Determining the efficacy of potassium oxalate containing strips to reduce dentinal fluid flow in situ

It is believed that dentine hypersensitivity is caused by a stimulus being applied to exposed dentinal tubules resulting in a transient pressure change, inducing movement of fluid in the tubules and subsequent activation of mechanoreceptors with a correlated pain sensation. This study aimed to use a flow cell model to measure the efficacy of a potassium oxalate containing gel strip in occluding dentinal tubules before and after housing within the oral environment. Dentine discs 1mm thick (n=40) were sectioned from whole human molars, and the hydrodynamic flow of fluid through the dentinal tubules in a 0.32cm2 sealed window was recorded at 206kPa. Flow rates were measured at baseline and post 10 minute treatment with a gel strip containing 3.14% potassium oxalate or no treatment. One treated and one un-treated dentine disc were separately housed in palatal appliances and worn by 20 healthy participants for 14 days, after which the flow rate of the samples was re-measured. Treatment with the potassium oxalate containing strip reduced flow rate from 68.0µl/min at baseline to 29.3µl/min which was highly significant (Wilcoxon Signed Rank Test, p<0.0001), following housing in the oral environment the flow rate was further reduced to 3.7µl/min. The flow rate of the non-treated discs reduced from 103.2µl/min at baseline to 16.0µl/min after oral housing which was also highly significant (Wilcoxon Signed Rank Test, p<0.0001). Following exposure to the oral environment, flow rates were compared using analysis of covariance for split mouth, placebo-controlled design. The discs pre-treated with the potassium oxalate containing strip provided significant reduction in flow rate when compared to the non-treated discs with estimated median of 3.6 and 10.5, respectively. This model was effective in showing the occluding potential of potassium oxalate containing strips in reducing fluid flow through dentinal tubules following treatment, as well as following 14 days of exposure to the oral environment.