Atmospheric nuclear weapon test history as characterized by the deposition of 14C in human teeth.

The 14C concentration in the collagen of human teeth was retrospectively investigated to determine whether its incorporation was related to atmospheric testing of nuclear weapons. Teeth were extracted for dental therapy from July 1987 to February 1988 from patients who were residents in Japan. Tooth collagen was extracted with HCl and converted to amorphous C by heating in a vacuum line. Specimens for 14C analysis were prepared by mixing the amorphous C with silver powder. The 14C concentration was measured by mass spectrometer. The 14C concentration in tooth collagen rapidly increased in 1961 after the bomb tests, peaked around 1967-1968, and then gradually decreased. The collagen of human teeth maintains the 14C concentration at the age of root completion for life. The results of this study indicate that the history of environmental contamination from atmospheric nuclear weapon's tests has been characterized by deposition of 14C in the tooth collagen 14C of human beings.

Multiple functions for NGF receptor in developing, aging and injured rat teeth are suggested by epithelial, mesenchymal and neural immunoreactivity.

We have used immunocytochemistry to analyse expression of nerve growth factor receptor (NGFR) in developing, aging and injured molar teeth of rats. The patterns of NGFR immunoreactivity (IR) in developing epithelia and mesenchyme matched the location of NGFR mRNA assayed by in situ hybridization with a complementary S35-labeled RNA probe. The following categories of NGFR expression were found. (1) There was NGFR-IR in the dental lamina epithelium and in adjacent mesenchyme during early stages of third molar formation. (2) NGFR-IR nerve fibers were posterior and close to the bud epithelium. (3) During crown morphogenesis NGFR expression was prominent in internal enamel epithelium and preodontoblasts; it faded as preameloblasts elongated and as odontoblasts began to make predentin matrix; and it was weak or absent from outer enamel epithelium, the cervical loop, and differentiated ameloblasts and odontoblasts. (4) When NGFR-IR nerve fibers entered the molars late in the bell stage, they innervated the most mature peripheral pulp and dentin in an asymmetric pattern which correlated more with asymmetric enamel synthesis than with mesenchymal NGFR-IR distribution. (5) The mesenchymal pulp cells continued to have intense NGFR expression in adult teeth, especially near coronal tubular dentin. (6) The pulpal NGFR-IR decreased in very old rats or subjacent to reparative dentin (naturally occurring or experimentally induced). (7) During root formation, the preodontoblasts had NGFR-IR but most root mesenchymal cells and Hertwig's epithelial root sheath did not. This work suggests that there are important epithelial and mesenchymal targets of NGF regulation during molar morphogenesis that differ for crown and root development and that do not correlate with neural development. The continuing expression of NGFR-IR by pulpal mesenchymal cells in adult rats was most intense near coronal odontoblasts making tubular dentin; and it was lost during aging, or subjacent to sites of dentin injury that caused a phenotypic change in the odontoblast layer.

Electron probe microanalysis of human teeth for the determination of individual age.

The calcium and phosphorus weight concentrations as well as the calcium/phosphorus weight ratio were determined by electron probe microanalysis both peritubularly and intertubularly in the dentine of 25 adults of varying age and sex, originating from our autopsy material. The studies were performed with a TESLA BS-300 scanning electron microscope coupled with an EDAX-149-10 X-ray detector and a BMG-38100 X-ray analyser with an accelerating potential of 15 kV, a sample current of 100 pA and a measurement time of 20 s. Peritubularly the Ca/P weight ratio of the hypermineralized part of the dentine decreases with age and is in close correlation with it (r = -0.9052) and this tendency is significant even at the level of 95% (P less than 0.05). The equation of the regression line is: Y = 37.17 x +139.37 where x is the age and y is the Ca/P weight ratio. The weight concentration of phosphorus is in an even closer correlation with age (r = 0.9712) and this correlation is also significant (P less than 0.01). The equation of the regression line is the following: y = 625.0 x -42.06 The close correlation of both the Ca/P weight ratio of the teeth and of the phosphorus weight concentration with the age allows individual age determination to be performed in the course of forensic medical and palaeoanthropological studies.

An analysis of paramagnetic centers in irradiated dentin using electron spin resonance.

