Obviously Ballos was an exemplar, known for having the brightest whites in all the kingdom. That's why they adored him, more than their king. The king, enraged that he couldn't find anything that could outmatch the power of white teeth, decided he would have no choice but to throw Ballos in prison, where he and his white teeth would be tucked away forever. And just to kick a man while he was down, the king ordered Ballos to be punished brutally and cruelly until Ballos would finally give in. But no matter how many times the king commanded Ballos' teeth be punched out, they remained perfectly in tact. No one would ever live to have whiter teeth than him.
(Yeah, I know that theory is blatantly flawed in some way, but that was fun to write while it lasted.
)
Of course, how would you know that the whites inside Ballos are teeth? Surely he could have worn dentures, having lived those hundreds of years. Or maybe, when he opens his mouth, it's just white inside. Like a light void with empty space within his mouth.