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Biomedical subjects

E Asmussen

Publications and source records attributed to E Asmussen.

At least 19 recordsLinked to original sources
PubMed1992

Modulus of resilience as predictor for clinical wear of restorative resins.

Eight posterior restorative resins were tested with respect to flexural strength, modulus of elasticity, and modulus of resilience. The mechanical properties were correlated to the two-year results of clinical wear tests. Linear relationships were found between flexural strength and clinical wear and between modulus of resilience and clinical wear. It was concluded that modulus of resilience be used in research and quality control for the prediction of clinical wear.

Acrylic Resins↗
PubMed1992

Effect of temperature and duration of post-cure on selected mechanical properties of resin composites containing carboxylic anhydrides.

Resin composites containing carboxylic anhydrides have recently been formulated for use as inlay materials. To optimize the post-cure, the present study measured the effect of post-cure temperature and duration on four mechanical properties of anhydride-containing resin composites. Temperatures were varied between 37 degrees C and 225 degrees C, and durations were varied between 0 and 24 h. An optimum in strength and stiffness was found when post-cure temperatures of 125-150 degrees C were used. Strength and stiffness were found to increase with increasing duration of post-cure. Due to discoloration of the resin composites when post-curing for 6 or 24 h, a post-cure period of 1 h was preferred.

Acrylamides↗
PubMed1992

Selected variables in bonding to dentin.

The aim of this study was to investigate the effect of three variables on the shear bond strength between a composite resin and dentin treated with a simplified Gluma system. Thickness of material (2 or 3 mm), distance between light guide and the surface of composite resin (0, 1, 3, or 5 mm) and irradiation time (10, 20, 40, or 60 s) were selected as variables. Thickness of material and distance between light guide and composite resin affected bond strength, but there was little influence of irradiation time under the conditions of the study. It is suggested that bond strength depends on the amount of light transmitted through the composite.

Composite Resins↗
PubMed1992

Influence of aldehydes on selected mechanical properties of resin composites.

The present study investigated whether propanol, a monofunctional aldehyde, was able to improve the mechanical properties of dental polymers. The underlying hypothesis was that a cross-linking reaction is possible between various functional groups of different polymers. Propanol was added to monomer mixtures, which were then made light-curing and loaded with filler. The monomer mixtures were varied with respect to monomer composition and content of aldehyde. Four mechanical properties of the experimental resin composites were determined. Addition of propanol gave rise to significant improvements in mechanical properties, which may be indicative of a cross-linking ability of monofunctional aldehydes. With the exception of modulus of elasticity, the mechanical properties of resin composites based on UEDMA/HEMA were superior to those of BISGMA/TEGDMA-based materials, even though the improvements in flexural strength and modulus of resilience were most pronounced for the BISGMA/TEGDMA-based resin composites.

Aldehydes↗
PubMed1992

Influence of ketones on selected mechanical properties of resin composites.

The present study investigated a concept for additional cross-linking of dental polymers, by which resistance to wear of resin composites might be increased. Bifunctional ketones were added to monomer mixtures, which were then made light-curing and loaded with filler. The monomer mixtures were varied with respect to type and ratio of monomer and ketone. For measurement of possible effects of the cross-linking agents added, four mechanical properties of the experimental resin composites were determined. Addition of the bifunctional ketone diacetyl resulted in the following increases in mechanical properties: diametral tensile strength, 11%; flexural strength, 29%; modulus of elasticity, 19%; and modulus of resilience, 50%.

Composite Resins↗
PubMed1992

Ketones in resin composites. Effect of ketone content and monomer composition on selected mechanical properties.

