Material and Methods: This in situ study utilised a single blind 4-day, 4-cell, split-mouth crossover design in 2 phases. Subjects wore 2 removable lower buccal appliances each holding four human dentine samples and the treatment regimens were a) strontium containing gel applied topically with finger, b) strontium containing gel applied with brushing, c) water applied topically with finger, and d) water with brushing. In phase 1, each group of dentine samples underwent twice daily treatments. Two dentine samples were removed from each side of the appliance at daily intervals. Tubule occlusion was scored using a visual 5-point categorical scale (1=Complete occlusion to 5=No occlusion) from scanning electron micrographs of dentine surface. Mean occlusion classification scores (MOC) from 3 independent examiners were analysed by an ANOVA. In phase 2, strontium uptake and release from the dentin was followed using Atomic Absorption spectroscopy after a single treatment application at 1 min, 4 and 8hrs of exposure to the in situ environment. Results: In phase 1, at day 4, MOC scores were a=3.9, b=3.9, c=4.4 and d=4.5. Analyses revealed significantly more occlusion with the novel gel either topically applied or with brushing compared to water applied topically or water with brushing. In phase 2, dentine strontium uptake (µg/mm2) after 8 hours was a) 0.26 b) 0.25 c) 0.05 and d) 0.04. Conclusions: This in situ study showed that the novel strontium containing desensitising gel (with or without brushing) provided greater occlusion than water (with or without brushing) and that significantly increased levels of strontium are still retained in the dentin in the oral environment, 8 hours after treatment application.