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PubMed1991

[Dorsal border of denture base after SR-Ivocap polymerization].

The amount of dorsal borderspace of upper-plates after polymerisating in different dental laboratories has been measured and compared by statistically methods. This result showed a conspicuously small deviation. The overall average was to be found in the range of only 227 microns +/- 10.5 microns after water-laging for 4 weeks. This amount is conformable to the results of Marx. There is no interpretation of the high values measured by Peroz recently. This present results confirm on the contrary the clinically verification of the SR-Ivocap-polymerisating equipment.

Denture Bases↗
PubMed1992

Reinforcement of acrylic resin denture base material with metal or fibre strengtheners.

The effect of different metal and fibre strengtheners on the fracture resistance of polymethylmethacrylate was tested. Different types of commonly used metal wire and glass fibre, as well as carbon and aramid fibres, were used as strengtheners in test specimens. There were 21 groups, and each group contained 12 test specimens. Each metal strengthener had a beneficial effect on the fracture resistance of the polymethylmethacrylate (P less than 0.001-0.01). Some fibres, which were silanized for better adhesion, also had strengthening properties.

Acrylic Resins↗
PubMed1981

The cytotoxic effect of denture base polymers.

The cytotoxic potential of autopolymerized pour and dough type resins and heat cured resins was studied by in vitro cell culture techniques. Human epithelial cells (NCTC 2544) were grown in Eagle's minimal essential medium on the surface of the polymer disks. The cell multiplication on the surface of the specimens was measured. One heat cured resin and one pour type resin demonstrated a slight cytotoxic effect. The other polymers gave a moderate cytotoxic effect. The study did not indicate any difference in the cytotoxicity of the polymers when manufactured by alternate processing methods.

Cells, Cultured↗
PubMed1991

The transverse strengths of three denture base resins.

Ten specimens each of (1) Lucitone 199, short- and long-cured, (2) Accelar 20, and (3) Triad materials were broken using a 3-point load on an Instron Universal testing machine after processing and air drying. Five specimens of each resin also were broken after storage in deionized distilled water at 37 degrees C for 30, 60, and 90 days. Triad material demonstrated the lowest transverse strengths of all three materials overall. However, Triad material was unaffected by water storage. The other resins all showed decreased strengths with water storage.

Acrylic Resins↗
PubMed1990

Further development and evaluation of high impact strength denture base materials.

The further development of poly(methylmethacrylate) reinforced with low molecular weight polybutadiene-based rubbers previously studied is described. The materials produced have been optimized with respect to impact strength and Young's modulus, giving results up to 0.13 J for the former whilst maintaining the latter at about 2.3 G.Pa. Additionally, the systems have been evaluated with respect to viscoelastic properties, water absorption and the effect of the latter on mechanical properties. Further work on the underlying mechanisms should lead to a greater understanding of these systems which could, in turn, produce more superior materials.

Adsorption↗
PubMed1989

Rapid curing of acrylic denture-base materials.

A rapid-cure polymerization of cure, including a terminal boil, with respect to transparency, residual monomer, mechanical properties, and generation of gaseous porosity. It was found that in order for porosity-free resin to be produced during rapid curing, a low concentration (approximately 0.26%) of benzoyl peroxide initiator in the powder component is vital, and a very small concentration (approximately 0.025%) of the chemical activator dimethyl-p-toluidine in the monomer component is an advantage. Mechanical properties were only influenced where substantial porosity existed, but it was recognized that a material "tailor-made" for rapid curing would be most welcome.

Acrylic Resins↗
PubMed1983

Fracture toughness of acrylic denture base.

This paper describes the application of two fracture toughness tests, the compact tension (CT) and the double torsion (DT) to homogenous poly(methyl methacrylate) and two-phase acrylics. Materials were tested in air as processed and after saturation for one month in water. Most materials gave stable crack propagation with these tests, allowing accurate measurement of crack velocity. Modulus and un-notched fracture strength (sigma f) were determined at an identical strain rate in bending to that used in the fracture toughness tests, allowing accurate calculation of the flaw size (a) for a material and an assessment of how applicable Linear Elastic Fracture Mechanics are to these materials.

Denture Bases↗
PubMed1993

Comparison of two different silane compounds used for improving adhesion between fibres and acrylic denture base material.

This study was aimed at clarifying the effects of two different silane compounds on the adhesion between the different fibres and acrylic resin. The fibres used as reinforcement in the acrylic resin test specimens were glass, carbon and aramid fibres and the silane treated and untreated versions of each type of the fibres were tested. The fracture resistance of the test specimens were assessed and the fibres were studied by a scanning electron microscope (SEM) to establish the adhesion between the fibres and acrylic resin. The results showed that silanization of glass and aramid fibres enhances the adhesion between the fibres and acrylic resin. The findings were confirmed by the SEM photographs taken. The use of a scanning electron microscope proved to be useful for the investigation of the adhesive properties of the materials used.

Acrylic Resins↗
PubMed1997

Basic study of a new denture base resin applying hydrophobic methacrylate monomer.

