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PubMedDate not supplied

The effectiveness of seven denture cleansers on tea stain removal from PMMA acrylic resin.

PURPOSE: In this study, seven denture cleansers were evaluated for their mode of action of tea stain removal from Perspex acrylic resin material. MATERIALS AND METHODS: Perspex acrylic resin specimens were stained using a combination of chlorhexidine and tea solution. The specimens were also treated with saliva to form an initial pellicle layer and facilitate the uptake of the stain. The capacity for stain removal was determined by measuring the optical density of the treated specimens by using a spectrophotometer. These were then exposed, for 5 minutes, to seven denture cleansers to demonstrate the percentage stain-removal ability of each cleanser. The same procedure was applied for roughened Perspex acrylic resin specimens. Water was used as a control in the two parts of the experiment. RESULTS: The products containing alkaline hypochlorite had the highest ability for removing stain from the acrylic resin material together with a bleaching effect. The results varied when the same denture cleansers were used on the roughened Perspex surface, and this was attributed to the presence of irregularities and porosities on the blocks. CONCLUSION: Denture cleansing agents containing hypochlorite and Boots Denture Cleaning Powder (constituents not stated by the manufacturer) exhibited the ability to remove stain from the denture base materials most effectively. Irregularities and porosities present on the denture surface played a major role in reducing the activity of denture cleaning agents and hence increased stain and plaque retention.

Acrylic Resins↗
PubMed2001

The effect of powder/liquid mixing ratio on the stiffness and impact strength of autopolymerising dental acrylic resins.

The stiffness of representative cured autopolymerising dental acrylic resins was determined by calculation of a secant modulus from measurements in tension of load and extension, and related to the powder/liquid mixing ratio. The impact strengths of autopolymerising, heat-cure and commercial resins were compared. It was found that while the stiffness of autopolymerising resins was unaffected by variations in powder/liquid mixing ratio, extension to failure was greater with lower powder/liquid ratios. The impact strength of autopolymerising resins was found to be greater than that of heat-cure resins, and a tentative explanation is offered. These findings may help to explain the pattern of failure of acrylic resin denture bases.

Acrylic Resins↗
PubMed2000

The effect of glass fibre-reinforcement on the transverse strength, deflection and modulus of elasticity of repaired acrylic resins.

AIM: To test the effect of reinforcement qualities of glass fibre in the repair of acrylic fractures. METHODS: Four types of heat-curing acrylic resin test specimens were fabricated. The bottom and sides of the specimens were placed in stone to form a repair template. Lines were drawn 3.5 mm on each side of the centring mark. The 45 degree-bevel joint margins were cut at these lines to simulate fracture and the centre section was discarded. A 1 mm gap was created between the margins before repair with autopolymerising acrylic resin with and without glass fibre. OUTCOME MEASURES: A three-point loading test was used to measure transverse strength, deflection and the modulus of elasticity of repaired acrylic resin joints. RESULTS: The transverse strength of acrylic resins was increased with fibres. CONCLUSION: Glass fibre-reinforcement significantly increased resistance to deflection and increased the modulus of elasticity.

Acrylic Resins↗
PubMed2003

[Clinical evaluation of two temporary restoration materials: Composite and self-cured acrylic resin].

OBJECTIVE: The purpose of this study was to compare the clinical application and effect of two temporary restorations materials: composite and self-cured acrylic resin. METHODS: 153 composite temporary crowns (and bridges) placed in 44 patients and 144 self-cured acrylic resin temporary crowns (and bridges) placed in 49 patients were evaluated according to the California Dental Association's (CDA) criteria and questionnaire. RESULTS: It showed that composite temporary crowns (and bridges) had better surface smoothness, marginal integrity and anatomic form than self-cured acrylic resin temporary crowns (and bridges). In the 49 patients with self-cured acrylic resin temporary crowns (and bridges), 67% and 88% of them complained of food impaction and mouth odor, while only 2% and 30% in the 44 patients with composite temporary crowns (and bridges) had the same complaint. CONCLUSION: Between the two temporary restoration materials, composite is better than self-cured acrylic resin.

