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PubMed2002

Stress distribution associated with loaded acrylic-metal-cement crowns by using finite element method.

The axisymmetrical finite element method (FEM) was used to compare stress distribution in a maxillary second premolar restored tooth. The three models were evaluated by crowning the tooth with Au-Pd alloy, Ni-Cr alloy and Ti alloy with acrylic. A longitudinal static force, 200 N in magnitude at an angle of 45 degrees was applied on the occlusal margin of each model. The tooth was assumed isotropic, homogenous and elastic. This numerical study was carried out using axisymmetric finite element models and calculation programmes were prepared by the authors using FORTRAN 77. Comparison of stress distributions was made in four regions of apex, cole, dentin-metal interface and metal-acrylic interface. The highest stress values were obtained when NiCr alloy with acrylic was used.

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↗
PubMed2001

Allergic contact stomatitis caused by acrylic monomer in a denture.

A 71-year-old edentulous man developed a severely painful red mouth at sites of contact with a new denture. Patch testing showed allergy to samples of the denture material and to 2-hydroxyethyl methacrylate. Patch testing to methyl methacrylate was negative. Prolonged boiling of the denture resulted in reversal of his symptoms and samples of this fully cured denture material produced negative patch tests. While allergy to acrylates is a rare cause of stomatitis, this possibility must be considered in patients presenting with oral symptoms. Material safety data sheets are unreliable in providing information regarding the type of acrylate present in the material. Hence, patch testing should be performed with a battery of acrylate allergens as well as with small samples of the denture material.

Acrylic Resins↗
PubMed2004

Clinical outcomes and complications of intraocular lens exchange in patients with opacified hydrophilic acrylic lenses SC600-2.

BACKGROUND: The purpose of this study was to present the outcomes of intraocular lens exchange in patients with opacified hydrophilic acrylic intraocular lenses. PATIENTS AND METHODS: Fifteen patients, who underwent uncomplicated phacoemulsification and hydrophilic acrylic intraocular lens (model SC600-2) implantation with good visual recovery, were re-referred to our department 76 - 188 weeks post-surgery due to progressive visual loss resulting from opacification of the implant. Intraocular lens exchange followed. The method of lens exchange is described. The effect on the best corrected visual acuity and on their refraction, the operative and postoperative complications are reported. RESULTS: All 15 patients underwent intraocular lens exchange. Twelve patients (80 %) had improvement of their best corrected visual acuity, in two cases (13 %) the best corrected visual acuity did not change, and in one case (7 %) the best corrected visual acuity deteriorated, this being attributed to progression of her age-related macular degeneration. None of the patients developed zonular dehiscence; in one patient the exchange was complicated with posterior capsule rupture, and an anterior chamber intraocular lens was implanted. One patient required cutting of the haptics before removal of the opacified intraocular lens. The mean Snellen (decimal) visual acuity was 0.35 (range 0.1 to 0.6) before lens exchange and 0.49 (range 0.1 to 0.6) six weeks after; the difference was significant (P < 0.05). Excluding the patient with the deterioration of her age-related macular degeneration, mean visual acuity of the remaining fourteen patients after the intraocular lens exchange was even better (0.56). CONCLUSION: Exchange of opacified hydrophilic acrylic intraocular lenses seems to be the only currently available effective treatment, leading to improvement of visual acuity.

Acrylates↗
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↗
PubMed2002

Sensory nerve-mediated nasal vasodilatory response to inspired ethyl acrylate.

The irritants acrolein, acetaldehyde, and acetic acid induce a rapid sensory nerve-mediated nasal vasodilatory response in the rat. The aim of the current study was to examine acute nasal sensory nerve-mediated acute responses to an irritant ester vapor, ethyl acrylate. For this purpose, the upper respiratory tract of the urethane-anesthetized male F344 rat was isolated by insertion of an endotracheal cannula, and ethyl acrylate-laden air was drawn continuously through that site at a flow rate of 100 ml/min for 50 min. Vascular function was monitored by measuring inert vapor (acetone) uptake throughout the exposure. Nasal flow resistance was also monitored during exposure, and plasma protein extravasation was measured by Evans blue dye leakage. At exposure concentrations of 100 to 400 ppm, ethyl acrylate induced a rapid nasal vasodilatory response, as indicated by increased acetone uptake rates. This response was maintained throughout the exposure. Changes in nasal flow resistance or in Evans blue dye leakage were not observed at these exposure concentrations. The vasodilatory response was diminished in animals pretreated with the sensory nerve toxin capsaicin, providing strong evidence that this response was sensory nerve mediated. Pretreatment with the carboxylesterase inhibitor bis-para-nitro-phenolphospahte at a dose sufficient to inhibit nasal carboxylesterase did not alter the response, suggesting that the parent ester, not the carboxylesterase metabolites, is primarily responsible for the sensory-nerve-mediated vasodilatory responses to this ester.

