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PubMedDate not supplied

Dimensional stability of acrylic resin materials after microwave sterilization.

Microwave sterilization techniques have previously been discussed in the literature, but there is need for information regarding the stability of acrylic resins subjected to these techniques. The purpose of this investigation was to measure and determine the potential influence of microwave sterilization on the dimensional stability of polymerized acrylic resin denture base materials. Uniform samples of previously heat-polymerized, autopolymerized, and visible-light-polymerized acrylic resins were measured for changes in weight and length before and after microwave exposure. All three acrylic resin materials maintained excellent stability; all materials had shrinkage values in the range of 0.02% to 0.03%. This is clinically insignificant compared to polymerization shrinkage, which averages 0.2%.

Acrylic Resins↗
PubMed1995

In-depth disinfection of acrylic resins.

This study demonstrated that bacteria penetrate three kinds of dental acrylic resin after a short time period. Samples of acrylic resin were contaminated with a variety of bacteria and were then placed in three different disinfecting solutions as directed by the manufacturers. After the specific dilution and immersion time, cultures were made from the resin samples. The only effective disinfectant was a 0.525% solution of sodium hypochlorite at a 10-minute immersion. It disinfected not only the surfaces but also the bacteria that penetrated the surfaces to a depth of 3 mm.

Acrylic Resins↗
PubMed1997

The effect of untreated UHMWPE beads on some properties of acrylic resin denture base material.

OBJECTIVES: To evaluate the effect of surface untreated ultra high molecular weight polyethylene (UHMWPE) beads on a range of properties of the polymerised acrylic resin denture base material. METHODS: UHMWPE in the form of surface untreated beads was added to acrylic resin denture base material in various percentages (2.5%, 5%, 7.5% and 10%) to form a composite material. The influence on doughing and manipulation times, transverse and impact strength and hardness characteristics were examined. RESULTS: The results indicated that the manipulation and setting times gradually increased as the percentage of UHMWPE beads in the acrylic resin powder increased. By increasing the percentage of incorporated UHMWPE beads, there was a decrease in modulus of rupture and impact fracture resistance. There was also an effect on the hardness with an increasing percentage of beads lowering the hardness value, although this was not consistent. CONCLUSION: It was concluded that the use of untreated UHMWPE beads is of no significant benefit to the properties of acrylic resin.

Acrylic Resins↗
PubMed2006

Adsorption of human salivary mucin MG1 onto glow-discharge plasma treated acrylic resin surfaces.

It has been suggested that altering the surface properties of acrylic resin material may change the nature of the adsorbed pellicle affecting denture retention and microbial adherence. This study aimed at evaluating the adsorption of salivary high molecular-weight mucins, a major component of denture pellicle, onto modified acrylic resin surfaces. (Poly) methylmethacrylate specimens were treated by glow discharge plasma technique, using hydrophilic 2-Hydroxyethylmethacrylate monomer or oxygen (O(2)) gas and hydrophobic Hexamethyldisiloxane monomer, at different discharge powers. Acrylic samples were incubated with high-molecular weight mucin, MG1 purified from saliva, the adsorbed fractions were transferred to nitrocellulose membranes by slot-blot technique, stained by periodic acid-Schiff and colour intensities were analysed by a colour densitometer. Higher amounts of mucins were adsorbed on all the surfaces modified by glow-discharge plasma treatment. Within the limitations of this study, it was concluded that glow-discharge plasma altered the surfaces of acrylic resin denture base materials and significantly increased the adsorption of high molecular-weight mucins at varying levels depending on plasma parameters.

Adsorption↗
PubMed1998

New acrylic resin composite with improved thermal diffusivity.

