A wash-out period between the cycles of 21 days will be performed. In the second "late" phase, a long-term subjective evaluation of dental discoloration will be obtained by means of the visual analysis of clinical photograph and new questionnaires. After 6 months from clinical trial (second stage of the study), frontal dental images of volunteers, collected during the first phase, will be printed on photographic paper and, then, visually analyzed, in blind, by the 22 volunteers themselves, as well as by 14 dentists and 13 oral hygienists ad hoc recruited. Dentists and oral hygienists, in particular, will be asked to observe two images of all the 22 subjects, i.e. after treatment with A or B mouthwash, and to answer to the question: "Which picture shows the most pigmented teeth?" Possible answers will be: "A, or B or no difference between the two images". Pigmentation will be also quantified using the numeric scale (0= no pigmentation to 10=strong pigmentation).