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At least 19 recordsLinked to original sources
PubMed2007

Internal adaptation and some physical properties of methacrylate-based denture base resins polymerized by different techniques.

This study evaluated the internal adaptation, porosity, transverse and impact strength of three denture base polymers: (1) conventional heat-polymerized, (2) microwave-polymerized, and (3) injection-molded resins. Internal adaptation was measured by weighing a vinyl polysiloxane film reproducing the gap between the denture base and the metallic master model of an edentulous maxilla. The measurements were performed immediately after finishing and after 30-day storage in water. Porosity was evaluated by weighing each specimen in air and in water using an analytical scale balance. Transverse strength test (three-point bending test) was performed using a universal machine under axial load, at a crosshead speed of 5 mm/min. Impact strength test (Charpy's test) was performed with a 40 kJ/cm load. Data were analyzed by ANOVA and Tukey test (alpha = 0.05). Internal adaptation, porosity, transverse and impact strength varied according to the type of acrylic resin and the processing technique. The injection-molded resin showed better internal adaptation compared with the conventional heat-polymerized and the microwave-polymerized resins, particularly after 30 days, but there was no relevant improvement of porosity, transverse and impact strength.

Acrylic Resins↗
PubMed2005

Effect of storage duration on tensile bond strength of acrylic or silicone-based soft denture liners to a processed denture base polymer.

OBJECTIVE: To investigate the effect of storage duration on the tensile bond strength of acrylic and silicone-based denture base materials with liners either heat-cured or auto-cured. MATERIAL AND METHODS: The denture liners investigated were Vertex soft (acrylic-based, heat-cured), Coe soft (acrylic-based, auto-cured), Molloplast-B (silicone-based, heat-cured), and Mollosil plus (silicone-based, auto-cured). The soft liner specimens were 10 x 10 x 3 mm and were processed between two PMMA blocks. They were tested following immersion in water at 37 degrees C for 1 day, 1 week, and 1, 3, and 6 months. Tensile bond strength was measured using a universal testing machine (Testometric Micro 500) at a crosshead speed of 20 mm/min (n = 10 specimens per experimental group). Multiple ANOVA and Tukey HSD were used to analyse the data at a pre-set alpha of 0.05. RESULTS: The results indicate that the tensile bond strength of acrylic-based soft liners is greater than that of silicone-based materials. The bond strength of all lining materials decreases with storage duration; the decrease being greatest for the acrylic-based soft liners. The decrease in bond strength of the auto-cured materials is greater than that of the heat-cured products. CLINICAL SIGNIFICANCE: Comparison of the materials in this study indicates that the silicone-based, heat-cured soft liner is superior, based on the tensile bond strength property. Use of silicone-based, heat-cured soft liners may provide better clinical success over a long period. These laboratory results need to be verified by clinical testing.

Acrylic Resins↗
PubMed2002

Effect of commercial acrylic resins on dimensional accuracy of the maxillary denture base.

Denture base dimensional changes were found with commercial thermocured acrylic resins. Fifteen stone cast-wax base sets were packed for routine flasking. Clássico, Vipcril, and Meliodent Multicryl acrylic resins were prepared according to manufacturer instructions. After final acrylic resin pressing, the flasks were placed in strain clamps and submitted to polymerization cycles in heat-water following manufacturer instructions. The resin bases were fixed on casts with instant adhesive and the sets laterally sectioned in the corresponding regions to the distal of canines (A), mesial of first molars (B), and posterior palatal zone (C). The gap between the stone cast and resin base was verified with a measuring microscope at five reference positions for each type of cut. The data were submitted to ANOVA and Tukey's test and a significant statistical difference between the commercial acrylic resins was shown. The pattern of distortion verified in the posterior palatal region was confirmed in the C cut with significant statistical differences among the three acrylic resins. However, there were no significant statistical differences in A and B cuts.

Acrylic Resins↗
PubMed1988

Colour effect of denture base on denture tooth materials.

A study using a HunterLab colorimeter was conducted to determine the colour effect of denture base materials on denture tooth acrylics. The results show that denture base materials create a measurable change in the chroma of denture tooth acrylics and suggest that optimal shade selection of teeth should include a determination of the background effects of denture base materials.

Acrylic Resins↗
PubMed1990

[Application of microwave for dental technique. 5. Injection molding system for resin base denture].

