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At least 217 records · Page 12Linked to original sources
PubMed2006

Influence of polishing of denture base resin and metal surfaces on wettability with water and saliva.

The purpose of this study was to investigate the influence of the surface roughness of denture base resin and metal on wettability with water and saliva. Solid specimens were produced using heat-curing denture base resin and Co-Cr alloy. After polymerizing or casting these materials, specimens with four different types of surface roughness were produced by a progressive polishing process using polishing papers (#240, #400, and #1,000) and cotton buffs. Surface roughness decreased significantly as the polishing process progressed (p<0.0001). Contact angle increased as surface roughness in metal specimens decreased, but decreased as surface roughness in resin specimens decreased (p<0.0001). Furthermore, differences in contact angle between tap water and saliva were larger in metal specimens (p<0.0001). These results suggested that with regard to the tissue surface of a denture base, the influence of its roughness on adhesive force differed according to the type of denture base material.

Acrylic Resins↗
PubMed1999

Fabrication of complete denture bases reinforced with polyethylene woven fabric.

Incorporation of 5 layers of woven, high-modulus polyethylene fiber into acrylic resin denture bases produces substantial improvements in mechanical properties and dimensional changes. A modified split-pack technique has been developed using conventional dental-laboratory compression molding to accommodate multiple layers of woven fabric in complete denture bases. A recess formed in the resin by a spacer allows the reinforcement to be embedded in the denture base without exposing the fibers. Embedded fibers do not compromise the esthetics of complete dentures.

Acrylic Resins↗
PubMed2001

Application of electrolyzed acid water to sterilization of denture base part 1. Examination of sterilization effects on resin plate.

Bactericidal activities of electrolyzed strong and weak acid waters for acrylic denture base resin were evaluated in order to discuss the applicability of these waters for sterilization of denture base. Only 1-minute immersion in the electrolyzed strong or weak acid water could completely eliminate the attached bacteria, Staphylococcus aureus 209P, on the resin plate. When the resin was relined with tissue conditioner, 5-minute immersion or 1- to 2-minute ultrasonic cleaning reduced the number of the bacteria from 10(5)/cm2 level to 10(1)/cm2 and no surviving bacteria could be detected after 10-minute treatment. These findings suggest that both the electrolyzed strong and weak acid waters are well applicable to the disinfectant for acrylic denture base showing excellent bactericidal activities in a significantly shorter treatment as compared with the conventional denture cleaning.

Acrylic Resins↗
PubMed1990

Denture base acrylic resins: friend or foe?

This article reviews the advantages and disadvantages of denture base acrylic resins. Improvements in areas such as strength and speed of cure are discussed. The authors also emphasize the necessity for investigating the effects of factors other than denture base materials on the incidence of troublesome dentures.

Acrylic Resins↗
PubMed1995

Development and assessment of an objective method of colour change measurement for acrylic denture base resins.

Current standard specifications for the laboratory evaluation of denture base materials require subjective assessment of colour stability. This study evaluates a new objective measurement technique for translucent denture base materials, by comparing quantitative data with the results obtained from a standard subjective method. Preliminary work on three representative commercial acrylic materials resulted in the selection of a white background for the quantification of colour change of these translucent materials. One half of each sample was exposed to artificial sunlight for 24 h. The colour of both exposed and unexposed resin was measured on the CIE L*a*b* scale using a photo-electric colorimeter. Significant changes in the b* and E* values (P < 0.01) were observed following light exposure. Objective data for a wide range of commercial materials were compared with the results of a subjective evaluation and it was shown that a change in b* of 1.5 units was discernable subjectively by eye for 100% of the cases. It is suggested that this method and limit value could form the basis of a new objective colour change specification for polymeric dental materials.

Acrylic Resins↗
PubMed1982

Colour stability of two self curing denture base materials.

It is important that denture base materials should be colour stable, yet some self curing materials do not fulfill this requirement. Two newly introduced materials, one a 'pour type' resin, were investigated using a sophisticated colorimetric instrument to assess colour changes that might result from contact with water and denture cleansers. Both materials showed measurable colour changes following a two week soaking period, but these were barely perceptible to the eye. The possible reasons for colour instability are discussed.

