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Results for “DENTURE BASES”

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At least 379 records · Page 21Linked to original sources
PubMed1990

Leachability of denture-base acrylic resins in artificial saliva.

We studied the influence of salivary acidity on leachability of denture-base acrylic resins with etiological interest in denture stomatitis because denture surfaces are frequently exposed to acidic conditions in the oral cavities. Auto-, heat-, and microwave-polymerized resins were immersed in artificial saliva with pH ranging from 4.0 to 6.8 at 37 degrees C, and leachables were pursued quantitatively with time. Methyl methacrylate, methacrylic acid, and benzoic acid leached from all resins. Their concentrations in the saliva were markedly high for auto-polymerized resins, while leachability of heat- and microwave-polymerized resins was so low that quantitative analysis of leachables was impossible. Lower pH showed higher concentrations of methyl methacrylate, although no apparent association was confirmed between salivary acidity and its own leachability. The concentrations of methacrylic acid increased remarkably with an increase in pH, which was probably due to hydrolysis of methyl methacrylate. These results suggest that chemotoxic actions of auto-polymerized resins are potentially ascribable to methyl methacrylate under more acidic conditions and to methacrylic acid under less acidic conditions.

Acrylic Resins↗
PubMed2004

[Visualizing living fibroblast on co-cultured denture base resin by green fluorescent protein marker introduced into the cell].

Visualizing living cells growing on co-cultured biomaterials is ideal for material biocompatibility evaluation in vitro. In this experiment, mouse fibroblasts L929 were labeled by introducing the gene coding enhanced green fluorescent protein (EGFP) marker into the cells. Morphology as well as proliferation of labeled cells surrounding or on the surface of co-cultured denture base resin slides were observed by use of phase-contrast microscope and fluorescent microscope directly. It was found that residual methyl methacrylate (MMA) in the denture base resin exhibited transient cytotoxicity to fibroblasts and this transient cytotoxicity could be eliminated by pre-extracting the resin with ddH2O for a short time. This fact demonstrated that even slight cytotoxicity of materials could be detected through imaging of living cells near material or material touched. And it was suggested that imaging of living cells co-cultured with biomaterial is helpful to understanding biocompatibility of materials more accurately.

Acrylic Resins↗
PubMed1982

Conversion in denture base polymers.

The purpose of this investigation was to determine residual monomers, the insoluble gel fraction, and singly reacted dimethacrylate monomers in heat-polymerized, auto-polymerized conventional and pour-type denture base materials. Residual monomers were determined by HPLC analysis of tetrahydrofuran extracts of denture base polymers. The gel fraction was determined by gravimetric analysis of the nonextractable portion. The pendant methacrylate groups in the gel fraction were determined by quantitative IR (infrared) spectrometry. It was demonstrated that the heat-polymerized materials had the lowest content of residual monomers. Generally, the content of pendant methacrylate groups in the gel was dependent on the initial quantity of crosslinking agent in the monomer liquids. The gel fractions of the heat-polymerized materials were larger than the quantity of reacted monomers and were also dependent on the quantity of crosslinking agent. These findings showed that some of the linear prepolymer, poly(methyl methacrylate) (PMMA), had been incorporated into the crosslinked polymer system. The gel fraction of the auto-polymerized pour-type materials corresponded to the quantity of reacted monomers, whereas the conventional auto-polymerized materials took an intermediate position between pour type materials and heat-polymerized materials in this respect.

Acrylates↗
PubMed1979

Comparison of the accuracy of denture bases by a non-parametric method.

A comparison of the accuracy of denture bases made from a conventional acrylic and four modified acrylic resins was made with the use of a non-parametric method. Twenty-five identical maxillary stone casts were made and five dentures for each resin were processed by conventional compression moulding techniques. The fit of each denture at the molar-to-molar region on its cast was evaluated by five evaluators who independently ranked the twenty-five dentures from best to worst fit after processing, after polishing, and after storage in water at 37 degrees C for 42 days. The ranking data were analysed by Kendall's coefficient of concordance, the Kruskal-Wallis statistic, and the Mann-Whitney test. Excellent agreement among observers was obtained. After storage in water, two modified acrylic resins, Hydrocryl and Vitalon II, had a better fit on their casts than the conventional acrylic, Lucitone Hypro. Luciton 199 had the same and Hircoe had a poorer fit than Lucitone Hypro.

Acrylic Resins↗
PubMed1980

Color matching dentures bases for non-white patients.

A technique has been described which offers an easy and practical approach to the matching of the basic color of the denture base to the basic color of the tissues. Further subtle characterization and customizations are compatible to the technique.

Color↗
PubMed2001

Effect of polyaramid fiber reinforcement on the strength of 3 denture base polymethyl methacrylate resins.

