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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↗
PubMedDate not supplied

[Effect of acrylic resin post-pressing time on dimensional change of total denture base].

The dimensional alterations of denture bases were verified in function of the acrylic resin post-pressing time. Twenty stone cast/wax base sets were confected for routine flasking procedure. Thermosetting acrylic resin (Clássico) was prepared according to the instructions of the manufacturer. After final pressing, the acrylic resin was submitted to polymerization in water at 74 degrees C during 9 hours, following the immediate, 6-, 12-, and 24-hour post-pressing times. The resin bases were fixed on the casts with instantaneous adhesive and the sets were laterally sectioned in the regions corresponding to the distal aspect of canines (A), mesial aspect of first molars (B), and posterior palatal zone (C). The gap between the stone cast and the resin base was measured with a comparative microscope at five referential positions for each kind of sectioning. Data submitted to ANOVA and Tukey's test showed that there was no statistically significant difference between the immediate and the 6-hour post-pressing times as well as between the 12- and the 24-hour post-pressing times. However, there was statistically significant difference between the immediate/6-hour groups and the 12-/24-hour groups.

Acrylic Resins↗
PubMed2006

Occupational allergic contact dermatitis disseminated from multifunctional acrylates in ultraviolet-cured lacquers.

A case of disseminated allergic contact dermatitis in a screen process printer is presented. The skin lesions were caused by multifunctional acrylates (methylpropane triacrylate and pentaerythritol triacrylate--highly positive patch tests (+ + +) after 48 and 96 h) present in ultraviolet cured transparent lacquer used in coat printed posters to make them weather-resistant. Patch tests with lacquer were also highly positive (+ + +) after 48 and 96 h. According to the safety sheet of the product, lacquer contained 85-90% of multifunctional acrylates. The patient showed disseminated dermatitis, however, no hypertrophied lesions on the hand skin, a characteristic symptom in persons exposed to acrylates, were observed.

Acrylates↗
PubMed1981

Identification or urinary mercapturic acids formed from acrylate, methacrylate and crotonate in the rat.

1. After administration to rats of methyl acrylate (I), methyl methacrylate (II) and methyl crotonate (III), urinary mercapturic acids were isolated and identified as the dicarboxylic acids N-acetyl-S-(2-carboxyethyl)cysteine (IV, R = H), N-acetyl-S-(2-carboxypropyl)cysteine (V, R = H) and N-acetyl-S-(1-methyl-2-carboxyethyl)cysteine (VI, R = H) and for a minor part as their monomethyl esters IV (R = CH3) and VI (R = CH3). 2. After a single dose of the acrylates (I), (II) and (III) (0.14 mmol/kg), the excretion of the thioethers amounted to 6.6 +/- 0.6, 0.0, and 2.0 +/- 0.6% dose respectively. 3. After 18 h previous administration of the carboxylesterase inhibitor tri-o-tolyl phosphate (0.34 mmol/kg) the excretion of the thioethers amounted to 40.6 +/- 2.1, 11.0 +/- 3.3, and 16.0 +/- 2.0% dose. 4. For methyl acrylate (I) the ratio of the excreted dicarboxylic acid and monomethyl ester was 20:1. After previous administration of tri-o-tolyl phosphate this ratio was 1:2.

Acetylcysteine↗
PubMed1983

Subchronic and reproductive toxicology studies on acrylic acid in the drinking water of the rat.

In the subchronic study acrylic acid was incorporated in the drinking water of Fischer 344 rats (15 per group) for three months at dosage levels of 0.75, 0.25, 0.083 or 0 g/kg/day. No deaths occurred during the study but several treatment-related effects were observed. At 0.75 g/kg/day dosage level, body weight gain was reduced as were food and water consumption. Changes in organ weights and clinical chemistry parameters were observed along with increases in urine specific gravity and protein concentration. Similar, though less profound, changes occurred at 0.25 g/kg/day. At 0.083 g/kg/day, the only effect was a reduction of water consumption by male rats. There were no significant treatment-related histopathologic changes. Many of the effects observed may have been the result of decreased water and food consumption rather than specific toxic effects of acrylic acid. In the reproduction study, the same dosages of acrylic acid were given to groups of 10 males and 20 females for 90 days after which the animals were mated. Treatment was continued throughout gestation and lactation. Treatment-related effects included decreased body weight gain, and reduced food and water consumption in F0 rats at the 2 highest dosage levels. Organ weight changes occurred in both F0 and F1 animals and reduced body weight gain was seen in the F1 pups at the highest level. No statistically significant changes in reproductive indices were observed, perhaps because of an atypical control group.