Acrylic Resins↗
PubMed1979

Processing factors affecting the clarity of a rapid-curing clear acrylic resin.

The difficulty in repeatedly producing unblemished, clear acrylic resin in the dental laboratory has hindered its wider use, despite its many advantages over coloured material. Recently, rapid-cure dental acrylics have been introduced, which are available in both clear and coloured forms. This investigation examined various factors which may influence the production of unblemished, rapid-curing, clear acrylic resin. Utilizing a quantitative assessment of clarity, the most important factor influencing the clarity of the resin is shown to be the choice of separating medium. Tin-foil produces extremely high clarity, but alginate mould separator causes surface blanching. However, this surface blanching can be removed by polishing. Porosity, caused by too rapid curing, and stone model dryness are of only secondary importance. Possible water contamination of the monomer liquid due to accidental exposure only affects clarity at very high levels of contamination.

Acrylic Resins↗
PubMed1991

Comparison of the adaptation of acrylic resin cured by microwave energy and conventional water bath.

Acrylic resin record bases made from three commercial resins were processed by water bath curing and by microwave energy. The adaptation of the record bases to a standard cast was measured to determine if there were any statistically significant differences in the fit that could be attributed to the differences in curing methods and the brands of resin. The results indicated a small statistically significant difference in favor of the water bath cure overall, but clinically there were no appreciable differences in the adaptation of the record bases with either curing method or the resins used. The adaptation of artificial dentures made from acrylic resin is clinically acceptable with either microwave curing or the water bath method.

Acrylic Resins↗
PubMed2006

Influence of acrylic resin polymerization methods and saliva on the adherence of four Candida species.

STATEMENT OF PROBLEM: There is limited information on the role of polymerization methods and saliva on the adherence of pathogenic Candida species, with the exception of the adherence of Candida albicans to acrylic resins and the relation of this to surface roughness and surface free energy, which appear to play a major role in the initial phases of microorganism adhesion. PURPOSE: This study evaluated the influence of polymerization methods and human whole saliva on the adherence of Candida species to acrylic resin surfaces. MATERIAL AND METHODS: Acrylic resin specimens (n=256) measuring 2.5 x 1.2 x 0.2 cm were heat (Classico) or microwave (OndaCryl) polymerized and evaluated for surface roughness using a profilometer, and for surface free energy by measuring the contact angle of a sessile drop of water. For the adherence assay, specimens of each acrylic resin were divided by lottery into 8 groups, according to whether they were exposed to human saliva or not (control), and to 1 of the 4 following suspensions: C albicans, Candida tropicalis, Candida dubliniensis, or Candida glabrata (1 to 5 x 10(6) cells/mL). Adhered yeasts were counted using an optical microscope at x400 magnification. Data were analyzed by 3-way ANOVA and the Tukey honestly significant difference test (alpha=.05). RESULTS: No statistical difference was found for roughness (P=.156), whereas higher surface free-energy values were found for the heat-polymerized acrylic resin (P=.0013). The overall adherence of Candida species was significantly decreased by human saliva (P<.001). CONCLUSION: Within the limitations of this study, saliva was capable of reducing the adherence of Candida species, whereas roughness and free energy did not influence the adherence rates. CLINICAL IMPLICATIONS: As growth on surfaces is a natural part of the Candida lifestyle, its colonization in denture users may be expected. The presence of human whole saliva, however, decreased the overall yeast adherence to the acrylic resin surface, whereas surface roughness and free energy did not interfere with the adherence of Candida species.

Acrylic Resins↗
PubMedDate not supplied

Effects of denture teeth on the dimensional accuracy of acrylic resin denture bases.

The Michigan Computer-Graphics Coordinate Measurement System was used to determine the effects of artificial denture teeth on the accuracy of acrylic resin denture bases. Two poly(methyl methacrylate) acrylic resins and two processing techniques were tested. Groups processed with denture teeth reproduced more accurate points than groups processed without denture teeth. Groups processed with a conventional heat-polymerized acrylic resin reproduced more accurate points than groups polymerized with an injection pressing type of acrylic resin.