Acrylic Resins↗
PubMed2006

The effect of two fibre impregnation methods on the cytotoxicity of a glass and carbon fibre-reinforced acrylic resin denture base material on oral epithelial cells and fibroblasts.

Acrylic resin dentures may have cytotoxic effects on oral soft tissues. However, there is sparse data about the cytotoxic effect of fibre-reinforced acrylic resin denture base materials. The purpose of this in vitro study was to determine the effect of two fibre impregnation methods on the cytotoxicity of a glass and carbon fibre-reinforced heat-polymerized acrylic resin denture base material on oral epithelial cells and fibroblasts. One hundred acrylic resin discs were assigned to five experimental groups (n = 20). One of the groups did not include any fibre. Two groups consisted of silane and monomer treated glass fibres (Vetrolex) impregnated into acrylic resin (QC-20) discs. The other two groups consisted of silane and monomer treated carbon fibres (Type Tenox J, HTA). Untreated cell culture was used as positive control. The human oral epithelial cell line and buccal fibroblast cultures were exposed to test specimens. The cytotoxicity of the test materials was determined by succinic dehydrogenase activity (MTT method) after 24 and 72 h exposures. Data were analysed with a statistical software program (SPSSFW, 9.0). A one-way analysis of variance (anova) test and Bonferroni test were used for the comparisons between the groups. All statistical tests were performed at the 0.95 confidence level (P < 0.05). After 24 and 72 h incubation, cell viability percentages of all experimental groups showed significant decrease according to the positive control cell culture. Fibroblastic cell viability percentages of silane and monomer treated fibre-reinforced groups were lower than the unreinforced group. Cell viability of monomer-treated groups displayed the lowest percentages. Elapsed incubation time decreased epithelial cell viability in silane-treated groups. Fibroblastic cell viability was not influenced by elapsed time except the unreinforced group.

Acrylic Resins↗
PubMed1992

The effect of disinfection procedures on flexural properties of denture base acrylic resins.

This study evaluates the effects of long-term disinfection immersion on the flexural properties of denture base resins; it was conducted against a background of increasing awareness of the importance of cross-infection control in dental clinics and laboratories. The transverse bend testing procedure used followed that specified in the International Standard for denture base polymers. The results demonstrate that alcohol-based disinfectants are not suitable for use with denture base materials of non-cross-linked acrylic resin.

Acrylic Resins↗
PubMed2000

Viscoelastic properties of denture base resins obtained by underwater test.

The viscoelastic properties of denture base polymers, such as poly(methylmethacrylate) (PMMA), polycarbonate (PC), polysulfone (PSF) and polyethersulfone (PES) which have been used in current clinical dentistry were investigated. In addition, water absorption, diffusion coefficient of water into material, cubical expansion, specific volume and residual monomer were also determined. From the results of this study, the viscoelastic behaviours of the denture base polymers in water have been discussed. The relaxation modulus (Er(5)) which was calculated using a stress at 5 s from the start of measurement for the specimen which reached an equilibrium moisture content (wet specimen), decreased from 23.1 to 25.5% compared with that of PMMA stored in a desiccator (37 degrees C) for 1 week (dry specimen). In contrast, this decreasing ratio was 7.0 to 10.0% for PC, PSF and PES. It is suggested that this phenomenon is caused by the increase of specific volume (cm3/g) with water absorption in each material. The water absorption of the PMMA group was relatively large in comparison with other material and was 1.81-1.85%. This value was within the range from 0.38 to 1.74% for PC, PSF and PES. The diffusion coefficients of water for PC, PSF and PES increased by approximately 1.5-2.7 times that of PMMA. Furthermore, the coefficient of cubical expansion of the wet specimen was larger than that of the dry specimen. The increasing ratio was 1.03-1.10 times for the PMMA group and 1. 18-2.38 times for PC, PSF and PES. The variation of Er(5) of the PMMA group with temperature in water was larger than those of PC, PSF and PES.

