Dr. Shahzadi Tayyaba Hashmi DNT 353 STEPHEN CURVE Dr. Shahzadi Tayyaba Hashmi

STEPHEN CURVE First described by Robert Stephen in 1943 Stephen curve is a graph plotted on pH level against time This graph will show the food intake will reduce pH level in the mouth to a level bad for teeth and then rises again with time Stephen curve shows how the pH level at neutral in the mouth is 7 and every time it drops below 5.5 and is seemed to be critical and acid attack happens

PRINCIPLE OF STEPHEN CURVE To assess the cariogenecity of different foods Represents the change of plaque pH over a period of time SIGNIFICANCE OF RESEARCH: Frequency of food intake is important which determines cariogenecity Total amount of food intake is not important

PRINCIPLE OF STEPHEN CURVE Relationship of food intake with PH level with respect to time

GRAPH DESCRIPTION The graph shows a pH below the critical level of 5.5 at which demineralization of enamel occurs following the intake of fermentable carbohydrates, acids and liquids After consumption, there is an elimination of acid, and return to normal saliva or plaque PH, at which repair of any destruction of enamel structure takes place (remineralization)

CRITICAL pH Critical pH: The critical pH is the pH below which enamel will begin to dissolve For enamel, critical pH is between 4.5-5.5 moles/L

STEPHEN CURVE Gradually over the following 30 minutes, the PH of the mouth begins to return neutrality and dissolving of enamel stops and products of saliva can begin to remineralize any dissolved enamel