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Biomedical subjects

E C Munksgaard

Publications and source records attributed to E C Munksgaard.

52 records · Page 3Linked to original sources
PubMed1985

Dentin-polymer bond in resin fillings tested in vitro by thermo- and load-cycling.

The effect of stress applied by thermo- and load-cycling to the bond between composite- and bonding-agent-treated dentin was tested. Cylindrical cavities in extracted human teeth, approximately one-half of the margins in dentin, were etched and treated with two bonding agents - Gluma and Clearfil Bond - before being filled with Silux composite. Forty specimens, some provided with cavity floor lining, were cycled several hundred times between 15 degrees and 50 degrees C, either immediately after light-curing or upon 24 hr of water storage. In all cases, microscopic inspection revealed unchanged adaptation at the dentin margins. Teeth with Class 3 and Class 5 cavities, ten of each and with the gingival margins entirely in dentin, were pre-treated and filled as above. The teeth were covered with a dye during loading and unloading in a manner simulating biting and chewing. Inspection of the cavity margins revealed absence of percolation at the dentin margins. It is concluded that effective bonding agents are necessary to prevent contraction gaps in resin-filled cavities where the margins are partly or entirely located in dentin.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1985

Dentin-polymer bond promoted by Gluma and various resins.

Gluma-treated dentin was covered with various resins before a microfilled composite was applied. The strength of the bond between dentin and composite established by this procedure was measured in shear and tensile tests. The effectiveness of the bonding was further tested by the width of the marginal contraction gap around fillings made in dentin by the above procedure. Resins containing propanal promoted shear bond strength of about 15 MPa. The tensile bond strength exceeded 22 MPa by one of the resins, but could not be measured because of frequent rupture in the composite. Between 30 and 70% of the fillings were without contraction gaps when propanal or p-toluenesulfinate-containing resins were used. It is proposed that oxygen inhibition of the polymerization on the dentin surface suppresses the bonding. Resins containing reducing agents may reduce oxygen inhibition and increase bonding by the adhesive.

Aldehydes↗
PubMed1985

Bonding of restorative resins to dentine promoted by aqueous mixtures of aldehydes and active monomers.

Effective bonding between restorative resins and hard dental tissues would eliminate the need for retentive undercuts and prevent the formation of marginal gaps. While bonding to enamel has found a satisfactory solution with the advent of the acid etch technique, bonding to dentine has been more elusive. Restorative resins may bond to dentine through mechanisms involving either the inorganic or the organic constituents of the dentine. In the present work the possibility of bonding to the organic part of dentine was investigated. Since the water present in the surface of moist dentine may impede bonding, the research was focused on adhesives that are operational in aqueous environments. Aqueous mixtures of aldehydes and certain active monomers constitute such adhesives. The strength of the bond between a restorative resin and dentine was measured using the mixtures as intermediaries. To remove the smear layer the dentine was pretreated with 0.5 M EDTA, pH = 7.4. Among the aliphatic aldehydes especially propionic aldehyde and glutaraldehyde were found to be effective. Aromatic aldehydes resulted in bonds of low strength. Among the monomers investigated HEMA (hydroxyethyl-methacrylate) gave rise to the bond of highest strength. Using an adhesive based on HEMA and propionic aldehyde or HEMA and glutaraldehyde bond strengths of 15 and 18 MN/m2, respectively, were obtained. The latter adhesive significantly reduced the width of the polymerization contraction gaps between resin and dentine.

Aldehydes↗
PubMed1979

Dentin proteins: chemistry, structure and biosynthesis.

One of the most abundant noncollagenous proteins of dentin is a phosphoprotein rich in aspartic acid and phosphoserine. This protein occurs in soluble and inextractable forms, the latter being associated with the insoluble collagenous matrix. This protein is capable of tightly binding a relatively high level of calcium. Biosynthetic and radioautographic data suggest that shortly after its biosynthesis, the phosphoprotein is transported and bound to the collagen at the predentin-dentin junction. This event is probably central to the mineralization process, though other glycoproteins may be involved.

Amino Acids↗
PubMed1979

Collagen in dentin.

The collagen synthesized by cultured odontoblasts related to dentin, was identified as type I and as type I trimer in nearly equal amounts. Analysis of in vivo synthesized collagen extracted from unerupted bovine teeth confirmed that type I trimer is a constituent of dentin, but presumably in small amount compared to type I collagen.

Animals↗
PubMed1977

Phosphoprotein from dentin. New approaches to achieve and assess purity.

Phosphorprotein extracted from rat incisors was purified by passage through a sulfonated polystyrene column. The phosphoprotein that emerged in the void volume contained 54% phosphoserine + serine and 36% aspartic acid and, in contrast to that obtained by DEAE-cellulose chromatography, was devoid of proline, valine, isoleucine, leucine, tyrosine, phenylalanine and arginine. Gel electrophoresis of the material purified on sulfonated polystyrene columns gave one major phosphate-containing band which would not stain with Coomassie Blue. EDTA or acetic acid demineralization yielded phosphoprotein preparations with identical compositions and electrophoretic properties. These data show that purification procedures reported earlier are insufficient.

Amino Acids↗
PubMed1977

The phosphoprotein of rabbit in cisors.

The phosphoprotein of continually erupting rabbit incisors was extracted from decalcified teeth and purified by gel filtration and ion-exchange chromatography. Chemical characterization revealed that its composition was very similar to that of rat incisor and bovine molar phosphoproteins. The presence of similar acidic proteins in the dentin of various mammals is consistent with the suggestion that they are involved in the mineralization process.

Amino Acids↗
PubMed1975

A field biopsy method for fluoride determinations in human surface enamel.

An enamel biopsy method was developed that is especially intended for use under primitive clinical conditions in field studies. Three successive enamel layers, each of 1 mum or less, were etched off the same delimited area of 3 mm2 by means of perchloric acid, using a microsampler with disposable tips. The biopsy technique was applicable to the vestibular surface of almost all teeth, causing no perceptible damage to the enamel surface. Based on cumulated data from the successive enamel layers, curves were drawn from which F levels at various depths in the outer 3 mum of the enamel could be interpolated. F levels in surface enamel of maxillary first premolars in 40 12-13-year-old children in a locale with 0.5 mg F/l in the drinking water were found to be 3,800, 2,400 and 2,000 parts/10(6) in three successive enamel layers of 0.6, 1.0 and 1.1 mum, respectively, demonstrating a decrease in F concentration of about 1,800 parts/10(6) within this depth interval. Identical F concentrations were found in bilateral premolars.

Adolescent↗