Purpose: To compare the efficacy of a 2.5% w/w smaller particle-size (ca 4 µm) calcium sodium phosphosilicate (CSPS) dentifrice (test) to an occluding dentifrice (8% w/w arginine) (comparator) and a negative control dentifrice in an 8-week, randomised, controlled, parallel-group, stratified (maximum baseline Schiff sensitivity score) study in adults with dentin hypersensitivity. Materials and Methods: The sensitivity of two selected teeth was assessed at baseline and after 1, 2, 4 and 8 weeks in response to evaporative (air) (Schiff sensitivity score and visual analogue scale [VAS]) and tactile (tactile threshold) stimuli. Results: Of 151 randomised subjects, 147 completed the study. Statistically significant changes from baseline were reported for test and comparator dentifrices at all weeks on all measures (p 0.05) with no statistically significant differences between them. The negative control dentifrice group was statistically significantly different from baseline in all measures by week 8 (p 0.05). Test and comparator dentifrices demonstrated statistically significantly greater improvements in Schiff sensitivity from week 2 compared to the negative control (p 0.05). There was a statistically significant difference in favour only of the comparator dentifrice over the negative control at week 8 when examining tactile threshold (p = 0.0435) and at week 4 with VAS (p = 0.0425), with no other between-group differences. The dentifrices were generally well tolerated. Conclusion: No statistically significant differences were found between a small particle size 2.5% w/w CSPS dentifrice and an 8% w/w arginine dentifrice in terms of a dentine hypersensitivity decrease. Keywords: calcium sodium phosphosilicate, clinical trial, dentine hypersensitivity, NovaMin, particle size