Acetone↗
PubMed1991

Acute toxicity, genotoxicity, and dermal carcinogenicity assessment of isooctyl acrylate.

Isooctyl acrylate (IOA) monomer is a complex mixture comprised predominantly of isomeric, eight-carbon alkyl esters of acrylic acid. Limited evidence from animal studies suggests that certain acrylate esters may be carcinogenic by the dermal route of exposure. The following studies were performed with IOA monomer: acute oral toxicity limit test in rats, primary dermal and ocular irritancy in rabbits, Ames Salmonella microsome assay, Saccharomyces cerevisiae D3 recombinogenicity assay, L5178Y TK +/- mouse lymphoma cell assay, and C3H/10T1/2 mouse embryo cell transformation assay. Finally, a limited dermal carcinogenicity bioassay was performed in which aliquots (25 microliters) of IOA monomer (5% v/v in acetone), IOA polymer (19% w/v in 70:30 acetone/heptane), or acetone (vehicle control) were applied to the shaved backs of male C3H/HeJ mice three times per week for the animals' lifetimes. IOA monomer had an acute oral LD50 in rats greater than 5000 mg/kg, was slightly irritating to the eyes and skin of rabbits on single exposures, and exhibited no genotoxic or cell-transforming potential. In the dermal carcinogenicity bioassay, no significant difference in mean survival times was observed between either treatment group and the control group. Animals treated with IOA monomer exhibited moderate dermatitis, surface crusting, hyperkeratosis, epidermal hyperplasia, diffuse melanosis, and one benign melanoma at the treatment size. Animals treated with IOA polymer exhibited varying degrees of dermatitis, surface crusting, and hyperkeratosis. Neither IOA monomer nor IOA polymer was carcinogenic under the conditions of the study.

Acrylates↗
PubMed1999

Influence of pigment concentration and particle size on adhesion of an acrylic resin copolymer to tablet compacts.

The effects of the particle size and the concentration of pigments in aqueous polymeric dispersions on the adhesive properties of an acrylic resin copolymer were investigated. Aqueous polymeric dispersions containing up to 20% (v/v) pigment were coated onto hydrophilic and hydrophobic tablet compacts, and polymer adhesion was assessed using a novel butt adhesion technique. An inverse relationship was found between the particle size of the pigment present in the aqueous polymeric dispersion and film-tablet adhesion. As the particle size of the pigment increased, the adhesive strength of the polymer to the tablet compact decreased. Increased concentrations of the opacifying agent titanium dioxide in the acrylic dispersion resulted in stronger film-tablet adhesion. No clear relationship could be established between the wettability of the tablet compact by the pigmented polymeric dispersion and the strength of film-tablet adhesion. The hydrophobicity of the tablet compact was found to affect the glass transition temperature of the polymeric film to a greater extent than the particle size, morphology, or concentration of the pigment incorporated into the acrylic dispersion.

Acrylic Resins↗
PubMed1986

A comparison of the effects of chlorhexidine gluconate, amphotericin B and nystatin on the adherence of Candida species to denture acrylic.

Pretreatment of denture acrylic with nystatin, amphotericin B and chlorhexidine gluconate significantly reduced the subsequent adherence of Candida species to acrylic, although chlorhexidine and nystatin were more effective than amphotericin B. The duration of chlorhexidine-mediated inhibition of adherence (up to 19 days) was much longer than that of amphotericin B (24 h) or nystatin (48 h). Exposure of stationary-phase cells of Candida species for a short period to sublethal concentrations of chlorhexidine, or growth of Candida species with sublethal concentrations of chlorhexidine for 24 h resulted in a reduction in the ability of the yeasts to adhere to denture acrylic. The organisms grown in the presence of chlorhexidine were more susceptible to spheroplasting with Zymolyase 20T, indicating that chlorhexidine affects the cell surface composition of Candida species.

Acrylic Resins↗
PubMed2004

Polyvinyl alcohol particles and tris-acryl gelatin microspheres for uterine artery embolization for leiomyomas: results of a randomized comparative study.

