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Results for “DENTURE BASES”

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At least 451 records · Page 25Linked to original sources
PubMed1994

The effect of esthetic fibers on the flow properties of an acrylic resin denture base material.

OBJECTIVES: This study was conducted to measure the effect of viscose rayon esthetic fibers on the flow properties of an acrylic resin denture base material. METHODS: Two testing methods using a needle penetrometer and an oscillating rheometer were employed on weighed proportions (0.1%, 0.2%, 0.8%, and 0.3%) of fiber. RESULTS: The results show that the fibers affect the flow properties of the polymer/monomer mix. Increasing the percentage of fibers decreases the flow of the material and reduces the doughing time. With increasing amounts of fiber, a rapid increase in the viscosity occurs with a corresponding adverse effect on flow properties. SIGNIFICANCE: It is concluded that these properties are important for the successful handling of acrylic materials since they can influence the accuracy and quality of the molded denture.

Acrylic Resins↗
PubMed1989

High-performance liquid chromatographic estimation of eluates from denture base polymers.

A quantitative analytical method using high-performance liquid chromatography is developed to estimate elution profiles of dental acrylic polymers used for denture bases. The method is applied to elution studies in distilled water of resins polymerized by different representative methods. Elution properties or 'leachabilities' vary depending on polymerization conditions. Methyl methacrylate, methacrylic acid and benzoic acid are eluted from autopolymerized resins at the highest eluate concentrations and are followed by heat- and microwave-polymerized resins. These results appear to be comparable to residual amounts of the eluates in resins and their cytotoxic potencies reported.

Acrylic Resins↗
PubMed1995

Bonding of resin teeth to the polymethyl methacrylate denture base material.

The objective of this study was to compare bonding of acrylic resin teeth treated in various ways to the polymethyl methacrylate (PMMA) denture base material. The joint surface of each acrylic tooth cured to heat-cured or autopolymerizing PMMA was either untreated, ground, or adjusted with mechanical retention. The bond to the PMMA was tested with a three-point loading test. To determine whether the bond failure was adhesive or cohesive, the fracture surfaces were analyzed visually and by scanning electron microscopy. The highest bond strength to both the heat-cured and the autopolymerizing PMMA was obtained by grinding grooves on the joint surface of an acrylic resin tooth before it was cured to the PMMA (p < 0.001). Heat-cured PMMA did not adhere to the acrylic resin tooth better than the autopolymerizing PMMA did (p > 0.05).

Acrylic Resins↗
PubMed1990

[Effects of fluoride releasing resin on the denture base on bovine enamel].

The first aim of this study was to investigate the amount of fluoride released from fluoride releasing resin for the denture base (F-resin). The second aim of this study was to determine the uptake of fluoride with bovine enamel, which was immersed in distilled water for 90 days in contact with F-resin. The results obtained were as follows: 1) The amount of fluoride released from F-resin decreased gradually. From the 10th day of immersion, the amount of fluoride released was almost constant. The fluoride could be detected on the 90th day. 2) The uptake of fluoride from F-resin was great both on the surface and the subsurface enamel. 3) The uptake of fluoride from F-resin was almost proportional to the immersing time.

Animals↗
PubMed1995

The effect of preparation conditions of acrylic denture base materials on the level of residual monomer, mechanical properties and water absorption.

OBJECTIVES AND METHODS: The curing of several commercial powder/liquid mixtures of acrylic denture base materials was carried out at different temperatures and curing times. The levels of residual monomer, tensile strength, percentage elongation before break and water absorption were measured. RESULTS AND CONCLUSION: It was found that the level of residual monomer determined by gas-liquid chromatography decreased with curing time and temperature increase. At the same time, the tensile strength was improved and water absorption decreased.

Absorption↗
PubMed1995

Biologic testing of leachable aromatic compounds from denture base materials.

The aromatic compounds phenyl benzoate (PB), phenyl salicylate (PS), and biphenyl (BP), which have previously been found to leach from poly(methyl methacrylate) denture base materials, were tested for cytotoxicity and biologic effects by L929 cells in culture. The octanol-water partition coefficient (log P(ow), a descriptor for the lipophilicity, was determined for the compounds. Cytotoxicity was evaluated by total cell growth and the plating efficiency test, and biologic effects by the total fatty acid composition of L929 cells. The commonly used tests, total cell growth and plating efficiency, did not show any significant changes of the cells due to the compounds. On the other hand, BP and PS, in particular, induced changes in the total fatty acid composition of L929 cells. The problem of bioavailability of aromatic compounds in cell culture assays and the relation to lipophilicity was addressed.

Animals↗
PubMed1989

[Effects of various enzymes on Candida albicans activity on denture base materials].

In this study, the effects of various enzymes to remove C. Albicans, contamined on to the different kinds of specimens prepared from 5 different denture base materials were investigated. All kinds of enzymes investigated were found to be effective, but both protase and the pure lipase were observed to be more effective than the others by their zero colonies calculated. It was decided that pepsin, trypsin and pancreatic amylase have less effects on C. Albicans than the others.

Amylases↗
PubMed1989

[Changes of microvascular patterns of the palatine mucosa under the denture base].

Microvascular changes of the denture-bearing mucosa on the hard palate of Japanese monkeys (Macaca fuscata) were investigated on microvascular casts utilizing the acryl plastic injection method (Taniguchi, Ohta et al. 1952, 1955) under SEM and ultrastructure of the endothelium of the blood capillary and surrounding tissues under TEM. The results obtained were as follows: 1. SEM findings of microvascular casts were by 10 days after setting the experimental denture capillary loops appeared a simple hair-pin shape. By 30 days the loops changed into a kind of sinusoidal networks. By 60 days the loops of the network began to sort out and to reform into hair-pin shape. 2. Aspects under the light microscope and SEM were essentially similar to those of its serial changes of the capillary loops. 3. Aspects under TEM were fenestrated capillaries have altered to continuous ones after 10 days, and again reformed to the fenestrated capillaries by 60 days. From the above results, it can be said that, although the subepithelial microcirculatory system is temporarily affected by the placement of an experimental denture, it may adapt itself to the mechanical stress of the pressure and so before recovering.

Animals↗