The citric acid content of human teeth.

Abstract

THE citric acid in the soft tissues and body fluids has been quite adequately I studied, 2 but less attention seems to have been paid the calcified tissues. Dickens3' 4 showed that 70 per or more of the citric acid in various animals is in the bones and may amount to 1000 mg. per of dry, fat-free bone. The citric acid of rats' bones was reported by Class and Smith5 to be 0.616 per and Nicolaysen and Nordb06 found 0.50 to 0.66 per cent. Thunberg7 reported that the bones of birds and fish contained large amounts of citric acid, i.e., 2.63 per and 2.67 per in the scapula and sternum, respectively, of the black-headed gull, 5.25 per in the spine of the herring, and an average of 4.25 per in the bones of other species of fish. According to Thunberg,' 9,10 egg shells may contain 0.03 to 0.35 per citric acid. MArtensson found 0.11 to 0.35 per citric acid in renal and vesical stones; three salivary concretions contained 0.58, 0.11, and 0.00 per citric acid, and two arthroliths from a knee joint contained 0.53 per and 0.40 per citric acid, but no citric acid was found in gallstones. Information on the citric acid of bones of domestic animals and man is meager. Thunberg12 determined the citric acid in the bones of horses, cattle, and man of the thirteenth and sixteenth centuries and found 0.9 to 9.3 per cent, 2.2 to 3.4 per cent, and 0.7 to 1.8 per citric acid, respectively. Attempts to correlate the age of the specimens with their citric acid content were accepted with reservation. Thunberg7 reported the femur, clavicle, rib, and vertebra of man to average 1.62, 1.88, 1.75, and 0.89 per citric acid, respectively. Data on the citric acid of teeth appears to be limited to the work of Thunberg8 who reported about 0.5 per cent in the teeth of cats, cattle, and swine, and to Free13 who found 540 mg. per and 110 mg. per in dog's dentin and enamel, respectively. The only report on human teeth appears to be that of Free3 who found 800 mg. per and 90 mg. per in the dentin and enamel, respectively. It appeared of interest, therefore, to add to the data of Free13 on human teeth and particularly to determine if any relation might exist between the citric acid content and the past dental caries history.