Relationship between enamel fluorosis severity and fluoride content.

OBJECTIVES: Enamel fluorosis is a hypomineralization caused by chronic exposure to high levels of fluoride during tooth development. Previous research on the relationship between enamel fluoride content and fluorosis severity has been equivocal. The current study aimed at comparing visually and histologically assessed fluorosis severity with enamel fluoride content. METHODS: Extracted teeth (n=112) were visually examined using the Thylstrup and Fejerskov Index for fluorosis. Eruption status of each tooth was noted. Teeth were cut into 100 µm slices to assess histological changes with polarized light microscopy. Teeth were categorized as sound, mild, moderate, or severe fluorosis, visually and histologically. They were cut into squares (2 × 2 mm) for the determination of fluoride content (microbiopsy) at depths of 30, 60 and 90 µm from the external surface. RESULTS: Erupted teeth with severe fluorosis had significantly greater mean fluoride content at 30, 60 and 90 µm than sound teeth. Unerupted teeth with mild, moderate and severe fluorosis had significantly greater mean fluoride content than sound teeth at 30 µm; unerupted teeth with mild and severe fluorosis had significantly greater mean fluoride content than sound teeth at 60 µm, while only unerupted teeth severe fluorosis had significantly greater mean fluoride content than sound teeth at 90 µm. CONCLUSIONS: Both erupted and unerupted severely fluorosed teeth presented higher mean enamel fluoride content than sound teeth. CLINICAL SIGNIFICANCE: Data on fluoride content in enamel will further our understanding of its biological characteristics which play a role in the management of hard tissue diseases and conditions.

[Calcium and phosphorus content in erupted and impacted teeth enamel. The study in vivo].

This study shows that there are significant differences in the content of minerals in the enamel of the teeth to erupt in the near future after the eruption. Based on the data it can be concluded that immediately after the eruption of the tooth enamel entering the aggressive environment oral loses a certain amount of minerals. This explains the high dental caries is in the first fern years after the eruption. All figures are of high relevance in the planning of prevention.

Dynamic light scattering study of an amelogenin gel-like matrix in vitro.

Amelogenin self-assembly is critical for the structural organization of apatite crystals during enamel mineralization. The aim of the present study was to investigate the influence of temperature and protein concentration on the aggregation of amelogenin nanospheres at high protein concentrations (>4.4 mg ml-1) in order to obtain an insight into the mechanism of amelogenin self-assembly to form higher-order structures. Amelogenins were extracted from enamel scrapings of unerupted mandibular pig molars. The dynamics of protein solutions were measured using dynamic light scattering (DLS) as a function of temperature and at acidic pH. At pH 4-5.5, three kinds of particles were observed, ranging in size from 3 to 80 nm. At pH 6, heating the solution above approximately 30 degrees C resulted in a drastic change in the solution transparency, from clear to opaque. Low pH showed no aggregation effect, whilst solutions at a slightly acidic pH exhibited diffusion dynamics associated with the onset of aggregation. In addition, at the same temperature range, the hydrodynamic radii of the aggregates increased drastically, by almost one order of magnitude. These observations support the view that hydrophobic interactions are the primary driving force for the pH- and temperature-sensitive self-assembly of amelogenin particles in a 'gel-like' matrix. The trend of self-assembly in a 'gel-like matrix' is similar to that in solution.

Effects of three concentrations of carbamide peroxide on the structure of enamel.

Carbamide peroxide bleaching agents have raised important questions on their potential adverse effects on the structure of enamel. The purpose of this study was to examine the effects of three carbamide peroxide bleaching agents in different concentrations (10, 16 and 35%) on the structure of enamel. Forty enamel slabs prepared from human third molars were divided equally among four groups. The specimens in the first and second group were subjected to 10% or 16% carbamide peroxide for 8 h per day for 6 weeks. Thirty-five percent carbamide peroxide was applied to the third group for 30 min a day for a 4 day period according to the manufacturers recommendation. The fourth group served as the control and was kept in artificial saliva during the test period. At the completion of the treatment, all the specimens were examined by infrared absorbtion spectroscopy and X-ray diffraction analysis. The results revealed that 10% or 16% carbamide peroxide did not seem to effect the structure of enamel, whereas 35% carbamide did affect the structure. The use of lower concentrations of carbamide peroxide (10-16%) is recommended over higher concentrations (35%) to avoid changes to the enamel.

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.

