Distribution of fluoride in clinically sound enamel surfaces of permanent upper incisors

Fluoride profiles of perikymata in enamel surfaces of human premolars

Twenty-five premolars (from Nagoya, Japan < 0.1 parts/10(-6)F in drinking water) were sampled to determine the fluoride content in imbrication lines of Retzius between the grooves and ridges of perikymata on the enamel surface. Eight small windows were formed on each surface in groove and ridge regions using an etched microsampling technique. By using a regression curve, y = ax(-b), fluoride concentrations were compared at depths of 1, 3, 5, 10, 20, 30 and 50 microm in the perikymata regions. Fluoride concentrations increased gradually from the age of 10 to 12 years on the premolar surfaces, but were significantly higher in 12-year-olds or older (erupted teeth) than in 10-year-olds or younger (unerupted teeth). No obvious difference in fluoride concentrations was found between males and females. In the outermost enamel ( < 5 microm depth), fluoride concentrations were significantly higher in the grooves than the ridges of the perikymata. Comparison of the exponential regression coefficients (-b) of the fluoride profiles showed a significant difference between the grooves and ridges. It was concluded that fluoride concentrations and profiles were higher in grooves than in ridges of perikymata, probably because they are naturally porous and are stagnation areas attracting dental plaque.

Adaptive crystal formation in normal and pathological calcifications in synthetic calcium phosphate and related biomaterials

Mineralization and crystal deposition are natural phenomena widely distributed in biological systems from protozoa to mammals. In mammals, normal and pathological calcifications are observed in bones, teeth, and soft tissues or cartilage. We review studies on the adaptive apatite crystal formation in enamel compared with those in other calcified tissues (e.g., dentin, bone, and fish enameloids) and in pathological calcifications, demonstrating the adaptation of these crystals (in terms of crystallinity and orientation) to specific tissues that vary in functions or vary in normal or diseased conditions. The roles of minor elements, such as carbonate, magnesium, fluoride, hydrogen phosphate, pyrophosphate, and strontium ions, on the formation and transformation of biologically relevant calcium phosphates are summarized. Another adaptative process of crystals in biology concerns the recent development of calcium phosphate ceramics and other related biomaterials for bone graft. Bone graft materials are available as alternatives to autogeneous bone for repair, substitution, or augmentation. This paper discusses the adaptive crystal formation in mineralized tissues induced by calcium phosphate and related bone graft biomaterials during bone repair.

The effects of non-fluoridated and fluoridated milk on experimental caries in rats

The aim of the present investigation was to determine the caries-protective potential of non-fluoridated and fluoridated milk and to compare the efficacy of different compounds of fluoride as additives to milk. OM rats were maintained in three experiments in a frequency-controlled feeding machine of König et al. (1968) or, during one study, in metabolic cages with diet MIT 200 for three weeks. They received (1) milk with Ca-Fluoride [solubilized by KA1-Sulfate], (2) NaF, (3) NaMFP, and (4) Na-Silicofluoride. Controls were supplied with water or NaF solution of the same concentration of 10 or 15 ppm F. In addition, raw milk was provided ad libitum for the rats in a preliminary test. At the beginning and the end of the experiments, the pH of milk, its fluoride concentration, the body weight gain, the caries score, the fluoride concentration of the outermost enamel surface, the percentage of the interproximal bacteria, and the fluoride ingestion and excretion were determined. The raw milk significantly reduced the animal caries score by around 40%. This effect was lower but reproducible under programmed feeding with milk of a reduced fatty content (1.5%). The addition of Ca-Fluoride, which was not totally ionized (6.5 ppm F), reduced the caries score again by around 40%. Increasing concentrations of NaF (5, 10, 15 ppm F), Na-Silicofluoride, or NaMFP showed similar caries-inhibiting effects without remarkable influence of the fluoride dosage used. The percentage of streptococci ranged from 30 to 60 in the fluoridated milk and control groups as well. The increasing fluoride deposition in the enamel reflected the various fluoride dosages offered. The rats receiving non-fluoridated milk or distilled water had a significantly higher incidence of dental caries than those receiving fluoridated milk. The permanent availability of fluoride during the animal tests caused a higher caries-inhibiting effect than in clinical human studies reported.

