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At least 37 records · Page 2Linked to original sources
PubMed2004

Effect of resin hydrophilicity and water storage on resin strength.

This study evaluated the change in the ultimate tensile strength (UTS) of five polymerised resin blends of increasing hydrophilicity, after ageing in distilled water or silicon oil. Resin blocks were prepared from each resin blend by dispensing the uncured resin into a flexible, embedding mould, containing multiple cavities. The resins were polymerised in the moulds under nitrogen at 551.6 kPa and light-activated at 125 degrees C for 10 min. After dry ageing for 24 h at 37 degrees C, the middle third of each resin specimen was trimmed into an 'I' shape. Fifteen control specimens were randomly selected from each resin blend for baseline UTS evaluation. The UTS of the experimental specimens were determined after 1, 3, 6 and 12 months of ageing in water or oil. The UTS of each group of resins at different storage periods in water or oil were analysed using the Friedman multiple ANOVA on ranks and Dunn's multiple comparison tests at 95% confidence level. Significant reduction (p < 0.01) in UTS was observed in Groups II-V resins after 12-month storage in water, while the most hydrophobic Group I resin showed no significant change (p > 0.05) in the same period. The percentage reduction in UTS increased with the hydrophilicity of the resin blends. Long-term water storage of hydrophilic resin blends such as those employed in dentine adhesives, resulted in a marked reduction in their mechanical strength that may compromise the durability of resin-dentine bonds.

Absorption↗
PubMed1999

Shear bond strengths for composite and autopolymerized acrylic resins bonded to acrylic resin denture teeth.

Statement of problem. Composite has been used to modify acrylic resin denture teeth. Purpose. This in vitro investigation examined the shear bond strengths between composite and autopolymerized acrylic resin bonded to acrylic resin denture teeth. Material and methods. The surface treatments used for the denture teeth included wetting with methyl methacrylate (MMA), vinylethyl methacrylate monomer (VEMA), unfilled liquid resin, composite bonding agent, and composite color modifier. Nonhydrated and hydrated denture tooth groups were included. A commercial composite was bonded to the denture teeth. The control group consisted of autopolymerized PMMA resin bonded to the acrylic resin denture teeth, and another group consisted of polyvinylethyl methacrylate bonded to acrylic resin denture teeth. The samples were thermocycled and tested in shear. Results. Acrylic resin denture teeth prewetted with MMA and treated with unfilled resin or a bonding agent had bond strength values comparable to the control group. VEMA was not as effective in promoting the bond. Composite color modifier did not produce a significantly weaker bond between the acrylic resin teeth and added composite. No prewetting of the teeth with MMA resulted in the lowest bond strength. Mean shear bond strengths for corresponding hydrated and non-hydrated groups were not significantly different. Conclusion. Bond strength of composite-to-acrylic resin denture teeth was comparable to the bond strength of autopolymerized acrylic resin.

Acrylic Resins↗
PubMed1999

The effect of delayed light exposure on bond strength: light-cured resin-reinforced glass ionomer cement vs light-cured resin.

Under clinical situations, the intervals between material mixing and light exposure during bracket bonding using light-cured resin-reinforced glass ionomer cement may vary for each individual bracket. This study evaluates the bond strength of light-cured resin-reinforced glass ionomer cement subjected to various time intervals between material mixing and subsequent light exposure. This investigation was conducted in two parts. The first part consisted of measuring the enamel surface temperature to define the conditions under which the second part of the study was carried out. One hundred fifteen subjects, 63 males and 52 females, participated in this study. The over-all mean temperature as measured with a noncontact infrared thermometer was 31.9 degrees C. The second part of this study assessed tensile and shear bond strengths of light-cured resin-reinforced glass ionomer cement subjected to immediate light exposure (time interval, 5 minutes) and bond strengths subjected to light exposure at 10, 20, and 40 minutes after material mixing. Light-cured resin-reinforced glass ionomer cement was then compared with light-cured composite resin. Mean tensile and shear bond strengths of light-cured resin-reinforced glass ionomer cement exposed after 40 minutes were 4.5 MPa and 20.5 MPa, respectively. This represented a reduction of approximately 20% when compared with the 5-minute group. Scheffé test showed no statistically significant differences between any two time intervals. Mean bond strengths of the light-cured resin decreased with time. Tensile and shear bond strengths of light-cured resin indicated high statistical significance within groups across time. It could therefore be concluded that the bond strength of light-cured resin-reinforced glass ionomer cement was not affected by the timing of visible light exposure; whereas, the bond strength of light-cured resin decreased as time intervals increased. Light-cured resin-reinforced glass ionomer cement may thus serve as an advantageous alternative to composite resin for bracket bonding.

