Objective. To compare the effects on enamel demineralization and fluoride (F) retention of two different brushing-rinsing regimens. Material and methods. An in-situ caries model with orthodontic bands was used for 8-9 weeks. A total of 20 orthodontic patients participated. They were randomized into two groups: (1) a test group using 5000 ppm F ( n = 10) with no post-brushing water rinsing; and (2) a control group using 1450 ppm F ( n = 10) with three sessions of post-brushing water rinsing. Orthodontic stainless-steel bands were applied to the two upper first premolars, leaving 2-3 mm of space away from the exposed buccal surface in order to accumulate plaque and provoke initial caries development. The teeth were extracted after 8 and 9 weeks, then analysed using quantitative light-induced fluorescence (QLF). Additionally, oral F retention was compared for the two groups. Results. In comparison to the control group, the test regimen resulted in a non-significant smaller QLF lesion area and a significantly lower average QLF loss of fluorescence ( P < 0.05). The highest F retention concentration under the band was found in the test group ( P < 0.001). Conclusions. The combination of using a 5000 ppm F toothpaste and no post-brushing water rinsing had a greater anti-caries potential and resulted in elevated oral F retention compared to a 1450 ppm F toothpaste with three sessions of post-brushing water rinsing. [ABSTRACT FROM AUTHOR]