Touch-up whitening refers to periodic treatments to maintain the brightness of teeth after the initial whitening. These can be done using at-home kits, whitening strips, or in-office procedures. Clients should be advised to schedule touch-ups regularly based on their lifestyle and diet to keep their smile bright. This is particularly important for clients who consume staining foods and drinks or smoke. Regular touch-ups help maintain the whitening results and prolong the effects of the initial treatment.