Professional In-Office Whitening is a highly effective method performed by a professional. It involves applying a bleaching agent directly to the teeth and activating it with a special light or laser. The process usually takes about an hour, and multiple sessions may be required for optimal results. With Over-the-Counter Whitening Products, your average whitening toothpastes, whitening strips, and whitening gels are  available at drugstores or online. These products contain lower concentrations of bleaching agents compared to professional treatments. While they can provide some improvement, the results may be less significant and take longer to achieve.