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.

Adenine nucleotide contents and ATPases activities in porcine deciduous dental pulp during the root formation, in fully formed root and during root resorption phases.

Nucleotide content and activity of certain enzymes were compared in pigs of various ages in order to study the energetic metabolism of deciduous dental pulps in the three phases of the cycle of tooth ontogeny, namely, root formation, fully formed root and root resorption phases. The frozen pulps were removed with the help of a screw vise and analysed for ATP, ADP and AMP contents and Ca2+ and Mg2+-ATPases activities. The highest ATP content in the first deciduous molar pulp was found when the tooth was still in an intrabony position. The calculated energy charge, although low for all groups, at this stage of development, indicated an activation of the consuming processes. In the root resorption phase, lowest ATP content and higher Ca2+ and Mg2+-ATPases activities were observed.

[Boron in dental hard tissues studied by 11B(p,alpha)8Be nuclear reaction]. / Il boro nei tessuti duri dentari studiato con la reazione nucleare 11B(p,alpha)8Be.

Boron's low atomic number and low concentration make its measurement in hard dental tissues difficult. Using nuclear reaction, the 11B(p,alpha)8Be*, enamel, dentine and radicular cement of 18 dental elements, ten healthy and eight decayed teeth, both permanent and deciduous were studied. The highest Boron concentrations were found in the two most superficial microns of the vestibular enamel in non-decayed incisors, particularly deciduous ones. Premolar and molar teeth showed lower Boron concentrations than frontal ones, decayed teeth revealed hardly any Boron. In confirmation of the prevailing exogenous contribution of this karyostatic trace element, on average, Boron concentrations were 2.5 times as high as dentine and 10 times as high as cement.

X-ray microanalytical histochemistry of human circumpulpar and mantle dentine.

An X-ray microanalytical histochemistry study was carried out, on thick sections observed under scanning electron microscopy, of five freshly extracted human premolars and five molars. In particular the circumpulpar and mantle dentine were examined to determine levels of calcium, phosphorus and sulphur, the basic elements involved in the process of biomineralization. Semiquantitative analysis was subsequently performed after the appropriate ZAF (Z, atomic number; A, absorption; F, secondary fluorescence) correction. Ca/P mass ratio was found to be similar for both regions in molars and slightly higher in circumpulpar dentine in premolars implying that this parameter is independent of the processes of biomineralization in the two dentinal regions. In contrast, statistically significant differences were recorded in sulphur content upon comparing mantle and circumpulpar dentine between premolars and molars (P less than 0.02). If sulphur, which has been associated with sulphated glycosaminoglycans (GAGs) decreases as mineralization progresses it would therefore seem reasonable to posit sulphur-rich areas in both topographical regions of the matrix--more significant in premolars than molars--able to undergo subsequent mineralization if required. The possible application of these findings in remineralization therapies is suggested.

Characterization of the molecular weights of bovine molar, rat incisor, and other phosphophoryns.

The phosphophoryns show anomalous behavior in solution, and are easily degraded during extraction. They appear in varied forms in the teeth of different species and differ in the teeth of the same species in a developmental and age dependent fashion. This set of properties has made the characterization of the phosphophoryns by biochemical means a difficult and controversial subject. Bovine molar phosphophoryn, bPP, has been characterized in detail by a variety of physical methods, and then compared with the PP from other species by DEAE-HPLC, gel electrophoresis, and immunological cross reactivity. The possible existence of a proPP biosynthetic precursor has been investigated by rat incisor organ culture and examination of the 32P and 14C labeled products. These studies all show marked differences in the Mr values for the PP from teeth of different species, even when they are antigenically cross-reactive.

Mineralization differences between human deciduous and permanent enamel measured by quantitative microradiography.

The mineralization levels of erupted buccal enamel from 24 deciduous teeth were compared to those of 28 permanent teeth. Sections were prepared in a defined plane using a lapping machine which gave plano-parallel sections. Mineralization levels were recorded by quantitative microradiography at 25 equivalent anatomical sites in each section. Deciduous incisors and canines were compared with their homologous successors: overall mineralization levels were lower in the deciduous dentition, with no significant differences being found close to the amelo-dentinal junction, but highly significant differences being found in the outermost sites. Deciduous molars were compared with premolars, and were also relatively less mineralized. However, deciduous molars did not show the consistent diminishing occlusocervical gradient observed in all other tooth types tested; on the contrary, they showed a cervical reversal with higher values than permanent premolar enamel. These results confirm the generally lower mineral levels in deciduous enamel, and provide quantitative information on site-specific mineralization levels.

Localization of 28 kDa calbindin in human odontoblasts.