Adolescent↗
PubMed1979

[Studies of dental methacrylic resin. (Part. 6) Adhesive strength of self-curing methacrylic resin to polymethylmetacrylates with various cross-linking density. (author's transl)].

The adhesive property of dental acrylic resin to resin teeth and denture base resins is an important property, in the case of preperating, repairing and rebasing denture. Then, as models of denture base resin and resin tooth, heat-curing methacrylic resins which were cross-linked with three kinds of polyethylene glycol dimethacrylate, i.e., EDMA, tri-EDMA, nona-EDMA, were prepared, and the tensile adhesive strengths of self-curing methacrylic resin to them were examined. The results were as follows. 1) The tensile adhesive strength under the dry condition was dependent on cross-linking density of adherent resin, and decreased according to the increase of concentration of cross-linking agent added in adherent resin. 2) The greater the number of chain members of cross-linking agent used to adherent resin was, the higher the adhesive strength was. In particular, the adhesive strength to adherent resin added with nona-EDMA in concentration from 16.7 to 30 mole%, agreed with the tensile strength of adherent resin itself indicating a favourable adhesion. 3) The adhesive strengths under the wet condition, that is, when specimens were immersed in water at 37 degrees C for 21 days, decreased from 30 to 50%, compared with that under the dry condition.

Acrylic Resins↗
PubMedDate not supplied

Demineralization around orthodontic brackets bonded with resin-modified glass ionomer cement and fluoride-releasing resin composite.

PURPOSE: Enamel demineralization adjacent to orthodontic brackets is one of the risks associated with orthodontic treatment. Glass ionomer cements have been shown to decrease enamel demineralization adjacent to brackets and bands but do not exhibit bond strengths comparable to resin composites. The purpose of this in vitro study was to compare a fluoride-releasing resin composite versus a resin-modified glass ionomer cement for inhibition of enamel demineralization surrounding orthodontic brackets. METHODS: Forty-five teeth were randomly assigned to 3 groups of 15 teeth. Fifteen were bonded with Concise (3M), a non-fluoride-releasing resin composite (control); 15 teeth were bonded with Light Bond (Reliance), a fluoride-releasing resin composite; and 15 teeth were bonded with Fuji Ortho LC (GC Corporation), a resin-modified glass ionomer cement. The teeth were placed in an artificial caries solution to create lesions. Following sectioning of the teeth in a buccolingual direction, polarized light microscopy was utilized to evaluate enamel demineralization adjacent to the orthodontic bracket. The area of the lesion was measured 100 microns from the orthodontic bracket and bonding agent. RESULTS: MANOVA (P < .0001) and Duncan's test (P < .05) indicated the resin-modified glass ionomer cement (Fuji Ortho LC) and the fluoride-releasing resin composite (Light Bond) had significantly less adjacent enamel demineralization than the non-fluoride-releasing resin composite control. However, there was no significant difference between the resin-modified glass ionomer cement and the fluoride-releasing resin composite. CONCLUSIONS: Based on the results of this in vitro study, it can be concluded that Fuji Ortho LC and Light Bond exhibit significant inhibition of adjacent demineralization compared to the non-fluoride-releasing control.

Acrylic Resins↗
PubMed2005

[A basic study on newly developed light-curing resins--Fitness, flexural properties and bond strength to self-curing resins].