To optimize the improvements by diketones of the mechanical properties of resin composites, diacetyl was added to two different monomer mixtures in different quantities. There was a positive correlation between content of diacetyl and tensile strength, flexural strength, and modulus of elasticity, respectively, of both the BISGMA/TEGDMA- and the UEDMA/HEMA-based materials. Addition of diacetyl did not influence the modulus of resilience significantly. Addition of diacetyl resulted in increases in mechanical properties which were of the same relative size for BISGMA/TEGMA-based materials as for UEDMA/HEMA-based materials. However, because of higher control values, except for modulus of elasticity, the properties of UEDMA/HEMA-based composites were superior to those of the BIGSMA/TEGDMA-based materials. A content of approximately 24 mole% diacetyl seemed to have optimum effect on mechanical properties, giving a mean increase of 25% in tensile strength, flexural strength, and modulus of elasticity.

Analysis of Variance↗
PubMed1991

Mechanical properties of three composite resins for the inlay/onlay technique.

The present study measured the diametral compressive strength, flexural strength, and modulus of elasticity of composite resins used in inlay/onlay systems. The effect of additional curing also was determined. SR-Isosit material had the highest diametral compressive strength, and SR-Isosit-Dentin material had the lowest flexural strength. The SR-Isosit composite resins had lowest elastic modulus and Estilux posterior C VS resin the highest. A negative correlation was found between diametral compressive strength and elastic modulus of the materials. It was concluded that the additional curing of Brilliant resin did not result in improved mechanical properties. For Estilux resin, additional curing increased flexural strength and modulus of elasticity.

Acrylic Resins↗
PubMed1991

Retention of composite inlays in enamel dentin cavities.

The retention of composite inlays depends on acid-etching of marginal enamel of the preparation. In many cases, only little marginal enamel is available, making loss of retention a liability. The present study evaluated the retention of three brands of composite inlays under various conditions. Inlays were fabricated and cemented in standardized enamel/dentin cavities prepared in extracted human teeth. The force necessary to extract a cemented inlay was used to express the retention of the inlay. The effects of thermocycling and choice of dentin-bonding agent on inlay retention were also determined. Inlays made of Estilux posterior C VS were more retentive than inlays of either Brilliant or SR-Isosit. The latter two products were found to provide similar retentive strengths. The retention of Estilux posterior C VS and SR-Isosit inlays declined when samples were thermocycled. Treatment with Gluma increased retention of inlays, resulting in retentive strengths of the same magnitude for all three inlay systems. The choice of dentin-bonding agent was found to affect composite inlay retention to a greater extent than the choice of either composite brand, mode of inlay curing, or effect of thermocycling.

Acid Etching, Dental↗
PubMed1991

Distortion of impression materials used in the double-mix technique.

According to the so-called double-mix technique for impression taking, a material of high and one of low viscosity set against each other. We found that a distortion of the joined materials occurred which may compromise the precision of the impression. The distortion of such combinations of materials of high and low viscosity was measured on beam-like specimens. Significant differences between materials were observed. The phenomenon may be explained by a swelling of the material of low viscosity. The swelling may be associated with a diffusion of unreacted compounds from the material of high viscosity into the material of low viscosity. Measurements of the swelling of specimens immersed in the catalyst component of unset material showed an increase in length of 2-5%.

Dental Impression Materials↗
PubMed1991

Marginal adaptation of a restorative resin polymerized at reduced rate.

The aim of this study was to investigate the effect of reduced rate of polymerization on the marginal adaptation of a composite resin inserted in dentin cavities treated with a simplified Gluma system. The effect on bonding strength to dentin and compressive strength was also investigated. The light intensity of the polymerization unit was lowered by the use of a transformer, and thus the rate of polymerization of the composite resin. When the resin was irradiated for 30 s at 110 V followed by 30 s at 220 V, the marginal adaptation was significantly improved. This condition resulted in acceptable values of bonding strength to dentin and diametral compressive strength. It is suggested that the reduced rate of polymerization may allow for increased flow of the material, decreasing the contraction stress in the filling.

Aluminum Oxide↗
PubMed1991

Retrograde root filling with composite and a dentin-bonding agent. 1.