The ESR spectra produced in irradiated dentin have been studied over a range of incident radiation energies from 50 kVp to 25 MVp. The behavior of the dentin ESR signal strength is similar to that of enamel as a function of the energy of the incident radiation. The magnitude of the dentin ESR signals are, however, up to 10 times smaller than the signals of dental enamel for a given radiation energy. The possible contributions of radiation interaction coefficients, chemical structure, and crystallite size to the differences in ESR spectra are discussed.

[Growth factors in human tooth development]. / Fattori di crescita nello sviluppo del dente umano.

Our research concerns the immunohistochemical localization of EGF and IGF-I receptors in the tooth germ, using monoclonal antibodies. The results show that in the early phases of human tooth development EGF and IGF-I receptors are present. At bud stage both receptors are localized at dental laminae level, in some epithelial cells of the tooth bud and in some mesenchymal cells. At cap stage the receptors are present in the outer and inner enamel epithelium, and in some cells of stellate reticulum. As far as concerns the mesenchymal cells, some cells of dental papilla in contact with enamel organ, are intensely positive. The immunopositivity is present also in some mesenchymal cells at follicular level. At late cap stage and at early bell stage receptors are not present at inner enamel epithelium level but they can be detectable in the mesenchyma of dental papilla and in some cells of the follicle. On the basis of these results it may be hypothesized that EGF and IGF-I can act as growth factors in the modulation of cellular proliferation and differentiation during the human tooth morphogenesis. Moreover, it is possible that these substances can play a role in the mesenchymal-epithelial interaction in the developing human tooth.

[The effect of pulp extirpation on the function of the hard dental tissues]. / Vliianie depul'pirovaniia na sostoianie tverdykh tkanei zuba.

The authors analyze the results of clinical and experimental studies of the status of hard dental tissues before and after pulp removal. The findings evidence that Ca and P levels reduce and O2 and oxide levels increase in the hard tissues of pulpless teeth, this probably resulting in changed color and friability of pulpless teeth. These data may be useful in dental surgery when forming carious cavities in pulpless teeth and in orthodontics to make pulp insertions with due consideration for the friability of pulpless teeth.

[Comparison of organic dentin matrix composition between bovine permanent and deciduous teeth].

Minor differences in chemical composition of permanent and deciduous teeth have been suggested, however, clear data on the difference in organic composition have not yet been established. In the present study, organic dentin matrix components of bovine permanent and deciduous teeth were investigated. Bovine permanent and deciduous dentin were obtained from respective incisors and divided into crown and root. They were crushed into powder and extracted with 4M guanidine-HCl (G-extract), and then with 0.5 M EDTA, 4M guanidine-HCl (E-extract). E-extracts from permanent crown and root dentin and also deciduous crown and root dentin were separately applied to DEAE-cellulose column and each peak was examined precisely by SDS-polyacrylamide gel electrophoresis (SDS-PAGE). A quantitative difference in organic matrix composition was recognized between permanent and deciduous dentin. Furthermore, a non-collagenous protein fraction, which existed in permanent teeth but not in deciduous ones, was discovered. This protein was purified as a single band in SDS-PAGE, which demonstrated an apparent molecular weight of approximately 30 Kd. Its amino acid composition was analyzed and the nature of this protein was discussed.

Immunohistochemical localization of glycosaminoglycans and proteoglycans in predentin and dentin of rat incisors.

We examined immunocytochemically the type and distribution of glycosaminoglycans and proteoglycans (PG) in predentin and dentin demineralized with EDTA after aldehyde fixation of rat incisors using (a) four monoclonal antibodies (1-B-5,9-A-2,3-B-3, and 5-D-4) which recognize epitopes in unsulfated chondroitin (C0-S), chondroitin 4-sulfate (C4-S), chondroitin 6-sulfate (C6-S), and keratan sulfate (KS) associated with the PG, and (b) monoclonal (5-D-5) and polyclonal antibodies specific for the core protein of large and small dermatan sulfate (DS) PG. Light microscope immunoperoxidase staining after pre-treatment of tissue sections with chondroitinase ABC localized the majority of stainable PG (C4-S, KS, DSPG, C0-S, and C6-S) in predentin and, to a lesser extent (C4-S and small DSPG), in the dentin matrix. The former site demonstrated relatively homogeneous PG distribution, whereas the latter site revealed that strong staining of C4-S and small DSPG was confined mostly to dentinal tubules surrounding odontoblastic processes, with only weak staining in the rest of the dentin matrix. These results indicate that there is not only a definite difference between PG of predentin and dentin but also a selective decrease in the concentration or alteration of these macromolecules during dentinogenesis and mineralization.