Absorption↗
PubMed2001

Denture base polymer Alldent Sinomer: mechanical properties, water sorption and release of residual compounds.

The aim of this study was to determine flexural properties, water sorption, solubility and release of residual compounds of a new paste type denture base polymer Alldent Sinomer. In addition, an effort was made to reinforce the denture base polymer with a polymer-pre-impregnated glass fibre reinforcement (Stick). Six rhombic test specimens were fabricated for the flexural test in accordance to the ISO 1567 standard. Water sorption and solubility was also determined as described in the ISO standard. Residual compound release into water was determined with the high performance liquid chromatography (HPLC) METHOD: The flexural strength of Sinomer polymer was 85.8 MPa and flexural modulus 2.73 GPa. Storing of test specimens in water reduced the flexural strength and the modulus. By adding the glass fibre reinforcement into the test specimen, the flexural strength and the modulus increased considerably (ANOVA, P < 0.001). The increase was minor with the reinforcement of low fibre content and high with the reinforcement of higher fibre content. Water sorption of the Sinomer polymer was 26.4 microgram mm-3 and solubility was 1.52 microgram mm-3. High performance liquid chromatography analysis revealed the release of 0.18 wt% fraction of compound which was determined as methylmethacrylate (MMA) monomer. The results of this study suggest that the new denture base polymer Sinomer passed the requirements of the ISO standards and that its mechanical properties can be increased considerably by an incorporation of a glass fibre reinforcement. The release of MMA monomer into water from the polymer should be taken into account when the polymer is used in denture bases of patients with an allergy towards MMA.

Absorption↗
PubMedDate not supplied

Color stability of denture base polymers.

One light-polymerized, three heat-polymerized, and three autopolymerized denture base polymers were exposed to coffee, tea, water at 50 degrees C +/- 1 degree C, as well as artificial sunlight and water, and evaluated for color stability. The color characteristics were determined using a computer-controlled spectrophotometer. Water sorption and solubility were assessed, and the materials were also chemically characterized. Coffee and tea stained the denture base materials superficially. Brushing with toothpaste and moderate grinding reduced discoloration to an acceptable level. All materials were relatively color stable when immersed in water at 50 degrees C +/- 1 degree C. The materials behaved differently when exposed to artificial sunlight and water.

Chromatography, Gas↗
PubMed1980

A multi-station machine for the fatigue testing of denture base materials.

A multi-station machine has been designed and built to determine the resistance to fatigue failure of denture base materials. The machine has enabled complete S-N curves to be plotted for conventional and reinforced denture base materials involving many megacycles of operation. The resistance to fatigue failure of conventional denture base polymers is similar to that of 'Perspex'; that of PMMA reinforced with carbon fibre is of an order of magnitude greater.

Biomechanical Phenomena↗
PubMed2006

Quantitative analysis of allergenic ingredients in eluate extracted from used denture base resin.

Allergenic ingredients extracted from used denture base resin were quantitatively analysed using a gas chromatograph/mass spectrometer and high performance liquid chromatography. Methyl methacrylate (MMA), hydroquinone (HQ), formaldehyde (FMA), benzoyl peroxide (BPO), benzoic acid (BA) and methyl benzoate (MB) were detected in a eluate from all of the dentures, while ethyleneglycol dimethacrylate (DME) was detected in the eluate from 87 dentures in use for <15 years. MMA, HQ, FMA, BPO and MB showed a decrease in correlation to the period of denture use, but continuing to be evident even after 29 years of use. The MMA showed the highest level of elution and a relatively moderate decrease over time. The elution of BA, on the contrary, showed an increase with the period of denture use up to about 10 years and subsequently reached a plateau. Our results indicate that purported allergens exist in the resin base and can be eluted into the oral cavity, even in patients using an old denture for a period of nearly 30 years.

Acrylic Resins↗
PubMed1998

Adherence of Candida albicans to denture-base materials with different surface finishes.