Avaliaçäo da correlaçäo da açäo iatrogênica causada pelo cetoprofeno e pelo diclofenaco potássico com os valores de algumas provas laboratoriais de uso em cirurgia odontológica aferitivas da hemostasia / Evaluation of the relationship of iatrogenic action caused by ketoprofen and potassic diclofenac and the values of some hemostasis tests

Objetivando avaliar aspectos da hemostasia pós-uso do cetoprofeno e do diclofenaco potássico em pacientes normo-reativos com necessidade e oportunidade de avulsäo de terceiros molares inferiores inclusos e/ou impactados, a autora apresenta, nesta tese, uma casuística de 51 (cinqüenta e um) pacientes, num estudo comparativo randomizado, os quais foram submetidos aos seguintes exames pré e pós operatórios: T.T.P.A., T.P., retraçäo de coágulo e contagem de plaquetas. Os resultados apresentaram-se dentro dos limites da normalidade e também näo foram registrados sangramentos clínicos pós-operatórios pós-uso do cetoprofeno e do diclofenaco potássico. O estudo permitiu concluir que nas posologias administradas o cetoprofeno e o diclofenaco de potássico näo interferiram nos mecanismos da hemostasia

Enamel fluoride concentrations in unerupted third molars and the influence of fluoridated water on caries scores.

Enamel fluoride concentrations in buccal and lingual surfaces were determined in successive layers obtained by the acid etch method. The 48 unerupted third molar teeth were from subjects who had lived continuously since birth in two Brazilian towns (Barretos and Ribeirão Pr-eto) with different fluoride levels in the drinking water but with similar socioeconomic conditions. The DMFT index was determined for children 7-12 years old living in the two towns. Enamel fluoride concentrations were significantly higher in the teeth from the town with higher fluoride levels in drinking water. The children residing in the community with near-optimum fluoride concentration in the water had mean DMFT scores that were less than half those found in the community with a low level of fluoride in the drinking water.

Alkali-soluble and insoluble fluoride in erupted and unerupted human enamel from a high fluoride area with a low fluorosis score.

The amounts of fluoroapatite and 'CaF2-like' fluoride (F) were determined in enamel of unerupted and erupted teeth that had been exposed in vivo to 1.8-2.6 parts/10(6) F in the drinking water and to brushing with F dentifrice at least once a day, and occasionally to a F mouth-rinse (0.022% F). Enamel was sampled by acid-etching and the F levels were measured with an adapted F ion-selective electrode. More F was built into the deeper enamel in the high-F area than in a similar low-F area. Unerupted enamel did not etch significantly (p > 0.05) deeper than erupted enamel. No significant differences (p > 0.05) were found in the F concentrations amongst the following: alkali-washed erupted, unwashed erupted, alkali-washed unerupted and unwashed unerupted at the outer most enamel (approx. 6 microns). However the erupted enamel (alkali-washed or not) showed higher F levels than unerupted enamel (alkali-washed or not) between approx. 6 microns and greater than 100 microns. The increase of F for this high-F area was about 100% in the deeper enamel while for a low-F area it was approx. 78% in the most outer enamel with no increase after a depth of about 20 microns. In contrast to a similar low-F area (water F < 0.10 parts/10(6)), no significant 'CaF2-like' F could be detected in erupted or unerupted enamel for the high-F area.

Fluoride profile in mature unerupted enamel following removal of surface organic material.

The aim of the present study was to determine fluoride profiles in mature unerupted enamel following removal of the surface organic material. Thirty teeth were randomly allocated into three groups. The surface organic material (Nasmyth's membrane) was left intact in group I; it was removed by tooth-brushing in group II, and in group III the surface organic layer was removed along with subsurface organic material by deproteinizing. Each tooth was then sectioned into halves and a standardized biopsy area was created. Initially alkali-soluble fluoride was extracted with 1M KOH followed by acid etch analysis to measure the remaining fluoride. No difference was seen in the alkali-soluble fluoride levels but residual fluoride concentrations were significantly reduced (p < 0.05) after deproteinizing but not after toothbrushing. It would appear that a substantial amount of fluoride (approximately 25%) in mature enamel from unerupted teeth can be removed by a deproteinizing agent, which may suggest an association of this fluoride with subsurface organic material.

Fluoride concentrations in unerupted fluorotic human enamel.

Unerupted fluorotic human enamel was obtained from teeth surgically removed from patients with dental fluorosis. Fluoride was measured in samples produced by serial acid etching from the surface to the interior of blocks of buccal and lingual enamel. The severity of fluorosis, according to the TF index, was determined from the macroscopic and microradiographic appearance of the specimens. The shape of the fluoride profiles was not affected by the degree of severity of fluorosis, but the fluoride concentrations increased with increasing severity of lesions. Fluoride concentrations were similar to those previously recorded in erupted fluorotic enamel and were not related to the length of time the teeth had been present in the jaws. It was concluded that the fluoride content of erupted fluorotic enamel represents fluoride acquired during tooth formation and that further uptake prior to eruption may be negligible.

Immunoassay evidence for a role of nerve growth factor in development of dental innervation.