Evaluation of analytical methods for fluorine in biological and related materials.

During the past two decades, some major pitfalls in fluorine analysis have been recognized and overcome. Therefore, it is important that facts be separated from fallacies in published literature on levels and forms of fluorine (ionic, bound, covalent, etc.) in biological materials, in order that correct perceptions of physiological, biochemical, and toxicological aspects of inorganic as well as organic fluorine compounds can be formed. Trace amounts of inorganic fluoride in biological samples can now be accurately determined with the fluoride electrode either directly or following diffusion, adsorption, or reverse extraction of fluoride (when necessary). The aluminum monofluoride molecular absorption technique provides an excellent rapid method for determination of trace amounts of inorganic fluoride (in the absence of organic fluorine). Fluorine in most organic fluorine compounds is not available for distillation, diffusion, or reverse-extraction. The sample needs to be ashed (open ashing) or combusted (oxygen flask, oxygen bomb, pyrohydrolysis) for covalently bound fluorine to be converted to fluoride ions. This can now be readily accomplished at room temperature by the reductive cleavage of the C-F bond with the sodium biphenyl reagent. Some recommendations for future research have been made.

Low-level lead exposure and the IQ of children. A meta-analysis of modern studies.

We identified 24 modern studies of childhood exposures to lead in relation to IQ. From this population, 12 that employed multiple regression analysis with IQ as the dependent variable and lead as the main effect and that controlled for nonlead covariates were selected for a quantitative, integrated review or meta-analysis. The studies were grouped according to type of tissue analyzed for lead. There were 7 blood and 5 tooth lead studies. Within each group, we obtained joint P values by two different methods and average effect sizes as measured by the partial correlation coefficients. We also investigated the sensitivity of the results to any single study. The sample sizes ranged from 75 to 724. The sign of the regression coefficient for lead was negative in 11 of 12 studies. The negative partial r's for lead ranged from -.27 to -.003. The power to find an effect was limited, below 0.6 in 7 of 12 studies. The joint P values for the blood lead studies were less than .0001 for both methods of analysis (95% confidence interval for group partial r, -.15 +/- .05), while for the tooth lead studies they were .0005 and .004, respectively (95% confidence interval for group partial r, -.08 +/- .05). The hypothesis that lead impairs children's IQ at low dose is strongly supported by this quantitative review. The effect is robust to the impact of any single study.

Morphologic and histochemical characteristics of the dental cuticle in teeth affected by prepubertal periodontitis.

A study was undertaken to determine the nature and composition of the cuticle found in teeth with generalized prepubertal periodontitis (PP). This was accomplished by using histological and histochemical methods on decalcified specimens. Forty-six permanent teeth which were extracted from three prepubertal periodontitis patients (siblings) were used. Nineteen of the 46 teeth were obtained with the facial or interdental gingiva. As a control, 20 healthy teeth extracted from 10 children for orthodontics reasons, and 22 teeth affected by terminal adult periodontitis (AP), were used. All the teeth with PP showed a thick coat covering the root surface from the cemento-enamel junction to the junctional epithelium. In some teeth the cuticle extended a few microns coronally to the cemento-enamel junction. The cuticle had a thickness which varied between 10 to 80 microns. It usually presented a very regular surface in the coronal portion of the root, and showed laminations suggesting appositional growth. In the middle and apical portions of the root exposed to the pocket, the cuticle was lobular with a very irregular surface and was covered with a thick microbial plaque. The staining reactions indicated that the cuticle was made of proteins probably derived from the inflammatory exudate. None of the healthy teeth examined nor those affected by AP showed a cuticle similar to those with PP. The cuticle formed on the teeth with PP appears to be an abnormal structure of proteinaceous nature, characteristic of these teeth, and may possibly play a role in the pathogenesis of the disease.