The objectives of this study were to evaluate fitness, bending properties, and bond strength of newly developed light-curing denture base resins (Eclipse, Dentsply) in contrast with conventional heat-curing denture base resins (Acron, GC). These evaluations were performed by fitting tests, bending strength tests, and shear bond strength tests. For the fitting test, 40 resin specimens, 20 for each resin, were made on plaster models, which simulated the maxillae edentulous ridge. The gaps between resin specimens and the plaster model were measured. The bending strength tests were carried out using 16 resin plate specimens (65 x 10 x 2.5 mm). The bending strength and elastic modulus for each denture base resin was calculated. For the shear bond strength test, self-curing resins were bonded to each resin and in total, 32 bonded specimens (20 x 4 x 2.5 mm) were made. The shear bond strength tests were carried out in order to evaluate the bond strength between the self-curing resin and each denture base resin. The results of these tests revealed that Eclipse exhibited better fitness to the plaster model, larger bending strength, and larger elastic modulus than Acron. Furthermore, the bond strength of Eclipse to self-curing resin was equivalent to that of Acron. These results suggest that Eclipse has excellent properties for application in clinical settings.

Chemical Phenomena↗
PubMed2002

Development of metal-resin composite restorative material. Part 4. Flexural strength and flexural modulus of metal-resin composite using Ag-In alloy particles as filler.

The flexural strength and flexural modulus of an experimental metal-resin composite, which used Ag-In alloy particle as the filler, were evaluated. The effect of acid treatment and heat treatment on the Ag-In alloy particle was investigated. The flexural strength of the experimental metal-resin composites ranged from 65.5 MPa to 91.0 MPa. The flexural strength of the metal-resin composite increased with the temperature of the heat treatment until 350 degrees C, but its effect varied with the concentrations of HCl of the acid treatment. A metal-resin composite, which used acid-treated and 350 degrees C heat-treated Ag-In alloy fillers, matched the requirement of strength of ISO 4049. The average of flexural modulus of the experimental metal-resin composite was 9.1 GPa. The flexural modulus of the metal-resin composite did not vary with the treatment conditions of the metal filler. The flexural modulus of a metal-resin composite, which used Ag-In alloy particle as the filler, was lower than that of Ag-Sn alloy metal-resin composite, which was reported previously. However, the flexural strength of the Ag-In alloy metal-resin composite was similar to that of Ag-Sn alloy metal-resin composite. We can control a flexural modulus of a metal-resin composite without decreasing flexural strength by choosing filler materials.

Algorithms↗
PubMedDate not supplied

Bond strength of a resin composite to a polyacid-modified resin composite under different conditions.

OBJECTIVE: The aim of this in vitro study was to evaluate the tensile bond strength values between polyacid-modified resin composite ("compomer") and resin composite materials under different conditions. METHOD AND MATERIALS: There were five experimental groups in the study. In group A, resin composite was placed directly on polyacid-modified resin composite surfaces. In group B, bonding agent was applied to polyacid-modified resin composite surfaces and then resin composite was placed on the compomer. In group C, compomer specimens were stored for 1 week and then resin composite was placed directly on these aged compomers. In group D, compomer specimens were again stored for 1 week, and then the bonding agent and resin composite were applied to the compomer surfaces. In group E, the surfaces of aged (1 week) compomers were roughened before the bonding agent was applied and the resin composite was placed on the prepared surfaces. A statistical analysis of the results was made with the Kruskal-Wallis test method. RESULTS: The mean tensile strength values of the groups were as follows: group A = 12.84 MPa; group B = 15.03 MPa; group C = 10.60 MPa; group D = 11.56 MPa; group E = 24.87 MPa. There were statistically significant differences between groups E and A; groups E and C; groups E and D; and groups C and B. CONCLUSION: Mechanical roughening of a polyacid-modified resin composite surface was found to be the most effective factor in increasing the tensile bond strength between an aged compomer and a resin composite.

Compomers↗
PubMed1987

Ion-exchange resins as potential phosphate-binding agents for renal failure patients: effect of the physicochemical properties of resins on phosphate and bile salt binding.