An injector and FRP denture flask were developed for injection molding and the fit of the denture base constructed with this injection molding system was evaluated. In addition, the flow and pressure of the dough, that is polymer-monomer mixture, in the mold space were investigated. The monomer of 10 mg/cm2 in the dough vaporized during the 5 minutes it took for the flash to be removed. When pressure of more than 55 kgf/cm2 was exerted to the dough, the dough was completely packed in the mold space. Fastening of the sprue with a bolt within 2 minutes after injection of the dough made the pressure of the dough increase to about 30 kgf/cm2. The dough in the mold space was maintained at a pressure of above 20 kgf/cm2 for microwave heating time. The adaptability of the resin base denture constructed with a combination of injection molding and microwave polymerization was 2 or 3 times greater than that of the denture constructed with microwave heating from the tissue side of the denture base.

Composite Resins↗
PubMed2000

Patterns of cell death induced by eluates from denture base acrylic resins in U-937 human monoblastoid cells.

The purpose of this study was to investigate in vitro the apoptosis- and necrosis-inducing potential of eluates from three heat-polymerized and four autopolymerized poly(methyl methacrylate)-based denture base resins. Our hypothesis was that the rate of cell death by apoptosis and/or necrosis induced by such denture base resins could be an important indicator of their cytotoxicity degree. U-937 human monoblastoid cells were exposed for 24 h and 48 h to eluates of 0.1 g/ml, 0.2 g/ml, 0.4 g/ml, and 0.8 g/ml extracted for 24 h and 48 h. The characteristics of apoptosis and necrosis were evaluated by flow cytometry and light and electron microscopy. Eluates from all resins enhanced cell death by apoptosis and necrosis in U-937 cells in a dose- and time-dependent fashion. Eluates from autopolymerized resins yielded higher percentages of apoptosis and necrosis than the heat-polymerized ones. The results support our hypothesis that eluates of poly(methyl methacrylate)-based denture base acrylic resins activate death-signaling pathways, and that the extent of this process reflects their biocompatibility degree.

Annexin A5↗
PubMed1987

A metal-based denture with soft liner to accommodate the severely resorbed mandibular alveolar ridge.

A technique is described for designing and making a mandibular denture, for patients with severely resorbed and compromised residual alveolar ridges. The denture base is stabilized by a mucostatic impression technique, myostatic denture base design, weight of a cast metal denture base, and noninterceptive occlusion with monoplane or Centrimatic posterior teeth. The hard metal denture base is made tissue-compatible by means of a soft denture liner attached to a specially relieved cast metal denture base. Over a 2-year period, this technique has successfully provided, in my practice, an alternative to residual alveolar ridge implants and other surgical interventions for 22 edentulous patients with severely resorbed and compromised mandibular residual alveolar ridges.

Alveolar Process↗
PubMed2000

The effect of heat- and auto-polymerized denture base polymers on clonogenicity, apoptosis, and necrosis in fibroblasts: denture base polymers induce apoptosis and necrosis.

Eluates from poly(methyl methacrylate)-based denture base polymers have recently been found to enhance death by apoptosis and necrosis in U-937 human monoblastoid cells. The present study investigated the potential of such polymers to induce apoptosis and/or necrosis and to alter clonogenicity in L929 murine fibroblasts. A fibroblast cell line was chosen because the impairment of fibroblasts subjacent to denture bases may result in a weaker or more permeable mucosa. Two aspects were addressed: the effect of direct contact with the denture base polymers and the effect of eluates extracted from the polymers. For this purpose L929 fibroblasts were seeded on disks manufactured from three heat-polymerized and four autopolymerized denture base polymers or in different concentrations of their eluates. The effects were evaluated by light, fluorescent, confocal and electron microscopy, counting of colonies, and flow cytometry. Disks and eluates of all polymers enhanced cell death by apoptosis and necrosis in L929 cells and decreased their clonogenic potential in a dose-dependent manner. Apoptosis was the main form of cell death. In general, the deleterious effects were stronger when cells were plated directly on the polymer disks than in the eluates. The autopolymerized polymers, except one, yielded higher percentages of apoptosis and necrosis than the heat-polymerized polymers. The results of the study indicated that poly(methyl methacrylate)-based denture base polymers trigger death-signals in L929 fibroblasts and open doors for possible modulation of the cell/biomaterial interaction.

Animals↗
PubMed2003

Water sorption, solubility and dimensional changes of denture base polymers reinforced with short glass fibers.