[Demineralization behavior, enamel permeability and the morphological characteristics in relationship to the stage of eruption of the permanent teeth]. / Demineralisationsverhalten, Schmelzpermeabilität und morphologische Besonderheiten in Abhängigkeit vom Durchbruchsstadium permanenter Zähne.

The posteruptive maturation of enamel is an important factor in caries disposition. In an experimental study the demineralization of enamel as well as its permeability and its morphological features in dependence of eruption stage were examined on extracted premolars. Chemical analysis showed variations in the Ca/P molar ratio. It is possible, that the instability of Ca-ions in crystalline configuration decreased during the time of eruption. The permeability of enamel decreased between 5 and 11.8%. It appears to be useful to concentrate preventive measure on this phase of dentition development.

A method to determine the end point of decalcification of hard tissue and bone.

A method for decalcification end point determination of mineralized tissue is described. The calcium content of the decalcification solution was determined colorimetrically with a "continuous automatic analyzer" with a high degree of accuracy. The end point method used has been tested on two decalcification methods, 5% nitric acid with or without ultrasonic treatment. The results suggest it is possible to quantitate the decalcification process.

Comparison of lead levels in human permanent teeth from Strasbourg, Mexico City, and rural zones of Alsace.

A comparative study of the mean lead concentrations in enamel and dentin of human premolars and permanent molars was conducted by means of a systematic sampling procedure with energy-dispersive x-ray fluorescence analysis. In a first series of analyses, no significant statistical differences in mean lead concentrations at various levels of enamel and dentin were noted between young patients of Strasbourg and those of small villages of Alsace, nor between elderly patients living in these two locations, despite the fact that motor traffic was significantly lower in the rural zones. However, in both locations, a significantly higher concentration of lead was observed in enamel and dentin in relation to age. In a second series of analyses, the mean lead concentrations of both dental hard tissues of premolars and permanent molars of young individuals from Strasbourg, rural Alsace, and Mexico City were compared. Significantly higher mean lead concentrations were found in enamel and dentin samples from Mexico City. This was most evident for inner coronal dentin (5.7 and 6.1 times greater than in teeth of Strasbourg and rural zones of Alsace, respectively) and for pulpal root dentin (6.9 and 8.9 times greater than in teeth of Strasbourg and rural zones of Alsace). It is proposed that the higher lead concentrations are related to the higher lead content of motor gasoline and to more intense traffic conditions. The dental hard tissues appear to be of value for the study of environmental lead pollution.

Zinc deficiency-induced changes in the lipid composition and ultrastructure of rat incisor teeth.

The lipids and ultrastructure of the forming, maturing and erupted parts of incisors were compared in rats fed a zinc-deficient diet for 28 days, pair-fed rats and control rats. The lipid levels in the forming portions of zinc-deficient incisors were 30-50% below control levels and were associated with longer Tomes' processes in the secretory ameloblasts, porosities in the forming enamel and fewer malachite green-aldehyde-phospholipid aggregates in the predentine. No marked structural changes were seen in the erupted portions of the teeth, although variations in lipid composition were detected both in the maturing and erupted parts. No differences were found between teeth from the 3 groups of animals for Na, Mg, Cl, Ca and P signals with the electron microprobe.

Dental development, skeletal maturation and body weight at birth in pig-tail macaques (Macaca nemestrina).

The degree of maturation of the deciduous dentition and the permanent first molar, as assessed from radiographs, was compared to body weight and carpal development in Macaca nemestrina at birth. All deciduous teeth were present in various stages of development. The permanent molar was represented by 1 to 4 mineralized cusps in 85% of the sample population. A dental maturation score, calculated for each animal, ranged from 12 to 19, with approx. 50% having a score of 17. Compared with the human dentition, that of the neonatal macaque was appreciably more advanced at birth. Carpal development and birth weight were much more variable than dental maturation. Because there appeared to be less variability in tooth development at birth than in the other maturational indicators, tooth formation may offer a better and more accurate estimate of physiological age in this species at this critical time of development.

[The structure, ultrastructure and physicochemical analysis of the hard dental tissues of the Viperidae]. / Structure, ultrastructure et analyses physico-chimiques des tissus durs dentaires des vipéridés.