A method is described, by which retrograde root filling with a composite resin can be performed. The cavity design is a slightly concave dissection of the apical part of the root, which is treated with the bonding agent Gluma followed by an application of Retroplast. Retroplast is a chemically curable composite containing silver for radiopacity and aerosil to obtain a suitable consistency. Endodontically treated teeth with a eugenol-containing root canal sealer did not affect the strength of the bond between Retroplast and apical dentin. A tight seal between the composite and the cavity surface was observed by light and SEM microscopy, and histology of tissue surrounding fillings placed in monkeys revealed absence of inflammatory cells around the filling and a close contact between filling and fibroblasts with collagenous fibers. In some cases, cementum and Sharpey's fibers formed in contact with the filling. Fillings placed in humans performed successfully in most cases, and the main causes of failure were either inadequate hemostasis during filling, or root fracture unnoticed by the time of filling. The retrograde technique promises a new treatment principle, with a root canal effectively sealed and the periapical ligament restored after apicoectomy.

Adolescent↗
PubMed1991

Influence of the solubility parameter of intermediary resin on the effectiveness of the gluma bonding system.

The aim of the present study was to investigate the effect of the solubility parameter of the intermediary resin in the Gluma system on the bonding to dentin. The solubility parameter of the resins was varied between 18.8 x 10(3) and 21.1 x 10(3) J(1/2)/m3/2 by varying the composition of the resin. The efficacy of the bonding system was determined by measurements of marginal gaps formed by polymerization contraction of a restorative resin in dentin cavities treated with the bonding system. The bonding system had maximum efficacy at a solubility parameter of the intermediary resin of delta = 20.0 x 10(3) J(1/2)/m3/2. This finding corroborates a concept of bonding to dentin that involves a mechanical interlocking by interpenetrating resins.

Analysis of Variance↗
PubMed1991

Influence of carboxylic anhydrides on selected mechanical properties of heat-cured resin composites.

Resin composites are still in need of improved abrasion resistance for them to be ideal restorative materials for use in large occlusal cavities. The present study proposes a concept for additional cross-linking of dental monomers, by which mechanical properties and possibly the resistance to abrasion of the resin composites are increased. Cyclic acid anhydrides were added as cross-linking agents to different monomer mixtures, which were then loaded with filler. The monomer mixtures were varied with respect to type and ratio of monomer and anhydride. For measurement of diametral tensile strength, flexural strength, modulus of elasticity, and modulus of resilience, specimens were initially cured by light and then post-cured for one h at 150 degrees C. Resin composites based on UEDMA and HEMA were found to be superior to BISGMA- and TEGDMA-based composites. Increases in mechanical properties were highest when unsaturated anhydrides were used. An optimal effect of anhydride addition was found in resin composites also containing methacrylamide. Such materials resulted in a 20% increase in the mechanical properties investigated.

Acrylamides↗
PubMed1991

Effect of 2-hydroxyethyl methacrylate in an Al2Ox3/glycine solution used as primer for dentin bonding.

The aim of this study was to investigate the effect of 2-hydroxyethyl methacrylate (HEMA) in an Al2Ox3/glycine solution used as primer for dentin bonding in combination with an experimental BISGMA-HEMA-based adhesive resin. With various amounts of HEMA in the Al2Ox3/glycine solution, a shear bond test showed a maximum strength at 50 wt% of HEMA. In this case, scanning electron microscopy examination showed a HEMA-infiltrated surface layer of the dentin along the interface between dentin and the adhesive resin. It is suggested that HEMA in Al2Ox3/glycine solutions may facilitate penetration of HEMA into etched or primed dentin.

Aldehydes↗
PubMed1991

Effect on bonding of curing through dentin.

The aim of this study was to investigate the effect of the thickness of dentin (1, 2, or 3 mm) placed between the light guide and the composite resin on the shear bond strength to dentin treated with a simplified Gluma system. The effects of the thickness of composite resin (2 or 3 mm), irradiation time (20, 40, or 60 sec), and shade (universal or brown) were also examined. The results showed that the thickness of dentin influenced bonding and interacted with the other three variables. It is suggested that dentin located between the light guide and composite resin may attenuate the light aimed at the bonding interface in the same manner as a layer of composite resin.

Color↗