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Biomedical subjects

E Asmussen

Publications and source records attributed to E Asmussen.

At least 127 records · Page 7Linked to original sources
PubMed1985

Composite wall-to-wall polymerization contraction in dentin cavities treated with various bonding agents.

Extracted human teeth are frequently used in studies on bonding of composites to dentin. However, little is known about the effect of storing conditions on the results recorded. The purpose of the present work was to measure the wall-to-wall polymerization contraction of a light-cured composite material with and without the use of five different dentin bonding agents in cylindrical dentin cavities prepared in extracted human teeth, either fresh or after storing for up to 4 wk in four different media. No effect of the storing conditions on the width of contraction gaps could be demonstrated when the teeth were stored in tap water or in a 1.0% aqueous chloramine solution. Aqueous solutions of either 0.1% benzalkonium chloride or 0.9% sodium chloride did occasionally affect the size of the contraction gap.

Adhesives↗
PubMed1985

Comparative study of dentin adhesives.

The marginal adaptation of Silux after application of different dentin adhesives was investigated in dentin cavities prepared in extracted human teeth. The cavity diameter ranged from 1.8 to 6.4 mm and the cavosurface angle was 90 degrees, 110 degrees, 135 degrees or 160 degrees. The investigation included the following adhesives: Clearfil, Creation 1150, GLUMA, NPG-GMA + PMDM, Palfique, Panavia, Scotchbond and Superbond. Silux Enamel Bond was used as control. The most effective adhesive was GLUMA followed by Superbond and then NPG-GMA + PMDM; Palfique, Panavia and Scotchbond were all less effective than NPG-GMA + PMDM, and both Clearfil and Creation 1150 were inferior to the control, Silux Enamel Bond. None of the adhesives were able to prevent the formation of marginal gaps when measured 10 min after polymerization. After water absorption for 1 day, only GLUMA and Superbond produced gapfree fillings. Increasing the cavosurface angle resulted in a significant improvement of the effect of all adhesives, the main reason for this being the reduced ratio volume of filling to area of cavity wall.

Adhesives↗
PubMed1985

Effect of combining dentin bonding agents.

The wall-to-wall polymerization contraction of a light-cured composite was measured in cylindrical dentin cavities treated with the bonding agents: Scotchbond, Clearfil Bond, Gluma/Scotchbond, Gluma/Silux Enamel Bond or Gluma/Clearfil Bond. Marginal gaps were prevented in 29 out of 30 cases when Gluma was used in combination with Clearfil Bond. This combination mediates a mean bond strength between composite and dentin of 20 MPa.

Adhesives↗
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↗
PubMed1984

Softening of BISGMA-based polymers by ethanol and by organic acids of plaque.

The Wallace indentation hardness is a determinant for the abrasion resistance of smooth surface resins. It was the aim of the present study to investigate the softening effect of ethanol and of organic acids of plaque on BISGMA-based polymers. The hardness was measured before and after soaking for 1 day in ethanol, acetic acid, propionic acid, or lactic acid. The last three liquids were found to induce a softening of the polymers. The softening effect was more pronounced when the polymer originated from monomer mixtures with low content of diluting monomer. This finding reflects the extent of polymerization of the polymers.

Acetates↗
PubMed1984

Formaldehyde as bonding agent between dentin and restorative resins.

The bonding of restorative resins to dentin by means of formaldehyde used in conjunction with an OH-containing monomer as intermediary was investigated. In this way a bonding to the organic constituent of dentin is conceivable. Mean bond strengths of 0.6 kg/mm2 were obtained. Bond strengths of this order of size may be of clinical interest.

Dental Bonding↗
PubMed1984

Effect of five adhesives on adaptation of resin in dentin cavities.

