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PubMedDate not supplied

Chronological development of the dentition of medically indigent children: a new perspective.

The following conclusions can be derived from the results of this study: A cross-sectional survey approach is useful in collecting and evaluating relatively large numbers of dentitions. With an increase in the number of categories pertaining to both development and the age, a sufficiently large sample size is necessary to establish validity. Increasing both the number of developmental stages and the number of age divisions makes for more precise measurement. There is a need for sex-specific standards, because females are significantly more advanced than males, in tooth formation. Comparison with other studies suggests that socio-economic status is a factor in tooth development. However, well-controlled epidemiologic studies are necessary to identify contributory factors. Presently, international surveys have not attempted this methodology; comparisons, therefore, between studies rely upon varied selection of populations and subjective charting of radiographs, which make any conclusions tentative, at best. Specific populations, because of wide ranges in developmental rates, must have their own charts. The traditional age-stage standard is too general and imprecise, to be useful for identification purposes.

Adolescent↗
PubMed1982

Formation of intermediate cementum. I: early mineralization of aprismatic enamel and intermediate cementum in monkey.

Intermediate cementum and aprismatic enamel outlines the dentinal surface in the crown and root. Since the formation of these tissues is incompletely known and there have been diverging opinions whether they are of epithelial or mesenchymal origin, the present study was undertaken to study the pattern of early mineralization of these hard tissue layers by means of scanning electron microscopy and tetracycline labeling in monkey teeth. The most apical portion of the forming roots were covered by smooth spherulites, distinctly different from "microspherites" in cementum and calcospherites in dentin. These spherulites were labeled by tetracycline in a way that showed that they were formed and mineralized in a phase separate from the adjacent dentin. Apical to the honeycomb pattern of prismatic enamel formation, in the crown, a zone of smooth spherulites in the aprismatic enamel was found. These spherulites were similar to the ones at the forming root tip. Tetracycline was incorporated into the aprismatic enamel, which was in contrast to the prismatic enamel where no fluorescence was found. The mineralization pattern of aprismatic enamel and intermediate cementum were similar as seen by both tetracycline labeling and scanning electron microscopy. Thus, it is suggested that they are of similar origin and that the epithelial root sheath participates in the formation of the intermediate cementum but not of the proper dental cementum.

Animals↗
PubMedDate not supplied

Calcifying odontogenic cyst associated with compound odontoma: a study on undemineralized material.

In a minority of cases of calcifying odontogenic cyst (COC) it is possible to observe the formation of dental hard tissues in the cyst wall. The use of undemineralized sections has allowed an evaluation of the mineralized tissues normally lost with the use of demineralizing agents. All the dental hard tissues presented a high degree of morpho- and histodifferentiation. The histochemical staining for calcium salts (von Kossa) showed the presence of areas of low mineralization in the portion of the lesion, where the tissue maturation was not complete. In conclusion the appearance of the dental hard tissues in this case of compound odontoma arising in the cyst wall of a COC is similar to that already described in compound odontoma not associated with COC.

Adult↗
PubMed1993

[Proteoglycans-phospholipids interactions: roles in dentine mineralization].

Electron-histochemical visualization of proteoglycans was carried out in the predentine and dentine of rat incisors. Using various techniques proteoglycans were seen to be located between the collagen fibres in predentine, whereas they were observed at the surface of groups of collagen fibres in dentine. The same distribution was found when electron histochemical techniques aiming to visualize phospholipids were used. This co-distribution may play role in the mineralization processes.

Animals↗
PubMed1994

[Effect of neodymium on the crystal structure of human dental enamel in vitro].

The possibility of neodymium incorporation into hard tissues of permanent teeth has been investigated. The amount of neodymium was determined by X-ray microprobe analysis. The result indicates that different phases of enamel apatite have been recristallised. Neodymium compounds have appeared while the amount of some minerals in enamel have decreased. Neodymium could be an effective agent in stabilization of the apatite structure of dental enamel.

Crystallization↗
PubMed1994

Resin adhesion to the ground young permanent enamel: influence of etching times and thermal cycling test.

The purpose of this study was to investigate the influence of etching times and thermal cycling test on resin adhesion on ground young permanent enamel. Two hundred and fifty bovine mandibular young permanent incisors were used. Materials used in this study were 40 phospholic acid gel, Photo Bond and Photo Clearfil A (Kuraray Co., Kurashiki, Japan) in the PCA groups and 37% phospholic acid gel, Scotch Bond and Silux (3M Co., St. Paul, MN) in the Silux groups. The etching times were 0, 10, 20, 30, and 60 seconds. Shear bond strengths were tested. After the shear bond strength test, the test surfaces of the enamel and the resin specimens were observed using the SEM. The etching times that showed the highest bond strengths were 60 seconds both in the Silux non-thermal cycled group (45.21 +/- 8.49 MPa) and the Silux thermal cycled group (33.40 +/- 5.75 MPa), and 20 seconds in the Silux non-thermal cycled group (35.25 +/- 6.60 MPa) and 30 seconds in the PCA thermal cycled group (45.21 +/- 8.49 MPa). In the PCA groups, the bond strengths were significantly increased by thermal cycling tests, however, in the Silux groups, the bond strengths were significantly decreased by thermal cycling tests.

Acid Etching, Dental↗
PubMed1994

Identification of new rat dentin proteoglycans utilizing C18 chromatography.

Although only one small PG has been identified in dentin until now, a preliminary investigation has shown indications of the presence of several new proteoglycans (PGs) in rat incisor dentin. The aim of the present investigation was to isolate and characterize these PGs, which were labeled with 35S to facilitate the analysis. C18 chromatography resolved five dentin PGs. Based on SDS-polyacrylamide gel electrophoresis, their size varied from 100 to 400 kDa. The core proteins of the first four PGs appeared as 25, 40, 70, and 115 kDa bands. They stained turquoise with Stains All but did not stain with Coomassie Brilliant Blue. The core protein of the fifth PG appeared at about 45 kDa. This core protein stained with Coomassie Brilliant Blue but not with Stains All. In all PGs, the glycosaminoglycans consisted mainly of chondroitin 4-sulfate. To investigate their incorporation into predentin (young dentin that is not yet mineralized) and dentin, rat dentin PGs were pulse-labeled by injecting rats with [35S]sulfate at 5, 28, 55, or 177 h before killing the animals. Radiolabeling of predentin PGs was highest after 5 h and decreased rapidly (76%) over the next 50 h. In dentin PGs, a large percentage (34%) of the final quantity of incorporated 35S (at 177 h) was already present at 5 h. C18 chromatography of dentin PGs for each of the four time intervals showed similar 35S distribution patterns representing all five PGs, whereas the predentin appeared to contain mainly the fifth PG. This study demonstrates the existence of several apparently novel PGs in dentin that can be resolved by the use of a new method. These PGs were found in mineralized dentin and are thought to be rapidly transported toward the mineralization front. Part of the predentin PGs, on the other hand, seems to be lost as mineralization proceeds.

Animals↗