Many factors may have come into why your teeth whitening didn't work as well as you hoped.
- The right product and concentration, and the proper method and duration, weren't chosen for your particular needs.
- Your trays were leaking, allowing the whitening product to leak out or saliva leak in and break down the product. Saliva actually breaks down your whitening product.
- The product degraded and was compromised by the conditions it was transported or stored in. By virtue of being a product designed to break down to work, whitening products are notoriously unstable.
- The product is expired.
- The product is too thick to be available to get into the tooth's microstructure.
- Your teeth have absorbed more organic long-chain stains, and it's time to whiten with a new method.