>>3196984A very quick cheap fix would be to get a clip-on macro lens for your phone. As for point-and-shoot cameras, the Coolpix line of Nikon cameras have a macro mode I can personally attest to being really good. However, the working distance is really short, which can be a problem in someone's mouth (something I don't know about with the clip-on macro phone lens). As for a DSLR, the Nikon D3400 plus its 18-55mm kit lens with a reverse ring and aperture adapter will work well. You get macro + a working distance that's outside the person's mouth. Keep in mind, that I think most DSLR's using a reversed lens will work fine for this.
