Fluoride concentrations and distribution in premolars of children from low and optimal fluoride areas.

We have compared the fluoride (F) concentrations from the enamel surface to the dentino-enamel junction (DEJ), and through dentine to the dentino-pulpal junction (DPJ) in premolars extracted from school children in Chemnitz (former Karl-Marx-Stadt), Germany (F: 1.0 ppm in the water supply), Erfurt, Germany (F: 0.2 ppm in the water supply) and Nagoya, Japan (F: 0.1 ppm in the water supply). In teeth from children in Cheminitz, Erfurt and Nagoya, the profiles of F distribution using an abrasive microsampling technique revealed high F concentrations in the enamel surface, with a substantial decrease towards a plateau in the interior. In dentine the F concentrations were higher than in enamel, and also decreased to a plateau from the DEJ, thereafter increasing considerably towards the DPJ. F concentrations at any depth in the enamel and dentine of teeth from Chemnitz were 2-3 times higher than those in Erfurt and Nagoya. There was no significant difference in F concentrations or distributions between Erfurt and Nagoya. Close to the DEJ in both enamel and dentine as well as the enamel surface and the DPJ side of dentine, higher F concentrations were observed in Chemnitz compared with Erfurt and Nagoya.

Distribution of fluoride in the dental tissues and their supporting mandibular bone from the same individual.

Dental and skeletal tissues have their own distinct fluoride distribution profiles. It was thought useful to compare these within individuals as normally comparisons are made between different groups of individuals. The average fluoride concentration decreased in the following order; cementum, alveolar bone, cancellous bone, mandible, dentine and enamel.

Magnesium distribution in human bone.

The present study was undertaken to reveal the magnesium distribution in human bone. Sixty human ribs, obtained from subjects aged 10-80 years of age, were used. Transverse sections were prepared from the middle region of the human ribs. Adjacent sections were ground to a thickness of about 1000 microns. One section was used for magnesium determination by atomic absorption spectrophotometry, and the other was used for analysis with X-ray microanalysis. Thirty micron thick samples were abraded continuously from the periosteal and the endosteal surfaces by abrasive microsampling, as previously described by Weatherell et al. Results showed that magnesium concentrations were higher in both the periosteal and endosteal surfaces and did not change with age in general, although it tended to be higher among teenagers and lower over 80 years old.

Glucose clearance from different surfaces of human central incisors and first molars.

The study examined the glucose clearance (retention) in saliva at different surfaces of these teeth in 23 subjects. The mouth was thoroughly rinsed for 15 s with 20 ml of a 0.5 M glucose solution. The concentrations of glucose absorbed by small pieces of paper, placed on the mesial, distal, labial (buccal), lingual and occlusal surfaces 3 min after rinsing, were measured using an immobilized enzyme system and an electrochemical sensor. On the maxillary and mandibular central incisors, the glucose concentrations on the labial surfaces were significantly higher than on all other surfaces and lowest on the lingual surfaces. In the mandibular molars, glucose concentrations were significantly higher on the buccal surfaces than on the lingual surfaces. Clear site-specific differences in glucose clearance were thus observed at the different tooth surfaces. It is considered that the differences in the glucose retention rate might be indicative of factors important for the site specificity of dental caries.

Distribution of fluoride in human dental calculus.

The distribution of fluoride in human dental calculus was investigated using a mechanical sampling technique and the fluoride electrode. The fluoride concentrations were highest at the outer surface of dental calculus and, then fell to a plateau for the interior of the calculus, rising again as the tooth surface was approached. The coefficient of variation of fluoride concentration was significantly greater in the sub- than in the supragingival calculus (p < 0.01). The supragingival calculus thus tended to show a smoother distribution profile for fluoride than the subgingival calculus. Total fluoride, average fluoride, and maximum fluoride concentrations were not significantly different in supra- and subgingival calculus. No significant different were observed between males and females.

The thickness of the sound and periodontally diseased human cementum.

Cementum of teeth previously analysed for fluoride was re-examined in order to determine whether or not periodontal disease had affected the thickness of the tissue. In the periodontally diseased teeth the cementum was thinner than normal in the middle region of the root. The apical cementum, however, was significantly thicker in periodontally diseased than in the sound teeth of subjects over 60 yr old. This may account for the higher total fluoride levels previously reported in the apical cementum of these same teeth.

Influence of occlusion on the fluoride distribution in rat molar cementum.

This study was undertaken to examine the influence of occlusion on the fluoride distribution in cementum following an experiment in which the occlusion in rats was locally altered by extracting the upper left molar. These and control rats with normal occlusion were given water containing 0 or 100 ppm fluoride for 12 weeks. The fluoride distributions in cementum from both first lower molars of the same animal were compared. The fluoride concentrations had increased throughout the tissue as a result of increased fluoride administration, irrespective of any changes in occlusion. They were, as usual, generally highest at or near the cementum surface and decrease towards the interior of the tissue. Where there had been a change in occlusion, the thickness of cementum was less than that of the contralateral tooth, but, despite this, the fluoride profiles in contralateral teeth were similar in both experimental and control rats. In the experimental rats, on the other hand, the total fluoride tended to be lower, and the mean fluoride tended to be higher in left molars without antagonists. These findings were never seen in the control rats. It was concluded that the alteration in occlusion influenced the fluoride distribution in the cementum through its effect on the rate of cementum formation.

