I was going to elaborate in my previous post, but I didn't think you'd be interested. Sorry!
You're right, the ordinary cap for graduate Stafford loans is $18.5k/year. Some professional programs are granted additional allowances, and dentistry is one of them. We're permitted an additional $20k/year in unsubsidized loans, up to a lifetime maximum of just a smidge under $190k for all government loans.