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.

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.

Chemical events during tooth dissolution

Information on chemical changes during enamel dissolution has been collected from investigations on hydroxyapatite solubility, enamel solubility, artificial lesion formation, and natural caries. Although hydroxyapatite and enamel will ultimately dissolve in acid or during caries, compositional changes also occur. Most notably, there is a preferential dissolution of calcium, both from hydroxyapatite and from enamel, and of carbonate and magnesium from enamel. Root dentin yields substantial amounts of magnesium on acid attack. Fluoride may be involved in surface zone formation during attack, but an additional theory of coupled diffusion is described. Calcium-deficient mineral is produced during an acid attack, and this has lattice parameters and solubility behavior different from those of stoichiometric material. The interaction of fluoride produces a more stable lattice, resisting dissolution and favoring accretion, and tending to counteract the effects of carbonate and magnesium in forming mineral. The provision of fluoride, albeit at low levels, in plaque fluid is seen as being important in maintaining the net integrity of the tooth. More information is also needed on the role of the organic phase in tooth structures during caries and acid attack.

Alkali-soluble and insoluble fluoride in erupted and unerupted sound enamel of human third molars in vivo

The amounts of firmly and loosely bound fluoride were determined in sound enamel of unerupted and erupted teeth which had been exposed in vivo for 1-16 yr to brushing at least once a day, and occasionally to mouth rinsing and the application of sealers. Enamel was sampled by an acid-etch procedure, and the fluoride levels were measured with an adapted fluoride ion-selective electrode. Unerupted enamel was etched significantly (p less than 0.05) deeper than erupted enamel up to a depth of at least 8 microns. Significant differences (p less than 0.05) were found between the mean enamel fluoride concentrations of unwashed and alkali-washed, erupted teeth up to a depth of at least 3 microns and also between unwashed or washed, erupted versus unwashed or washed, unerupted teeth. At a depth of 3 microns, the fluoride treatments of enamel had increased the total amount of fluoride by approx. 78% of which approx. 53% was loosely bound fluoride (like CaF2) and 47% firmly bound (like fluorapatite). No increase in sound enamel fluoride as a result of topical treatments over a period of up to 16 yr could be found at a level deeper than 20 microns.

The relative distribution of fluoride in erupted and unerupted enamel of human third molars from a low fluoride area

Acid-etch biopsies were taken from the centre of the mesio-lingual, disto-lingual, disto-buccal and mesio-buccal cusps of non-carious erupted (n = 16, aged 18-28 years) and unerupted (n = 21, aged 18-28 years) teeth. The donor subjects had lived continuously in a low fluoride area (F water less than 0.1 parts/10(6] from birth, and had had no systemic fluoride supplementation. Tooth brushing, mouth rinsing and the application of sealers were the only fluoride-containing anti-caries programmes practised singly or in combination. Six successive acid-etchings were taken from each of the four cusps, and the fluoride levels in the etching solution were measured with an adapted, fluoride ion-selective electrode. Up to a depth of about 10 microns, unerupted enamel was etched significantly (p less than 0.05) more deeply than erupted enamel, which might be explained by changes in its composition. Up to a depth of approximately 10 microns, significantly more fluoride was found in erupted than in unerupted enamel. This difference may mainly be attributed to the effect of fluoride from the oral environment on erupted enamel. Fluoride concentrations, up to a depth of approximately 3 microns, were (p = 0.07) higher in the buccal cusps than in the lingual cusps of erupted molars, but not at the other etch depths. There were no significant differences (p greater than 0.10) between the buccal and lingual cusps of the unerupted molars at any depth. No significant correlations between enamel fluoride concentrations and age could be found either for erupted or unerupted third molars.

