Properties Of Denture Base Polymers Research Articles

Flexural properties of denture base polymers reinforced with a glass cloth–urethane polymer composite

Objectives. A newly designed light-cured reinforcement made from urethanemethacrylate oligomer and woven glass cloth has orthotropic anisotropy. This is produced for incorporation into the outermost position under the greatest tension in denture base resins. In this study, the flexural properties of self-, heat-, and light-curing reinforced resins were determined. Methods. The silanized glass cloth was soaked in urethanemethacrylate oligomer containing camphorquinone and 2-(dimethylamino)ethylmethacrylate. It was sandwiched between two pieces of polyethylene film and pressed to form a reinforcement sheet 0.3 mm in thickness, which was light-cured and prepared using four different surface conditions: with or without the polyethylene film and with or without a bonding agent. The reinforcement sheet was fixed in a fluorocarbon resin mold 3 mm in thickness, which was filled with self-, heat-, or light-curing resin and cured. The cured laminated plate was cut for flexural testing (40×7×3 mm 3). A three-point flexural test was carried out at a crosshead speed of 2 mm/min and a span length of 30 mm. In this study, the glass fiber content was measured at percentages by weight because it was not possible to determine accurately the volume of the various polymers. Results. The baseline flexural strengths of the self-, heat-, and light-curing resins were 76.2, 68.6, and 55.6 MPa, respectively, and these values were increased to 271.7, 216.4, and 266.5 MPa by the reinforcement sheet. The baseline flexural moduli of self-, heat-, and light-curing resins were 2.0, 2.4, and 2.1 GPa, respectively. These values were increased to 7.2, 5.1, and 6.6 GPa by the reinforcement sheet. SEM photographs revealed good impregnation of the glass fiber within the polymer matrix. Significance. The differences in the flexural strengths and flexural moduli of the control and reinforced specimens were significant ( p<0.01).

Factors that affect the rheologic properties of acrylic resin denture base materials

The rheologic characteristics of different formulations of acrylic resin denture base materials are presented in this study. This is of practical significance in selecting resins with optimum rheologic properties for denture base construction. The materials are characterized in respect to their constituents, mean powder particle size and distribution, molecular weight averages and distributions, and glass transition temperature. A comparison of the polymers indicates that smaller particles saturate with monomer more readily, and this results in a higher viscosity. A higher viscosity for higher molecular weight and lower viscosity for lower molecular weight have been observed. Increasing the percentage of copolymerization increases the viscosity. No correlation has been found between the rheologic properties of denture base polymers and the powder glass transition temperature.

Effect of the curing cycle on residual monomer levels of acrylic resin denture base polymers

It has been shown previously that high levels of residual monomer have a deleterious effect on the properties of denture base polymers. Levels of residual monomer were determined on a homopolymer and a copolymer using gas-liquid chromatography. A wide range of recommended and ‘short cut’ curing cycles were then investigated which produced values ranging from 0.56 to 18.46%. From the ranges examined an optimum cycle of 7 h at 70°C and 1 h at 100°C was established which was used to polymerize 23 currently available synthetic denture base polymers. Only small differences were found between the materials tested with a range from 0.54 to 1.08% of residual monomer.

Determination of doughing and manipulation times of acrylic resin denture base material and a proposal for a specification for a packing plasticity test

The doughing and manipulation times of a range of acrylic resin denture base polymers are presented in this study. The methods evaluated were: (i) probing following American Society for testing materials specification, F451-76; (ii) hole penetration following British Standard, 2487: 1989 and International Standard Organisation, 1567: 1988; (iii) probing using a penetrometer employing a 20 g load and 1 mm diameter needle; (iv) oscillating rheometer apparatus used at a fixed frequency of 1 Hz by sweeping through a programmed linear increase in strain. The results indicate that each of the methods is capable of evaluating the doughing and manipulation times of the unprocessed polymers. It is concluded that the Bohlin VOR Oscillating Rheometer is excellent for investigating the flow properties of denture base polymers but it cannot be recommended for a standards specification test because of the high cost. The penetrometer method has been shown to be superior to the current standards specification test and would be ideal for a packing plasticity standards test.

Methacrylate-based polymeric dental materials: conversion and related properties. Summary and review.

The present summary and the following papers (I-VIII) are submitted in partial fulfillment of the requirements for the degree of Doctor Philosophiae at the University of Oslo.I. Composition of dental resin and composite materials. Acta Odontol. Scand. 1981, 39, 133–146Co-author: I.J. SjovikII. Remaining methacrylate groups in composite restorative materials. Acta Odontol. Scand. 1978, 36, 75–87Co-author: S.A. SvendsenIII. Conversion in different depths of ultraviolet and visible light activated composite materials. Acta Odontol. Scand. 1982. 40, 179–192 Co-author: H. oysaedIV. Compressive creep of light cured resin based restorative materials. Acta Odontol. Scand. 1982. 40, 319–324Co-author: H. oysaedV. Flexural properties of denture base polymers. J. Prosthet. Dent. 1980, 43. 95–104Co-author: S.A. SvendsenVI. Compressive creep of denture base polymers. Acta Odontol. Scand. 1980, 38, 169–177Co-author: S. EspevikVII. Conversion in denture base polymers. J. Biomed Mater. Res. In press Co-author: H. oysaedVIII....

Flexural properties of denture base polymers

Heat-polymerized denture base materials with the cross-linking agent 1,4-BDMA and with different amounts of the cross-linking agent EGDMA have similar flexural properties. At the relatively low loading rate of 2 N/minute all the heat-polymerized denture base materials investigated have better flexural properties than the autopolymerized pour- and dough-type materials. The autopolymerized materials with the cross-linking agent 1,4-BDMA have flexural properties intermediate to the heat-polymerized and the autopolymerized resins with the cross-linking agent EGDMA. The various autopolymerized resins behave differently, probably due to varying amounts of pendant methacrylate groups. Due to so-called solvent crazing, denture base polymers have poorer flexural properties when tested in water than in air.