Osmotic stimulation of human dentine and the distribution of dental pain thresholds

Abstract

It has been established that there is a relationship between osmotic pressure and pain-producing power when CaCl 2 solutions in the range 200–2800 atm are applied to dentine ( Anderson and Ronning, 1962). Experiments have been performed in an attempt to explain previous failure to confirm this relationship with other solutions. The experiments fell into two groups: those with solutions in the range 25–700 atm and those in the range 200–2800 atm. A decline in sensitivity during an experiment was observed as previously but was found to be caused only by solutions in the high range of osmotic pressure. Because of this decline in sensitivity, only the first results of every sequence of stimulations with the high range of osmotic pressures is comparable with results from the low range of osmotic pressures. Comparable data over the entire range of osmotic pressures 25–2800 atm was obtained by selecting only the first results of every series in the high range and using all the results in the low range of osmotic pressures. When this selection was made, the points on a graph of pain-producing power and log osmotic pressure fell on a sigmoid curve. This curve can be considered to represent the distribution of pain thresholds within the group of subjects, defined in units of log osmotic pressures. Probit transformation has shown that this distribution is normal (Gaussian). Osmotic pressure can therefore be taken as the effective stimulus common to all the solutions used in evoking pain from dentine.