To improve the water sorption of poly(methyl methacrylate), new hydrophobic monomers, such as norbonyl and phenyl methacrylate, were studied to determine the resin with lower water sorption with no decrease in mechanical property. Water sorption of the copolymers of the hydrophobic monomers and MMA decreased with the increase in the concentration of the monomers. Compressive and bending strength of the copolymers were higher than that of PMMA, and the elastic modulus in bending was the same as that of PMMA. In addition, the transverse-deflection values satisfied ADA specifications. Dynamic mechanical thermal analysis of the copolymers showed a similar tendency to that of PMMA in spite of the introduction of bulky groups, such as norbonyl and phenyl, in the polymer molecule. The polymerization shrinkage in volume was in the following order: norbonyl < phenyl < methyl methacrylate.

Compressive Strength↗
PubMedDate not supplied

Reinforcement of acrylic resin denture base with a Ni-Cr alloy plate.

A pilot study was conducted to evaluate the strengthening effect of a Ni-Cr metal plate on an acrylic resin test specimen. Test specimens were retained using a mechanical method and adhesion with 4-META resin. Three positions of the metal plate were evaluated: on the compression surface, on the tension surface, and in the middle layer. A three-point bend test was used to compare physical properties of the specimens with metal-plate reinforcement to a resin specimen without reinforcement. No advantage was derived from placing the metal plate in the center of the resin. Both methods of retention produced improved physical properties when placed on either the compressive or tensile side, but the greatest advantages were gained when an adhesive-retained plate was placed on the side in tension.

Acrylic Resins↗
PubMed2000

Adding silanes to MMA: the effects on the water absorption, adhesive strength and mechanical properties of acrylic denture base resins.

The adhesive strength of porcelain artificial teeth and polymethylmethacrylates (PMMAs), which contained silanes with various number of vinyl or ethoxy groups, and the mechanical and physical properties of the PMMAs were measured. Four types of PMMAs with silanes showed high adhesive shear strength and caused fractures in the porcelain. Water absorption of the PMMAs increased with the addition of silane, but that of one type with silane was almost the same as the PMMA only type. The flexural strengths of the PMMAs with silane, except for one type, showed no significant differences compared with that of PMMA (p < 0.05). The Tg levels of all PMMAs with silane fell less than that of PMMA. From these results, it was found that PMMA with silane from three vinyl groups and one ethoxy group showed excellent chemical bonding to porcelain and low water absorption.

Absorption↗
PubMed1989

The effectiveness of two disinfectants on denture base acrylic resin with an organic load.

This study compared the biocidal effectiveness of chlorine dioxide and 5.25% sodium hypochlorite (diluted 1:10) on acrylic resin strips inoculated with Staphylococcus aureus, Candida albicans, or Escherichia coli in the presence of an organic load. Sterile acrylic resin strips were immersed in a solution containing 10% horse serum and 10(5) to 10(7) organisms/ml for each type of organism, then disinfected in chlorine dioxide, sodium hypochlorite, or 0.9 sterile saline for 30 seconds or 1, 2, or 4 minutes. After disinfection, the strips were neutralized and incubated for 72 hours. The results showed a difference between the ability of chlorine dioxide and sodium hypochlorite to kill the test organisms on acrylic resin strips when organic matter is present. Chlorine dioxide achieved complete disinfection of all three organisms within 2 minutes. Sodium hypochlorite achieved complete disinfection of all three organisms within 4 minutes.

Bacteria↗
PubMed2005

Deformation and flexural properties of denture base polymer reinforced with glass fiber sheet.

The purpose of this study was to investigate the deformation and flexural properties of acrylic and urethane polymers reinforced with glass fiber sheet. Four types of specimen--self-curing resin plate (R), light-curing oligomer plate containing a reinforcement (GO), and self-curing resin plate containing a reinforcement on one (GR) or both (GRG) sides--were prepared with three thicknesses: 1.5, 2.4, and 3.0 mm. Gaps between polymerized test specimen and a standard metal plate were measured at the corner (C), middle of the long sides (LS), and middle of the short sides (SS). The gaps for R were 0-2.0 microm. GO and GR markedly deformed at Points C, LS, and SS, and the degree of deformation increased as GO became thinner. Flexural strength was significantly increased by the reinforcement (p < 0.05). The flexural moduli of 3.0-mm thick R, GO, and GR were significantly smaller than that of 1.5-mm thick specimens.

Composite Resins↗
PubMed2003

Effect of the curing conditions on the properties of an acrylic denture base resin microwave-polymerised.

OBJECTIVES: The aim of this study is to evaluate the effect of the different conditions of curing on the residual monomer levels, hardness and impact strength of a microwave-polymerised acrylic resin. METHODS: The material was polymerised in a microwave oven in four different conditions of power and curing time. The kinetics of release of residual monomer in water was evaluated by spectrophotometric method up to 24 h. The hardness of the sample was determined by the Rockwell method and the impact strength tested by the Charpy method. The results were subjected to statistical analysis using ANOVA and Tukey's test for comparison. RESULTS: The levels of residual monomer were found dependent upon the curing conditions and they were correlated with the values of impact strength. Significant differences were observed in this property regarding the analysed conditions (p<0.001). CONCLUSIONS: From the appropriate selection of power and time of curing of the resin, it is possible to optimise the level of residual monomer and a low cytotoxicity keeping at the same time the best mechanical properties.

