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At least 19 recordsLinked to original sources
PubMed1994

Dental enamel in relation to ionized calcium and parathyroid hormone. Studies of human primary teeth and rat maxillary incisors.

The aims of this thesis were to evaluate the role of lowered calcium values in blood on enamel formation and mineralization, and further to analyze whether the calcium regulating parathyroid hormone (PTH) would have any effects on the forming and mineralizing enamel. DENTAL ENAMEL AND IONIZED CALCIUM: Human primary teeth from two groups of infants were clinically and histologically examined. One group (n = 25) was born with optimal perinatal conditions. The infants had low, but not hypocalcemic values on day 1 when compared with days 3 and 5 postpartum. The second group of infants (n = 11) was subjected to blood exchange transfusion on the first few days postpartum. All infants developed very low values of blood ionized calcium due to the treatment, and the infants had a mean of three hypocalcemic days. Enamel aberrations were seen in both groups, but only four infants had multiple enamel aberrations located at levels corresponding to the enamel development at the time of the birth. Low values of blood ionized calcium alone were not associated with enamel aberrations, as the aberrations were only seen in infants subjected to more than three blood exchange transfusions. The neonatal line was present in all teeth investigated, thin lines dominated, and the widths were not dependent on the levels of blood ionized calcium during the first few days after birth. Rats were also used to investigate whether the maxillary incisor enamel would be affected during a diet-induced hypocalcemic state. Of ten experimental rats, nine had normal enamel, indicating that hypocalcemia in rats does not generally affect the enamel. DENTAL ENAMEL AND PARATHYROID HORMONE: Rats was used in a study where they were subjected to daily injections of PTH. Three different doses were used and the experimental periods were 7 and 14 days. In a pilot part, enamel aberrations were seen but not in the main study performed later. The main difference in experimental design between the pilot and the main part of the study was the use of hard tissue marker, oxytetracycline, at start of the pilot part. For this reason, a separate study was performed to evaluate the use of oxytetracycline in hard tissue research. The results clearly demonstrated that oxytetracycline itself induces enamel aberrations and so it was not used in the main study of parathyroid hormone. As no enamel aberrations were seen in the main part, it was concluded that the doses of PTH used do not seem to affect enamel formation and mineralization.

Amelogenesis↗
PubMed1975

Composition and structure of dental enamel: elemental composition and crystalline structure of dental enamel as they relate to its solubility.

The same elements, 21 in number, were found in both acid-resistant and acid-susceptible enamel specimens by ion microprobe analyses. However, there were differences in the concentrations of 14 elements between groups. Of the 16 trace elements found in enamel, the concentrations of K, F, and Na in parts per million were the greatest. Enamel surface analyses showed V and Zn were more concentrated in acid-resistant specimens by factors of 7.4 and 6.1 respectively, followed by nine other elements, the last molybdenum, that were just slightly more prevalent in acid-resistant enamel. Four elements were equally concentrated in both groups of samples, and only one trace element, B, was more abundant in the acid-susceptible samples by a factor of ten. Ca and P were predominantly more abundant in acid-resistant speciems, and C, H, and O were more concentrated in acid-susceptible samples. The enamel substance in acid-resistant and acid-susceptible groups was found to be similar by these methods. --Ion microprobe: the same elements were detected in both groups. Four trace elements (titanium, lead, Cl, and lithium) were equally abundant in the two groups. --Electron diffraction: the crystal structure type was the same in both groups of samples. --Infrared absorption: the crystalline substance showed the same spectra in both groups. The enamel substance in the two groups of specimens was found to be dissimilar by these methods. --Ion microprobe: the concentrations of 11 trace elements as well as Ca and P were greater in acid-resistant enamel. The concentrations of C, H, O, and B were greater in acid-susceptible enamel. --X-ray diffraction: crystallites in the acid-resistant specimens were larger by a factor of more than two. Enamel solubility appears not to be related to atomic species but associated with one, some, or all elements quantitatively and also with its physical form (crystallite size and probably density).

Calcium Phosphates↗
PubMed1996

Mechanical defects in dental enamel vs. natural dental caries: observer differentiation using Ektaspeed Plus film.

