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PubMed1989

[Effects of 1-hydroxyethylidene-1, 1-bisphosphonate (HEBP) on the unimpeded eruption rate and the dental hard tissue formation in rat mandibular incisor].

To understand the mechanism of eruption in continuously growing teeth, the relationship between the rate of eruption and formation of dental hard tissues was examined following administration of 1-hydroxyethylidene-1, 1-bisphosphonate (HEBP), an inhibitor of hard tissue formation. Three experimental groups of rats received daily subcutaneous injections of 9, 18 or 36 mg P of HEBP/kg, respectively, for 7 days. Tetracycline was also injected to mark the dentine in some animals. To maintain an unimpeded state, all four incisors in each rat were shortened repeatedly during the experimental period. Eruption rates of the mandibular incisors were measured by a photographic method. Transverse sections of the mandibles were cut and histological, microradiographic and fluorescent micrographic examinations were done. Significant decreases of the eruption rates were found in all experimental groups following the administration of HEBP. However, differences were not marked among the three experimental groups. It was also shown that matrix formation and calcification of the dentine were markedly inhibited following the administration of HEBP. Matrix formation and calcification of the enamel were also inhibited by the drug administration. It is assumed that the eruption of the rat incisor is not closely associated with the formation of dental hard tissues and their calcification.

Animals↗
PubMed1977

A comparative study of alkaline phosphatase in calcifying cartilage, odontoblasts and the enamel organ.

The enzyme alkaline phosphatase (AP) (EC 3.1.3.1) in three different calcification areas was studied by means of a spectrophotometric micro method using p-nitrophenylphosphate as a substrate. Rat maxillary incisor odontoblasts and enamel organ from the zones of matrix formation and maturation and tissue from rabbit metatarsal cartilage were allowed to react with the substrate in glycine-NaOH buffer at room temperature. The reaction was found to be linear for a minimum of 20 min. The pH optima for AP from these tissues were in the pH range of 10.0-10.3. In order to compare AP from the four calcification areas different parameters were studied. Heating at 56 degrees C or 60 degrees C for varying times revealed that the enzymes were almost completely inactivated after 10 min. Mg2+ ions activated the enzymes by about 25% at concentrations of 2.5 mM (enamel organ 1.25 mM); while only higher concentrations of Mg2+ had an inactivating effect, Ca2+ and PO3-4 ions were inactivating at varying concentrations. F- ions showed no effect on AP activity at concentrations below 250 mM (enamel organ 125 mM) but caused inactivation of the enzymes at about 50% at 1 M. EDTA was found to be a very effective AP inactivator at concentrations above 0.06 mM, whereas urea did not noticeably affect the enzyme reactions at concentrations below 1 M. At higher concentrations, inactivation was observed. In order to determine AP localization in the epiphyseal plate successive 40-mum-thick, freeze-sectioned slices were analyzed. The activity was highest nearest the zone of cartilage calcification and decreased towards the reserve cell zone. It was concluded that the same AP isoenzyme is present in these quite different calcification loci.

Alkaline Phosphatase↗
PubMed1996

Immunolocalization of the small proteoglycan decorin in human teeth.

The immunolocalization of decorin was studied by confocal laser scanning microscopy and transmission electron microscopy. In the apical area of developing teeth, labelling for decorin was found in the dental papilla cells, prodontoblasts and also in the Hertwig's epithelial cells. Mantle dentine and the initial predentine were negative. In circumpulpal dentine, intense reactivity extended along the calcification front and dentinal tubules. Fluorescence was also evident in odontoblast cell bodies and their processes in predentine. None was perceived, however, in the predentinal matrix. Faint staining was observed on the calcified dentinal matrix. Immunoelectron microscopy revealed staining for decorin in collagen fibrils lining the predentine-dentine junction, and where arrays of labelled filaments were noted orthogonal to the collagen fibrils. Staining extending from the calcification front was observed in the matrix adjacent to the dentinal tubule. The decorin observed at the calcification front might regulate the mineralization of dentinal matrix.

