Nashville crooner with gleaming choppers tells MTV News he studied to be a dentist 'before all this rock-and-roll stuff.'By Gil Kaufman, with reporting by Kara Warner Paul McDonald Photo: Getty Images Nashville's Paul McDonald has quickly established himself as one of the more dynamic finalists in this year's "American Idol" top 13. From his sparkly Nudie-style suit to his Chris Martin-esque shuffling dance moves and thousand-watt smile, the raspy-voiced indie singer has carved out his own unique place amid the teen crooners and R&B stylists. Judge Jennifer Lopez has already commented a few times about McDonald's smile, telling him on Wednesday night's first top-13 performance show that his grin was infectious and spread to the audience during Paul's take on a Ryan Adams song. "I brush 'em once or twice a day, I try to keep them decent," he smiled last Thursday at the afterparty for the top 13.