Desensitizing toothpastes containing potassium nitrate have been used since the 1980s while toothpastes with potassium chloride or potassium citrate have been available since at least 2000. It is believed that potassium ions diffuse along the dentinal tubules to inactivate intradental nerves. However, as of 2000, this has not been confirmed in intact human teeth and the desensitizing mechanism of potassium-containing toothpastes remains uncertain. Since 2000, several trials have shown that potassium-containing toothpastes can be effective in reducing dentin hypersensitivity, although rinsing the mouth after brushing may reduce their efficacy.