STATEMENT OF PROBLEM: Studies have shown that physical characteristics of denture base materials may affect patient acceptance of denture prostheses by altering sensory experience of food during mastication. Thermal diffusivity is one material property that has been cited as being important in determining gustatory response, with denture base acrylic resins having low thermal diffusivity compared with denture base metal alloys. PURPOSE: This study prepared and characterized experimental acrylic resin composite material with increased thermal diffusivity. MATERIAL AND METHODS: Sapphire (Al2O3) whiskers were added to conventional denture base acrylic resin during processing to achieve loadings of 9.35% and 15% by volume. Cylindrical test specimens containing an embedded thermocouple were used to determine thermal diffusivity over a physiologic temperature range (0 degree to 70 degrees C). RESULTS: Thermal diffusivities of the sapphire containing composites were found to be significantly higher than the unmodified acrylic resin. Thermal diffusivity was found to increase in proportion to the volume percentage of sapphire filler, which suggested that the high aspect ratio ceramic particles formed a pathway for heat conduction through the insulating polymer matrix. CONCLUSION: The thermal diffusivity of denture base acrylic resin was increased by the addition of thermally conducting sapphire whiskers.

Acrylic Resins↗
PubMed2006

An in vitro investigation of the effect of the addition of untreated and surface treated silica on the transverse and impact strength of poly(methyl methacrylate) acrylic resin.

Silica is a commonly used filler in dental materials and as a reinforcing agent in industry. The aim of this study was to further investigate the effect of the addition of untreated and a novel surface treated silica on the transverse bend and impact strength of acrylic resin denture base material. It was hypothesized that the silica/resin composite materials would have an improved flexural and impact strength than the conventional heat-cured acrylic resin. Three types of untreated and two of treated silica powder were used in this study. The range of percentages used were 1%, 0.5%, 0.2%, 0.1%. The treated particles were coated with hexamethyldisilazane or dimethyldichloridesilazane. Conventional heat cured acrylic resin was used as a control. The modulus of rupture for all groups of acrylic resin containing silica was significantly lower than for the control. The modulus of elasticity was not significantly greater than the control group. For the impact strength statistical analysis revealed a significant difference between the groups. There was a nonsignificant increase in the impact strength for specimens compared to the control. In conclusion the addition of silica to poly(methyl methacrylate) denture base materials did not produce a significant improvement in the transverse bend or impact strength compared to conventional heat-cured acrylic resin. The incorporation of untreated and surface treated silica cannot be recommended as a method of reinforcement.

Acrylic Resins↗
PubMed2006

Water sorption of heat-polymerized acrylic resins processed in mono and bimaxillary flasks.

This study evaluated water sorption in heat-polymerized acrylic resins processed in monomaxillary flasks by water bath and in bimaxillary flasks by microwave energy and water bath. Fifty heat-polymerized acrylic resin specimens were fabricated according to the 12th specification of the American Dental Association and assigned to 3 groups: group 1 was processed by water bath in monomaxillary metallic flask; group 2 was processed by microwave energy in bimaxillary PVC flask; and group 3 was processed by water bath in bimaxillary metallic flask. Specimens were submitted to water sorption test, means were calculated and analyzed statistically by Student's t-test. Means (in g/cm3) were: group 1--0.024085, group 2--0.025312 and group 3--0.022098. Microwave energy processing and the amount of stone and resin used in the bimaxillary PVC flask did not influence water sorption; specimens processed in bimaxillary metallic flask by water bath presented lower water sorption means, suggesting an inadequate polymerization of the acrylic resin mass.

Absorption↗
PubMed1993

The release of chlorhexidine from modified dental acrylic resin.

A method for the incorporation of chlorhexidine into acrylic resin using monomer together with the pattern of release of chlorhexidine from treated resin into water at 37 degrees C is described. Release from polished and unpolished resin, and from acrylic prepared by short-curing and dry-curing processes are investigated. The pattern of release in all cases was of an exponential nature, showing a rapid release within the first 10 days becoming almost constant at a level of 0.4-1.5 micrograms cm-2 at about 20 days. Release was still evident at the end of the test period in all cases. Release of chlorhexidine into water from the short-cure specimens was accompanied by release of monomer, evident from the odour of the test solutions, indicating that polymerization was not complete.

