An in situ Study Investigating Sub-Surface Dentine Tubule Occlusion of Dentifrices following an Acidic Challenge

This in situ study aimed to evaluate the depth of penetration and constituents of deposits formed within dentine treated with desensitising dentifrices designed to occlude dentine tubules; one containing 8% strontium acetate, 1 040 ppm sodium fluoride (Sen-sodyne ® Rapid Relief) and the other containing 8% arginine, cal-cium carbonate, 1,450 ppm sodium monofluorophosphate (Col-gate Sensitive Pro-Relief ® ) to negative control paste and water. This clinical study was a single-centre, randomised, crossover, sin-gle blind design. Twenty-eight healthy participants wore two intra-oral appliances each retaining four human dentine samples for two periods of four days. Samples were power brushed twice daily with test products and subjected to an agitated grapefruit juice acid challenge on days three and four. Eighteen dentine samples were randomly selected from those used in the study and were dry frac-tured. One half of each fractured sample was coated with carbon for EDX analysis and the remaining half gold coated for SEM im-aging. Imaging and analysis took place consistently from the cen-tre of each sample. Samples treated with 8% strontium on days one and two (pre-acid) and day four (post-acid) and samples treated with 8% arginine on day four (post-acid) revealed sub-surface de-posits covering 80% (SD 10%) of the dentine surface. These were statistically significant versus controls (p < 0.01). Tubule occlusion from tubule occlusion dentifrices occurred within 5 μm (SD 2 μm) of the dentine surface. The 8% arginine on days one and two and water and control paste on days one and four revealed no sub-surface deposits. Within the limitations of this study, cross-sec-tional SEM analysis suggests that the positive control dentifrices more likely demonstrated occlusion of tubules sub-surface in den-tine compared to negative controls. EDX analysis was insufficient-ly sensitive to detect the nature of deposits. The clinical component of this study was funded by Glaxo-SmithKline.