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Biomedical subjects

E Asmussen

Publications and source records attributed to E Asmussen.

At least 73 records · Page 4Linked to original sources
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↗
PubMed1991

[Color stability of three composite resins used in the inlay/onlay technique].

The color stability of three composite resins used in the inlay/onlay technique was determined by means of irradiation with UV-light and by water storage. Generally, water storage resulted in greater changes in color than did UV-light, but no correlation was found between the results of the two chromogenic procedures. The microfilled composite resin was the least color stable, but none of the resins had alarmingly low color stability.

Color↗
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 Dentin 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.

Acrylic Resins↗
PubMed1991

[A comparison of accuracy in seating and gap formation for three inlay/onlay techniques].

The accuracy (fit) of MOD inlays of three brands of composite resin was determined by measuring the axial discrepancy (marginal opening in the approximal area). The axial discrepancy varied between 17 and 121 microns. Directly manufactured inlays were more accurate (axial discrepancy: 17-26 microns) than indirectly manufactured inlays (axial discrepancy: 40-121 microns). Inlays of a microfilled resin, SR-Isosit, were less accurate than inlays of two hybrid materials, Brilliant Dentin and Estilux posterior C VS (axial discrepancy: 121 microns vs 44 and 41 microns respectively). There was a tendency for 24-hour-old inlays to be less accurate than 10-min-old inlays. The formation of marginal gaps due to contraction of the resin cement was assessed in a light microscope on cemented single-surfaced inlays. Gaps were not formed when enamel margins were etched or dentin margins treated with a dentin-bonding agent of high efficacy. Gaps (2.4-5.6 microns) were formed, however, at untreated dentin margins and at margins treated with dentin-bonding agents of low efficacy.

Acrylic Resins↗
PubMed1991

[In-depth polymerization of a light-activated resin cement].

The potential for in-depth cure of the light-activated resin cement TULUX-CEM was investigated. Disks of TULUX-CEM were irradiated through a layer of inlay/onlay material of varying thickness. After the irradiation, the hardness of the disks was measured. It was found that the resin cement became softer as the thickness of overlying inlay/onlay material increased from 2.0 to 3.5 mm. At a thickness of 4.0 mm, the resin cement remained unpolymerized. It was concluded that in certain situations the in-depth cure of resin cements activated only by light may not be sufficient.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1990

Effect of disinfecting solutions on surface texture of alginate and elastomeric impressions.

The effect of immersion in six disinfecting solutions on the surface texture of 10 impression materials was investigated. Assessment of the surface texture was based on measurement of the ability to reproduce fine detail. Impressions were taken of a roughness standard, i.e. a steel block with known roughness. After setting, the impressions were either stored at room temperature for 24 h, for control, or immediately immersed in a disinfecting agent for 60 min (in one case 10 min), and after 24 h poured with gypsum. After another 24 h, the roughness of the dies was recorded with a profilometer. Three addition-curing silicones were left unaltered by disinfection. For the remaining seven materials, the ability of detail reproduction was changed for some of the combinations of impression material and disinfecting solution. In general, this meant a reduction of detail reproduction, but occasionally an improvement of the surface texture resulted from disinfection. Changes in surface texture were most often brought about by a solution of chlorinated trisodium phosphate. It was concluded that elastomeric impression materials reproduced fine detail better than did alginates and that both types of impression material may be immersed in specific disinfecting solutions for as long as 1 h without the surface texture being impaired.

Alginates↗
PubMed1990

Color stability of three composite resins used in the inlay/onlay technique.

The color stability of three composite resins used in the inlay/onlay technique was determined by means of irradiation with UV-light and by water storage. Generally, water storage resulted in greater changes in color than did UV-light, but no correlation was found between the results of the two chromogenic procedures. The microfilled composite resin was the least color stable material, but none of the resins had alarmingly low color stability.

Color↗
PubMed1990

Flexural and fatigue strengths of root canal posts.

This study measured the flexural and fatigue strengths of root canal posts of different alloy, design, and diameter. Fixed posts were loaded up to a preset force and the number of loadings endured until fracture was recorded at each loading force. The flexural strength was defined as the maximum force a post could endure before fracture when loaded once. The fatigue strength was determined as the maximum force a post could endure when loaded 10,000 times. Both modes of strength were found to increase with increasing diameter. Aluminum posts had lower flexural and fatigue strengths than posts of titanium, stainless steel, and a Ag-Pd alloy, all of which had strength values of about the same magnitude. Among the investigated brands, Triax and Radix were stronger than the others at comparable diameters. The high strength of Triax may be explained by the design of the post, whereas a superior alloy may account for the high strength of Radix.

Dental Alloys↗
PubMed1990

Marginal adaptation of resin in relation to application technique and use of a calcium hydroxide liner.

The marginal adaptation of a restorative resin was examined in cone-shaped cavities prepared in extracted human teeth. The use of a thin layer of a Ca(OH)2 liner in the bottom of the cavities did not influence the wall-to-wall (wtw) polymerization contraction and it did not affect the gap-reducing efficacy of a dentin-bonding agent. The wtw contraction was markedly increased when the restorative resin was applied in two layers parallel to the free surface of the cavity; the reason for this is supposed to be that the ratio between the volume of the filling (V) and the area of the cavity wall (A) is increased for the second layer compared to the V/A ratio found in cavities filled with one increment.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1990

Mechanical properties of heat treated restorative resins for use in the inlay/onlay technique.