The effect of resin type, degree of cross-linking, bead size, and surface area on the phosphate and bile salt binding characteristics of five strongly basic Dowex anion-exchange resins in the chloride form was studied. The maximum uptake of phosphate (expressed as uptake of phosphorus) from sodium phosphate solutions was 137, 82, 86, 138, and 76 mg of phosphorus per gram of dry Dowex resins XF 43311, XY 40013, XF 43254, XY 40011, and XY 40012, respectively. The presence of simulated gastric or intestinal fluids resulted in small but insignificant alterations in phosphorus uptake by the resins. The resins all bound similar amounts of phosphorus and taurocholate (80-100% of the total phosphorus and taurocholate in solution) at physiological concentrations of phosphate and bile salt. Dowex resins XY 40013 and XF 43254, with identical physicochemical properties, but different bead sizes and surface areas, bound similar amounts of the bile salt sodium taurocholate at all taurocholate concentrations, indicating that binding was not restricted to the surface sites on the resin bead. The 2% cross-linked resins bound 3-4 times more taurocholate than the 8% cross-linked resins (at high taurocholate concentrations); the smaller pore size of the latter resins probably presents a greater mechanical exclusion barrier than the larger pore size of the 2% cross-linked resins.

Anions↗
PubMed1995

Transverse bond strength of repaired acrylic resin strips and temperature rise of dentures relined with VLC reline resin.

This study measured the transverse strength of polymethyl methacrylate heat-cured resin samples repaired with Triad visible light-cured reline resin with and without bonding pretreatments and with autopolymerizing resin, and it measured the temperature rise of Triad resin during relining of complete dentures at various curing cycles. The results indicated that pretreatment with either monomer or Triad bonding agent improved the bond of the Triad visible light-cured reline resin to the heat-cured resin. However, the use of the monomer rather than bonding agent resulted in a stronger bond and obtained values similar to those of samples repaired with autopolymerizing resin. Polymerization of samples repaired with Triad resin in the curing unit for two cycles of 5 minutes with 1 minute between cycles resulted in bubble formation and severe distortion of the heat-cured resin in the samples. Curing of the relined dentures for 10 minutes as recommended by the manufacturer raised the average peak temperature to 120 degrees C. In addition, it was shown that interrupting the light curing cycle attenuated the temperature rise, but it also resulted in a relatively softer reline resin. A continuous light curing of at least 5 minutes with the adjunct temperature rise is required to reach 1-hour hardness of 21.8 Vickers hardness number of the Triad reline resin.

Acrylic Resins↗
PubMed1992

The shear bond strength between human enamel and composite resin placed with cured or uncured unfilled resin.

The shear bond strength between enamel and composite resin placed with an unfilled resin layer was tested under several conditions: The unfilled resin layer was either blown thin or left unthinned, and pre-cured alone or cured with the composite resin. Shear testing showed that the bond to enamel was slightly enhanced for Pekalux and was significantly enhanced for Durafill VS when the unfilled resin was not pre-cured. Thinning of unfilled resin slightly increased the bond strength of Pekalux and decreased the bond strength of Durafill VS. A majority of the specimens fractured at the composite resin-unfilled resin interface, and more than half of all interface failures occurred in specimens in which the unfilled resin had been pre-cured. The results indicated that the link between composite resin and the unfilled resin layer was enhanced by simultaneous curing.

Analysis of Variance↗
PubMedDate not supplied

Influence of interchanging adhesive resins and self-etching primers on the mechanical properties of adhesive resins.

This study determined the influence of interchanging adhesive resins and self-etching primers on the mechanical properties of adhesive resins. Four commercially available two-step self-etching primer systems were used. To measure microtensile strength, 0.5-mm thick dumbbell-shaped slabs of each combination of adhesive resin and self-etching primer were prepared. After 24 hours storage in 37 degrees C distilled water, these specimens were subjected to microtensile testing at a crosshead speed of 1.0 mm/minute. Fourier transformation infrared spectroscopy was used to determine the degree of conversion. The percentage of residual double bonds, including pendant and monomeric double bonds, was calculated by comparing the obtained ratio against uncured adhesive resin. The degree of conversion of the adhesive resins was obtained by subtracting the %C=C from 100%. Two-way ANOVAs, followed by Tukey tests, were done. The microtensile strengths and degree of conversion varied with different combinations of self-etching primer and adhesive resin. Numerically, the highest microtensile strengths were obtained when the primer/adhesive resin combinations from the same manufacturer were used. When the different combinations of self-etching primers and adhesive resins were mixed, the microtensile strength and degree of conversion of the adhesive resins tended to decrease for some combinations. Within the limitations of this study, which was far removed from clinical situations, the role of the self-etching primers on the mechanical properties of adhesive resins should be considered to create an authentic resin-dentin interface.