PURPOSE: To determine if the type of embolic material used for uterine artery embolization (UAE) for leiomyomas has an impact on short-term recovery or the effectiveness of embolization. MATERIALS AND METHODS: One hundred patients were randomly assigned to undergo UAE with polyvinyl alcohol (PVA) particles or tris-acryl gelatin microspheres. Short-term, in-hospital medication use and pain levels were recorded. After discharge, symptom severity, temperature, and medications used were recorded daily for 1 week and symptom levels were measured for weeks 2-4. Three months after embolization, contrast material-enhanced magnetic resonance imaging examinations were evaluated blindly to determine the extent of leiomyoma infarction. Symptom and quality of life (QOL) status was determined with use of questionnaires. Analysis was completed with use of chi(2) analysis, Fisher exact tests, Student t tests, and analysis of variance as appropriate. Regression analysis was used to analyze the impact on outcome of baseline factors (other than type of embolic agent). RESULTS: No significant differences were noted at baseline between the two treatment groups. On average, there were significantly higher volumes of tris-acryl microspheres used (9.0 mL vs 3.0 mL; P =.0001), whereas microcatheter occlusion was more common with PVA (28% vs 4%, P =.001). There were no differences in pain severity, other postprocedural symptoms, or medication use between the two treatment groups. There were also no differences in the frequency of incompletely infarcted leiomyomas, degree of improvement in symptom score, patient satisfaction, or QOL. CONCLUSION: No substantive differences were detected between outcomes of embolization with PVA particles or tris-acryl gelatin microspheres.

Acrylic Resins↗
PubMed1985

Effect of chlorhexidine gluconate on the adherence of Candida species to denture acrylic.

The effect of pretreatment of denture acrylic with chlorhexidine gluconate on the subsequent adherence of Candida albicans GDH 2346 was measured in vitro. Adherence was significantly reduced by pretreatment with chlorhexidine; maximal inhibition was achieved by incubation at room temperature for 30 min in 2% chlorhexidine. Inhibition of adherence was greatest when the organisms were grown in conditions that enhanced adherence the most, i.e., growth to stationary phase in high concentrations of galactose and sucrose. Yeasts grown in high concentrations of galactose, which were the most adherent to acrylic, were also the most sensitive to the fungicidal action of chlorhexidine gluconate, whereas those grown in a low concentration of glucose were the least adherent and also the most resistant. Adherence to acrylic of seven strains of C. albicans isolated from active infections (I strains) and grown in medium containing 500 mM sucrose was significantly higher than that of four strains obtained from asymptomatic carriers (C strains). A spectrum of adherence values was obtained when various yeasts other than C. albicans were tested.

Acrylic Resins↗
PubMed1993

Occupational respiratory disease caused by acrylates.

Acrylates are compounds used in a variety of industrial fields and their use is increasing. They have many features which make them superior to formerly used chemicals, regarding both their industrial use and their possible health effects. Contact sensitization is, however, one of their well known adverse health effects but they may also cause respiratory symptoms. We report on 18 cases of respiratory disease, mainly asthma, caused by different acrylates, 10 cases caused by cyanoacrylates, four by methacrylates and two cases by other acrylates.

Acrylates↗
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↗
PubMed1983

The abrasion of acrylic resin by cleaning pastes.

The physical removal of plaque from dentures by brushing is important in the maintenance of oral health. However, there is a danger that brushing will abrade acrylic resin. A machine using a rotary brushing action was therefore utilized for laboratory tests of possible cleaning pastes, employing a toothbrush with good access and adaptability to denture surfaces. Crest toothpaste produced the most abrasion on acrylic resin, Dentu-Creme the least. An experimental paste produced an appreciably lower abrasion rate. Self-cured specimens wore more than heat-cured ones. The rate of abrasion decreased as the temperature was raised. Brushing with water alone, or with a 10% solution of soap, did not produce detectable wear. The wear produced by proprietary cleaners when hand brushing the lingual flanges of dentures and flat blanks of heat-cured acrylic was also measured. Boots denture cleaning paste produced the greatest abrasion, Dentu-Creme the least. The wear measured by reference to a glass plane was at least twice that recorded by the decrease in depth of a groove. The machine did not quantitatively produce the same abrasion as hand brushing, nor did it qualitatively rank the pastes in the same order of abrasiveness. The clinical relevance of these results is discussed.

Acrylic Resins↗
PubMed1991

Evaluation of the level of residual monomer in acrylic denture base materials having different polymerization properties.

The aim of this study was to evaluate the level of residual monomer in acrylic denture base materials having different polymerization properties. The investigation included a conventional-type acrylic cured under heat and pressure, as well as a pour-type resin polymerized by an injection-moulding technique at room temperature and under pressure. It was found that the residual monomer content ranged from 0.22-0.54% in pour-type resin, and from 0.23-0.52% in routinely used resins when the specimens were analysed by high performance liquid chromatography. These findings revealed that there were no significant differences between the two types of acrylic in terms of their residual monomer content.

