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Effects of Food Acids on Human Teeth in Vitro

Many studies have been made comparing the effects of acids on human teeth with varying results. To clarify what happens to the enamel of teeth, three food acids and two liquids commonly consumed by humans were tested. A 0.055% solution of phosphoric acid (the concentration in a cola beverage) a 0.1 M solution of citric acid (simulating orange juice), and a 0.05 M solution of oxalic acid (representing spinach and some other vegetables) were used. Also included were a cola beverage and orange juice. Human teeth were cut in half vertically with a Gillings-Hamco thin sectioning machine. The plane of sectioning was chosen to provide similar sections for each half. A fine blade was used so that a minimum amount of material was lost in the process. To duplicate the conditions in the mouth more closely it was necessary to coat the root area of the teeth with paraffin. This left only the enamel exposed to the acid. A different color paraffin was used for each of the test solutions as a means of identification. Half of each tooth was then placed in 15 ml of distilled water in a 25 ml stoppered tube and the other half in 15 ml of the acid solution being tested. Eight pairs were tested because the probability of all eight being equally affected by the acids, on the null hypothesis, is 1/256 or 0.0039. Five solutions were used and this meant 40 teeth or 80 halves.