Adult↗
PubMedDate not supplied

The differences in the chronology and calcification of second molars between angle Class III and Class II occlusions in Japanese children.

The purpose of this study was to examine the differences in the times of eruption and calcification of the permanent dentition between skeletal class III and class II groups. (And also to examine the relationship between the time of eruption and the type of malocclusion) Fifty-three children, ages seven to ten years, were selected. Of these, twenty-six children (twelve boys and fourteen girls) were Angle class III with minus ANB and twenty-seven children (eleven boys and sixteen girls) were Angle class II with five or more ANB. Panoramic radiographs and cephalometric radiographs were used. The panoramic radiographs showed that the calcification of the maxillary second molars in class II were earlier than in class III using Nolla's classification. There was no statistically significant difference, however, for mean values of calcification stages, using Nolla's classification, between boys and girls. The cephalometric and panoramic radiographs showed that the times of eruption and calcification were earlier in the maxillary second molars than in the mandibular second molars for class II. In contrast, the times of eruption and calcification were earlier in the mandibular second molars than in the maxillary second molars for class III. The times of eruption and calcification of the maxillary molars were significantly related to the length of the ANS-PNS. The longer the ANS-PNS, the earlier were the times of eruption and calcification. There was a significant relationship between the ANB angle and the time of eruption, as well as the ANB angle and calcification. The larger ANB had earlier calcification and chronology of maxillary second molars.

Cephalometry↗
PubMedDate not supplied

A radiographic investigation of third-molar development.

In view of limited investigations it was considered worthwhile to determine the impact of race, age, and gender on the development and calcification of third molars. Results showed that calcification of third molars could be estimated by observing one quadrant. The crown calcification process begins and is completed earlier in blacks. There were no significant gender differences.

Adolescent↗
PubMed2003

Radiographic evaluation of third molar development in Spanish children and young people.

Third molar development was evaluated in 786 young people aged between 4 and 20 years, all patients at the School of Dentistry of the University of Granada. The development of third molars and of mandibular second premolars and second molars was determined according to the stages proposed by Nolla. The onset of mandibular third molar formation was observed at very variable ages in this series, ranging from 5.86 to 14.66 years. The first developmental stages of maxillary third molars are not usually visible radiographically, which can lead to an incorrect diagnosis of agenesis. We found no significant relationship between the gender or age of the patient and the presence or absence of third molars. However, the presence/absence of the third molar can be predicted in 82.82% of cases when there is some degree of calcification of mandibular second molars and second premolars.

Adolescent↗
PubMed1989

[Ultrastructure of microcalcifications of the pulp mesenchyme of human deciduous teeth].

Scanning electron microscopic observations of pulp calcifications in deciduous molars were correlated with microradiographic findings. Numerous spherical calcifications were found in appearance similar to those in the permanent dentition. In a second type, mineralization took the form of diffuse deposits of calcium. The discrete diffuse foci coalesced into large islands of mineralized connective tissue. A third type of calcification was observed in which rhombic crystals were associated in a spherulitic pattern. The exact cause of the crystal formation is unknown. Moreover, as we are aware, the spherulitic calcifications have never been previously reported in this location. The preliminary results indicated that mineralization in the pulp of deciduous molars, takes a variety of forms, suggesting that calcium deposition can occur by different processes.

Dental Pulp↗
PubMed1989

The effect of fluoride drop administration on dental caries increment--a longitudinal study.

