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At least 469 records · Page 26Linked to original sources
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↗
PubMed1992

Endocrine dysfunction in Kearns-Sayre syndrome.

Kearns-Sayre syndrome (KSS) is a form of mitochondrial myopathy in which specific clinical features, namely progressive external ophthalmoplegia, pigmentary retinal degeneration and cardiac conduction defects, occur. KSS has also been associated with a variety of endocrine and metabolic disorders, in particular short stature, gonadal failure, diabetes mellitus, thyroid disease, hyperaldosteronism, hypomagnesaemia, and bone, tooth and calcification abnormalities. A case is described exhibiting all of these features. A survey of the literature was conducted to determine the prevalence of these conditions among reported cases. Cases with hypoparathyroidism were considered separately to see if they constituted a distinct subgroup with multiple endocrine dysfunction. Short stature was common, being documented in 38% of cases. Gonadal dysfunction before or after puberty was also common (20% of cases) and affected both sexes equally. Diabetes mellitus was recorded in 13% of cases, half of which required insulin. Thyroid disease, hyperaldosteronism and hypomagnesaemia were uncommon but were probably not looked for in many cases. Bone or tooth abnormalities and calcification of the basal ganglia were found both in those with and without hypoparathyroidism. While endocrine and metabolic dysfunction was found more commonly in those with hypoparathyroidism this is likely to be due to increased recognition rather than increased prevalence. No evidence of an autoimmune polyendocrine syndrome including hypoparathyroidism was found.

Child↗