There are differences between the two teeth whitening productes, including:
 
Strength of bleaching agent. Over-the-counter home use products and dentist-supervised at-home products usually contain a lower strength-bleaching agent from 10% carbamide peroxide, which is equivalent to about 3% hydrogen peroxide, up to 22% carbamide peroxide. In-office, professionally applied tooth whitening products contain hydrogen peroxide in concentrations ranging from 15% to 43%.

Additional protective measures. In the office setting, your dentist will apply either a gel to the gum tissue or use a rubber shield, which slides over the teeth, previous to treatment to protect your gums and oral cavity from the effects of the bleaching. Over-the-counter products don't provide these extra protective measures.

Mouthpiece trays. With dentist-supervised at-home bleaching products, your dentist will take a print of your teeth and make a mouthpiece tray that is adapted to accurately fit your teeth. This customization allows for maximum contact between the whitening gel, which is applied to the mouthpiece tray and the teeth. A custom-made tray also minimizing the gel's contact with gum tissue. Over-the-counter whitening products also contain a mouthpiece tray, but the "one-size-fits-all" approach means that the fit will not be exact. Ill-fitting trays can irritate the gum and soft tissue by allowing more bleaching gel to seep onto these tissues. With in-office procedures, the bleaching agent is applied directly to the teeth.

Supervised vs. unsupervised process. Dentist-supervised at-home bleaching and in-office treatments offer additional benefits corresponding to over-the-counter procedures. Initially, your dentist can perform an oral examination and consider your complete medical history, which can be helpful in determining how your teeth became discolored and if bleaching is an appropriate course of treatment based on your type and extent of stains and type, number and location of restorations. After that your dentist can better match the type of stain with the best treatment, if appropriate, to lighten those stains. With dentist-supervised bleaching procedures, your dentist will likely want to see you a couple of times to ensure you are following directions, to make sure the customized tray is fitting properly, to inspect your gums for signs of irritation, and to generally check on how the teeth whitening process is proceeding. With over-the-counter bleaching products, you are on your own.

Costs. Over-the-counter bleaching systems are the least expensive option, with costs ranging from $20 to about $150. Depending on where you live and the extent of the procedure, dentist-supervised home bleaching systems range in cost from approximately $150 to $300 per upper or lower set of teeth, or $300 to $600 for the whole mouth.