Analysis of Variance↗
PubMed1989

[Establishment of a composite resin inlay technique. Part 1. The effects of various curing modes on mechanical properties of composite resins].

The effects of the curing mode on mechanical properties of composite resins were examined. Four resins as inlay, and three chemically-cured and five visible light-cured restorative resins were employed. The resin specimens were prepared by three kinds of curing modes; regular setting (according to the manufacturer's instruction), subsequently added light and heat curing after regular setting, and subsequently added heat and pressure curing after regular setting. Knoop hardness, flexure strength, compressive strength, and diametral tensile strength were determined. All restorative composites were remarkably increased in knoop hardness number due to the subsequently added curing methods. Both subsequently added curing methods provided higher flexure strength to all restorative resins, and particularly in the chemically-cured resins the flexure strength provided by the subsequently added light and heat curing was higher than those by the subsequently added heat and pressure curing. Compressive strength and diametral tensile strength were slightly increased by the subsequently added curing methods with the restorative resins. No correlation was found between the filler distribution and the mechanical properties provided by the subsequently added curing methods. The subsequently added heat curing seems to be preferable for creating higher mechanical properties of resins. The IC-2 resin, experimentally designed for resin inlay, seems to be the most promising resin for inlay restoration, based on the mechanical properties, and further detailed laboratory and clinical researches are required.

Composite Resins↗
PubMedDate not supplied

Enhancement of resin bonding to heat-cured composite resin.

The purpose of this study was to evaluate the effectiveness of various surface treatments used to enhance the bond strength of resin cements to two different laboratory-processed composite resins. Seventy specimens of a microfilled composite resin (Concept) and 70 specimens of a micro-hybrid composite resin (Herculite XRV) were fabricated in metal wells and subjected to heat (250 degrees F) and pressure (85 psi) curing. An additional 70 specimens of each material were fabricated in the shape of disks and also subjected to the same heat/pressure curing. All composite resins were subjected to one of seven treatment regimens. The like-treated specimens were then bonded together using dual-curing resin cement and a uniform seating force (106 gm). After 7 days, bonded specimens were thermocycled 1000 times at 5 and 55 degrees C, and debond shear strengths were determined on a Universal Testing Machine. The use of microabrasion (50 microns aluminum oxide at 60 psi) and ceramic layer deposition (30 microns aluminum oxide with a ceramic additive at 75 psi) consistently improved the shear bond strength of the resin cements to both composite resins. The other treatment combinations provided varying effects. In conclusion, microabrasion or ceramic layer deposition are preferred methods to enhance the bond of resin cements to composite resins.

Acid Etching, Dental↗
PubMed1991

Shear bond strengths of resin luting cements to laboratory-made composite resin veneers.

Retention problems have been reported with the clinical use of indirect microfilled resin veneers. This study used 24-hour shear tests to assess the bond strengths of such a resin veneer compared with other veneer types. The effect of different resin luting cements and resin veneer surface treatments were analyzed to elucidate factors by which retention could be increased. The six resin luting systems investigated showed a range of bond values. Debonding occurred primarily at the veneer/cement interface. G-Cera material produced the weakest bonds to Isosit-N resin. Surface treatment of Isosit-N veneers resulted in bond strength changes. Sandblasting reduced the force required for bond failure; Special Bond resin increased it slightly. Improving retention of prefabricated resin veneers proved difficult. Etched hybrid resin veneers delivered higher bond strengths than micro-filled resin veneers but not significantly. Etched porcelain veneers, however, provided consistently the strongest bond strengths with cohesive, as opposed to adhesive, bond failure.

Acid Etching, Dental↗