Acrylic Resins↗
PubMed1983

Fabricating acrylic resin baseplates for complete dentures.

A technique for fabricating acrylic resin baseplates for complete dentures has been described. With this technique multiple sets of baseplates can be made at a time for a set of master casts. As with all polymethyl methacrylate resins, polymerization shrinkage is present. However, by using denture repair acrylic resin, shrinkage is minimized. Furthermore, when necessary, conventional procedures can be applied to stabilize the baseplates.

Acrylic Resins↗
PubMed2006

The investigation of solubility values,water sorption and bond strength of auto-polymerising and heat-polymerising acrylic resin materials.

In this study the solubility, water sorption and the bond strength of auto-polymerising and heat-polymerising acrylic resins were investigated. Two auto-polymerising and five heat polymerising acrylic resin materials were used for this study. Thirty-five specimens were prepared (50 mm in diameter and 0.5 +/- 0.01 in thickness) for water sorption and solubility tests. In order to examine bond strength, specimens were prepared in 2.5 x 10 x 64 mm dimensions. These specimens were repaired with QC and major repair acrylic. Some specimens were kept in distilled water for 50 hours, and others for 30 days. The strength of the bond was measured by a Pull-Compress device. As a result of the variance analysis; water sorption, solubility and the bond strength between acrylic resins were identified as statistically significant (P < 0.001). The water sorption of the major acrylic resin specimens were lower than the other materials (P < 0.001).

Absorption↗
PubMed1999

Time-related wettability characteristic of acrylic resin surfaces treated by glow discharge.

STATEMENT OF PROBLEM: Adhesion and cohesion have important roles in denture retention, and attempts have been made to improve the wettability of the acrylic resin material by surface treatments. PURPOSE: This study examined the initial and subsequent wettability of an acrylic resin denture base material treated under air or argon plasma atmosphere before and after exposure to air or distilled water. MATERIAL AND METHODS: Acrylic resin specimens were treated with plasma under air or argon atmosphere and were either exposed to air or distilled water for up to 60 days. Wettability characteristics of the acrylic resin specimens were determined by contact-angle measurements after 2 hours and after 60 days. Surface composition of the specimens also was analyzed with x-ray photoelectron spectroscopic (XPS) measurements. RESULTS: Statistically significant difference was found between control and each of the plasma treatment groups (P <.05). Although the storage condition and storage period caused statistically significant difference on contact angle values (P <.05), atmosphere type did not have any effect on the results (P >.05). XPS spectra of the plasma-treated specimens differed from control specimens only in the O1s region with a narrower and more intense peak that could be assigned to -COH groups. During 60 days of exposure, the O/C atomic ratios decreased within the first 2 weeks but settled to 0.40 and 0. 32 up to 60 days compared with 0.26 for untreated control specimens. CONCLUSION: Glow discharge plasma altered the surfaces of the acrylic resin and increased thc wettability as shown both by XPS and contact-angle measurements, and plasma treatment seemed to offer a durable (at least up to 60 days) wettability.

Acrylic Resins↗
PubMed2003

Surface texture and some properties of acrylic resins submitted to chemical polishing.

The effects of chemical polishing on dental acrylic resin properties are not well clarified. This study evaluated the effect of chemical and mechanical polishing on the residual monomer release (RM), Knoop hardness (KH), transverse strength (TS) and surface texture (ST) of a heat- and self-cured acrylic resin. Four groups were formed: GI-self-cured resin/mechanical polishing; GII-self-cured resin/chemical polishing; GIII-heat-cured resin/mechanical polishing; GIV-heat-cured resin/chemical polishing. Following the polishing procedures, specimens were stored in distilled water at 37 degrees C. The KH and RM measurements were taken after 1, 2, 8 and 32 days of storage, and TS after 2, 8 and 32 days. Surface texture was observed under SEM evaluation. Results were compared statistically at a confidence level of 95%. The following conclusions were drawn: (1) regardless of the acrylic resin and the period of analysis, chemical polishing increased RM levels, reduced KH, and did not affect TS significantly; (2) water storage increased the surface hardness of GII and GIV; (3) GII and GIV showed a smooth and wavy surface under SEM evaluation.

