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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↗
PubMed2003

Tooth formation and the mandibular symphysis during the first five postnatal months.

Schedules based on tooth development are useful in age assessments of children, but in early infancy they are based on only a few studies. The radiographic appearance of the mandibular symphysis during the first postnatal months has not gained attention. The present study describes the formation of teeth and the development of fusion between the mandibular halves during the first five postnatal months, as seen in panoramic tomograms taken in medicolegal autopsies of 29 ethnic Finns, 19 boys and 10 girls, at the Department of Forensic Medicine, University of Helsinki. In the majority of the infants, the criteria of sudden infant death (SID) were fulfilled. The stages of tooth formation used were those applied by Moorrees et al. with one modification (Nyström et al.). Mineralization of all primary teeth proceeded rapidly during the first postnatal months, the change being on average two developmental stages in four months. Considerable variation in tooth development existed in infancy. The mandibular halves were separated at birth. Complete fusion had occurred in the majority of infants aged four months, and the tomograms of the remaining infants showed a thin vertical line in a part of the symphysis. The marked changes, which during the first postnatal months occur in the radiographical appearance of the mandibular symphysis, and in the formation of primary teeth, provide valuable information for age assessments of infants.

Age Determination by Teeth↗
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↗
PubMed2003

Putative membrane receptor for 1,25(OH)2 vitamin D3 in human mineralized tissues during prenatal development.

The calciotropic hormone, 1,25(OH)2vitamin D3[1,25(OH)2D3], controls the formation of dental and bone mineralized tissues. The role of nuclear 1,25(OH)2D3 receptor has been extensively studied in the diverse secretory cells, i.e., osteoblasts, chondrocytes, ameloblasts, and odontoblasts. A nongenomic pathway also has been characterized and related to the interactions of 1,25(OH)2D3 ligand with a putative cell membrane receptor. This recognition moiety called 1,25(OH)2vitamin D3 membrane-associated, rapid-response steroid-binding [1,25D3-MARRS] protein is investigated here in the craniofacial skeleton of human embryos and fetuses. Immunolocalization using a specific Ab099 against chick intestinal basolateral 1,25D3-MARRS protein was performed. The data show a complementary expression pattern of the membrane receptor when compared with published data on the nuclear receptor, notably during amelogenesis. In mandible, membrane receptors for 1,25(OH)2D3 were identified in the heterogenous bone cell population, including osteoblasts and osteoclasts. Differential 1,25D3-MARRS protein levels were observed in distinct developmental stages and anatomical sites of tooth and bone, suggesting the existence of cross-talk between local factors and 1,25D3-MARRS protein expression.

Gestational Age↗
PubMedDate not supplied

Developmental stages of the third molar in Israeli children.

PURPOSE: The purpose of this study was to examine the developmental stages of the third molar in Israeli children, compare its development in boys and girls, in the maxilla and mandible, right to left sides in various age groups, and relate the developmental stage to chronological age. METHODS: Panoramic radiographs of 693 healthy children and adolescents (328 boys and 365 girls) ages 7 to 16 were analyzed using a modified 6-stage method. Since the 16-year-old group was too small for statistical analysis, it was later excluded from the study. Radiographs were obtained from patient files. RESULTS: There were no significant differences in the development of the third molar between boys and girls and between right and left sides. Slight differences were found between the maxilla and mandible. The first appearance of a radiolucent bud was at age 8.7 in the mandible and 9.3 in the maxilla. Crown completion was observed on average at age 11.7 in the maxilla and 11.8 in the mandible. CONCLUSIONS: There was a high correlation between third molar development and chronological age. Agenesis can be determined conclusively if no radiolucent bud is present beyond age 14. The modified 6-stage method allowed more accurate determination of developmental stages.

Adolescent↗
PubMed2003

Hypomineralised first permanent molars and the orthodontist.

AIM: This paper discusses the orthodontic implications that need to be considered when a child presents with hypomineralised permanent molars. The various historical and present day orthodontic approaches are outlined and indications for the various sequences or extraction of first permanent molars presented.

Child↗
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↗
PubMed1990

[Comparisons of effects of vitamin D3 metabolites on mineralization: utilization of incisor dentin in parathyroidectomized rats].