Determination of volumes of fluid in the mouth by fluoride dilution.

A dilution technique, with fluoride as a marker, has been developed to measure the volume of saliva and other fluids in the mouth. Immediately after swallowing, a small amount of fluoride solution is placed in the mouth, mixed with the oral fluids, and expelled from the mouth. The fluoride concentration of the expelled oral fluid is measured and the volume of fluid in the mouth at the time of spitting calculated from the fluoride dilution. Mean values of 0.75 +/- (SD) 0.28 ml for males and 0.72 +/- (SD) 0.16 ml for females were recorded. The accuracy of the volume determination is about +/- 0.10 ml in vivo. This technique has provided a convenient and rapid means of determining saliva volumes. It could also be used to determine rates of secretion and may prove useful in the clinic for assessing a patient's salivary competence.

Distribution of fluoride in sound and periodontally diseased human cementum.

Fluoride distribution was investigated by an abrasive micro-sampling technique. The fluoride concentration increased with age in both sound and diseased cementum. In sound teeth, the fluoride profiles (distribution of fluoride from the surface to interior) of the middle and apical cementum were similar. In the diseased cementum the profile of the middle region tended to be more variable than that of the apical cementum, suggesting a possible effect of the oral environment on the fluoride profile at this site.

Distribution of fluoride across human primary enamel.

The distribution of fluoride was described in detail from the incisal to the cervical region in 10 pairs of primary lower central incisors. Fluoride analyses were done on the right incisors; optical microscopic studies were done on the left. The distribution data obtained from fluoride analyses of the right incisors were superimposed on micrographs of sections through the left incisors. An abrasive microsampling technique (Weatherell et al., 1985) was used to determine the fluoride concentration and distribution. Fluoride concentration was the highest at the enamel surface and decreased from there to the interior. The fluoride distribution did not level off to an even plateau in the enamel interior, as suggested by earlier studies. Apart from the high concentration in the surface region, the fluoride levels in prenatal and postnatal enamel were rather similar. The fluoride concentration tended to be low at the neonatal line.

Distribution of fluoride in the cementum of human deciduous canines.

This study was undertaken to determine the fluoride distribution in human deciduous cementum. Ten pairs of sound deciduous canines, extracted from children aged 6-9 years, were examined. The teeth were sectioned, and specimens of cementum were removed from the buccal or lingual aspect of the sections. Samples were removed sequentially by abrasion, from the cementum surface to the cementum-dentine junction, and their fluoride content determined as described earlier. The concentrations of fluoride were highest at or near the cementum surface and decreased towards the interior of the tissue. Concentrations and patterns of fluoride distribution were characteristic of the individual subjects. The distribution patterns of fluoride in the contralateral teeth from the same subject were also fairly similar.

Distribution of fluoride concentration in the rat's bone.

The present study was undertaken to determine the fluoride distribution profile in the rat femur. Male Wistar rats were divided into four groups and given water containing 0, 25, 50, and 100 ppm of fluoride, respectively, for 10 weeks. The fluoride distribution from the periosteum to the endosteum was determined in each specimen after sampling using the abrasive microsampling technique. In the outer circumferential lamellae, the concentration of fluoride was relatively high in the periosteal layer and then decreased gradually towards its interior. In the haversian and interstitial lamellae, it was lower and roughly constant through the tissue. In the inner circumferential lamellae, it rose again to reach the highest level towards the endosteal surface. Fluoride concentration throughout the cortex increased significantly with increasing intake of fluoride. These increases were especially marked at periosteal and endosteal surfaces.

Kinetics of fluoride in the oral fluids.

The normal concentration of fluoride in saliva is about 1 mumol/L, which is somewhat less than that in plasma, and the salivary concentration is relatively independent of flow rate. Even this low concentration appears to be significant in terms of maintaining the integrity of tooth mineral. After fluoride consumption, the level in plasma peaks within less than an hour, and this produces a corresponding increase in salivary levels, which achieve baseline values usually within a few hours. At low concentrations (less than 4 mmol/L) in oral fluids, fluoride undergoes only slight reaction with tooth mineral to form fluorohydroxyapatite. However, at higher concentrations calcium fluoride is formed on the tooth surface. Although this mineral is sparingly soluble in saliva, the process of dissolution is retarded for periods of up to a week or longer by surface deposition of salivary phosphate and pyrophosphate. The rate of clearance of exogenous fluoride from saliva is prolonged when initial concentrations are high, due to the deposition of CaF2 on the tooth surface and its gradual dissolution. The clearance rate is also not constant throughout the mouth, but shows considerable site-specificity. In general, clearance is much more rapid lingually than buccally. This appears to be due to the greater lingual exposure to secretions from the major salivary glands, principally the submandibular, whereas buccally, mainly minor mucous gland secretions are present, and these are very viscous and flow at a slow rate.