PURPOSE: The interactive effects of synthetic polyaramid reinforcement fibers on the transverse strength of intact and repaired heat-polymerized denture base acrylic resins were investigated. MATERIALS AND METHODS: Three polymethylmethacrylate (PMMA) polymers were tested: Acron MC (GC International Corp, Scottsdale, AZ), Lucitone 199 (Dentsply International Inc, York, PA), and Microlon (The Hygienic Corp, Akron, OH). With each polymer, there were 2 controls and 4 experimental groups (n = 9 per group). The treatment groups were intact heat-polymerized PMMA control, PMMA with unreinforced repair, PMMA with polyaramid reinforced repair, intact polyaramid reinforced heat-polymerized PMMA control, polyaramid reinforced PMMA with unreinforced repair, and polyaramid reinforced PMMA with polyaramid reinforced repair. The transverse fracture strengths of the samples were measured with a 3-point bending test on a Zwick Universal Testing Machine (Zwick of America, Inc, East Windsor, CT). RESULTS: The highest mean strength at fracture was recorded with intact polyaramid reinforced heat-polymerized PMMA controls for all resins. Analysis of variance showed significant differences in transverse strength (p < .05) by experimental group, by material, and by interaction of group and material. Tukey HSD (honestly significant difference) Multiple Comparisons Test (alpha = 0.05) showed that intact polyaramid reinforced heat-polymerized PMMA controls were significantly stronger than intact heat-polymerized PMMA controls and all the other treatment groups. Use of polyaramid reinforcement in repair of unreinforced PMMA or polyaramid reinforced PMMA did not result in significantly increased transverse strength. CONCLUSIONS: Polyaramid reinforcement significantly increased the transverse strength of intact heat-polymerized PMMA. Polyaramid fibers did not significantly increase strength to reinforce PMMA repairs.

Acrylic Resins↗
PubMed1990

Three-dimensional stability of new denture base resin systems.

Ten maxillary dentures were constructed on standard-sized casts in each of four acrylic resins. Uniform placement of the artificial teeth and thickness of the base were maintained by use of a silicone rubber mold. Metal shot was luted in preselected positions to the dentures and the land of the cast. Frontal, lateral, and occlusal radiographs were made of the dentures at time intervals of (1) before processing, (2) after processing, (3) immediately after removal from the cast, and (4) 30 days later. Study of the radiographs revealed significant variations in position of the metal shot from the before-processing baseline within each group of dentures and significant differences between groups of dentures.

Acrylic Resins↗
PubMed1989

The effect of an elevated level of residual monomer on the whitening of a denture base and its physical properties.

It has been suggested that incomplete or faulty processing leading to a high level of residual monomer is a factor in denture whitening. Laboratory tests which simulate the cleaning procedures used by patients presenting with whitened dentures have been carried out on specimen strips of acrylic denture base material with high or low levels of residual monomer. The results show that these samples exhibit similar changes and that the high level of residual monomer had no effect on the whitening process, this being attributable to the cleaning method. The major factor responsible for whitening is confirmed as a high water temperature irrespective of the presence of the denture cleaning agent. However, some physical properties were adversely affected by a high residual monomer content (due to the processing method) which has serious consequences for denture-wearing patients. The use of short/low temperature curing cycles now common in many dental laboratories should be avoided.

Acrylic Resins↗
PubMed1990

[Importance of posterior tooth-to-denture base discrepancy in the development of skeletal open-bite malocclusion].

This paper describes the relationship between the development of skeletal open-bite malocclusion and the tooth-to-denture base discrepancy. The cases which have a severe skeletal open-bite malocclusion are presented to evaluate the causing factor of the anterior open-bite. The anterior open-bite was associated with inferiorly positioned maxillary molars caused by the squeezing out effect of the tooth-to-denture base discrepancy, especially those in posterior part of dentition (posterior discrepancy), which provided a less steep maxillary occlusal plane in the denture frame. It was suggested that the posterior discrepancy induced a descending movement of the posterior teeth followed by a change of the occlusal plane and this effect of the posterior discrepancy was important factor in developing anterior open-bite malocclusion.

Cephalometry↗
PubMedDate not supplied

Reinforcing effect of a Ni-Cr alloy plate on an acrylic resin denture base.

The authors previously reported on the strengthening effect of a thin Ni-Cr plate on an acrylic resin test specimen in the three-point bending test. This study evaluated the reinforcement of acrylic resin denture bases by measuring the strain distribution in the palate of a maxillary complete denture. It was found that this reinforcing technique led to a uniform distribution of strain in the palatal area of the maxillary denture and a reduction of strain in the midpalatal area.

Acrylic Resins↗
PubMedDate not supplied

Biocompatibility of visible light-polymerized denture base resins.

The biocompatibility of three commercial formulations of visible light-polymerized denture base resins was studied to determine its effects on the RNA and DNA synthesis of oral epithelial cells in vitro. Isotope incorporation into RNA or DNA was measured after 24 hours of incubation with isotope and 48 hours of exposure to resin. The resins were shown to significantly inhibit the synthesis of both nucleotides as compared to a heat-processed resin control. Increasing the polymerization time can mitigate the toxicity of some of the resins. The air barrier coatings used to prevent oxygen inhibition of polymerization increased the toxic effects of two resins and decreased that of one of the materials. These investigations suggest that visible light-polymerized denture resins may impair the replication of oral epithelial cells. DNA synthesis is more sensitive to the toxic effects of the materials, which may relate to the ability to cause mucosal pathology. The cytotoxic effects may relate to the presence of unpolymerized resin constituents or polymerization by-products.

Acrylic Resins↗