[Suspected mineralization disorders in the deciduous dentition after Duvadilan use during pregnancy (case reports)].
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Child, Preschool↗
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Progressive mineralization pattern of developing enamel during the maturation stage.
The maturation stage of developing enamel may be divided into three substages: First, a secondary mineralization increase appears from the surface toward the deeper layer; then, a tertiary mineralization increase takes place from the deeper layer toward the surface; and finally, the narrow subsurface layer mineralizes heavily and attains the highest degree of mineralization of all layers.
Animals↗
Organ culture of tooth germs: relationship between alkaline phosphatase and mineralization in vitro.
In the 3rd day 2nd molar of the hamster, mineralization of the tooth germ has been studied in vitro starting from unmineralized predentine stage up to secretory amelogenesis. The explants were cultured in BGJb medium containing 15% foetal calf serum. The biochemical data on whole tooth germs were compared morphometrically with its main calcifying components. The alkaline phosphatase seems not to be related to cell-division but more to mineralization. There the alkaline phosphatase appeared to be more correlated with the phosphorus than with the calcium uptake. Its function in mineralization of the tooth germ seems also to be more expressed in dentinogenesis than in amelogenesis.
Alkaline Phosphatase↗
[Solubility and remineralization rate of the enamel of deciduous teeth].
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Biopsy↗
A review of clinical research on the use of prenatal fluoride administration for prevention of dental caries.
From a theoretical standpoint, primary teeth could benefit from prenatal exposure to dietary fluoride supplements. Permanent teeth are unlikely to benefit from the procedure. Additional research on placental transfer of fluoride, and mechanisms of action of fluoride is indicated. Despite encouraging trends in existing data, administration of dietary fluoride supplements to pregnant women cannot be recommended at this time, because conclusive clinical evidence that the procedure reduces dental caries in the teeth of offspring is lacking. Well-controlled clinical trials should be carried out to establish the possible value of prenatally administered dietary fluoride supplements.
Child↗
Contribution of electron microscopy to oral biology: a review.
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Animals↗
Canine eruption into grafted bone in maxillary alveolar cleft defects.
Forty-six patients with clefts of the alveolus who had received alveolar bone grafts (secondary osteoplasties) at ages 7-14 years, were studied. A total of 64 affected canines from 18 bilateral and 28 unilateral alveolar cleft patients was available. Follow up orthopantomographs were examined to determine the state of root development and spontaneous canine movement through the grafted site. The postoperative observation period ranged from 2-8 years (mean 4.3 +/- 1.5). All test canines erupted through the graft. Spontaneous eruption occurred for 27% of test canines, 17% required surgical uncovering (either bony or soft tissue), and 56% required surgical uncovering and orthodontic assistance to accomplish eruption. All patients required orthodontic treatment to accomplish arch alignment. The prognosis for canine eruption through a graft site is most favorable if the graft is performed at 1/4-1/2 canine root formation and when the patient is aged 9-12 years. The post graft observation period is very important and requires complete cooperation between the orthodontist and the surgeon.
Adolescent↗
[The cariostatic mechanisms of action of fluorides. A review].
In the past the inhibition of caries by fluorides was ascribed to the reduced solubility of enamel due to the incorporation of F- into the enamel mineral. During the last years the understanding of the cariostatic mechanism has changed fundamentally. Based on these new findings the loosely bound fluorides, which are present in the surroundings of the teeth after application of topicals, are regarded as decisive for the caries preventing effect by causing an inhibition of demineralization, enhancing the remineralization process and supporting the precipitation of CaF2. The formation of CaF2 is induced after application of topicals, and the material stays relatively stable in the mouth, due to adsorbed HPO4(2-) ions at the surface of CaF2. During the cariogenic challenge, CaF2 releases F- ions due to the reduced concentration of HPO4(2-) ions at acidic pH values. The CaF2 therefore functions as a pH-controlled F(-)-reservoir and is the most important supplier of free F- ions during the cariogenic challenge.
Dental Enamel↗
[Chemotherapy and dental growth].
A prospective study about the development of the mandibular second right molar, has been performed with 17 chemotherapy treated children in the Paediatric Oncology department of the Centre Oscar-Lambret (Lille). Our method is based upon the measure of the crown or root length for different periods: periods with or without chemotherapy. These measurements have been performed every 6 months for 18 months with orthopantomograms. We notice for both the crown and the root: a significant difference in growing speed between periods with an without chemotherapy; a speeding up of the mineralization at the end of the treatment rejoining the average figures of a healthy test population.
Adolescent↗
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↗
[Does the application of a fluoride lacquer modify the de- and remineralization of initial carious lesions in vitro?].
Bovine enamel specimens with artificial initial lesions were fluoridated with a fluoride lacquer (Duraphat) for 6 hours. Subsequently artificial plaque (Streptococcus mutans, FA1) was grown on the enamel blocks in an artificial mouth. During the experimental period (23 days) the specimens were continuously rinsed with synthetic saliva and with sucrose twice daily. Nonfluoridated specimens served as controls. At the end of the experiment microhardness was evaluated in three levels parallel to the enamel surface. In addition, the concentration of KOH-soluble and structurally bound fluoride was determined. In the fluoridated specimens microhardness increased in levels near the surface of the lesion, but decreased in the next two lower levels. However, in the nonfluoridated enamel specimens microhardness decreased in all three levels and was more pronounced compared to the fluoridated specimens. At the end of the experiment no KOH-soluble fluoride could be determined on the surfaces of the artificial lesion. In contrast, structurally bound fluoride was significantly increased in the fluoridated specimens. A single application of the fluoride lacquer on initial enamel lesions resulted in remineralization of the outer enamel layers even under persisting cariogenic conditions. However, lesion progression could not be inhibited totally.