Acrylic Resins↗
PubMed1996

Unrestricted linear dimensional changes of two hard chairside reline resins and one heat-curing acrylic resin.

The selection and use of hard chairside reline resins must be made with regard to dimensional stability, which will influence the accuracy of fit of the denture base. This study compared the dimensional change of two hard chairside reline resins (Duraliner II and Kooliner) and one heat-curing denture base resin (Lucitone 550). A stainless steel mold with reference dimensions (AB, CD) was used to obtain the samples. The materials were processed according to the manufacturer's recommendations. Measurements of the dimensions were made after processing and after the samples had been stored in distilled water at 37 degrees C for eight different periods of time. The data were recorded and then analyzed with analysis of variance. All materials showed shrinkage immediately after processing (p < 0.05). The only resin that exhibited shrinkage after 60 days of storage in water was Duraliner II; these changes could be clinically significant in regard of tissue fit.

Acrylic Resins↗
PubMed1997

The effect of surface treated UHMWPE beads on some properties of acrylic resin denture base material.

UHMWPE in the form of experimental surface treated beads was added to acrylic resin denture base material in various percentages to form a composite material. The influence on doughing and manipulation times, and transverse and impact strength was examined. The results indicated that the manipulation times, were not significantly affected as the percentage of UHMWPE beads in the acrylic resin powder increased. Increasing the percentage of incorporated UHMWPE beads resulted in an inconsistent decrease in the modulus of rupture and no effect on the impact fracture resistance. It was concluded that the use of treated UHMWPE beads is of no significant benefit to the properties of acrylic resin.

Acrylic Resins↗
PubMed1987

Functional modification of acrylic resin monoplane occlusions.

Patients with acrylic-resin monoplane occlusions were recalled over a 6-month to 6-year period. The intention was to obtain casts of the dentures in order to study the anteroposterior wear pattern for classifiable variations from the original monoplane occlusion. The lateral component of the wear pattern was not examined during this study. The project revealed wear patterns that were classifiable in terms of the recognized prosthetic occlusal plane forms--namely, the Monson curve, a reverse curve, or a persistence of the original monoplane. Right and left aspects of the maxillary occlusal plane were examined as separate entities and lateral asymmetry was evident in most patients. No attempt was made to quantify the extent of wear as in the studies of Harrison.

Acrylic Resins↗
PubMed1978

[Hydrogen peroxide, chloramine T and chlorhexidrine in the disinfection of acrylic resin].

The effectiveness of 3% h drogen peroxide, 5% chloramine T and 0,5% chlorhexidine gluconate solutions in disinfection of acrylic resine plates massively infected with oral flora was analysed. The acrylic resine plates used for investigations, were infected in vitro with mixed salivary flora characterized by small numbers of yeast-like fungi (1st group), or great number of these microorganisms (2nd group). Infected plates were exposed to solutions of analysed disinfectants during various time periods. After rinsing or inactivation of disinfectant residues, acrylic plates were put into bacteriological medium and incubated during 7 days period in 37 degrees C. The results of this study indicated the effectiveness of acrylic plates disinfection to be dependent on used disinfectant, time of exposition, and microorganisms present on the surface of acrylic resine. The solutions of disinfectants were less active in the cases of plates infected with material containing great numbers of yeast-like microorganisms. Among analysed disinfectants 0,5% solution of chlorhexidine was characterized by most effective and rapid activity, whereas 3% solution of hydrogen peroxide was found to be the least effective.

Acrylic Resins↗
PubMed1998

Light-curing acrylic resin as an orthodontic baseplate material.

Heat-curing autopolymerizing (self-cure or cold-cure), thermoplastic, and light-curing acrylic resin are the most commonly used orthodontic baseplate materials. While cured acrylic resins present few problems to the patient, in the laboratory acrylic resin has to be sprayed, mixed, or packed in a fume-extraction unit because of the harmful fumes emitted by the raw inflammable chemicals. Light-curing material, on the other hand, is virtually nonflammable and has virtually no aroma. A light-cure technique for the construction of orthodontic baseplates is described. While buildup of the baseplate is slightly slower than for self-cured material, the shorter time involved in trimming and polishing means that overall construction is faster. It is easier to obtain a uniform thickness with light-cured material, and it provides superior fit. These results, however, are subject to more extensive clinical trials. The only apparent disadvantage is the fine powder produced during trimming. Even with a bench equipped with an extraction unit, it is advisable to use a face mask to prevent the inhalation of dust.

