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At least 73 records · Page 4Linked to original sources
PubMed1975

A radiographic study of rostral tooth development in young Friesian cattle.

Twenty-nine British Friesian cattle fed the same diet, slaughtered at various weights and including bulls, steers (castrated males) and females (heifers) were examined. The stage of their rostral tooth development was recorded both visually and radiographically. Insufficient animals were present in each sex and slaughter weight treatment group to allow any comparison between them. When the data for each sex were compared, no statistically significant differences were seen between the mean ages at which bulls, steers and heifers attained each stage of dental development as determined from their radiographs. The results for all 29 cattle were then combined. This combined data showed a relationship between age and those stages of tooth formation which could be differentiated by examination of the X-ray films. As most phases of tooth formation occurred within well defined limits, it is suggested that radiographs of rostral tooth development might be used to estimate the age of cattle.

Age Factors↗
PubMed1975

Mandibular cheek tooth development and its relationship to age in young Friesian cattle.

The oral and intra-osseous development of each of the six manidibular cheek teeth found in the permanent dentition of cattle was studied. The animals used were all British Friesians, of varying sex, and slaughtered at different weights at ages between 13 and 22 months. The various stages of development observed in each tooth together with the mean age and age range at which they were seen are recorded. Significant differences were found between the ages at which several of the developmental stages were seen in most of the teeth and indicated that tooth formation in the Friesian cattle studied tended to fall within well defined age limits.

Age Determination by Teeth↗
PubMed1975

Sexual dimorphism in dentition mineralization.

This study determined for 121 boys and 111 girls of the serial experimental group of the Burlington Growth Centre the age, time interval and age sequence of 14 stages of mineralization of all tooth types. The two sexes differed significantly in the age at which the stages of tooth mineralization appeared, and in the length of the interstage intervals. In the canines, there was maximum sex difference in mineralization, which was almost 20 per cent and resulted from a delay in the boys. Changes in sequence of mineralization were due to delay rather than to acceleration. Sex differences in tooth mineralization manifested themselves before puberty, and mineralization was not accelerated at puberty. In contrast, post-pubertal mineralization of third molars appeared to be accelerated in both sexes and occurred earlier in the boys.

Age Factors↗
PubMed1975

The relationship of maxillary cheek tooth development to age in young Friesian cattle.

Radiographs were taken of both the right and left sets of maxillary teeth in 23 Friesian cattle of known age. The stage of development of each permanent tooth was ascertained and the degree of root resorption in the deciduous premolars was noted. All stages in individuals were later than for those of the mandibular cheek teeth except in the case of the first permanent premolar. As with mandibular cheek tooth development stages of formation occurred within certain age limits.

Age Factors↗
PubMed1976

[Ultrastructural changes in cells of the inner enamel epithelium, stratum intermedium and reticulum stellatum in the enamel organ of the upper incisor of the Wistar rat at different phases of amelogenesis].

An electronmicroscopical study of the enamel organ of the upper incisors germs of Wistar rats was performed to analyse the ultrastructural features of the cells of the inner epithelium, the intermediate layer and the stellate reticulum, during preimary, young, transitional and mineralized enamel phases of amelogenesis. So, it was observed that the mitochondria in the ameloblasts are ovoid before the beginning of the enamel matrix formation and in the primary and young enamel phases. However, in the transitional and mineralized phases, these organelles are long and tortuous and some are characterized by a compact structure. In the cells of intermediate layer and stellate reticulum, the mitochondria are ovoid until the beginning of the mineralized phase. At the ending of this phase, these organelles are very long and present irregular form; many of them show also a compact structure. The "zonula adhaerens" could be observed only in the ameloblasts of the primary and young enamel phase. The cytoplasm of ameloblasts, during primary and young enamel phases is characterized by an abundance of free ribosomes and a branular endoplasmic reticulum; but during transitional and mineralized enamel phases, the cytoplasm of these cells shows little granular endoplasmic reticulum and free ribosomes, but ehe agranular endoplasmic reticulum is present. The granular endoplasmic reticulum and free ribosomes are abundant in the cells of the intermediate layer and stellate reticulum at the ending of the young enamel phase, in the transitional enamel phase and in the beginning of the minieralized phase. During different phases of amelogenesis, in the three above referred layers of the enamel organ, were also studied the features of the Golgi apparatus the presence and topographic distribution of the pigment granules, as well as the lysosomes, desmosomes and the tonophibriles.

