The Citrate Content of Whole Teeth, Dentin and Enamel

Abstract

For a long time it has been appreciated that citrate is a constituent of milk and urine. With the development of more accurate and specific methods (1, 2) for the determination of citrate, this ion has been recognized as a constituent of many tissues and body fluids. The occurrence of citrate in the animal body has been reviewed by Smith and Orten (3). Scherst6n (4) has shown that there is quite a large amount of citrate in semen and in the secretion of the seminal vesicles, the concentration in semen being as high as 410 mg. per 100 cc. and in the secretion of the seminal vesicles as much as 633 mg. per 100 gm. which is comparable to the amounts of citrate found in milk and in alkaline urine. These observations have been extended by Huggins and Neal (5) who found in 9 samples of human prostatic fluid, citrate concentrations ranging from 480 to 2688 mg. per 100 cc. Dickens (6) discovered that bone contains a very large amount of citrate, the concentration ranging from 272 mg. per 100 gm. up to as high as 1660 mg. per 100 gm. in dried powdered bone. This investigator isolated both the pentabromoacetone derivative of citric acid and pure citric acid from bone meal. The present report describes studies made of the occurrence of citrate in whole teeth and in separated enamel and dentin. EXPERIMENTAL Twenty sound human teeth of different varieties were cleaned of all organic debris and were dried in an oven at 100°C. These dried teeth were then ground in a steel mortar so that the material had the consistency of a powder. This powder was analyzed for citrate according to the method described below. Three large canine teeth from a dog were treated in a similar manner.To determine citrate on the pooled whole teeth a 50 mg. sample was suspended in 50 cc. of 10% trichloroacetic acid to which 3 cc. of 50% sulfuric acid were added. This mixture was heated to boiling with a resultant solution of the ground tooth powder, and the solution was then analyzed for citrate by the colorimetric method of Pucher, Sherman and Vickery (2).Separation of enamel and dentin was accomplished by the method of Brekhus and Armstrong (7). The separated dentin and enamel were dried and analyzed by the same method used for the whole ground teeth.The results of the citrate analyses on the teeth are summarized in Table I.

The Effects of Age and Fluoride Exposure on Fluoride, Citrate and Carbonate Content of Human Cementum

“…This dry weight value is highly consistent with the findings for human dentin. 35,37,39,42 For example, Zipkin and Gold 37 reported mean citrate content of 0.88% for 194 samples of human dentin. The only published data on citrate content of human cementum appear to be those of Brudevold et al, 24 who report dry weight values from 0.70-0.80%.…”

“…In teeth the citrate content of human permanent enamel is about 0.1% 35 37 and of dentin about 0.9% [35][36][37]38 on a dry, fat-free basis. Data on fluoride-citrate relationships in teeth appear to be limited and equivocal.…”

The Important Role and Implications of Citrate in the Composition, Structure, and Function of Oral/Periodontal/Craniofacial Tissues

“…The typical concentration of citrate in bone ranges from ~20–100 μmols/gram (micromoles/gram tissue weight); as compared to most other tissues in which the citrate concentration is ~0.2–0.4 normalμmols/gram [3, 4]. When adjusted for tissue water content (Table 1), bone contains ~25–75 fold higher citrate than most other tissues.…”

“…In 1943, Free [ 4 ] reported that animal and human teeth and periodontal tissue contained high citrate levels; due to the high citrate concentrations in dentin and cementum. In contrast, enamel contains low citrate concentration.…”

“…In dealing with such issues the dental community must recognize the important role and implications of citrate relating to the composition, structure, and function of the oral/periodontal/ craniofacial tissues. Although the presence of high citrate levels in bone and in teeth has been known since 1941–1943 [ 3 , 4 ], it has been ignored by the medical and dental community for the past ~40 years. Notably, citrate in bone and teeth is not mentioned in most contemporary textbooks and reviews; and it is not presented in lectures to medical and dental students, or to postgraduate students.…”