The agony of root canal surgery and the need for tooth fillings could soon be ended after scientists discovered a way to make a rotting tooth repair itself using a laser beam. Just five minutes under a laser was enough to kickstart the healing process inside the mouth, the researchers found. The new technique—although only tested on rats so far—could prevent the need for fillings for some types of decay, and may eventually replace painful and expensive root canal treatment. Researchers, which included experts from the US government’s dental research team, found a blast of intense light from a laser...