Acrylic Resins↗
PubMed2002

An investigation into the transverse and impact strength of "high strength" denture base acrylic resins.

A range of materials, often marketed as high strength resins is available. These materials are often expensive options to conventional heat-cured acrylic resin. The aim of this study was to investigate transverse and impact strength of five "high strength" acrylic resin denture base materials. A conventional heat-cured acrylic resin was used as a control. Specimens were prepared as specified in the International Standard Organization (ISO 1567: 1988) and British standards for the Testing of Denture Base Resins (BS 2487: 1989) and the British Standard Specification for Orthodontic resins (BS 6747: 1987) for transverse bend and impact testing. The impact strength was measured using a Zwick pendulum impact tester and the transverse bend strength measured using a Lloyds Instruments testing machine. The results showed that Metrocryl Hi, Luctitone 199 and N.D.S. Hi all had an impact strength which was significantly higher than the control. For the modulus of rupture, there was a significant difference between Sledgehammer and the other groups. There was no significant difference between the other groups and the control. For the modulus of elasticity, Sledgehammer produced the highest value followed by the control. The remaining four materials had a modulus of elasticity less than the control.

Acrylic Resins↗
PubMed2001

Heat-cured acrylic resin repaired with microwave-cured one: bond strength and surface texture.

This study evaluated the influence of chemical surface treatments in the repair strength of a heat-cured acrylic resin (Lucitone 550, (LU)). A total of 70 specimens were made with LU according to American Dental Association (ADA) specification No. 12. Of these, 14 remained intact and were used as a control group (GI). A total of 56 specimens were selected randomly. These specimens were cut in the middle (10 mm), repaired with a microwave acrylic resin (Acron MC (AC)), and processed in a microwave oven for 3 min at 500 W. Prior to the repair, the surface of the cut ends received different chemical treatments (GIII = AC monomer dipping/30 s; GIV = acetone dipping/30 s; GV = acetone dipping/15 s + blast of air + AC monomer dipping/15 s; GVI = no wetting treatment). However, 14 intact specimens made with AC formed a second control group (GII). The effect of the chemical treatments on the surface texture of LU was observed with scanning electron microscopy. Flexural test results were submitted to paired t-test and showed statistical differences (P < 0.05) only between the pairs GIV-GV and GIV-GVI. Strength mean values of repaired specimens were statistically lower (79-90%) than GII mean values. Strength mean values of GVI and GIV were 93 and 106%, respectively, of GI mean, showing no statistical differences. Scanning electron microscopic observations revealed various effects of the chemical treatments on the denture base resin surface. In conclusion, the wetting surface treatments affected the bond strength between the two acrylic resins, and no statistical differences in strength were observed between intact heat-cured denture base material and the same material repaired with microwave acrylic resin.

Acetone↗
PubMed1996

Acrylic resin denture repair with adhesive resin and metal wires: effects on strength parameters.

The fracture of acrylic resin dentures is an unresolved problem in prosthodontics. In this study one brand of denture base acrylic resin was used to make specimens in the form of strips and maxillary denture bases. The specimens were cut and repaired with one type of an autopolymerizing adhesive resin and metal wires. The mechanical properties of the repaired specimens were measured, and the efficiency of each method was evaluated. The statistical results of this study revealed that geometric characteristics of a maxillary denture combined with the shape and pretreatment of reinforcement were the controlling factors for the overall mechanical behavior. Furthermore this study revealed that data with clinical significance can only be obtained by testing specimens similar to the original items used in dental practice.

Acrylic Resins↗