Acrylic Resins↗
PubMed1999

[Comparative analysis of tissue reaction to acrylic resin materials in studies on Wistar strain rats].

The study takes up the issue of assessing rat tissue reaction to operatively inserted implants of different acrylic resin materials used in prosthetic dentistry. The materials subjected to analysis were polyacrylics: Vertex Soft, Vertex R.S., Vertex S.C., Superacryl and silicone material Molloplast B. The prolongation of life and the dynamic development of prosthetic treatment have caused removable dentures to be used longer and among more people. Polymerised acrylic resin material of these dentures is a potential pathogenic factor to the oral cavity mucosa which is in contact with it. As many as 20 to 70% of patients using removable acrylic dentures suffer from prosthetic stomatopathy. It is considered that the mucosa irritation may be caused by denture trauma, a mycotic infection or toxic action of some components of acrylic materials. Therefore the use of new generation acrylic materials in producing prosthetic dentures needs a precise assessment of undesirable local and systemic effects. A comparative analysis of the effect of correctly polymerised acrylic material on rat mucosa, parotid glands and lymphatic nodes was carried out. Systemic toxicity of these materials was assessed. Acrylic plates were prepared from the most often used acrylic resin materials in the Department of Prosthetic Dentistry PAM and a silicone material (these materials were polymerised precisely according to the producers instruction). Before implantation the plates underwent a thermodynamic analysis in order to ensure that the polymerisation process was carried out correctly and to determine thermal resistance of particular materials. Next sterile acrylic plates were implanted in rats under general anaesthesia. The animals were divided into 6 groups, 10 rats each. In four groups acrylic plates were implanted, in one group silicone material plates were implanted and it represented the comparative group, in one control group an incision of the buccal mucosa was made. The rats were observed during a period of 6 weeks, they were weighed every two weeks and no loss in body mass was noted (Tab. 1). After 6 weeks the rats were anaesthetised with ether and dissectioned. Biopsy specimens were taken from the buccal mucosa, porotid gland and lymphatic cervical nodes around the plates in order to make histological specimens. Blood samples were also taken to carry out blood cell counts and liver tests to determine eventual systemic toxicity of the studied acrylics. Histological specimens were stained with hematoxylin and eosin. In borne cases in order to precisely assess the intercellular substance other staining methods were used such as van Gieson, PAS and silvering of precollagen fibres on reticulum. Prepared specimens were assessed in a light microscope in magnification of 80 to 400. Basing on specimens of the control group an analysis of tissue reaction to the particular tested acrylic resin material was carried out. It was ascertained that the most irritative properties to the rat buccal mucosa were caused by self-cure acrylic material--Vertex S.C. This polymer caused in all rats in the tested group a reactive hypertrophy of cervical lymphatic nodes (Tab. 2 and Fig. 3). The least damaging effect on the surrounding tissues was caused by heat-cured acrylic resin material Superacryl (Fig. 4). The tested materials had no damaging effect on the rat parotid gland and did not have a toxic action on the internal organs.

Acrylic Resins↗
PubMedDate not supplied

Chairside polishing of heat-cured acrylic resin: an SEM and EDA study.

