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Results for “Tooth Calcification”

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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↗

PubMed1986

The innermost layer of cementum in rat molars: its ultrastructure, development, and calcification.

The present study describes the ultrastructure of the innermost layer of cementum (ILC) in the rat molars and discusses its developmental process and calcification mechanisms. The following points are the main results of this study: The ILC is a thin layer, about 2.0 micron thick, intensely stained with hematoxylin but not stained by silver impregnation. Electron microscopically, it is composed of substances stained with ruthenium red and chronic phosphotungstic acid presumed to be proteoglycans and a few thin collagen fibrils. Periodontal fibers penetrate the ILC only a short distance, and do not reach the root dentin surface. The ILC begins to form on the root dentin surface, just after the disintegration of Hertwig's epithelial root sheath. At the same time, matrix vesicles and spherical bodies, which may be derived from the matrix vesicles, appear on the surface of the developing ILC. Dental sac cells show higher cell activities than the epithelial sheath cells. Observations support the view that the dental sac cells secrete the ruthenium red positive material. On the basis of the above findings, the ILC is suggested to be formed by the dental sac cells and calcified by the matrix vesicles derived from these cells. The ILC can be regarded as a specialized cementum between the root dentin and the cementum in the strict sense, serving the connection of the two tissues.

Animals↗

PubMed1989

Calcification of the permanent first molars observed in panoramic radiographs.

We investigated the development (calcification) stages of the permanent first molars of Japanese children by classifying them into 14 stages by the criterion of Moorrees, et al., using 11,167 panoramic radiographs, 5,759 of boys and 5,408 of girls, between the ages of 2 years 0 months and 14 years 11 months. The following information was obtained from calculations of the average chronological ages for the development stages of these teeth. 1) The development of first molars was earlier in girls than boys. This was particularly true during the middle phase of development. 2) A first molar on one side developed at the same rate as its counterpart on the other side, regardless of differences in sex or arch. 3) In both boys and girls, the development of the mandibular first molars was about one month earlier than that of the maxillary first molars at each stage. 4) When these results were compared with those of Nolla, Moorrees and Haavikko, who pioneered this field of study, it was clear that the development of the teeth in Japanese is different from that in Caucasians. 5) We made charts of the development of the first molars in Japanese which can be applied in routine clinical practice.

Adolescent↗

PubMed1956