OBJECTIVES: To assess the in vitro adherence of Candida albicans to heat-cured hard and soft denture-base materials with varying surface roughness, and to observe the effect of a mixed salivary pellicle on candidal adhesion to these surfaces. METHODS: In vitro adhesion assays on heat-cured acrylic resin (Trevalon), Molloplast B and Novus using the type strain of C. albicans (NCPF 3153A). Surfaces for the assays were prepared using clinically appropriate rotary instruments. Unstimulated, pooled and clarified whole saliva was used to assess its effect on adhesion. RESULTS: Significantly greater adhesion of C. albicans to rough rather than smooth surfaces was found (P < 0.001), as well as increased adhesion to the machined soft lining materials compared with acrylic. Pre-coating denture-base materials with saliva reduced candidal adhesion on all materials. CONCLUSIONS: Rough surfaces on denture-base materials promote the adhesion of C. albicans in vitro. However, saliva reduces adhesion of C. albicans and thus diminishes the effect of surface roughness and free surface energy differences between materials.

Acrylic Resins↗
PubMedDate not supplied

Surface roughness of denture base acrylic resins after processing and after polishing.

PURPOSE: Circumstances exist in which the need to adjust denture base acrylic resins is necessary. This process obviously alters the surface of the polished denture base. The purpose of this study was to compare the effects of three chairside polishing kits and conventional polishing on four denture acrylic resins. MATERIALS AND METHODS: Twenty-four 30 x 30 x 2 mm acrylic resin specimens were fabricated with each of four acrylic resins: autopolymerizing, heat processed, injection molded, and microwaveable. One side was polished conventionally with pumice and polishing compound. The other side was polished with one of three chairside polishing kits: Axis, Brasseler, and Shofu. Each side was evaluated by a Dektak 8 Programmable Stylus Profiler to determine the surface roughness (Ra). RESULTS: One-way analysis of variance (ANOVA) revealed that: (1) There was no significant difference in the time it took to polish the specimens with the chairside polishing kits (F=2.118, p=0.14). (2) There was a significant difference in surface roughness between the acrylic resins before any polishing, with the injection-molded and heat-processed being less rough than the autopolymerizing (F=4.588, p=0.005). (3) There was a significant difference in surface roughness between the acrylic resins when conventionally polished, with the injection-molded and microwavable being less rough than the autopolymerizing (F=4.503, p=0.005). Factorial ANOVA revealed that: (1) There was no significant difference in the surface roughness among the chairside polishing kits (F=1.209, p=0.30). (2) There was a significant difference between the acrylic resins, with the heat-processed, injection-molded, and microwaveable being significantly less rough than the autopolymerizing (F=6.610, p=0.0001). (3) There was no significant interaction between the acrylic resins and the chairside polishing kit in the amount of surface roughness (F=1.728, p=0.12). An independent t-test revealed that conventional polishing was significantly smoother than polishing with the chairside polishing kits (t=3.847, p=0.0001). CONCLUSIONS: It was concluded that time was not a factor in using any of the chairside polishing kits. It is recommended that conventional polishing be used after adjustments to the cameo surface of denture acrylic resin.

Acrylic Resins↗
PubMed1987

The use of computed tomography in the detection of radiolucent denture base material in the chest.

With the introduction of acrylic resin denture base materials to the dental profession, radiolucency was recognized as a significant deficiency at an early stage. Continuous research into the production of a radiopaque material has been directed at including radiopaque glasses, salts or metals powders in an otherwise radiolucent polymer. However, the majority of new dentures are still made in radiolucent material which is notoriously difficult to locate by conventional radiography and reports continue to appear relating to the inhalation or ingestion of dentures (or fragments of them), occasionally leading to the death of the patient. Advances in radiographic techniques and equipment have seen the development of computed tomography (CT). This has proved invaluable as a diagnostic aid for disease and therapy but little attention appears to have been given to the use of this sophisticated technique in the detection of foreign bodies, in particular those of dental origin. This study investigates the use of CT in the detection of radiolucent denture base material. The results suggest that CT has substantial advantages over conventional radiography in the detection of this material and should be considered as a valuable diagnostic aid in those patients thought to have inhaled dentures or fragments of dentures.

Acrylic Resins↗