Acrylic Resins↗
PubMed2004

Surface roughness of acrylic resins submitted to mechanical and chemical polishing.

Surface roughness is extremely important as it influences micro-organism accumulation and consequently oral health. The aim of the present study was to evaluate the influence of mechanical polishing (MP) and chemical polishing (CP) on surface roughness of four heat-cured denture base acrylic resins. Twenty sample discs were prepared for each of the following acrylic resins: Classico (CL), QC 20 (QC), Acron MC (AC) and Onda Cryl (ON). The first two are boiling cured resins and the latter two are microwave cured. After curing and deflasking, samples were ground and subdivided into two groups: MP, which received pumice slurry, chalk powder, soft brush and felt cone, at a bench vice; and CP, which received fluid specifically for chemical polisher. Surface roughness was measured using a Surf Corder SE 1700 rugosimeter. Data collected were statistically analysed by analysis of variance followed by Tukey's test. Surface roughness means in mum were: CL-MP: 0.0350; CL-CP: 0.2298; QC-MP: 0.0307; QC-CP: 0.1792; AC-MP: 0.0312; AC-CP: 0.2700; ON-MP: 0.0321; ON-CP: 0.2949. It can be concluded that MP produced significantly smoother surfaces than CP and that surface roughness because of MP was not influenced by acrylic resin type, whereas this was not true of CP.

Acrylic Resins↗
PubMed2005

Adherence of Candida albicans to glow-discharge modified acrylic denture base polymers.

An important aetiologic factor in the pathogenesis of denture-induced stomatitis, is the presence of numerous yeasts, usually Candida albicans, on the fitting surfaces of dentures. In the present study, effect of glow-discharge plasma, a technique applied to increase surface wettability of acrylic resins, on candidial adherence was evaluated. The durability of glow-discharge modification with saliva coating was also evaluated. Samples including control and experimental groups were prepared by using heat compression mould technique. To create a hydrophobicity gradient, experimental groups were exposed to a radiofrequency glow discharge in an O2 atmosphere under different discharge powers. To characterize the wetting properties, an expression of surface hydrophobicity, contact angle measurements were performed by the sessile drop method. The organism used was C. albicans (ATTC10321). Acrylic samples were coated with unstimulated whole saliva collected from a healthy man. The fungal suspension was poured on saliva-inoculated samples and incubated at 37 degrees for 2 h. The samples were then fixed with glutaraldehyde and Gram stained. Adhered candidial cells were examined by light microscope. Diffuse Reflectance FTIR (DRIFT) and scanning electron-microscope examinations were also performed to evaluate the surface composition and roughness of the test groups. Glow-discharge plasma was found to be an effective means of increasing surface wettability even with salivary pellicle. Amounts of candida cells adhered were significantly higher in all the plasma treated surfaces than the unmodified control group (P < 0.001). It was concluded that improving the surface wettability of acrylic resins by glow-discharge plasma in O2 atmosphere increased the adherence of the C. albicans.

Acrylic Resins↗
PubMed2006

Specifications provided by practitioners for fabrication of removable acrylic prostheses in Tanzania.

This study aimed at determining the standard of communication between practitioners and dental laboratory technicians in fabrication of removable acrylic prosthetic appliances using written prescriptions. Three hundred and seventy-nine prescriptions submitted to the Dental Laboratory of Muhimbili National Hospital (January 1998-May 2004) were assessed for their instructive quality. Only specifications necessary for the fabrication of a removable acrylic prosthesis were considered. Analysis was according to type of appliances and indicated specifications by practitioners. EPI 6 was used with chi-square test for statistical analysis at a 0.05 level of significance. All 379 prescriptions had designation of practitioner and type of appliance indicated and most were authorized by doctors (67%; n = 254) and for partial dentures (86.5%; n = 328). The majority of the complete dentures (13.5%; n = 51) were authorized by students (49%; n = 25) in comparison with partial dentures (86.5%; n = 328) that were authorized mainly by doctors (71.9%; n = 236). Teeth required (83.4%; n = 316) was the most indicated specification and interns were the most instructive of practitioners. For complete dentures, the only significantly indicated specification was appointment date for occlusal registration. The most significantly indicated specifications for partial dentures was teeth required followed by appointment date for fitting, shade, claSPS and secondary impression. The standards of communication between practitioners and dental laboratory technicians in the fabrication of removable acrylic prostheses are generally inadequate as most required specifications were not indicated by practitioners. Work undertaken by technicians should be accompanied by a detailed written prescription, completion of work authorization be included in the curriculum and Dental Laboratory Vouchers in use be evaluated.

Acrylic Resins↗