Ameloblasts↗
PubMed1991

Possible functions of alkaline phosphatase in dental mineralization: cadmium effects.

In mineralizing dental tissues the non-specific alkaline phosphatase, using paranitrophenylphosphate (p-NPP) as substrate, is also capable of splitting inorganic pyrophosphate (PPi). In contrast to the p-NPP-ase part of the enzyme, the PPi-ase part requires Zn2+ as a cofactor for its hydrolytic activity. The PPi-ase activity of the enzyme can be inhibited by cadmium ions (Cd2+), perhaps by replacing Zn2+ from the active site of the enzyme molecule. In addition to splitting PPi, the PPi-ase part of the enzyme may also be involved in the phosphorylation process of yet undetermined organic macromolecules. Cd2+ inhibits this phosphorylation process. Inhibition of the PPi-ase activity can also be accomplished by ascorbic acid known for its capacity to complex bivalent cations. Ascorbic acid may accordingly also remove Zn2+ from the active site of the PPi-ase. It is suggested that in developing dental tissues alkaline phosphatase is not only associated with the transport of phosphate ions towards the mineralization front, but is also involved in the phosphorylation of organic macromolecules, a process activated the PPi-ase part of the enzyme.

Alkaline Phosphatase↗
PubMed1991

[Extremely delayed mineralisation of a first premolar in conjunction with submerged deciduous molars--a case report].

This case report presents a patient with extremely delayed mineralisation of a first upper right premolar and simultaneously congenitally missing second premolars. While the germs of the first premolars are usually detectable on dental X-ray films at the age of three or four years, the demonstrated patient was older than 13 years when the first premolar became visible. As the right first bicuspid actively erupted normal root growth took place, and once the tooth is in its normal position its anatomy can be considered normal. With the eruption of the permanent tooth the periodontal situation improved considerably in the region where depression of its predecessor had taken place. As a practical clinical consequence one should take into consideration that mineralisation of a first premolar can be extremely delayed in cases with congenitally missing second premolar teeth.

Adult↗
PubMed1991

[Maturation of enamel and tooth eruption].

The tertiary maturation of the erupting tooth needs much more time than it is supposed in literature. Possibly the completion is in accord with the decline of the caries activity at the end of the second decade of lifetime. With the aid of polarizing microscopy, electron microprobe, microhardness testing (Vickers) and scanning electron microscopy different stages of posteruptive maturation from human and other mammalian teeth were analysed. The mineralization level in the outer surface of human enamel is completing little by little in more than 5 years after eruption. This state is in the ruminant tooth obvious never within reach in consequence of the specific physiological conditions. The maturating mineralization after our preliminary findings is fundamentally different to remineralization.

Animals↗
PubMed1990

[The crystallinity of hypomineralized rat enamel caused by fluoride administration].

It has been well known that there are extreme amounts of inter-crystalline spaces and large amounts of enamel matrix in fluorosed human enamel. Our previous study discussed the fact that amelogenins in developing fetal enamel matrix protein may have a role in regulating or controlling enamel crystal growth. These results positively suggest that amelogenins degradation may be associated with the etiology of fluorosed enamel. The purpose of this study was to examine the relationship of the crystallinity of fluorosed enamel of rats and the molecular weight of enamel matrix protein. The crystallinity of fluorosed enamel of rats, caused by the ingestion of fluoride containing water was evaluated with the microbeam x-ray diffraction analysis and the molecular weight of enamel matrix protein was examined by SDS-polyacrylamide-gel electrophoresis. The results obtained in the study are summarized as follows. 1) The plasma fluoride level of rats increased linearly with the fluoride concentration in the drinking water. 2) The microradiographs of maturing incisor enamel of the group with 100 ppmF- and 200 ppmF- injected showed diffused radiolucent zone from the subsurface toward the dento-enamel junction. The disturbances in enamel mineralization were most apparent in the 200 ppmF- group. 3) The crystallinity of the radiolucent zone of the fluorosed enamel decreased in both the a and c-axis directions, and particularly decreased more in the a-axis compared with the control. 4) The pattern of the SDS-polyacrylamide gel electrophoresis of the enamel protein in the mature stage showed higher remaining molecular weight of amelogenins in rats in the 100 ppmF- and 200 ppmF- group. These results suggest that in hypomineralized enamel caused by long-term administration of fluoride containing water, the degradation of amelogenin protein was disturbed, and consequently the crystallinity of enamel apatite decreased.

Amelogenin↗