Flash teeth whitening is a two-step, once-daily method for whitening teeth that combines the use of a fine aerosol mist of a stabilized, concentrated hydrogen-peroxide solution and a saliva-activated, effervescent oral powder that is poured directly onto the tongue. An in-vivo study was conducted to evaluate the efficacy and safety of the flash teeth whitening method at three timed intervals in a 3-week period. Objective and subjective tooth-shade rating methods were used at baseline, after initial treatment, and after 1 and 3 weeks of once-daily use. A significant whitening effect was observed. Data also indicated a progressively improved whitening effect, suggesting that sequential use may optimize the whitening results, with maximum whitening occurring between 1 and 3 weeks of once-daily use. The study demonstrated that flash teeth whitening effectively whitens teeth. This novel method is suitable for safe use as an out-of-office treatment as a primary whitener, or as a maintenance method for keeping whitened teeth white, offering dentists a potential alternative tooth whitening recommendation that is easy to use, safe, and effective and improves the condition of soft tissue when used as directed.