The rat incisor is continuously growing throughout the animal's life recording the state of mineralization within its dentin at all times. Therefore, it was assumed that the incisor dentin was suitable material for studying the effects of various drugs on such mineralization. The present study set out to examine the effects of vitamin D3 metabolites on the remineralization of dentin and the serum calcium level in parathyroidectomized (PTX) rats. Male Wistar rats weighing about 200-250 g were parathyroidectomized. Each rat was given daily 12 g of a synthetic diet containing 0.1% Ca and 0.4% P (normal P) or 0.06% P (P deficient) without vitamin D. Exp. I: Three groups of rats given a normal P diet were orally administered vehicle, 25 (OH) D3 (50 IU/rat) or 1,25 (OH)2D3 (5 IU/rat) for 5 days from the 28th day after PTX, respectively. Exp. II: Two groups of rats given a normal P diet or a P deficient diet were further divided into 4 sub-groups and intramuscularly administered 0, 5,000, 10,000 or 20,000 IU of vitamin D3 on the 9th day after PTX, respectively. The active vitamin D3, 1,25 (OH)2D3 restored the mineralization of the dentin which had been suppressed following PTX, and elevated the serum calcium level to about 9 mg/dl. However, the 25 (OH) D3 neither restored the mineralization of the dentin nor elevated the serum calcium level in the PTX rats. At doses below 1,000 IU, vitamin D3 could not restore the mineralization of the dentin. However, at massive doses above 5,000 IU, the mineralization was restored in proportion to the dose. The serum calcium levels also increased in proportion to the dose. It is assumed that the increase of the serum calcium level was mainly due to the enhancement of calcium absorption from the intestine by vitamin D3. Both remineralization of the incisor dentin and increase of the serum calcium level were more marked in groups of rats given a P deficient diet than in those given a normal P diet. In all cases in the present experiments, the degree of mineralization of the dentin seemed to correspond with the degree of elevation of the serum calcium levels. These results suggest that the remineralization of the dentin in the PTX rats was attributable to the effect of the vitamin D3 metabolites on serum calcium regulation. Relative biological activities of 1,25 (OH)2D3, 25 (OH) D3 and vitamin D3 on the remineralization of dentin were estimated to be 1, less than 0.02 and less than 0.001, respectively.

Animals↗
PubMed1990

[Demineralization behavior, enamel permeability and the morphological characteristics in relationship to the stage of eruption of the permanent teeth].

The posteruptive maturation of enamel is an important factor in caries disposition. In an experimental study the demineralization of enamel as well as its permeability and its morphological features in dependence of eruption stage were examined on extracted premolars. Chemical analysis showed variations in the Ca/P molar ratio. It is possible, that the instability of Ca-ions in crystalline configuration decreased during the time of eruption. The permeability of enamel decreased between 5 and 11.8%. It appears to be useful to concentrate preventive measure on this phase of dentition development.

Bicuspid↗
PubMedDate not supplied

[The effect of magnesium sulfate electrophoresis and galvanization on the mineralization of teeth and bones].

Effects of Mg2+ electrophoresis and galvanization on tooth and bone mineralization was experimentally studied with the use of radioactive Ca and P isotopes. Mg2+ electrophoresis and, to a lesser degree, galvanization enhanced 32P incorporation in incisors and maxillary bones. Mg2+ significantly increased 45Ca incorporation in teeth and maxillary bones. Experimental data permit clinical trials of Mg2+ efficacy in patients with disordered mineralization and remineralization.

Animals↗
PubMedDate not supplied

[Hypomineralization of milk teeth of prematurely born children--effect of some factors for its origination].

A comparative study was carried out between two groups of children--115 prematurely born and 4830 full-term babies in order to establish the effect of pregnancy duration of the origination of hypomineralization of the milk teeth. The effect of the following factors was also studied and compared: complications of pregnancy, feeding of the newborn and diseases during early childhood of full-term and prematurely born children. The authors established that the prematurely born children were a risk group for the origination of milk teeth hypomineralization. The complications of pregnancy, mixed or bottle feeding as well as the frequent illnesses are additional aggravating factors in the origination of milk teeth hypomineralization. The authors recommend timely follow-up care and prophylaxis of all prematurely born children.

Bottle Feeding↗
PubMed1989

[Evaluation of remineralization solutions on the milk teeth].

The milk incisors of 80 infant-school children were demineralized. For the following 3 weeks the children then rinsed their mouths with mineral solutions. By manifold replica yields (analysis by light- and scanning electron microscope) and colouring tests a positive influence of calcium and phosphorus holding solutions, among others with magnesium, too, on the remineralization was discovered.

Child, Preschool↗