Process at the dentist. Dentists use products that contain a much higher concentration of whitening ingredients. While at home products may use around 3% whitening ingredients, dentists can use from 15% to 43%. To protect the gums from this higher solution they may use a protective gel or rubber shield. Along with the whitening solutions, dentists use heat, light, or a combination of both to speed up the process. To obtain teeth that are up to eight shades brighter it may take several office visits, each from half an hour to an hour long. Getting your teeth whitened by a dentist can give you instant results and guarantees that you get proper care for your teeth.