The effect of fluoride drop supplementation was investigated in a longitudinal study initiated in 1980. The def-t and DMF-T indices were used to estimate the incremental caries rate of the deciduous and first molars of 211 children aged 7-8 and 9.5-10.5 years. No statistically significant differences between the experimental and control def-t and DMF-T scores were found after 3 years. The incremental caries rate of the deciduous dentition of the experimental group was found to be significantly lower than that of the control group (def-t = 0.61 and 1.07 respectively), whereas the difference in the caries increments of the first molars was not significant (DMF-T = 1.62 in both groups). It is estimated that the efficacy was due to the long-term cariostatic effect of the topically acting fluoride on the erupting primary dentition, whereas the permanent dentition (first molars) had already completed calcification of the crown, but had not erupted at initiation of the study. It was estimated that the most effective cariostatic benefits would be apparent in the late erupting teeth of this study group.

Child↗
PubMed1992

Clinical observations on the development of third molars.

In order to investigate the developmental conditions of third molars in Japanese, we studied the panoramic radiographs taken during dental treatment at the Pediatric Outpatient Section of Osaka Dental University Hospital of 9,111 children (4,646 boys and 4,465 girls) between the ages of 7 years 0 months and 16 years 11 months, in addition to 2,769 panoramic radiographs of students of this university (2,312 men 457 women) kept by the Department of Oral Radiology. The following results were obtained. 1. Calcification of the third molars in both boys and girls began as early as 7 years 6 months in the maxilla and 7 years 0 months in the mandible. The average age for initiation of calcification in the maxilla was 9 years 4 months for boys, and 9 years 2 months for girls, while the ages in the mandible were 9 years 1 month and 8 years 9 months, respectively. 2. The average age for completion of the third molar crowns in the maxilla was 11 years 8 months for boys and 11 years 5 months for girls, while in the mandible it was 12 years 4 months and 12 years 3 months, respectively. 3. At greater than 13 years of age, the tooth germ could be found in boys about 70% of the time in the maxilla and 75% of the time in the mandible, while these figures for girls were 65 and 80%, respectively. 4. All four third molars were present in 52.3% of the males and 45.5% of the females, while 9.5% of the males and 12.0% of the females had no third molars at all. 5. The direction of eruption was classified as either vertical, mesial, horizontal, distal, or buccal/lingual type. The rate for the vertical type in males was 70% in the maxilla and 45% in the mandible, while these figures for females were 50 and 40%, respectively. 6. Microdontia of the third molars appeared only in the maxilla. 7. Congenital absence of the third molars was more common in females than males, and occurred more frequently in the maxilla than in the mandible. The results of this study allow a better understanding of the third molars of Japanese and provide an aid to planning in such areas of clinical pediatric practice as guiding occlusal development.

Adolescent↗
PubMedDate not supplied

Radiographic evaluation of third-molar development in a group of Turkish children.

The aim of this investigation was to evaluate the crypt formation and calcification of the maxillary and mandibular third molars according to age and gender on panoramic radiographs in a group of Turkish children. Four hundred panoramic radiographs of 188 female and 212 male dental patients, ages six to thirteen years, were examined by two observers. The interrater reliability was tested by Kappa statistics. The earliest age for maxillary third molar crypt formation was eight years; mandibular third molars could be seen radiographically as early as seven years.

Adolescent↗
PubMed1990

[Radiographic study of formation and calcification of the third molar].

A total of 500 orthopantomographic X-rays of Mexican children and teenagers of either sex, aged 7-18, were studied in order to ascertain the development and calcification stages of their third molars, as well as the most frequent anomalies related with them. It was observed that the dental bud appears between ages nine and eleven, and that the third molar is absent in 32.4% of the population, with a predominance of females over males. It was also found that 7.4% of molars evidenced malposition during their early stages of development. In view of such findings, the authors consider that a diagnosis of oligodontia and malposition of the third molar, cannot be established before age 13.

Adolescent↗
PubMed1990

[Dentofacial manifestations in children with vitamin D-dependent Rickets type II].

