'd still be 4 years wasted and a whole bunch of loans if you wanted to work as a lawyer.
Now if you were suing dentists for malpractice, that's an entirely different story, but I think medical malpractice is a bigger business, so an MD/JD combo would be more useful in that sense.