The presence of 28 kDa calbindin in human odontoblasts was studied by use of specific antibodies raised against chick duodenal 28 kDa calbindin, in immunofluorescence, immuno-peroxidase, and electron-microscopic labelling experiments. The calbindin-like protein was detected mainly in the cytoplasm of odontoblast cell bodies, in their processes and occasionally in their nuclei. Correspondingly, at the ultrastructural level, immunoreactive material was associated with the cytosol, microfilaments and cilia. These findings suggest that human odontoblasts express a 28 kDa vitamin D-dependent calcium-binding protein, unlike those of rats and mice in which ameloblasts are the only cells immunoreactive for the protein.

Mineral and protein concentrations in enamel of the developing permanent porcine dentition.

Calcium, phosphorus and protein analyses have been performed on developing permanent enamel from the mandibular dentition of the domestic pig. The pattern of mineralization and protein loss was similar from tooth to tooth and similar to teeth from other species. Comparison of different teeth at the same developmental stages (secretion--stage 1, transition--stage 2 and maturation - stage 3) revealed remarkably similar concentrations of calcium, phosphorus, and protein regardless of tooth type. These data were similar to those from other deciduous dentitions, except that maturing/mature tissue in the pig seemed less well mineralized.

[Enamel pearls in the deciduous teeth]. / Les perles d'émail des dents de lait.

A microradiographic study of 40 human deciduous teeth showed an unexpected high frequency (33%) of enamel pearls at the junctional interradicular line of the molars. An electron probe analysis showed that the composition of the pearls is similar to that of the coronal enamel. The pearls are located on normal dentine and are in contact with a hypermineralised layer separating cementum from dentine. It is hypothesised that the origin of this hyaline layer and the observed high frequency of pearls is not due to a possible differentiation of Hertwig sheath cells but results from variations of an usual biological process.

Perinatal stress and increased fluctuating asymmetry of dental calcium in the laboratory rat.

Recent studies have consistently reported an increased magnitude of fluctuating dental, long bone, and membranous bone asymmetry as a function of perinatal stress. The present study was designed to test the hypothesis that increases in the fluctuating asymmetry of calcium may be related to the metric changes in these calcium-dependent systems. Pregnant rats were exposed to noise stress from conception through weaning. Bilateral lower first molars were extracted from the neonates, and calcium levels were determined using a standard atomic absorption technique. Levels of fluctuating asymmetry of calcium were found to be significantly increased (p less than .01) in the audiogenic noise-stressed group compared to unstressed, normal controls. These results follow the pattern reported earlier for metric analysis of the dentition and support a stress-induced calcium-transport-disruption hypothesis.

[Isolation of a phosphoprotein from preeruptive dentin from molars of domestic pigs (Sus scrofa domesticus)]. / Isolierung von Phosphoprotein aus Dentin präeruptiver Molaren des Hausschweins (Sus scrofa domesticus).

Isolation of a phosphoprotein from dentin of pre-eruptive molars of Sus scrofa domesticus. A protein with a relative molecular mass of 60,000 kD was isolated from dentin of unerupted pig molars. The electrophoretically homogeneous protein was identified as phosphoprotein with a specific staining procedure. The phosphorylation degree is 75%. The amino-acid composition and the molecular mass were compared with values of other species.

Production of a monoclonal antibody to enamelins which does not cross-react with amelogenins.

Developing enamel matrix contains a complex mixture of proteins whose characterization is essential to an understanding of amelogenesis. It is not known whether each component is the product of an individual gene, or whether they are interrelated by physiologic or artifactual breakdown. To define these relationships, monoclonal antibodies were prepared to enamel proteins and we have previously reported the characterization of six antibodies to amelogenins which did not react with enamelins (Christner et al. (1985) Arch. Oral Biol. 30:849-854). We now report the isolation of antibody to enamelins which stains the enamel matrix but does not cross-react with amelogenins. These results suggest that amelogenins and enamelins are distinct classes of proteins.

Lead in teeth: the influence of the tooth type and the sample within a tooth on lead levels.

Different sections of permanent teeth have been sampled and the lead levels estimated using carbon furnace AAS. Very high levels of lead (500-3400 micrograms g-1) and other trace metals (Cd, Cu, Fe and Zn) occur on the surface of the teeth, falling off rapidly a few micrometers into the teeth. Lead levels in the bulk enamel of incisors vary depending on the position within the tooth, the highest values occur on the lingual side near the gums and the lowest levels on the labial side near the tooth top. The ratio of the concentration of lead in enamel to dentine and to circumpulpal dentine was found to be 1:2:6, and within the dentine the lead levels were highest in the root dentine. The root dentine in the permanent teeth of eight, near complete or representative, sets of teeth was analysed for lead. The ratio ([Pb]tooth/[Pb]total set) decreased in the order: first molars greater than central incisors greater than lateral incisors greater than canines greater than premolars greater than second molars greater than third molars. This order inversely correlates with the age of formation or eruption of the teeth, i.e. the older teeth have the highest levels of lead in the dentine. Dentine appears to be the best material to use to estimate lead, particularly in relation to the integrated lead intake of a person. Dentine lead was determined in a small sample of deciduous teeth obtained from children living in rural areas. The levels were found to be slightly less than for children living in new housing urban areas and significantly less than for children living in older houses of urban areas.