Calcification of the teeth, size of the teeth and dental arches, facial growth and calcification of the carpal bones were studied in three children with clinically different severities of vitamin D-dependent rickets (DDR), type II, with alopecia, which is 1,25-dihydroxyvitamin D-receptor-defect rickets and is particularly resistant to treatment with calciferol analogues. They were treated in a pediatric clinic with large doses of 1 alpha-hydroxyvitamin D3(1 alpha-(OH)D3) and 2 g/day of calcium lactate. The results were as follows: 1. Hypoplasia of enamel of the deciduous teeth was not found. 2. In the deciduous teeth, large pulp chambers and thin dentin were seen in radiographs before treatment. In patients 1 and 2, these abnormalities were reversed by treatment. In patient 3, who had the severest manifestations, large pulp chambers and thin dentin decreased but still remained. 3. Growth of permanent teeth was retarded before treatment and during resistance to treatment. After effective medication, it caught up and was corrected. 4. Problems concerning maxillary and mandibular growth were not found. However Nasions of three patients were more front and lower and Orbitals were lower than standard. 5. In patients 1 and 2, the calcification of carpal bones was accelerated and in patient 3 retarded. 6. Mesiodistal dimensions of erupted deciduous and permanent teeth were within the standard range, except for patient 3, who had smaller lower deciduous teeth. 7. A ground section of the extracted upper right first deciduous molar from patient 3 showed abundant inter-globular dentin and lack of pre-dentinal layer. From the above findings, it was felt that in all probability dentinogenesis was disturbed by the DDR type II. Abnormally large pulp chambers and thin dentin could be corrected by effective medication. In patients with vitamin D-dependent rickets type II, oral hygiene for caries prevention is the most important procedure, because the pulp will be infected immediately after initiation of dental caries. After effective medication, permanent teeth and jaw bones will probably grow normally.

Carpal Bones↗
PubMed1996

Structural and calcification patterns of the neonatal line in the enamel of human deciduous teeth.

The neonatal line of the enamel in human deciduous teeth was observed by scanning electron microscopy using secondary and backscattered electron signals. The neonatal line containing irregular structures of enamel prisms with disordered crystal arrangements was basically formed by the abrupt bending of the prisms towards the root. Usually, the prisms gradually bent back again to regain their previous orientation, but the prisms in the inner and the surface layer sometimes ran straight ahead after bending. The prism sheath regions showing hypocalcification contained a relatively large amount of organic material as shown by treatment with chromium sulfate. When etched with ethylenediaminetetraacetic acid (EDTA), such prism sheath regions were extensively eroded due to the lower density of crystals caused by the abrupt bending of the prisms. Abnormally shaped prisms and small prismless areas were occasionally present. The neonatal line formed by the double bending of the prisms is likely to represent a particular type of rhythmic Retzius line rather than a pathologic Retzius line, whereas the hypocalcified sheath regions may be similar to those of some pathologic lines of Retzius.

Child↗
PubMed1996

Calcium deficiency, diet and dental disease in pet rabbits.

Poor calcification of the teeth and the bones of the skull predisposes pet rabbits to dental disease. This study is a preliminary investigation into the dietary habits of pet rabbits. Owners were questioned about the feeding preferences of their pets. Manufacturers of rabbit foods were asked about the calcium, phosphorus and vitamin D content of their foods and how they had decided upon the formulation of their rations. Samples of rabbit food were analysed for calcium and phosphorus. Rabbits were found to be selective feeders. Rabbit food from pet shops consists of a mixed ration, of which the most commonly rejected ingredients were pellets and whole grain. The food manufacturers reported that calcium, phosphorus and vitamin D supplements are incorporated into the pellets. Food analyses demonstrated that rejection of the pellets and whole grain from the food can reduce a rabbit's calcium intake to below the minimum dietary requirement. The rabbit's unusual calcium metabolism is discussed. Calcium deficiency may cause osteomalacia but dietary excess may cause urolithiasis. Vitamin D deficiency may also exacerbate calcium deficiency. Recommendations are made for preventing calcium deficiency and dental disease in rabbits.

Animal Feed↗