Acrylates↗
PubMed1984

Cross-reaction patterns in guinea pigs sensitized to acrylic monomers.

The cross-reaction patterns of selected acrylate and methacrylate esters were investigated using the guinea pig maximization test. Methacrylates were less potent sensitizers than acrylates. Cross-sensitization was found between (meth)acrylates with closely related core structures, most extensively between hydroxyethyl and hydroxypropyl congeners. The importance of considering not only the functional group but also the core structure when assessing potential interactions was emphasized as butanedioldiglycidylether, hexamethylenediisocyanate and hexanedioldiacrylate--all with linear 6-atom cores and different functional group--cross-reacted.

Acrylates↗
PubMedDate not supplied

Development of a microencapsulated form of cefuroxime axetil using pH-sensitive acrylic polymers.

Cefuroxime axetil (CA) was encapsulated in pH-sensitive acrylic microspheres in order to formulate a suspension dosage form. Using this microencapsulated form it was expected to prevent leaching of the drug from the microspheres into the suspension medium and to assure the release of the drug in the first part of the intestine, thus avoiding changes to its bioavailability. For this purpose, CA was microencapsulated within several types of acrylic polymers by the solvent evaporation and the solvent extraction techniques. The acrylic polymers selected were: Eudragit E (positively charged and soluble at pH 5), Eudragit L-55 (negatively charged and soluble at pH > 5.5) and Eudragit RL (neutral, insoluble, but readily permeable). The influence of the polymer electrical charge on the stability and in vitro release of CA was investigated. Though Eudragit E microspheres presented good morphological characteristics and dissolution behaviour, the analysis of the stability of CA in the presence of Eudragit E by HPLC, indicated a negative interaction between both compounds. However, formulations made of Eudragit L-55 and RL in the ratios 100:0 and 90:10 were adequate in terms of the stability of the encapsulated CA. The dissolution studies showed a critical pH between 5.2 and 6.0, which allowed the complete release of CA in a short period. Furthermore, these polymer microspheres were shown to be efficient in masking the taste of CA.

Acrylic Resins↗
PubMed1983

Studies on the hydrolysis of biocompatible acrylic polymers having aspirin-moieties.

Both the homogeneous and heterogeneous hydrolysis of five new acrylic polymers having aspirin-moieties, i.e. polymers of beta-(acetylsalicylyloxy)ethyl methacrylate, beta-(acetylsalicylyloxy) propyl methacrylate,beta-(acetylsalicylyloxy) ethyl acrylate, beta-hydroxy-gamma-(acetylsalicylyloxy) propyl methacrylate, beta-hydroxy-gamma-(acetylsalicylyloxy) propyl acrylate were investigated in acidic or alkaline medium at 30 degrees C or 60 degrees C, respectively. It was observed that the chief hydrolyzed product is always aspirin with minor amount of salicylic acid.

Acrylates↗
PubMed2005

Comparison of the long-term clinical results of hydrophilic and hydrophobic acrylic intraocular lenses.

This study was performed to compare the incidence of posterior capsular opacity (PCO) and refractive errors between hydrophilic (ACR6D, Corneal) and hydrophobic (MA60BM, AcrySof) acrylic intraocular lenses (IOLs) over a 3-year follow-up after phacoemulsification surgery. The patients with AcrySof implanted in one eye and Corneal in the other eye were categorized as Group 1 (n=28), while those with one or both eyes implanted with IOLs of the same kind were categorized as Group 2 (AcrySof, n=90; Corneal, n=95). Refractive errors were evaluated at 3 months and 3 years postoperatively. The incidence of visually significant PCO was investigated 3 years postoperatively. Postoperative refractive values at 3 months were not significantly different between the two groups. However, refractive values at 3 years were significantly different between two IOLs in both groups [AcrySof -0.37+/-0.43D, Corneal -0.62+/-0.58D in Group 1 (p=0.04); AcrySof -0.38+/-0.52, Corneal -0.68+/-0.54 in Group 2 (p<0.01)]. The incidence of visually significant PCO was 14% and 32% in Group 1, and 13% and 28% in Group 2, for the AcrySof and Corneal implants, respectively. The incidence of visually significant PCO of hydrophilic acrylic IOLs was higher than that of hydrophobic acrylic IOLs in the 3-year follow-up. The postoperative 3-year refractive value of Corneal showed myopic shift.

Acrylic Resins↗
PubMedDate not supplied

Long-term rates of PCO following small incision foldable acrylic intraocular lens implantation in children.

