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At least 325 records · Page 18Linked to original sources
PubMed1995

Properties of highly cross-linked autopolymerizing reline acrylic resins.

Transverse bend strength tests and water sorption and solubility tests were done to compare the properties of highly cross-linked autopolymerizing reline resin with those of conventional non-cross-linked autopolymerizing reline resins. The relationship between composition and properties of autopolymerizing reline resins was also investigated. Highly cross-linked reline resins and the one that contained mainly poly(methyl methacrylate) and methyl methacrylate had a higher transverse bend strength and modulus of elasticity than the other reline resins (p < 0.01). The highly cross-linked reline resins also had significantly lower water sorption than the other reline resins (p < 0.01). Reline resins, except for one, had significantly higher solubility than heat-polymerizing denture base acrylic resins (p < 0.01).

Acrylic Resins↗
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↗
PubMed1978

Acrylic resin copings: an adjunct to fixed restorative dentistry.

A simple technique for fabricating and several uses for acrylic resin copings have been presented. These techniques apply to many aspects of restorative dentistry and often are used in combination with each other. Master cast fabrication, interocclusal registrations, and verification of die accuracy can be done using the copings during a one-appointment sequence. The use of resin copings is especially helpful for the inexperienced dentist, permitting high quality dentistry with a minimum of mistakes and frustations. For the experienced fixed prosthodontist they provide another approach to treatment.

Acrylic Resins↗
PubMed1990

[Micro powder retention for retaining acrylic resin veneers. 1. Application of pressure sensitive adhesive].

Powder retentions are widely used in clinical for retaining acrylic resin facing of veneered crown. These retentions show relatively high bond strength and easy manipulation compared with the traditional retention devices of bar, hole, bead, loop and etc. However, the particle size of powders commercially available are above 250 microns and reduced the thickness of facing resin. Thereupon, smaller diameter of powder were trially applied, however, microparticles were submerged under adhesive and undercut effective for retaining resin was lost. In this research, a new powder retention system adopted pressure sensitive adhesive was studied. The trial adhesive includes volatile solvent like as the traditional adhesives. However, the solvent vapors rapidly and the adhesive applied onto the wax pattern showed pressure sensitivity. Six different sizes of spherical powder were used and the smallest and largest particle size were 90-110 microns and 230-250 microns respectively. New powder retention system applied sensitive adhesive exhibited excellent bond strength to photo polimerized composite facing resin and denture base resin. The powder of 110-130 microns diameter showed shear bond strength values of above 200 kgf/cm2 after 30,000 thermocycles.

Acrylic Resins↗
PubMed2004

Polymerization time for a microwave-cured acrylic resin with multiple flasks.

This study aimed at establishing the polymerization time of a microwave-cured acrylic resin (AcronTM MC), simultaneously processing 2, 4, and 6 flasks. Required time was measured according to the parameters: monomer release in water, Knoop hardness, and porosity. Samples were made with AcronTM MC in different shapes: rectangular (32 x 10 x 2.5 mm) for monomer release and porosity; and half-disc (30 mm in diameter x 4 mm in height) for Knoop hardness. There were four experimental groups (n = 24 per group): G1) one flask (control); G2) two flasks; G3) four flasks, and G4) six flasks. At first, polymerization protocol was similar for all groups (3 min/450 W). Time was then adjusted for G2, G3, and G4, based on monomer release evaluation in the control group, obtained by spectrophotometer Beckman DU-70, with emitting wave of 206 nm. Knoop hardness test was performed using a Shimadzu HMV 2000 hardness tester, and 10 indentations were performed on each specimen's surface. Porosity was assessed after specimens were immersed in black ink and the pores counted in a microscope. Results showed that the complete polymerization of the resin occurred in 4.5 min for two flasks (G2); 8.5 min for four flasks (G3); and 13 min for six flasks (G4), all with 450 W. Statistical analysis revealed that the number of flasks does not interfere with polymerization, Knoop hardness, and porosity of the resin. Results showed that polymerization of microwave-curing resin with more than one flask is a viable procedure, as long as polymerization time is adjusted.

Acrylic Resins↗
PubMed2000

Locking acrylic resin dental stent for image-guided surgery.

This article presents a procedure for fabricating a locking acrylic resin dental stent for use in image-guided base-of-skull surgery and neurosurgery. The stent offers advantages over conventional bone screw-anchored systems to surgeons and patients. In view of the increasing use of image guidance in base-of-skull surgery and neurosurgery, prosthodontists will meet a growing demand for this type of device in the future.

Acrylic Resins↗
PubMed1976

A new skin protecting ointment against acrylic resins.

In order to protect the hands of dentists, dental technicians and dental nurses from direct contacts with acrylic monomer, a new type of protective monoglyceride containing ointment has been introduced. The monoglyceride-based ointment was found to prevent penetration of the monomeric part of an autopolymerising acrylic resin and was also shown to have significantly smaller decreasing influence on the ability to manipulate instruments and materials than a compared silicone-based ointment. Furthermore, even with addition of 1% by volume of the monoglyceride-based ointment there was no marked influence on the mechanical properties (elastic modulous and ultimate tensile strength) of an investigated acrylic tray material.

Acrylic Resins↗
PubMed1999

Bond strengths of silicoated and acrylic resin bonding systems to metal.

STATEMENT OF PROBLEM: The Kevloc bonding system is based on the bond of acrylic resin with the metal surface, in contrast to the Silicoater system, which covers the metal surface with a SiOx-C layer. Bonding prevents the occurrence of the marginal gap between the metal and the resin, which causes weaker bond strengths and discoloration. PURPOSE: This investigation examined the bond strength values achieved by using the Kevloc technique on Ag-Pd and Co-Cr alloys, and compared them with those obtained by the Silicoater technique. After artificial aging, shear testing of the specimens was performed. MATERIAL AND METHODS: A microscope image analyzer measured the thickness of bonding layers to reveal any marginal gap. RESULTS: No marginal gap was noticed for either technique. The Kevloc technique provided better results than Silicoater regardless of alloy used. Immersion in water (7.64 to 8. 05 MPa) and thermocycling (6.12 to 6.95 MPa) reduced the initial bond strength values (12.52 to 12.94 MPa), but the breakdown occurred between the opaque layers or between the opaque and the resin, thus giving a cohesive type of failure. CONCLUSION: The dental alloy used did not affect bond strengths and artificial aging caused reduction in bond strengths. The Kevloc bonding system exhibited higher bond strengths than Silicoater, but the marginal gap was not seen for either bonding system.

Acrylic Resins↗
PubMed1976

[Cutaneous manifestations due to acrylic resins used in printing].

In the plant of a large newspaper, the manufacture of printing plates using photopolymer acrylic resins, in the place of lead, resulted in a series of orthoergic and allergic manifestations in the workers. Chemical analysis resulted in the isolation of a tetraethylene glycol diacrylate, the harmful nature of which was proven by allergological studies. Its replacement by tetrathylene glycol dimethacrylate eliminated the problems seen (study based upon 300 allergological tests).

Acrylic Resins↗
PubMedDate not supplied

Dimensional contour stability of acrylic resin bases for complete dentures before and after water sorption.

PURPOSE: To evaluate the dimensional contour variations of acrylic resin denture bases before and after storage in water. MATERIALS AND METHODS: The fit of 40 bases was evaluated by measuring the thickness of a layer made with silicone placed between the bases and the casts. The measurements were repeated on a new set of silicone layers after having stored the bases in water for 42 days. RESULTS: Significant differences were found both for the maxillary and the mandibular bases. CONCLUSION: Water sorption had an important effect on the contour of the prosthetic bases.

Absorption↗