Cylindric dentin cavities ranging from 2 to 6 mm in diameter were treated with different dentin adhesives: Clearfil, Gluma, NPG-GMA + PMDM, Scotchbond or Superbond before filling with Silux. The maximal contraction gap was measured 10 min after curing and compared with results from cavities where an adhesive was omitted. The effectiveness in reducing contraction gaps increased in the following order: Clearfil, Scotchbond, NPG-GMA + PMDM, Superbond and Gluma.

Acrylic Resins↗
PubMed1984

Bond strength between dentin and restorative resins mediated by mixtures of HEMA and glutaraldehyde.

We investigated the bond strength between restorative resin and dentin pre-treated with mixtures of HEMA and glutaraldehyde. It is suggested that the mixture acts by forming a chemical bond of HEMA molecules to a collagen-glutaraldehyde reaction complex. Subsequently applied resin will then co-polymerize with the collagen-linked methacrylate groups. Statistical analysis of the results from varying mixtures of HEMA and glutaraldehyde revealed that the bond strength was highly dependent on the HEMA concentration, with a maximum at 35%, and nearly independent of the glutaraldehyde concentration when greater than 3%. The highest mean bond strength was about 1.8 kg/mm2, and bond strength of this order of size may be attractive for clinical use.

Acrylates↗
PubMed1983

Bonding of restorative resins to dentin by means of methacryloylchloride and methacryloyl-R-isocyanate.

The bonding of restorative resins to dentin by means of an intermediary monomer containing a carboxylic acid chloride or an isocyanate group was investigated. Such intermediary monomers are supposed to react with the organic constituent of dentin. Bond strengths were enhanced by the use of the intermediary monomers, resulting in mean bond strengths of 0.13 kg/mm 2. Bond strengths of this order of size are probably too low to be of clinical interest.

Acrylates↗
PubMed1983

Factors affecting the color stability of restorative resins.

The color change resulting from storage in water was measured on a number of experimental and proprietary complex resins. The experimental resins contained varying amounts of amine (DEPT or DEBA), benzoyl-peroxide (BPO) and inhibitor (MHQ). The proprietary resins had earlier been analyzed as regards the composition of the monomer and the content of amine and peroxide. The color change of DEPT-containing resins was positively correlated with the DEPT/BPO ratio, and negatively correlated with the monomer content of BISGMA. DEBA-containing resins were more color stable than resins containing equimolar concentrations of DEPT. The color change was independent of MHQ up to a certain concentration; above this the color change increased with the amount of MHQ. In general, the light activated materials were more color stable than the chemically activated materials. The color change was not affected by pH, but decreased when the oxygen had been removed from the storage water. The test for color stability using UV-light irradiation gave results for proprietary resins that were not correlated with the results obtained by water storage.

Chemical Phenomena↗
PubMed1983

Opacity of glass-ionomer cements.

The translucency of the first generation of glass-ionomer cements to appear on the market was too low to be cosmetically satisfactory. In the present study the opacity of newer editions of glass-ionomer cements was evaluated and compared with that of a well-known composite resin. Disc-shaped specimens were placed on black and on white backings, the luminous reflectances measured and corrected to a specimen thickness of exactly 1 mm, whereafter the contrast ratio was calculated. The newer glass-ionomer cements were found to be more translucent than the first generation of glass-ionomer cements on the market. However, the opacity still needs to be reduced to reach the level of a composite resin. It was further established that early water contact results in a considerable increase in opacity.

Composite Resins↗
PubMed1982

Microscopical analysis of fractured restorative resin/etched enamel bonds.

The purpose of the present work was to analyze the boundary structures of fractured restorative resin/etched enamel bonds. The fracture patterns were studied by scanning electron and optical microscopy. The three main types of failure observed were classified as: apparent interfacial failure, failure in the bulk of the restorative resin and failure in the bulk of the enamel. The fracture of the resin/etched enamel bond in the case of the apparent interfacial failure was located in the resin very near the interface. No true interfacial debonding occurred in any of the bonds studied.

Acid Etching, Dental↗