The value of imaging modalities in enabling the observer to detect proximal dental caries has been tested previously using both natural carious cavitations and mechanical defects. This study compared the ability of dentists to detect mechanically created defects and natural dental carious cavitations on the proximal surfaces of extracted teeth, and to differentiate between the two. Detection rates according to lesion depth were also investigated. There was a difference in the ability of readers to detect natural proximal dental carious cavities and mechanical defects in the proximal enamel. The odds of detecting artificial cavities was 2.92 times the odds of diagnosing natural caries cavitations. There was great variation in the ability of the dentists to identify natural and artificial lesions. According to logistic regression, when the cavity depths are equal, the mechanical defects in the proximal dental enamel are easier to identify than are natural enamel dental caries cavitations. The odds ratio charts provided from this study show the depths of mechanical and natural lesions that are comparable in diagnostic challenge. These charts might permit rough approximations to be made when comparing previously published papers that variously use both mechanical defects and natural caries. Use of poorly designed in vitro models for testing can produce a false guide to the clinical performance of diagnostic systems.

Dental Caries↗
PubMed2000

Calcium transport across the dental enamel epithelium.

Dental enamel is the most highly calcified tissue in mammals, and its formation is an issue of fundamental biomedical importance. The enamel-forming cells must somehow supply calcium in bulk yet avoid the cytotoxic effects of excess calcium. Disrupted calcium transport could contribute to a variety of developmental defects in enamel, and the underlying cellular machinery is a potential target for drugs to improve enamel quality. The mechanisms used to transport calcium remain unclear despite much progress in our understanding of enamel formation. Here, current knowledge of how enamel cells handle calcium is reviewed in the context of findings from other epithelial calcium-transport systems. In the past, most attention has focused on approaches to boost the poor diffusion of calcium in cytosol. Recent biochemical findings led to an alternative proposal that calcium is routed through high-capacity stores associated with the endoplasmic reticulum. Research areas needing further attention and a working model are also discussed. Calcium-handling mechanisms in enamel cells are more generally relevant to the understanding of epithelial calcium transport, biomineralization, and calcium toxicity avoidance.

Ameloblasts↗
PubMed1994

Association between dental enamel opacities and dental caries in a north Wales population.

This study examined the association between enamel opacities and dental caries in a population from North Wales with low levels of fluoride in the drinking water. Those subjects with only diffuse (n = 317) types of opacity had a mean DMFS of 1.6 (+/- 3.4) compared with those having only demarcated (n = 1,408) opacities of 3.4 (+/- 4.3). The group with both (n = 317) types of defect present had a DMFS of 2.4 (+/- 3.7) and the group with no defects (n = 1,496) had a DMFS of 2.7 (+/- 3.8). These differences were statistically significant (p < 0.001). Possible reasons for these differences are discussed.

Child↗
PubMed2000

Formation of alkali-soluble fluoride on the surface of human dental enamel after treatment with fluoridated gels: influence of the pH variation and of the treatment time.

The aim of this study was to quantify, in vitro, the formation of CaF2 after the application of three fluoridated gels: one neutral, one acidulated and another highly acidulated, on a bovine enamel dental surface treated with a Dijkman's demineralizing solution (1990). 145 sections were utilized, obtained from 145 sound teeth and divided into seven groups: C (enamel without treatment); FN1 (enamel demineralized and treated with neutral gel for 1 minute); FN4 (enamel demineralized and treated with neutral gel for 4 minutes); FFA1 (enamel demineralized and treated with acidulated gel for 1 minute); FFA4 (enamel demineralized and treated with acidulated gel for 4 minutes); FAA1 (enamel demineralized and treated with highly acidulated gel for 1 minute) and FAA4 (enamel demineralized and treated with highly acidulated gel for 4 minutes). The formation of CaF2 was analyzed by SEM and chemically by Caslavska's method (1975). The average and standard deviations from the groups studied were respectively: C-0.63; 0.38; FN1-23.06; 16.52; FFA1-54.11; 49.00; FAA1-43.87; 32.66; FN4-34.92; 23.00; FFA4-67.91; 42.36; FAA4-56.03; 38.96. (Mann-Whitney non-parametric test). The time of application did not interfere in the CaF2 formation from the acidulated and highly-acidulated gels. A minor concentration of fluoride and amount of pH from highly-acidulated gel did not affect the higher formation from the CaF2 in relation to the acidulated gel in both cases when the application was evaluated.

Acidulated Phosphate Fluoride↗
PubMed1978

[Thermic behavior of dental enamel, dentin and selected dental materials].

The linear coefficient of expansion of enamel, dentin as well as selected dental working materials is estimated by means of holographic-interferometric measurements. A good correlation was found between hard dental texture and a phosphate glass envisaged for use with lasers. The possible effects of the greatly increased coefficient of expansion of tested composites is discussed.

Biophysical Phenomena↗