The present study, using classical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, infrared spectroscopy, has shown the dental hard tissues of the fangs of Viperidae (poisonous serpents with terrestrial or semi-aquatic habits) to be constituted of: a calcified outer layer, 0.4 microns thick, made of very small needle-like crystals, randomly distributed. The calcified outer layer contains organic invaginations inducing pores at the surface and many collagen fibres incompletely mineralized, which may suggest enameloid. a calcified inner layer, in the wall of the poison canal. The calcified inner layer, 0.6 microns thick, is constituted of very small crystals, which are parallel to each other and perpendicular to the calcified outer layer. It might be the inner layer of enameloid, an orthodentine, whose tubules present a special lateral branching system resembling a fish bone. The TEM data, which show the dentine to be constituted of very small ill-defined crystals and incompletely mineralized collagen fibres are corroborated by chemical analyses which reveal a poorly mineralized apatite with high carbonate content.

Fluorochrome labelling in Roman period skeletons from Dakhleh Oasis, Egypt.

A histological aging study of femoral midshafts in a late Roman period sample from the Dakhleh Oasis, Egypt, showed discrete fluorochrome labelling. The fluorochrome is yellow-green in colour and fluoresces at a wavelength of 525 nm. The labelling occurs at the mineralization fronts and is so distinct that several histomorphometric measurements were made. The percent labelled surface values ranged from 6.03% to 59.34%, and the mean distance between labels ranged from 13.57 to 20.63 microns. Teeth from several individuals were also labelled within the enamel matrix. Comparisons were made between the patterns of fluorescent labelling from this population and from patients treated with interval and continuous dosages of tetracycline. The results collectively indicate that the fluorochrome is most likely tetracycline that made its way into the bone (in vivo) via stored grain contaminated by Streptomycetes. The labelling was differential, much like that of the patient on interval doses of tetracycline, so it is argued that the tetracycline was ingested occasionally, probably on a seasonal basis. The lack of bone infection in the adults (n = 29) suggests that the tetracycline may have provided some antibiotic protection in this population.

[Blood, teeth and hair: 3 different materials used to evaluate exposure to lead and cadmium in children living in an industrial zone]. / Sangue, denti e capelli: tre diverse matrici utilizzate per valutare l'esposizione al piombo e al cadmio in bambini residenti in zona industriale.

There is a general agreement that children are a population at increased risk with respect to lead and cadmium exposure and to adverse health effects resulting from increased exposure. Different biological indicators such as blood hair and teeth have been used to evaluate lead and cadmium exposure in humans. However, up to date, it has not been established which is the best indicator to provide an assessment of internal exposure. The aim of the present study was to examine the levels of lead and cadmium in hair, blood and teeth of children living from birth in an industrialized area near Modena. The relationship between these indicators of exposure and children characteristics such as sex, weight, height, blood pressure and smoking habits of parents was also examined. 142 children (71 males and 71 females) representing 20.8% of those aged 6-7 years living in Sassuolo (Modena) have been included in the study. The geometric means of lead in blood, hair and teeth were 11.2 micrograms/dl, 7.24 micrograms/g and 6.16 micrograms/g, respectively. Hair lead were significantly related to both blood and teeth values (r = 0.226, p = 0.007 and r = 0.186, p = 0.027, respectively). Mean cadmium concentrations were 0.47 mu/l in blood, 0.17 micrograms/g in hair and 47.9 ng/g in teeth and no significant correlation was observed between the three biological matrixes examined. Significant correlations were found between lead and cadmium in both hair (r = 0.427, p = 0.000) and teeth (r = 0.224, p = 0.007). In addition, for lead content in teeth, a significant difference between boys and girls was observed; females showed higher values than males (6.77 micrograms/g vs 5.61 micrograms/g; t = 2.23 p = 0.028). Taking into account the individual characteristics of children, a negative relationship was found between Pb levels in teeth and height (r = -0.217, p = 0.024). Systolic blood pressure values were positively associated to cadmium hair levels in males but not in females (r = 0.281; p = 0.053). From the results of the present study it appears that blood, hair and teeth provide different information to predict lead and cadmium exposure of children. Hair seem to be a useful global indicator of total environmental pollution.