Acrylic Resins↗
PubMed1995

Residual monomer content and its release into water from denture base materials.

OBJECTIVES: The aim of this study was to determine the content and amount of residual monomer released from heat-cured and chemical-cured polymethyl methacrylate (PMMA) during storage in water. METHODS: Residual monomer was extracted from ground PMMA with tetrahydrofuran and from the storage water with n-hexane. Samples were analyzed by using HPLC-chromatography. Duration of the storage period in water was up to 8 wk at temperatures of +22 degrees C and +37 degrees C. RESULTS: Residual monomer content of chemical-cured PMMA was higher than that of heat-cured PMMA. The effect of storage temperature was significant (p<0.001). During the first day of storage at +37 degrees C, the monomer release from chemical-cured PMMA was 1906.7 ppm and from the heat-cured PMMA 34.5 ppm and that release was higher at +37 degrees C than at +22 degrees C (p<0.001). SIGNIFICANCE: This study suggests that the amount of released monomer can be diminished by storing the PMMA product in water for at least 1 d before use, preferably at +37 degrees C.

Analysis of Variance↗
PubMed1989

[Histochemical investigation on glycogen in the epithelium of mucosa under denture base].

Accumulation of glycogen in the epithelium of the oral mucosa was evaluated in relation to the existence of wound and inflammation of the oral mucosa histochemically and histopathologically. Antemolar rhombus (the anterior part of the intermolar palate) of adult Wistar rat was employed as experimental area. Experimental wound of palatal mucosa was made by excision of crestal one third of the palatine ruga. Inflammation of the connective tissue was artificially induced by the insertion of silk thread or silk thread immersed in 5% formalin in the connective tissue parallel to the crest line of palatine ruga. The experimental area was examined histochemically and histopathologically up to 72 hours after experimental operation. In excision wound the accumulation of glycogen was observed in prickle cell layer of the epithelium after 24 hours. Although the inflammatory reaction was observed more prominently in the thread inserted connective tissue, the accumulation of glycogen in the epithelium could not be detected. The findings of this study suggested that inflammation itself does not induce the accumulation of glycogen in the epithelium of the oral mucosa and the accumulation could be an indication of wound and/or its healing process of oral epithelium.

Animals↗
PubMed2004

Flexural properties of denture-base polymer reinforced with glass-fibre polysulphone composite.

The aim of this study was to determine the effect of glass-fibre composite reinforcement on the flexural strength and flexural modulus poly-methyl methacrylate (PMMA). Prefabricated electrical glass-fibre polysulphone composite rods (GF/PSu), 3mm in diameter, were incorporated in cylindrical, heat polymerizing PMMA specimens with diameters of 4, 5 and 6mm respectively (n = 10). These specimens were compared with PMMA control groups of similar dimension. A three point loading test was performed in air after storage of specimens in water at 37 degrees C for 8 weeks. The following variables were measured : Flexural Strength (FS) and Flexural Modulus (FM). The data were analyzed using one way analysis of variance (ANOVA). After testing, the fracture zone was evaluated using a scanning electron microscope (SEM). The glass-fibre reinforcement used in this study significantly enhanced both the FM and FS values of PMMA. This enhancement was, however, progressively reduced in relation to an increase in cross-sectional dimension of the specimens. SEM evaluation revealed delamination and fracture of the glass-fibres in the polymer matrix.

Adhesiveness↗
PubMedDate not supplied

An investigation of self-reinforced poly(methyl methacrylate) denture base acrylic resin using scanning electron and atomic force microscopy.

PURPOSE: The aim of this study was to examine the interfacial region of poly(methyl methacrylate) (PMMA) reinforced with untreated and surface-treated PMMA fibers in both chopped and continuous form using scanning electron and atomic force microscopy. MATERIALS AND METHODS: Acrylic resin specimens incorporating untreated and surface-treated (with butadiene styrene latex emulsion) PMMA fibers were examined using a scanning electron microscope and an atomic force microscope. RESULTS: There was evidence of random arrangement of untreated and surface-treated chopped fibers throughout specimens with areas of dense fiber aggregation and other areas containing few or no fibers. For the untreated and surface-treated fibers in continuous forms (a single and 2 unidirectional layers), there was evidence of fiber displacement and buckling, together with variation in interfiber spacing. For the specimens containing surface-treated continuous fibers in a cross-ply arrangement that had demonstrated a substantial improvement in the modulus of rupture, there was no evidence of fiber buckling, and the layer of butadiene styrene was consistently thin and even in comparison to weaker specimens. CONCLUSION: The thickness of the rubber layer and the fiber arrangement (in terms of fiber displacement and interfiber spacing) may be important factors in the success of the reinforcement.

Acrylic Resins↗