The aim of this study was to determine water sorption, solubility and dimensional stability of injection and compression-molded polymethyl methacrylate based denture base polymer that was reinforced with various concentrations and lengths of E-glass fibers. For water sorption and solubility, 20 test groups with different fiber contents and lengths of fibers were prepared. Test specimens without fibers were used as a control. The water sorption and solubility was measured after 90 days water storage. For dimensional stability, rhombic test specimens were prepared and the dimensional changes were measured after processing, drying and storing in water for 4 days and 30 days and were compared with those on the brass model. The water sorption and solubility of injection-molded denture base polymer was lower compared to compression-molded specimens (p < 0.05). The dimensional accuracy of denture base polymer was not affected with fiber reinforcement (p > 0.05).

Absorption↗
PubMed1987

Cast aluminum denture base.

The laboratory procedures for a cast aluminum base denture have been presented. If an induction casting machine is not available, the "two-oven technique" works well, provided the casting arm is kept spinning manually for 4 minutes after casting. If laboratory procedures are executed precisely and with care, the aluminum base denture can be cast with good results.

Aluminum↗
PubMed2003

Dimensional stability and dehydration of a thermoplastic polycarbonate-based and two PMMA-based denture resins.

This study compared the dimensional stability and dehydration of a thermoplastic polycarbonate denture base resin with two conventional polymethyl methacrylate denture base resins. Maxillary complete dentures were fabricated from the three denture materials and the accuracy of fit along the posterior palatal border of the cast used in processing was measured. Measurements were conducted at five palatal locations immediately after processing and at 7 and 30 days during immersion in water (23 degrees C) and at 7 and 30 days during dehydration (23 degrees C, 65-75% relative humidity). Percentage mass loss during dehydration was determined with an electronic balance. The thermoplastic material was separately compared with each of the conventional resins using a modified Welch two-sample t-test, with a Bonferroni correction for P values. For mean palatal dimensional change, the thermoplastic resin was generally not statistically different from the conventional resins after processing and during immersion (P > or = 0.06), but was generally less than the conventional resins during dehydration (P < or = 0.02). For mean percentage mass loss, the thermoplastic resin consistently showed much smaller, statistically significant values compared with the conventional resins (P < 0.001). It was concluded that the thermoplastic resin should show dimensional changes in service comparable with the conventional resins, but less dimensional change caused by dehydration.

Acrylic Resins↗
PubMed1999

Achieving an even thickness in heat-polymerized permanent acrylic resin denture bases for complete dentures.

Permanent denture bases form the fitting surface of a denture and are constructed on a master cast, in heat-polymerized acrylic resin. These bases are strong and rigid and demonstrate both the fit and retention of the final prosthesis. General recommendations suggests a thickness of between 1.5 to 3 mm for these bases. The normal procedure for producing such a denture base is to manually adapt materials to the cast, in their plastic state, before processing. Such procedures are liable to distortion and variation in the thickness of the resultant denture base and may be unreliable. This article describes a method for achieving a consistent thickness in a heat-polymerized, permanent, acrylic resin denture base through the use of a vacuum-formed, thermoplastic blank as a template. The method is simple, and results in a denture base with a consistent even thickness.

Acrylic Resins↗
PubMedDate not supplied

Adhesion of a new light-polymerized denture base resin to resin teeth and denture base materials.

Shear adhesive strength tests were conducted to examine the adhesion of a newly developed light-polymerized denture base resin (LPR) to resin teeth and denture base materials. When LPR was bonded to these materials with a new light-activated bonding agent, the adhesive strength improved greatly. Adhesive strengths of LPR to denture base metals were greater than, or similar to, the metal adhesive autopolymerized resin containing 4-META. Compared with the metal adhesive heat-polymerizing resin, the LPR adhesive values were less when bonded to pure titanium but greater for 18-8 stainless steel and the gold-silver-palladium alloy.

Acrylic Resins↗
PubMed1989

[Application of superplastic titanium alloy for denture base--Part 1. Adaptability of the titanium alloy denture base].

The adaptability of the upper complete denture base made from superplastic alloy 90Ti-6A1-4V was investigated by measuring the space between the master model and the denture base. The denture bases showed a high adaptability with the space less than 0.1 mm, whereas after curing resin for denture, it became worse especially with the heat-curing resin. In addition, the thinnest area of the denture base was observed at the middle of the plate with 38% reduction in thickness, and distortion of the base plate of 0.55mm thickness by curing resin was found to be nearly the same as that of type 304 stainless steel plate of 0.50 mm thickness.

Dental Alloys↗