PURPOSE: This study investigated the surfaces produced on two commonly used heat-cured acrylic resins by two chairside polishing systems compared to conventional lathe polishing. It used energy dispersive analysis (EDA) and scanning electron microscopy (SEM) to investigate the abrasive materials bonded in the silicone points that are marketed for chairside polishing of acrylic resin. MATERIALS AND METHODS: Using the three polishing systems (conventional as control, Shofu acrylic polishing system [AcryPoint], and Kenda Queen silicone polisher), three operators polished specimens using a defined protocol. Specimens were subjected to SEM and confocal microscopy. EDA was undertaken on the silicone polishing points. RESULTS: Conventional polishing produced the superior surface, followed by the surfaces produced by the Shofu system and then Kenda Queen. However, both chairside polishing systems produced smoother surfaces on acrylic resin than the surfaces produced by either steel or tungsten carbide burs. Both the Shofu acrylic polishing system and Kenda Queen silicone polisher contain beads of cerium, which is widely used in industry for polishing of glass. CONCLUSION: Silicone polishing points marketed for polishing of acrylic resin could be used to produce smooth surfaces that have been adjusted with burs where there is no access to a laboratory lathe.

Acrylic Resins↗
PubMed2004

Influence of mechanical and chemical polishing in the solubility of acrylic resins polymerized by microwave irradiation and conventional water bath.

OBJECTIVES: The aim of this work was to evaluate the solubility of acrylic resin activated by microwave irradiation (MI) or water bath (WB), when submitted to chemical (CP) or mechanical (MP) polishing. METHODS: Forty acrylic resin samples were made and processed either by water bath (74 +/- 1 degrees C, 9 h) or microwave irradiation (500 W, 3 min). After deflasking, the samples were finished with aluminum oxide sandpapers in decreasing granulations till reaching similar dimensions. The samples were divided into four groups according to the association between kind of polymerization and polishing: A (WB + CP), B (WB + MP), C (MI + CP) and D (MI + MP). Solubility test was performed for each group and percentile solubility was calculated. Data were statistically analyzed using variance analysis and Kruskal-Wallis. RESULTS: The average of percentile solubility (%) was obtained: A = 0.07, B = 0.02, C = 0.04, D = -0.14, however, no significant difference was found between types of polishing in the samples polymerized by water bath (A and B). When processed by microwave irradiation (C and D), there was significant difference between the applied methods of polishing, so that mechanical polishing lead to a lower solubility. SIGNIFICANCE: Solubility is a property of acrylic resins, representing not reacted substances releasing that could promote tissular reactions in prosthesis users. The association between polymerization by microwave irradiation and mechanical polishing showed less residual substances releasing for heat-cured acrylic resins, reducing the probability of developing tissular reactions.

Acrylic Resins↗
PubMed2005

Effect of deep-freezing on some properties of acrylic resin.

The objective of this study was to evaluate the effect of freezing the acrylic resin polymer/monomer dough mix on a range of properties of the polymerized denture base material. Powder and liquid of acrylic resin were mixed and at the dough stage transferred to a deep freezer and frozen for periods of 24 h, 1 week, 1 month, 3 months, and 6 months. At the end of the storage time, sufficient dough was removed, thawed, packed, and polymerized, and specimens were prepared from the polymerized plates. A control series was prepared from dough which had followed conventional mixing and packing procedures without freezing. The strength properties, hardness, and flash thickness were examined. Statistical analysis was carried out using ANOVA (one-way and two-way) with multiple range tests. The flexural strength was significantly (p=0.03) increased and the impact strength, hardness, and flash thickness were not affected by freezing the material during the dough stage. The flexural modulus was significantly (p=0.0001) reduced when the storage time in the freezer was increased to 3 months. Six months' frozen material proved to be unpackable. It was concluded that the acrylic resin polymer/monomer dough mix can be stored in the freezer for up to 1 month without any statistically significant effect on the properties of the polymerized denture base material.

Acrylic Resins↗
PubMed1990

[Effect of temperature during polymerization on mechanical properties of acrylic resin].

Mechanical properties of heat curing acrylic resin obtained by polymerization for long period of heating at a temperature lower than conventional temperatures were examined. The mechanical properties of the resin were lower than those of the resin cured at 100 degrees C. The results of high performance liquid chromatography and differential scanning calorimetry suggested that the poor mechanical properties were due to significant amounts of residue monomer and benzoyl peroxide in the resin, but is not to changes molecular weight.

Acrylic Resins↗