Dyson's new $499 toothbrush has a camera inside it, and the camera can't see through toothpaste foam. Which explains why Dyson is suddenly selling toothpaste. The camera is a 1mm macro lens with 100,000 pixels, tucked under the bristles. It shoots 28 frames a second into a model trained on 470,000 dental images, spots the gap between two teeth, and fires a jet of mouthrinse into it within 100 milliseconds. Flossing while you brush. Six years and 16 million lines of code to get there. Nearly…