Elements in marginal seals at amalgam-tooth interfaces.

X-ray micro-analysis was used to determine the elemental composition of the tooth, amalgam, and base material of ten aged, amalgam-restored, posterior teeth after they had been fractured across the amalgam-tooth interface. Subsequently, replicas were used to remove marginal seal material from each interface for examination by x-ray micro-analysis. The results show that P and Sn were present in all marginal seal material analyzed. Ca, Cl, Cu, Fe, S, and Zn were present in the marginal seals of various numbers of specimens.

Characterization and immunocytochemical localization of dentine phosphoprotein in rat and bovine teeth.

Dentine phosphoprotein (DPP) was isolated from unerupted bovine molars and from rat incisors. The proteins were characterized biochemically and used to immunize rabbits and guinea pigs. Antibody activity was investigated by enzyme-linked immunosorbent assay (ELISA). Guinea-pig anti-rat DPP did not cross-react with bovine DPP, but rabbit anti-bovine DPP did cross-react with rat DPP. Anti-rat DPP antiserum was applied to cryotome sections of rat molar tooth germs and DPP immunoreactivity was seen in dentine, odontoblasts, odontoblast processes and pre-ameloblasts. Anti-bovine DPP antiserum reacted positively in bovine dentine and dentinal tubules. When this antiserum was applied to rat tissue, predentine was positive but dentine was negative. Adsorption experiments with DPP, purified by methods including and excluding precipitation with calcium, suggested that non-calcium precipitable DPP is present in rat predentine. Rat and bovine DPP are thus species-specific and DPP is synthesized by the odontoblasts, transported through their processes and secreted into the dentine.

Specific immunohistochemical localization of osteonectin and collagen types I and III in fetal and adult porcine dental tissues.

Affinity-purified antibodies have been used in combination with the peroxidase-antiperoxidase technique to study the distribution of osteonectin and collagen types I and III in porcine dental tissues. Tissue sections (2 mm thick), including unerupted (fetal) or erupted (adult) teeth, were fixed in periodate-lysine-paraformaldehyde, demineralized in 12% w/v ethylenediaminetetraacetic acid, and after embedding, 6 micron sections were prepared for immunolocalization. Strong staining for osteonectin was observed in dentine of unerupted teeth and in the associated alveolar bone. Light to moderate staining was observed in the dental pulp, stratum intermedium, stellate reticulum, and the reticular elements in the endosteal spaces. In erupted teeth, osteonectin staining in dentine was concentrated around dentinal tubules and the associated alveolar bone stained with variable intensity. Cementum was poorly stained. However, the periodontal ligament and reticular material in the endosteal spaces showed moderate to strong staining. Weaker staining was apparent in the pulp and lamina propria of the gingiva. In comparison, type I collagen showed a similar distribution to osteonectin in both fetal and adult tissues, whereas type III collagen was generally restricted to the periodontal ligament, reticular elements of the endosteal spaces, and Sharpey's fibers in bone and cementum. Both odontoblast and ameloblast layers in fetal tissues stained for osteonectin and type III collagen.

Tooth wear, solubility and fluoride concentration of molar-tooth surfaces in rats maintained on simultaneous or separate intake of food and fluoridated drinking water.

Eighty rats, 20 days old, were fed a hard pellet diet and deionized or fluoridated (25 parts/10(6) F-) drinking water respectively for 40 days. Half were maintained on simultaneous food and water intake for 3 h, daily, and the remainder on separate intake of food for 3 h followed by drinking water for 3 h, daily. Scanning electron micrographs of the occlusal surface of right maxillary first molars were used for scoring wear. The mandibular and left maxillary molar surfaces were used for solubility and fluoride concentration determinations. Intake of food and water separately did not affect wear significantly, whereas solubility and fluoride concentration of the molar surfaces were significantly increased. Wear, solubility and fluoride of the molar surfaces respectively were highly significantly increased in the rats provided with fluoridated water. Increase in fluoride uptake is due in part at least to the increase in sites available for uptake due to tooth wear. Acid dissolution of worn tooth-surface enamel is greater than that of intact enamel.

Lead in teeth of weanling rats received via the maternal drinking water.

Pregnant rats were dosed with 0, 3 or 10 parts/10(6) lead (as acetate) in their drinking water, during pregnancy and during lactation until 21 days post partum. The litters were killed at the age of 21 days and the incisors, first, second and third molars analysed for lead by atomic absorption spectrophotometry. The findings confirmed that even at low concentrations lead has an affinity for hard tissues. The mean lead levels of the teeth of the three groups differed at the 1 per cent level. Pb levels of the first and second molars and the incisors also differed at the 1 per cent level. No significant differences between the four types of teeth within a group could be demonstrated. The no-effect level of Pb administered in drinking water, to the mother during lactation, and during pregnancy, was lower than 3 parts/10(6).