Several previous studies using food consumption tables or diet records have estimated that children aged 1 to 12 years resident in fluoridated (1 ppm) areas receive, on average, between 0.05 and 0.07 mg fluoride/kg body weight from foods and drinks alone. In this study, the duplicate-diet approach, which is a more accurate method of determining nutrient intake, was used to determine if levels of fluoride intake from foods and drinks are similar to those estimated from food consumption tables or diet records. Duplicate portions of all foods and drinks consumed over 24 hours by 66 children aged 3 to 4 years resident in fluoridated and low-fluoride areas of New Zealand were collected on three separate days over a period of 12 months and analyzed for fluoride. Fluoride intake from the use and ingestion of toothpastes and fluoride supplements was also determined for each child. It was hypothesized that the total amount of fluoride received by children in low-fluoride areas from diet, toothpastes, and fluoride supplements was similar to that received by children in fluoridated areas from diet and toothpastes. The mean fluoride intake from foods and drinks alone in the low-fluoride areas was 0.008 ± 0.003 mg/kg body weight (0.15 ± 0.06 mg/day; n = 34) and in the fluoridated areas was 0.019 ± 0.009 mg/kg body weight (0.36 ± 0.17 mg/day; n = 32). The mean fluoride intake from foods and drinks and toothpastes in the low-fluoride areas was 0.027 ± 0.012 mg/kg body weight (0.49 ± 0.25 mg/day) and in the fluoridated areas was 0.036 ± 0.015 mg/kg body weight (0.68 ± 0.27 mg/day). Fluoride intake from diet alone did not exceed 0.04 mg/kg body weight (0.74 mg/day), and fluoride intake from diet and toothpaste did not exceed 0.07 mg/kg body weight (1.31 mg/day). The results suggest that levels of fluoride intake from foods and drinks alone as estimated by the duplicate-diet approach are much lower than previously estimated from food consumption tables or diet records. It was calculated that if all children in the low-fluoride areas were to take currently recommended dosages of fluoride tablets, which have been based on dietary surveys and diet records, then the total fluoride intake of some children in the low-fluoride areas would exceed that of their counterparts in the fluoridated areas. The results suggest that currently recommended dosages of fluoride tablets need to be further reduced if dental fluorosis in children is to be avoided.

Fluoride analyses of baby foods were carried out using a microdiffusion technique, which was found to be reproducible and accurate with less than 8% error. Analysis of 113 baby foods and drinks showed a wide range of fluoride concentrations: 0.01-0.31 mg F/kg for baby milk products; 0.04-0.72 mg F/kg for meat products; 0.04-0.70 mg F/kg for cereals; 0.03-0.48 mg F/kg for vegetable products; 0.03-0.07 mg F/kg for fruits; 0.02-0.28 mg F/kg for desserts, and 0.01-0.51 mg F/l for baby drinks. None of the baby foods and drinks contained fluoride of a sufficiently high concentration to be of concern or likely to contribute to enamel mottling, when used in the normal way.

Enamel formation (amelogenesis) in the human dentition begins in utero. The process has been investigated widely in the primary dentition in animals, and to a much lesser extent in humans. Studies have confirmed that amelogenesis occurs in distinct stages. 1 Each of these stages may be affected by extreme systemic physiological changes with hypoplasia, hypomineralization, or opacities of enamel. Mineralization begins at 15-21 weeks in intrauterine life in the incisor teeth, at 19-22 weeks in the canines, and at 16-22 weeks in the molars. Major disturbances before, or in the early period after birth may be reflected in the enamel of the primary dentition. Skeletal mineralization in utero is maximal in the last trimester. Of the 30 g of calcium typically present in the term infant’s skeleton, 25 g will be laid down in this trimester. Calcium is deposited chiefly as hydroxyapatite. The higher rate of calcium accretion during this period of calcium deposition in the skeleton, and part of the period of enamel calcification of the primary teeth overlap. Following premature birth the infant is unable to match the intrauterine accretion rate of calcium, which predominantly resides in the skeleton. Indeed calcium intakes often only average 75 mg/ kg/day, compared with the in utero accretion rate of 120-150 mg/kg/day. The level of skeletal mineralization can be assessed using photon absorptiometry at a single peripheral skeletal site. 2 This technique has demonstrated that infants of fewer than 32 weeks gestation at birth have gross reductions in bone mineral content (BMC) upon reaching full-term when compared with those born full-term. ~ Reductions in BMC have been found to be approximately 40-50% when related to age. Enamel defects in primary teeth have been described in preterm infants and have been linked to disorders of calcium metabolism, particularly to premature neonatal hypocalcemia, Vitamin D dependency rickets, or hypoparathyroidism.4, 5 A study of 106 children born prematurely found enamel hypoplasia in 37%, chiefly in the maxillary incisors. 6 Seow et al. 7 showed that in very-low-birth-weight (< 1500 g) prematurely born children, the prevalence of enamel hypoplasia was 62.3%, and 27.3% in low birth weight (1500-2500 g) children, compared with 12.8% in controls. No one factor could be related to the primary tooth enamel hypoplasia, but laryngoscopy and orotracheal intubation also may contribute to developmental defects of the upper anterior primary teeth. 8-11 Early hypocalcemia is a poor guide to neonatal calcium homeostasis, since it is almost universal in preterm infants and is also temporary in nature. The question arose as to whether enamel defects -namely defects in dietary mineral supply -are related to osteopenia of prematurity, and whether a measure of the degree of osteopenia could be used to predict enamel defects. The purpose of this present study was to examine the relationship between enamel defects in the primary dentition and BMC in premature infants.

Eight adults ingested five different toothpastes with and without 1,000 ppm (1 microgram/g) fluoride added as NaF or Na2PO3F. The systemic fluoride absorption was estimated by by comparing the areas under salivary fluoride concentration curves produced after the toothpaste ingestion. Of the toothpastes investigated--chalk, dicalcium phosphate dihydrate, silica or alumina with sodium monofluorophosphate, and silica with sodium fluoride--the fluoride absorption was found to be statistically significantly lower only from the dicalcium phosphate dihydrate toothpaste. Measuring changing fluoride levels in saliva appears to be an acceptable non-invasive technique for following systemic fluoride absorption.

The absorption and excretion of fluoride in a group of 25 infants (<6 years of age) were followed for up to seven hours after the ingestion of a known quantity of either sodium monofluorophosphate alone in solution, or toothpastes with sodium monofluorophosphate and an abrasive of either hydrated silica or dicalcium phosphate dihydrate. Fluoride appeared to be well-absorbed based on the excretion patterns found. From the results, it was concluded that parents of pre-school-aged children should now be given appropriate advice regarding their children's use of fluoride toothpaste. Such use of fluoride toothpaste should be closely supervised by the parents, and only a smear of paste, about the size of a pea, should be used, particularly where fluoride supplements are used. Because of the likelihood of toothpastes with even higher amounts of fluoride being marketed, it would also appear that toothpaste manufacturers and researchers in caries prevention should look further at the problem of fluoride absorption from toothpastes in infants.