Mineral density and mineral loss after demineralization at various locations in human root dentine. A longitudinal microradiographic study.

From intact roots of human cuspids 83 dentine specimens were cut. The specimens with known location and thickness were embedded in a holder of polymethyl methacrylate and microradiographic images were made. From the longitudinal microradiography (LMR) measurements the average mineral density (kg/m3) of the sound human dentine specimens was calculated. All specimens were subsequently demineralized using a constant composition method in a solution containing 3 mM CaCl2.2H2O, 3 mM KH2PO4, 50 mM CH3COOH and 0.2 ppm fluoride as NaF at pH = 5 for 24 h. After demineralization the LMR measurements were repeated to calculate the amount of mineral lost. The data show that there is no correlation between: (1) the location of a dentine specimen in the root and the mineral density of sound human dentine, (2) the location of a dentine specimen in the root and the degree of demineralization after 24 h and (3) the mineral density of sound human dentine and the demineralization degree. This information is useful for future in vitro and in vivo studies on human roots.

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.

The contribution of CO3(3-) and CO2- to the ESR spectrum near g = 2 of powdered human tooth enamel.

The ESR spectrum near g = 2 of powdered human tooth enamel from upper central incisors and lower canines was studied as a function of microwave power, irradiation, and storage time. The results clearly demonstrate that the ESR spectrum is composite with at least five paramagnetic species contributing to the signal. The main stable component is assigned to CO2-. Two other components arise from CO3(3-) radicals, one of which is demonstrated to be the same center as is present on a phosphate site in sodium- and carbonate-containing calciumapatite.

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.

The microcrystal alignment in human tooth enamel from carious and non-carious teeth in relation to caries susceptibility.

The degree of microcrystal alignment in the intact enamel from carious and non-carious upper incisors, lower incisors and upper canines was determined by means of electron paramagnetic resonance. The results show that a low degree of alignment is not a generally valid indication for caries-susceptibility. Upper canines have a high degree of crystallite alignment whereas lower incisors have a relatively low one. With the exception of the upper central incisors no differences in microcrystal alignment are found between the intact enamel from carious and non-carious lower incisors and upper canines. These results indicate that a possible caries-susceptibility of tooth enamel reflected by low R-values is not solely determined by the degree of microcrystal alignment.

Proton-induced X-ray emission analysis of Zn, Sr and Pb in human deciduous tooth enamel and its relationship to dental caries scores.

The absolute concentrations of these elements were obtained by calibration with the animal-bone standard of the International Atomic Energy Agency. From exfoliated deciduous incisors and canines of 193 6- and 9-year-old children living in four Finnish towns, 77 enamel samples from subjects with low and high caries (dmfs = 0 and greater than 6, respectively) were analysed. There were no statistically significant correlations between Zn and caries, or Pb and caries, but a weak positive correlation existed between Sr and caries (r = 0.341; p less than 0.001). The lead concentration in incisors (8.1 +/- 5.3 parts/10(6)) was twice as high as in canines (4.1 +/- 2.6 parts/10(6)), whereas the Sr concentration was lower (63 +/- 18 and 85 +/- 13 parts/10(6), respectively) emphasizing the importance of relating such analysis to the tooth type.

Apatite crystallite alignment in sound human tooth enamel studied by E.S.R.

The degree of microcrystal alignment in enamel of clinically sound upper and lower central incisors, canines and premolars was determined by means of electron paramagnetic resonance. The results show that the degree of alignment depends on the individual properties of the enamel as determined by biological variations, tooth morphology and tooth position. Upper incisors and canines have a much higher degree of crystallite alignment as compared to all other teeth investigated. These results indicate that the caries susceptibility of tooth enamel is not defined only by the degree of microcrystal alignment.

Prism arrangement in human cusp enamel deduced by X-ray diffraction.

Analysis of the many X-ray diffractograms obtained from the regions along the bands of Hunter-Schreger, and a series of X-ray patterns taken by tilting the specimen with respect to the incident X-ray beam over a wide range of tilt angles, showed that the fibre axis of the crystal aggregates in each zone of the bands not only deviated in opposite directions but also tilted at an angle of about 50 degrees with respect to the central axis of tooth enamel. Comparison with previous studies enabled a fundamental and simplified three-dimensional model of human cusp enamel to be constructed, consisting of two groups of spirally-arranged structure which would probably be elastic enough to fulfil its unique functions in occlusion and mastication.

[Determining the overall density of permanent human teeth and its relation to the carrier's age (author's transl)]. / Ermittlung der Gesamtzahnidichte permanenter menschlicher Zähne und ihr Aussagewert zum Lebensalter des Zahnträgers.

(1) The pyknometer method was used to determine the specific gravity of the roots, central portions (necks), and crowns of 130 human teeth (incisors, canines, premolars, molars) obtained during autopsies. The overall density or specific gravity was calculated as the mean of the values obtained for these portions of permanent teeth. To test the relation between the total specific gravity and the carrier's individual age, a simple linear regression was calculated. It was not possible for a definite relation to be found between the specific gravities of teeth and the age of their carriers. (2) Limits to determining the individual age from the specific gravity of teeth are set especially by the factors discussed in this paper, by pathological influences, and by variations of specific gravity within isolated hard dental tissue. In human teeth, age-dependent physiosclerosis of bradytrophic tissue obviously is in the form of re- or transmineralization without major changes in the degree of mineralization and is usually overlapped by other phenomena. In addition, preparative and technical faults may result in false specific gravities being obtained. (3) Specific gravities of portions of teeth and total specific gravities determined therefrom cannot be used to find the carrier's age and, therefore, should be dismissed as means of identifying age by methods of forensic stomatology.

Lead content of deciduous teeth of children in different environments.

The lead content of teeth of children in five different environments has been measured to determine the relative contribution of different sources of lead. The importance of lead paint in children living in dilapidated housing is clearly observed, but no effect attributable to automobile exhaust or industrial emissions is apparent. High lead levels were found among children living in new public housing projects within the high lead area of the city, even though a lead paint problem presumably should not exist in the projects themselves. The data are analyzed to determine the frequency with which excessive lead contents occur in the problem area in comparison to a low risk area.

Lead levels in human deciduous teeth in Tennessee.

Deciduous teeth were analyzed by atomic absorption spectroscopy for lead content to ascertain the extent of lead exposure in certain areas in Tennessee. The data were analyzed to clarify the relationships between tooth lead content and race, sex, age, tooth type, economic status, and place of residence. Results indicated that blacks had slightly higher lead concentrations than whites; however, the age and sex of the person or the type of tooth analyzed had little effect upon the lead content. The major factors were shown to be economic status and, indirectly, place of residence.

Prediction models for 90Sr in shed deciduous teeth and infant bone.

Shed deciduous teeth were collected in 1966-69 in Denmark, the Faroes and Greenland from children born in the period 1953-63. 235 samples of crowns were analysed for 90Sr. The 90Sr levels in deciduous tooth crowns were related to the fall-out rate and the accumulated fall-out. The tooth levels in children born in 1950-62 could be described with the same equation as the 90Sr bone levels in 1-yr-old infants born in 1962-68. The prediction models for 90Sr in teeth and bones showed that for given amount of fall-out the Faroese levels became nearly twice as high as the Danish. The maximum teeth and bone levels were found in children born in 1963, where the Faroese level was estimated from the prediction model to be 24 pCi 90Sr/g Ca.