PURPOSE: To evaluate the long-term incidence of postoperative posterior capsular opacification (PCO) in children undergoing small incision foldable acrylic lens implantation with at least 2 years of follow up. METHODS: In 18 children, 26 eyes underwent small incision cataract extraction with posterior chamber foldable acrylic lens implantation. The posterior capsule was left intact in all patients at the time of surgery. RESULTS: With a mean follow up of 2.75 years and a mean age at surgery of 8.25 years, 13 of 26 eyes (50%) developed visually significant PCO requiring intervention. In the group of children under 4 years of age, 5 of 5 eyes (100%) developed visually significant PCO, while 8 of 21 eyes (38%) in the group of children over 4 years of age developed opacification. Four of 26 eyes (15%) required two procedures (either repeat Nd:YAG laser capsulotomy or pars plana secondary membrane removal) to clear the visual axis. CONCLUSION: In this study, the incidence of PCO following small incision acrylic lens implantation in children over 4 years of age is lower than those rates reported by conventional large incision rigid lens techniques with a minimum of 2 years follow up. This technique has advantages over conventional techniques in older children because it offers less surgical intervention, a lower cost to patients, and less risk of vitreous and retinal complications.

Acrylic Resins↗
PubMed2006

Effect of mica and glass on acrylic teeth material's color.

The purpose of this study was to evaluate the effect of two different ratios of silanized mica filler and milled glass fiber reinforcement on the color of acrylic denture teeth materials. Ten acrylic resin discs made of acrylic denture teeth material (PMMA) obtained from the manufacturer were used as the control group. Four experimental groups were modified from the control group's PMMA material by adding a ratio of 5% or 10% by weight of silane-treated mica filler or milled glass fibers. Each group consisted of 10 specimens. Measurements were performed using a spectrophotometer CM-2600d, and the color changes were characterized in the Commission Internationale d'Eclairage L*a*b* color space. deltaE* values of 5% mica-, 10% mica-, 5% glass-, and 10% glass-containing sample groups were 2.46, 3.03, 2.16, and 2.59 respectively. There were statistically significant differences in L*, a*, and b* values between the control group and each test group. It was shown that when PMMA denture teeth material was modified with silane-treated mica filler or silane-treated milled glass fibers for the purpose of reinforcement, it would also cause significant changes to the original color of the material.

Acrylic Resins↗
PubMed2006

Effect of adhesive primer developed exclusively for heat-curing resin on adhesive strength between plastic artificial tooth and acrylic denture base resin.

Despite progress in the development of denture base resin and artificial tooth materials, dental clinics are still plagued with artificial teeth falling off the denture base--due to poor bond strength--after denture delivery. Against this background, this study sought to examine the effect and durability of an adhesive primer developed exclusively for heat-curing resin on the adhesive strength of heat-curing denture base acrylic resin to plastic artificial tooth. Test specimens were divided into four groups according to the treatment method of the artificial tooth's test bonding surface: air abrasion, adhesive primer application, adhesive primer application after air abrasion, and pretreatment only (control). After heat curing of acrylic resin onto the bonding surface, shear test was performed for two storage periods: 24-hour versus 100-day water storage. From the results obtained, it was revealed that the evaluated adhesive primer was significantly effective in increasing adhesive strength between artificial tooth and acrylic resin, although specimens were stored in water for 100 days.

Acrylic Resins↗
PubMed1989

Impact properties of acrylic denture base resin. 2. Effect of temperature and residual monomer on impact characteristics.

The temperature dependence of the impact strength, resilience, and toughness of the acrylic denture base resins on temperature changes was examined by using a modified impact testing machine. In addition, the creep properties and the residual monomer of their resins were measured; and considering these properties, the impact characteristics of the denture base resins were discussed. With an increase in temperature, the impact properties of all the acrylic denture base resins tested decreased. Furthermore, there was an adequate correlation between the impact characteristics and the amount of the residual monomer. The coefficient of correlation was 0.92 for the impact strength, -0.95 for the resilience and 0.94 for the toughness. For the cold cured acrylic resins, both elastic moduli obtained by the impact test and by the creep test increased obviously according to an increase in the time which elapsed after polymerization.

Acrylic Resins↗
PubMed2002

[Absorption and scatter with an acrylic plate attached to the front of an X-ray beam limiting device].

We measured X-ray absorption and scatter with an acrylic plate attached to the front of the X-ray beam limiting device. The acrylic plate played the role of an added filter, absorbing the low energy element of the X-ray beam and decreasing the surface dose to 4.3% of the extreme height as a result. However, the surface dose outside the irradiation field increased to 35.3% of the extreme height, and the scatter dose increased to 47.8% of the extreme height. An acrylic plate with the minimum thickness necessary should be used to decrease unnecessary exposure outside the irradiation field.

