Dentin phosphophoryn binding to collagen fibrils.

The interaction of rat incisor phosphophoryn with native turkey tendon collagen fibers has been examined by electron microscopy. The binding of phosphophoryn to the tendon fibril surfaces is quite selective. The phosphophoryn is seen as positively or negatively stained globular particles predominantly at the "e" band in the collagen gap region in transmission electron micrographs of the phosphophoryn-reacted fibrils. The selectivity of binding to the fibrils was obtained in the presence of calcium ions, which bind avidly to phosphophoryn. The specific association of phosphophoryn at the "e" band suggests a possible regulation of mineral deposition within the gap regions of the collagen fibrils.

Long-term sealing properties of amalgam restorations: an in vitro study.

Conventional and high-copper Class V amalgam restorations showed leakage after seven months' storage in artificial saliva and thermal-stressing. The rate of marginal microleakage was not significantly affected by the application of a Copal varnish after this period. At the 14-month storage and thermal-stressing period, all varnished and unvarnished high-copper restorations and the varnished conventional amalgam restorations showed significantly improved sealing properties in the occlusal wall compared with the seven-month period. The unvarnished conventional amalgam restorations appeared to have reached their peak sealing level by seven months under the conditions of this experiment. No significant improvement in the sealing properties of either the conventional or high-copper amalgam restorations was achieved after the 14-month period by the application of Copal varnish.

The use of extraction replicas in scanning electron microscopy for the elemental analysis of marginal seals.

Elemental analysis of marginal seal material on 20 bulk samples of occlusally restored teeth have shown that, generally, more elements were detected in the seal material analyzed on the bulk restoration or fractured tooth surfaces than when such material was extracted using a nitrocellulose replica prior to analysis. No mercury was detected in any of the extracted seal material and only three of the replica specimens contained silver. This implies that the technique of using extraction replicas to remove material from the amalgam-tooth interface for subsequent x-ray microanalysis can provide an accurate elemental composition. The details of fabrication and the advantages of using high resolution nitrocellulose replicas for extracting marginal seal material from teeth for subsequent x-ray microanalysis are described.

Pulpal responses to amalgam restorations in cavities with and without smear layer removal.

A conventional low copper amalgam was placed in cavities with and without smear layer removal and the amalgam restorations were covered with a resin overlay. The restored teeth were retrieved at 2, 28 and 56 days postoperatively in order to test for leakage and then pulpal reactions. More inflammation was seen in the teeth from which the smear layer had been removed. Abscesses were present in 6 teeth at 28 days but only one was associated with demonstrable bacteria. This study does not support smear layer removal before insertion of low copper amalgam restorations.

Elements in marginal seals at amalgam-tooth interfaces.

X-ray micro-analysis was used to determine the elemental composition of the tooth, amalgam, and base material of ten aged, amalgam-restored, posterior teeth after they had been fractured across the amalgam-tooth interface. Subsequently, replicas were used to remove marginal seal material from each interface for examination by x-ray micro-analysis. The results show that P and Sn were present in all marginal seal material analyzed. Ca, Cl, Cu, Fe, S, and Zn were present in the marginal seals of various numbers of specimens.

Protein conformation in rat tooth enamel.

Orientated 0.47 nm reflections in X-ray diffraction patterns of developing rat tooth enamel were confirmed using a wide range of specimen preparations and experimental conditions. This indicates that some of the organic matrix proteins adopt a beta-sheet conformation.

Dental caries and sucrose intake in five South African preschool groups.

Dental caries, debris (DI-S) and sugar intake were determined for 766 rural Black, urban Black, coloured, Indian and White children, using standardized techniques. In general sucrose intake, both quantity and frequency was low in rural Black children yet these children had relatively few caries-free individuals and higher than expected mean dmft scores. Comparison with earlier studies in the same localities has shown a worsening of dental caries in all groups except the White, in which the situation has improved. Sucrose consumption declined in rural Black, and White groups, remained steady in urban Black children and increased in coloured and Indian groups.

Enamel rod relations in the developing rat incisor.

Scanning electron microscopic and X-ray diffraction studies have shown that mandibular rat incisor teeth have two sets of rods which decussate at angles between 60 and 80% in both the most immature zone and the zone just beyond the opaque margin. A less well oriented interrod enamel component was found at right angles to both sets of rods. The information provides additional views of this complex tissue. Furthermore, it has been shown that the Wistar rat incisal enamel ultrastructure facilitates the use of X-ray diffraction to determine molecular relations between the crystals and matrix constituents as the rods are not all at 90 degrees to one another.

Experimental marginal leakage around dental amalgams placed in artificial cavities.

Experimental marginal leakage of high- and low-Cu amalgam restorations placed in acrylic teeth, where the cavities were untreated or painted with denatured collagen and/or a CaP slurry, was assessed after specimens were stored in a 1% NaCl solution for ten days and for one yr. All specimens stored for ten days showed severe marginal leakage. High- and low-Cu amalgam restorations placed in untreated acrylic teeth cavities formed seals after a storage period of one yr, indicating that these materials are able to form a seal without interacting with a natural tooth cavity interface. Cavities treated with denatured collagen also formed seals in the long-term group. It was apparent that, when the CaP slurry was used, generally more leakage resulted after the year's storage period than when amalgam restorations were placed in uncoated acrylic cavity surfaces or in those painted with denatured collagen.

Experimental microleakage around ageing dental amalgam restorations: a review.

In vitro and in vivo experimental microleakage around ageing dental amalgam restorations has been reviewed. The methodologies, materials and results were examined and discussed. The initial experimental microleakage which occurred around unlined/unvarnished dental amalgam restorations and the development of leakage around lined/varnished dental amalgam restorations underlines the problem of attaining a permanent effective seal around dental amalgam restorations. The limitations of microleakage studies have been outlined and the importance of an understanding of the chemical changes which occur in the microcrevices stressed. This understanding may facilitate the production of a lifelong successful dental amalgam restoration and perhaps the development of an anticariogenic amalgam type fissure sealant.

The effects of cavity smear layer removal on experimental marginal leakage around amalgam restorations.

Unvarnished freshly-packed dental amalgam restorations leak initially. However, with time, a marginal seal is usually effected. It is not known whether the smear layer which forms during cavity preparation is associated with this leakage pattern. This study was undertaken to evaluate experimental marginal leakage around amalgam restorations (left in situ for one and 12 wk) which had been placed in cavities prepared with and without removal of the smear layer in vital and devitalized teeth. The cavities were obturated with two types of dental amalgams, a conventional and a dispersed-phase amalgam. The excised teeth restorations were subjected to a fluorescent dye marginal leakage experiment. All of the short-term specimens leaked severely, but some of the long-term specimens displayed significant sealing properties. No significant differences were found between the two types of amalgams. However, the non-vital tooth specimens and cavities without smear layers displayed significantly improved sealing properties.