Distribution of fluoride across human dental enamel, dentine and cementum

This was determined across the entire width of sections from 20 mandibular premolars, containing enamel, coronal dentine, root dentine and cementum. An abrasive technique was used to sample all three dental tissues in a single experiment. In the profiles of fluoride distribution, fluoride concentration was thus precisely related to the position of the tissue sample. There was a marked increase in the fluoride content of coronal and root dentine, at least until the age of about 50 years. There had been uptake of fluoride by the root dentine and cementum throughout the life of the tooth. There was no evidence of any change in the fluoride content of enamel with age.

Superficial fluoride levels and response to in-vitro caries-like lesion induction of enamel from Bristol (U.K.) and Birmingham (U.K.) human deciduous teeth

Surface enamel fluoride levels were measured in deciduous canine teeth from Bristol, with non-fluoridated water supplies, and Birmingham, with fluoridated water supplies. Three populations studied were from Bristol (teeth shed before 1960), Bristol (after 1975) and Birmingham (after 1975). Up to 75 micron from the enamel surface, fluoride concentrations of post-1975 Bristol and Birmingham teeth were, respectively, X 1.3 and 3.4 greater than those of pre-1960 Bristol teeth. The increase in the Bristol teeth is presumably due mainly to the increased use of fluoride-containing toothpastes, that in Birmingham to fluoridated water plus the use of fluoride toothpastes. No difference in the rates of penetration into enamel of acid-gel induced, caries-like lesions were found between the two Bristol populations; Birmingham teeth showed a reduction of 10 per cent in penetration rate. It is suggested that raised fluoride levels in surface enamel do not reduce solubility sufficiently to account, by themselves, for the recent nationwide marked reduction in caries in children. Possibly, the raising of plaque fluoride levels is a more important factor, affecting demineralization, remineralization and bacterial activity.

Enamel-fluoride levels in deciduous and permanent teeth of children in high, medium and low fluoride areas

The surface enamel-fluoride concentration (approximately 4 microns) of both deciduous and permanent teeth of the central upper incisors were determined in 5-7 and 11-13-year-old children, who were born and bred in isolated areas with naturally high (3.7 parts/10(6)), medium (0.6 parts/10(6)) and low (less than 0.1 parts/10(6)) fluoride in the drinking water. Samples were taken in vivo by an acid-etch procedure and fluoride levels measured with an adapted fluoride-ion selective electrode. There were no significant differences in the fluoride concentrations or between etching depths between boys and girls, none between the contralateral incisors nor between the etching depths of deciduous and permanent teeth either in a single area or the three different ones. However, a highly-significant difference (p less than 0.01) was found in the enamel fluoride levels between the deciduous and permanent teeth in a fluoride area or among the three different fluoride areas. The ratio of the mean enamel fluoride concentration of permanent teeth to that of deciduous teeth increased with rise in fluoride in the drinking water. It is concluded that the different lengths of time, during which the crowns of deciduous and permanent incisor mineralize, contribute to this differing ratio.

Uptake of fluoride by human surface enamel from ammonium bifluoride and consequent reduction in the penetration in vitro by caries-like lesions

In-vitro fluoride uptake by mid-coronal, premolar enamel surfaces from topically-applied solutions of NH4HF2 was determined using a multi-electrode system for fluoride and calcium analyses. In tooth surfaces dehydrated with 100 per cent ethanol before the topical application of 1 per cent aqueous NH4HF2, there was a 2-3-fold increase in fluoride concentration up to a depth of 50 microns and fluoride enhancement to a total depth of 100 microns into the enamel. Caries-like lesions were induced in vitro in both treated and untreated enamel by the use of acidified, 6 per cent hydroxymethyl-cellulose gel containing 0.04 per cent hydroxyapatite at pH 4.5. After 120 days exposure, the mean depth of lesion penetration in the controls was 149 (+/- 34) microns. No lesions occurred in half the treated specimens; in specimens with lesions, the mean depth of penetration was 19 (+/- 3) microns. Thus, NH4HF2 was a potent inhibitor of caries-like lesion formation in vitro.