Animals↗
Study on morphology of mandibular corpus and ramus influencing the eruption of mandibular first permanent molar.
The mandibular first permanent molar has been reported to be the first permanent tooth to erupt. However, according to the recent reports, a considerable increase in the number of children has been observed with the eruption of the mandibular first permanent molar after the eruption of the mandibular central incisor. The purpose of this study is to investigate whether there is any morphological difference in the mandible including the mandibular corpus and the ramus between the subjects with the mandibular first permanent molar erupting prior to the mandibular central incisor (Group A) and the subjects with the mandibular central incisor erupting prior to the mandibular first permanent molar (Group B). Lateral, posteroanterior, 45-degree oblique cephalometric radiographs and dental plaster models were used as the materials. Based on the data statistically analyzed, the results are summarized as follows: 1. No significant differences were found in the conventional angular lateral cephalometric measurements between the two groups. 2. No significant difference was found in the mandibular length between the two groups. 3. Significant differences were found in the mandibular corpus and the ramus between the two groups. In other words, the children in Group A have a narrower ramus, longer corpus and a larger eruption space for the mandibular first permanent molar than the children in Group B. These results indicate that even though there was no significant difference in the anteroposterior dimension of the mandible between the two groups, the internal proportion of the mandible represented as the ratio between the corpus and ramus was significantly different. This may suggest that the different proportional constituents of the mandible have a close relationship with the eruption timing of the mandibular first permanent molar.
Cephalometry↗
Some guidelines for collection and reporting of nonhuman primate growth data.
Some basic guidelines were offered to aid researches in planning and implementing the collection and reporting of data on growth and development of nonhuman primates. Weight and linear dimensions are the most frequently used measures of growth, and asseous and dental development are the most useful indicators of general bodily maturity. Estimates of sexual development can be made from general bodily maturity but more accurate assessments are based on the appearance of certain secondary sex characters. The most useful growth data are obtained from repeated, regularly scheduled examinations of the same individual. Standard procedures for measuring the external body utilize certain specific measuring points and measurements. Serial radiographs are also extremely valuable. When reporting data, age of subjects should be given in years and decimals. Means and other measures of central tendency and variability should be reported separately for each species, subspecies, and sex.
Animals↗
[Scanning electron microscopy of the resorption surface of deciduous teeth].
Based on a study of ten deciduous human teeth, (front teeth and molars) under a Scanning Electron Microscope type Tesla BS 300 we could observe that the differences of the mineralization levels are more striking in the peritubular dentin, then in the intertubular structures. The structural transformation increases by approaching the resorption surface. Near the enamel the resorption surface shows a two-edged demineralization. The mineralized part near the enamel is probably the result of the protecting processes of the human organism.
Dentin↗
Surface structure of tooth germs from newborn infants: a light and scanning electron microscopical study.
Tooth germs from the mandibles of 5 stillborn infants were examined by scanning electron microscopy and light microscopy in order to investigate the surgace structure at different stages of mineralization. The surface of the completed enamel of the incisal third of the incisors was smooth, indicating that amelogenesis was at an end. The interface relief between ameloblasts and enamel matrix on the remaining part of the incisors, and on the forming cusps, was characterized by numerous deep pits caused by the Tomes' processes of the ameloblasts. When parts of the organic matrix were removed by sodium hypochlorite, the crystals were exposed as needle-shaped structures. Towards the bases of the cusps the pits gragually smoothed out, continuing as a narrow even surface zone corresponding to the first formed aprismatic enamel. In this zone circular holes 1 micronm were encountered which the light microscope studies showed were dentinal tubules passing into the enamel. At the bases of the cusps there was a rather abrupt demarcation toward a surface zone exhibiting countless slender villi. The light microscope observations indicated that these villi represented the first formed dentine after the basement membrane had disappeared.
Amelogenesis↗
[The effect of the initial level of mineralization of the erupting molars on their caries susceptibility].
A method for predicting caries of permanent molars at the stage of enamel mineralization has been developed. It is based on measuring the electric conductivity of hard dental tissues. A total of 100 children have been examined over time (for 7 years), starting from the age of 5 to 6 when permanent molars are just erupting and after they appear. The erupting molars are characterized by different levels of mineralization which determines tooth resistance or liability to caries. The initial level of mineralization of erupting molars is the earliest and sufficiently objective prognostic criterion which helps start individual preventive measures.
Adolescent↗
Recombination of epithelial root sheath and dental papilla cells in vitro.
Hertwig's epithelial root sheath (HERS) cells were isolated and recombined with ectomesenchymal cells in vitro utilizing extracellular matrix components as substrate. After 14 days in culture, HERS cells were differentiated and exhibited a stratified organization. These features resembled those observed in vivo as epithelial rests of Malassez. A mineralization process was also present in HERS cells, in which calcium salts were deposited. This mineralization was correlated with the strong immunoexpression of osteopontin by HERS. The results obtained add support to the possible role of HERS in the secretion of hypocalcified material on the root during early cementogenesis.
Animals↗