Unless for a wall hanger, straightening bent alloy handlebars and then riding to any significant degree is foolhardy at best. Bars get bent generally for two reasons, a significant crash or long term metal fatigue (the dreaded droop) both of which should relegate the bars to the recycling bin. Compare the price of a pair of new bars to new teeth if you think I'm wrong (and that's if you only face plant...ever seen what happens when bars break while riding? I have, not pretty) and if you still want to straighten and use such damaged goods, I'll show you natural selection in action.