Absorption↗
PubMed1997

Cracked acrylic ventricular assist devices after using a Doppler stethoscope and ultrasound transmission gel to predict impending pump failure: a case report.

At Saint Louis University Health Sciences Center, bi-ventricular assist devices were placed in a patient after failure to wean from bypass. These acrylic devices are known to be used for post cardiotomy failure. Acrylics and other plastics are used in extracorporeal circuitry. Plastics have been known to crack when exposed to certain chemicals and conditions. This case describes the use of ultrasound transmission gel as another ingredient that causes cracking of centrifugal assist devices made of acrylic plastic.

Acrylates↗
PubMed2000

[Clinical and experimental observation of glistening in acrylic intraocular lenses].

PURPOSE: To study whether the glistening on implanted acrylic intracular lenses increases or not. METHOD: 1. Prospective study: We studied the glistening on 49 implanted acrylic intraocular lenses, particularly the time of appearance and increase after glistening appeared. 2. EXPERIMENT: We kept an intraocular lens immersed in saline solution at 50 degrees centigrade for two hours and then moved this lens into saline solution at 35 degrees centigrade, and observed this lens during immersion. RESULTS: 1. Prospective study: Glistening was present in 28 eyes (57%), and appeared from 2 to 16 months postoperatively. A few months after appearance it become stable and did not increase further. 2. EXPERIMENT: On the 10th day after observation, we could see glistening on the lenses. The points of glistening were 10 microns or less in size, and did not change during 60 days of observation. CONCLUSION: The glistening in acrylic intraocular lenses seemed to become stable a few months after appearance. This our experimental method is useful, because it gives us glistening similar to clinical cases in a short time.

Acrylates↗
PubMed2000

Chelation in metal intoxication. XLIV: Efficacy of alpha-mercapto-beta-(5-substituted, 2-furyl) acrylic acids in mobilizing intracellularly bound cadmium in rat.

The efficacy of alpha-mercapto-beta-(2-furyl) acrylic acid (MFA), alpha-mercapto-beta-(5-sodiumsulfonate, 2-furyl) acrylic acid (MSFA) and alpha-mercapto-beta-(5-acetoxymethyl, 2-furyl) acrylic acid (MAFA) to mobilize intracellularly bound cadmium in liver and kidney was investigated in rats pre-exposed to cadmium. MFA was effective in reducing cadmium levels of hepatic and renal supernatant cytosolic fraction (SCF) while MSFA and MAFA were effective in lowering cadmium levels of renal SCF and hepatic SCF respectively. All the chelating agents also enhanced the excretion of cadmium more in feces than in urine. However, substitution on the furan ring lowered cadmium mobilizing efficacy of the parent compound, MFA. The treatment with MFA did not affect the status of endogenous zinc and copper while the treatment with MSFA and MAFA enhanced their excretion. MSFA increased hepatic and renal zinc and renal copper while MAFA increased their copper levels.

Acrylates↗
PubMedDate not supplied

An examination of the stress distribution in a soft-lined acrylic resin mandibular complete denture by finite element analysis.

PURPOSE: The aim of this study was to calculate the effect of a soft liner on stress distribution within a mandibular complete denture. Although patients have welcomed soft-lined complete dentures, early fracture is one of the main reasons for failure. To minimize and prevent prosthesis fracture, the understanding of the stress distribution within a prosthesis is important. MATERIALS AND METHODS: A 3-dimensional finite element model of a mandibular complete denture for a severely reduced residual alveolar ridge was constructed. The stress was calculated with linear static finite element analysis. The stress distribution in the soft-lined acrylic resin mandibular complete denture was compared with that of a conventional acrylic resin denture. The resulting stresses were displayed in terms of von Mises equivalent stress and the major principal stresses according to 5 different loading conditions: vertical loads in premolar, molar, and incisor regions; and oblique loads in premolar and molar regions. RESULTS: Oblique loads produced higher levels of stress in the labial notch regions than vertical loads, where tension was the primary mode of stress. Significantly reduced levels of von Mises stress were calculated in soft-liner layers under all loading conditions. Acrylic resin denture base portions, however, exhibited higher levels of von Mises stress in soft-lined complete dentures. CONCLUSION: Three-dimensional finite element analysis gave a realistic explanation of denture fractures and patient response to mandibular complete dentures with and without soft linings. Control of excess lateral occlusal contact might be helpful to reduce the probability of a fracture in soft-lined mandibular complete dentures.

Acrylic Resins↗