Nerve growth factor (NGF) is known to have an essential role in prenatal development of spinal and trigeminal primary sensory neurons serving nociceptive functions. Investigation of a possible function of NGF in development of intradental innervation has recently begun with the demonstration by others of NGF mRNA and NGF receptor in the pulp. The pulp is of special interest in this respect because of its late development and unusual properties of its innervation. In the present study, use of a sensitive ELISA for NGF has made it possible to detect and measure NGF antigen in pulps of developing rat molars. Pulps contained relatively high concentrations of NGF before and during the time of innervation development.

Carbonate content in developing human and bovine enamel.

The present study describes the detailed changes in carbonate distribution throughout the different stages of development in human and bovine enamel, from early formation to maturation. Twenty-two human maxillary and mandibular deciduous anterior teeth and 46 bovine teeth were studied. The major mineral ions, calcium and phosphorus, were also analyzed to facilitate comparison of carbonate content with progressing mineralization. The results showed that as enamel matured and mineral concentration increased, carbonate concentration decreased. The observed decrease in percent carbonate per weight enamel mineral may be due to dilution by an influx of relatively carbonate-free mineral, and could, in part, explain the observed increase in crystallinity of enamel mineral as the tissue matures.

Influence of posteruptive age of enamel on its susceptibility to artificial caries.

Epidemiologic studies and caries experiments with animals have suggested that caries susceptibility of teeth decreases with age. Observations on the changes in the dental tissues and their environment with age have pointed out that a process commonly referred to as 'posteruptive maturation' of the dental enamel may be responsible. To test this assumption 10 unerupted third molars and 56 erupted human premolar teeth of various posteruptive ages were subjected for 130 days to an acid gel for caries-like lesion formation in vitro. Sections of the teeth were examined with polarized light and 'contour maps' were drawn with the approximate porosity of the lesions. The results were: unerupted = 833 microns (+/- 261); erupted of posteruptive age 0-3 years = 561 microns (+/- 150), 4-10 years = 470 microns (+/- 136), 11-30 years = 459 microns (+/- 192) and over 30 years = 297 microns (+/- 89). These findings show a decrease in the susceptibility of enamel to artificial caries with increasing age, which was especially marked at and shortly after eruption. This may be explained by a completion of mineralization of the outer enamel at about eruption, by a maturation process of the outer enamel posteruptively and by a reduction in the permeability of enamel occurring through to old age. The fluoride content of the mid-coronal buccal surface enamel under study was found to decrease posteruptively with age, therefore not accounting for the decreasing caries susceptibility.

Dental pulp lipids from Bos taurus during odontogenesis.

During the fetal development of the dental pulp, the various lipid classes show no substantial differences in their relative ratios but differences occur between deciduous and permanent teeth. By chromatography, the amount of free cholesterol was found decreased in deciduous and permanent teeth as compared to fetal teeth. Esterified cholesterol increased in permanent teeth and triglyceride levels were high only in developing permanent teeth. Phosphatidylcholine, sphingomyelin and phosphatidylserine were present in higher concentration in permanent unerupted teeth, while phosphatidylethanolamine was at first constant but then decreased during development in the permanent unerupted teeth. These data suggest that lipid changes are related to the assembly of plasma membranes and to the establishment of the innervation during ontogeny and postnatal development of dental pulp.

Electrochemical impedance characterization of human and bovine enamel.

The alternating current impedance characteristics of human and bovine enamel slices were measured in vitro. An electrochemical cell containing two platinum gauze electrodes and 0.01 mol/L KCl buffered to pH 7.4 at 20 degrees C was used. The electrodes were attached to a potentiostat that was connected to a microcomputer-controlled frequency-response analyzer. Measurements were made at discrete frequencies between 1 Hz and 65 kHz by application of a sinusoidal potential of 50 mV (rms) across the assembled cell. The impedance was calculated from the input potential and the resulting measured flow of current. For quantitative evaluation of these measurements, an equivalent circuit was postulated. It contained five passive electronic components and accurately modeled the different specimens. Values for individual electrical components in the equivalent circuit were estimated by complex non-linear least-squares regression analysis. This study demonstrated that it is possible to measure and quantitatively distinguish between the impedance characteristics of: permanent human, deciduous human, and bovine enamel, as well as the enamel from a variety of sites from human teeth, some of which had been extracted prior to being fully erupted. Proposals are made as to which physical properties in the specimens are modeled by individual components in the equivalent circuit.

[Study on the content of certain elements in retained teeth]. / Badanie zawartosci wybranych pierwiastków w zebach zatrzymanych.

The content of calcium, phosphorus.potassium and zinc was determined in 21 retained canine teeth and in a control group of canine teeth erupted completely. In the measurement the method of X-ray fluorescence was used. The obtained results were subjected to statistical analysis. In relation to control canines the retained teeth contained significantly more calcium and phosphorus and significantly less potassium. No significant differences were found in zinc content.

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.