Distribution of fluoride across cementum, dentine and alveolar bone in rats.

This study was undertaken to determine the fluoride distribution in cementum and neighboring hard tissues of the rat after different levels of fluoride administration via the drinking water. Specimens of cementum with underlying dentine and adjacent bone were removed from the distal roots of the first lower molars. The fluoride distribution in each specimen was determined in samples removed sequentially using an abrasive microsampling technique. Fluoride concentrations were highest at or near the surface and decreased towards the interior of cementum, dentine and alveolar bone in both control and experimental groups. With increasing fluoride intake, concentrations increased throughout the tissue. The distribution patterns of fluoride in cementum of contralateral teeth from the same animal were similar. Fluoride concentrations in cementum were higher than those of dentine and alveolar bone.

Differences in fluoride concentrations in the enamel surfaces of lower first premolars from young human males and females.

There are unconfirmed, reported differences in fluoride concentration in the tooth surfaces of male and female children whose average age was 13.5 yr (range 11.5-15.7 yr) and whose teeth might therefore have been exposed for 2-3 yr after eruption to the oral environment. Thirty-two unerupted and 24 erupted mandibular first premolars were now examined. These had been extracted for orthodontic reasons from children aged from 9 to 10 yr. Samples were removed by acid etching from small areas of the enamel surface, and the fluoride and phosphorus concentrations determined with an electrode and by colorimetry, respectively. Three sites on the buccal surface and one site in the centre of the lingual surface were investigated. Fluoride concentrations were higher in erupted than in unerupted enamel. The fluoride concentration of erupted enamel from the female teeth was significantly higher than that of the males (in contrast to the previous findings), although no analogous differences emerged in the fluoride concentrations of the unerupted enamel.

Site-specific variations in the concentrations of substances in the mouth.

Estimates of the concentration of soluble substances in the oral fluids have generally been obtained by the analysis of whole saliva, either mixed in the mouth or obtained directly from the salivary duct. Such values may give little indication of concentrations at any particular site in the mouth. This is partly because substances do not always move easily about the mouth and also because there are large regional differences between the rates of oral clearance or retention of substances dissolved in saliva. Differential patterns therefore develop and are related, via the patterns of salivary flow, to the anatomy and physiology of the mouth. There are general features in these patterns common to all mouths and variations, which relate to characteristics of the individual, which may influence the rates of reactions occurring at different sites. The patterns may be associated with the site-specific patterns of dental disease, and they may have implications with regard to the best use of pharmaceutical agents. This paper describes some of the more recent data, problems and future possibilities in this hitherto unexplored area of oral physiology.

A microbiological study of early caries of approximal surfaces in schoolchildren.

A cross-sectional epidemiological study has been undertaken to relate the bacterial composition of approximal dental plaque with the earliest stages of caries development in schoolchildren. Small samples of plaque were removed from multiple sites around the contact areas of 42 premolars extracted for orthodontic reasons from 29 schoolchildren (mean age = 13.5 yr). Caries diagnosis was based on polarized light microscopy and contact microradiography of thin sections cut through the sample sites. Fifty-seven percent of sites (37/60) showed histological evidence of demineralization. Both the isolation frequency and the mean percentage viable count of mutans streptococci and Actinomyces viscosus were higher at sites with early caries, although mutans streptococci could not be detected at 37% of sites with early caries. At these latter sites, the proportions of Veillonella were markedly reduced. Lactobacilli were rarely isolated and were never recovered from caries-free surfaces. Analysis of the data shows that the relationship between plaque bacteria and enamel is neither merely passive nor indifferent, and that particular stages of lesion formation may be associated with different combinations of bacteria.

Potential benefits of toothpaste advertising on dental health.

This paper considers the effect of advertising on the sales of various brands of toothpaste. It has attempted to investigate the relationship between the level of sales of a brand and those of its competitors. Econometric estimations of the demand-function for toothpaste have been made and the authors have tried to determine the interrelationships between advertisement and toothpaste sales. The findings cast doubt upon the efficiency of the present system of competitive advertisement and suggest a possible alternative approach to the marketing of toothpaste which could increase sales and, at the same time, beneficially influence dental health.

Retention of glucose in oral fluid at different sites in the mouth.

Using glucose as a marker, a detailed study of retention at 5 different sites in the mouth of 1 subject and a less detailed examination of 4 selected sites in the mouths of 10 other subjects revealed site-specific differential patterns of oral retention (or clearance). These patterns seemed independent of sometimes large, absolute day-to-day variations in oral retention which occur in all subjects but appeared to vary somewhat between subjects, probably reflecting slight differences in the anatomy and physiology of the individual mouth. In general, the patterns resembled those recently derived from studies of other oral phenomena such as rates of diffusion out of plaque, fluoride uptake by mineral and hydrogen ion concentrations in plaque. They will dictate the concentrations and thereby influence the activity of all extraneous substances in different regions of the oral cavity and may relate to the site-specific patterns of oral disease.