Inlay/onlay materials based on composite resins have recently been introduced. It was the aim of the present study to investigate the effect of post-curing temperature on selected mechanical properties. Four different composite resins were produced. The composite resins had identical filler content, but varied with respect to the content of the monomers BISGMA, TEGDMA, UEDMA, and HEMA. After initial curing by light, the materials were post-cured at 37, 100, 125, 150, 175, or 200 degrees C for 1 h. We then measured diametral tensile strength, flexural strength, and modulus of elasticity. These properties were found to vary with the composition of the material. Composites containing UEDMA or UEDMA/HEMA were stronger and stiffer than BISGMA/TEGDMA formulations. The optimum post-curing temperature was 150 degrees C, but the increase in strength and stiffness was moderate, only about 9%.

Composite Resins↗
PubMed1990

In vivo fractures of endodontically treated posterior teeth restored with amalgam.

The cumulative survival rate (retention of both cusps) and the fracture pattern of 1639 endodontically treated posterior teeth were assessed in a retrospective study. All teeth had an MO/DO or an MOD cavity restored with amalgam without cuspal overlays. The 20-year survival rate of teeth with an MO/DO cavity was markedly higher than that of teeth with an MOD cavity. The lowest survival rate was found for the upper premolars with an MOD cavity: 28% of these teeth fractured within 3 years after endodontic therapy, 57% were lost after 10 years, and 73% after 20 years. Generally, the cusp most prone to fracture was the lingual one, and lingual fractures caused significantly more damage to the periodontal tissues than did facial or total crown fractures. The severity of periodontal damage increased with posterior location of the tooth. By far the most serious failures, irrespective of the cavity type, were found for the upper second molar, as 10 of 29 fractures led to extraction. It is concluded that amalgam, especially in MOD cavities, is an unacceptable material for restoration of endodontically treated posterior teeth if used without cuspal overlays.

Analysis of Variance↗
PubMed1990

In vivo fractures of endodontically treated posterior teeth restored with enamel-bonded resin.

The cumulative survival rate of 190 endodontically treated posterior teeth were assessed in a retrospective study; all teeth had an MO/DO or an MOD cavity restored with a composite resin without cuspal overlays after previous acid-etching of the enamel. In contrast to our previous study on endontically treated posterior teeth restored with amalgam, the survival rate of the MOD resin-restored teeth was equal to that of MO/DO teeth. Teeth restored with a light-activated resin had a much lower survival rate than teeth restored with a chemically-activated material, the cause presumably being that the light-activated resins were insufficiently irradiated. Nearly 25% of the teeth had been restored with a microfilled resin for anterior use and these teeth had a lower survival rate than had teeth restored with a macrofilled or hybrid resin. It was also found that a beveling technique did not decrease the fracture rate while the use of an intermediate layer of low-viscosity resin resulted in a significant improvement.

Bicuspid↗
PubMed1990

Storage stability of solutions of pyruvic acid/glycine used in adhesive bonding.

The rate of deterioration of pyruvic acid/glycine solutions used as common pretreatment of enamel and dentin in the Gluma bonding technique was investigated. Bond strengths between composite resin and enamel/dentin were measured. The bonds were mediated by pyruvic acid/glycine solutions, applied from 0 to 6 months after the time of manufacture. Bond strengths to enamel varied between 8.6 and 13.5 MPa and to dentin between 6.2 and 18.0 MPa. The pH of the solutions rose slightly during the experimental period, but no statistically significant change in bond strengths was observed.

Acid Etching, Dental↗
PubMed1990

Effect of dentin adhesives on contraction of restorative resins in cavities surrounded by acid-etched enamel.

Enamel-surrounded cavities prepared in extracted human teeth were treated with an enamel-bonding agent, one of two commercial dentin adhesives (Scotchbond 2 and Tenure), or one of two recent modifications of the Gluma system. In all cases the enamel margins were subjected to some form of acid etching. The cavities were filled with one of two different light-cured posterior resins, and the wall-to-wall polymerization contraction was assessed in the enamel surface level and, after grinding, measured and presented as linear shrinkage in the dentin surface level. The linear shrinkage varied from 0.66% in the control group, in which only composite resin was applied, to 0.28% in a group in which the cavities were pretreated with dentin adhesive. No difference could be demonstrated between the dentin adhesives or between the dentin adhesives and the enamel-bonding agent.

Acid Etching, Dental↗
PubMed1990

Effect of polyacrylic acid treatment of dentin on adhesion of glass ionomer cement.

This investigation measured the effect of polyacrylic acid treatment of dentin on adhesion of glass ionomer cement. The dentin was ground on paper no. 220 or no. 500 and treated with a polyacrylic acid solution of 10% or 25% for either 10 or 30 sec. The differences observed in the scanning electron microscope between the differently treated dentin surfaces were not reflected in the bond strength results. Only variations in surface texture due to different coarseness of grinding influenced the adhesion. For specimens ground on paper no. 220, pretreatment with polyacrylic acid enhanced adhesion of glass ionomer cement. Polyacrylic acid had no effect on bonding between glass ionomer cement and dentin ground on paper no. 500.

Acid Etching, Dental↗
PubMed1990

[Glass ionomer cement and dentin: effect of pretreatment with polyacrylic acid].

This investigation measured the effect of polyacrylic acid treatment of dentin on adhesion of glass ionomer cement. The dentin was ground on paper No. 220 or No. 500 and treated with a polyacrylic acid solution of 10% or 25% for either 10 s or 30 s. The differences observed in the scanning electron microscope between the differently treated dentin surfaces were not reflected in the bond strength results. Only differences in surface texture due to different coarseness of grinding influenced the adhesion. As to specimens ground on paper No. 220, pretreatment with polyacrylic acid enhanced adhesion of glass ionomer cement. No effect of polyacrylic acid was found on bonding between glass ionomer cement and dentin ground on paper No. 500.

Acid Etching, Dental↗