Time-course of the Relief of Hypersensitive Dentin by Potassium Oxalate

Objectives: The outer ends of the tubules of hypersensitive dentin are patent, and the hypersensitivity can be relieved by sealing the tubules with calcium oxalate, precipitated from a solution of potassium oxalate. The objective is to determine the time-course of this desensitization.
Methods: The experiments were done on 10 premolars and 1 molar of 4 subjects (34-37yrs). Potassium oxalate (3%) was applied (3mins) to an area of hypersensitive, cervical dentin on each tooth, and rinsed off. The sensitivity of the dentin was tested with standardized mechanical, cold (5° saline), osmotic (6M CaCl₂) and air blast stimuli before (control), and at 0min, 30min, 60min, 1day, 3days and 7 days after treatment. The subject recorded the intensity of any pain produced by placing a mark on a 100 mm visual-analogue scale (VAS).
Results: Compared with controls, the median VAS recorded with each form of stimulus decreased significantly (P<0.05; Repeated Measures Analysis of Variance on Ranks; Dunnett's post-hoc) at each time following treatment except at 0min. The median VAS for mechanical, cold, osmotic and air blast stimuli decreased from 60, 80, 70 and 60 respectively for the controls, to 40, 30, 50 and 10 after 30min; 50, 20 20 and 10 after 60min; 10, 20, 40 and 30 after 1day; 20, 15, 20 and 15 after 3 days; and 10, 5, 15 and 10 after 7 days. After 0min the values were 60, 60, 55 and 40.
Conclusions: Oxalate treatment did not reduce the sensitivity of hypersensitive dentin as rapidly as it blocks fluid flow in the tubules and reduces the hydraulic conductance of dentin, which are immediate effects. Its effect on hypersensitive dentin must be due to some other consequence of tubule closure, such as a change in the composition of the dentinal fluid.