Once whitened, the teeth generally remain stable but can dull back after a period although usually staying whiter than what they started. The frequency of factors likely to darken the teeth like smoking, coffee, tea, red wine, and cola can all accelerate this process. The good news is that use of a few touch up applications of tooth whitening gel in a tray is usually more than sufficient to bring your smile back up to full brightness again. Typically many of our patients consider purchasing some refill whitening syringes 1-3 years following completion of their original teeth whitening treatment.