Potassium nitrate is known to interfere with the nerve impulse and is commonly found in desensitizing toothpaste.19 Potassium nitrate products raise the extracellular potassium ion concentrations and affect polarization. When the concentration is sustained over time, the synapse between nerve cells is blocked, the nerve excitation is reduced and the tooth is less sensitive to the stimuli. A number of studies, published since the early seventies, have investigated the use of potassium nitrate (KNO3) as an effective active ingredient in treating dentinal hypersensitivity.20-34
A four-week exposure time is widely used in these clinical trials because results have shown that this time is needed for 5% KNO3 to exert its desensitizing effect.23 The use of a broadly accepted positive or negative control toothpaste formulation or product has been increasingly used over the years in comparative trials because the condition itself can appear to be self-resolving within the time scale of the study. Over time, investigators have chosen various methods to capture subjective responses; controlled reproducible stimuli and objective measurements are preferred.
In 2006, the Cochrane Collaboration published a systematic review26 of potassium nitrate toothpastes for the treatment of dentinal hypersensitivity based on clinical trials conducted up to the year 2005 involving KNO3 toothpaste compared to non-KNO3 toothpaste. This review focused on studies that incorporated similar methods in order to determine if KNO3 is an effective agent in reducing dentinal hypersensitivity. The results were obtained by measuring tactile (Figure 5), thermal, and air blast stimuli as well as patients’ subjective assessment of pain during everyday life. The exposure periods ranged from six to eight weeks, reporting outcome measurements as a mean change from baseline.
The meta-analysis included six studies,27-32 and all showed a significant effect on sensitivity assessed by air blast and tactile methods at the 6 to 8 week follow-up. However, there was no significant effect observed at the 6 to 8 week follow-up for the subjective assessment. The authors concluded the support for the efficacy of potassium nitrate toothpaste for dentinal hypersensitivity was based on a very small sample size, thus evidence of the effectiveness of KNO3 is not clear, suggesting more clinical trials need to be conducted and published. There is no current research published to support a different conclusion than what is stated above even though new product lines are being marketed.
Some products that contain potassium nitrate include Sensodyne ProEnamel®, Crest® Sensitivity, Crest Sensi-Relief Plus Scope Toothpaste, Colgate® Sensitive Pro-Relief Enamel Repair Toothpaste, Arm & Hammer® Advanced Whitening Sensitive, Tom’s of Maine™ Maximum Strength Sensitive and Opalescence Whitening Sensitivity Relief Toothpaste.