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Doray PG, Li D, Powers JM. Color stability of provisional restorative materials after accelerated aging. J Prosthodont 2001; 10:212-6. [PMID: 11781969 DOI: 10.1111/j.1532-849x.2001.00212.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
PURPOSE Color of 11 provisional restorative materials (4 acrylic resins and 7 resin composites) was evaluated by reflection spectrophotometry immediately after fabrication, after aging for 15 kJ/m(2), and after aging for 60 kJ/m(2) to determine relative color stability under experimental aging conditions. MATERIALS AND METHODS Specimens of provisional restorative materials were polymerized according to manufacturers' instructions and aged in an artificial aging chamber with exposure to a total ultraviolet irradiation of 60 kJ/m(2) in increments of 15 kJ/m(2). Color was measured by CIE L*a*b* on a reflection spectrophotometer before and after aging. Color change (Delta E*) was calculated and analyzed statistically by analysis of variance with repeated measures after 15 and 60 kJ/m(2) intervals of aging. RESULTS Statistically significant changes in color were observed after accelerated aging at both the initial and final aging intervals. Five of the 11 provisional materials tested showed perceptible color change (Delta E* from 3.6 to 9.3) after accelerated aging of 15 kJ/m(2). Seven of the 11 provisional materials tested showed perceptible color change (Delta E* from 3.4 to 9.4) after accelerated aging of 60 kJ/m(2). CONCLUSIONS Clinically perceptible color changes (Delta E* Delta 3.3) can be expected in some acrylic resin and composite resin provisional materials after accelerated aging.
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Kameyama A, Kawada E, Takizawa M, Oda Y, Hirai Y. Influence of different acid conditioners on the tensile bond strength of 4-META/MMA-TBB resin to Er:YAG laser-irradiated bovine dentin. THE JOURNAL OF ADHESIVE DENTISTRY 2001; 2:297-304. [PMID: 11317376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Abstract
PURPOSE This study evaluated the effect of acid conditioners on resin bonding to dentin following irradiation with an Er:YAG laser and investigated the characteristics of resin bonding to the laser-treated dentin. MATERIALS AND METHODS Extracted bovine teeth were cervically sectioned to expose a dentin surface. After polishing, the dentin was irradiated with an Er:YAG laser. Aqueous solutions of 10% citric acid (10-0) or 10% citric acid/3% ferric chloride (10-3) were then applied to the laser-treated surface as acid conditioners. After the acid treatment, a PMMA rod was bonded to the irradiated dentin using 4-META/MMA-TBB resin, and miniaturized dumbbell-shaped bonded specimens were prepared. These specimens were subjected to tensile testing, and fractured surfaces were observed with field-emission scanning electron microscopy (FE-SEM) to determine the mode of fracture. Additionally, the resin-dentin interfaces were observed under FE-SEM. RESULTS The tensile bond strength of acid-conditioned bonded specimens was lower than that of specimens not subjected to acid treatment (11.1 MPa) in the laser-irradiated group. No significant difference was observed between 10-0 and 10-3 treatments. 10-3 treatment yielded the highest bond strength (24.6 MPa) in the nonirradiated group, as opposed to only 7.7 MPa in the laser-treated group. Cohesive failure in the dentin was observed in almost all specimens in the irradiated group. Furthermore, a 10- to 30-micron-thick resin-penetrated layer was observed at the interface between the dentin and resin. CONCLUSION These results suggest that the effect of acid conditioners on resin bonding to dentin differs according to whether the dentin has been laser irradiated or not.
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Del Bel Cury AA, Rached RN, Ganzarolli SM. Microwave-cured acrylic resins and silicone-gypsum moulding technique. J Oral Rehabil 2001; 28:433-8. [PMID: 11380783 DOI: 10.1046/j.1365-2842.2001.00684.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
This study evaluated the residual monomer (RM), Knoop hardness (KHN) and transverse strength (TS) of two microwave-cured acrylic resins (Acron MC(R) (A), GC Dent. Ind. Corp., Tokyo, Japan and Onda Cryl (O), AO Classico Ltda, São Paulo, Brazil) when processed with an all-type III gypsum moulding technique (G) or a silicone-gypsum moulding technique (S). One hundred and forty four specimens were fabricated and equally distributed into four groups (AG, AS, OG and OS). The TS tests were conducted after 48 h of water storage, and KHN values were obtained after 24, 48, 72 h and 30 days. The RM was determined every 24 or 48 h over a period of 288 h. The acrylic resins were prepared and processed according to the manufacturer's directions. Both AS and OS showed the highest means (P < 0.05) for RM (microg cm-2) only after 24 h (AS = 56.84 +/- 27.39/AG = 7.51 +/- 5.75/OS = 3.59 +/- 1.60/OG = 1.02 +/- 0.3), 48 h (AS = 28.99 +/- 9.35/AG = 2.65 +/- 2.17/OS = 2.37 +/- 0.84/OG = 0.68 +/- 0.49) and 72 h (AS = 15.98 +/- 9.01/AG = 1.40 +/- 0.57/OS = 1.87 +/- 0.52/OG = 0.75 +/- 0.44). Both AS and OS showed the highest means (P < 0.02) for KH after 24 h (AS = 18.69 +/- 2.3/AG = 17.79 +/- 0.7/OS = 18.41 +/- 1.0/OG = 16.04 +/- 0.6). After 48 h the mean values for OS and OG differed significantly (P < 0.03) (OS = 18.67 +/- 0.8/OG = 16.75 +/- 0.8). No differences of KHN were found among the groups during the storage periods. The TS values for A and O were not affected by either G or S (P > 0.05). Silicone-gypsum mould technique affected the RM and KHN of the resins in the first 2 and 5 days of analysis, respectively. The type of mould did not affect TS, and the acrylic resins differed from each other for all properties regardless of the type of mould.
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Memon MS, Yunus N, Razak AA. Some mechanical properties of a highly cross-linked, microwave-polymerized, injection-molded denture base polymer. INT J PROSTHODONT 2001; 14:214-8. [PMID: 11484567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
Abstract
PURPOSE The impact strength and the flexural properties of denture base materials are of importance in predicting their clinical performance upon sudden loading. This study compares the impact and transverse strengths and the flexural modulus of three denture base polymers. MATERIALS AND METHODS The investigation included a relatively new microwave-polymerized polyurethane-based denture material processed by an injection-molding technique, a conventional microwave-polymerized denture material, and a heat-polymerized compression-molded poly(methyl methacrylate) (PMMA) denture material. Impact strength was determined using a Charpy-type impact tester. The transverse strength and the flexural modulus were assessed with a three-point bending test. The results were subjected to statistical analysis using a one-way analysis of variance and the Scheffé test for comparison. RESULTS The impact strength of the microwave-polymerized injection-molded polymer was 6.3 kl/m2, while its flexural strength was 66.2 MPa. These values were lower than those shown by the two compression-molded PMMA-based polymers. The differences were statistically significant. The flexural modulus of the new denture material was 2,832 MPa, which was higher than the conventional heat-polymerized polymer but was comparable to the other microwave-polymerized PMMA-based polymer. The difference in the flexural modulus was statistically significant. CONCLUSION In terms of the impact and flexural strengths, the new microwave-polymerized, injection-molded, polyurethane-based polymer offered no advantage over the existing heat- and microwave-polymerized PMMA-based denture base polymers. However, it has a rigidity comparable to that of the microwave-polymerized PMMA polymer.
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Wolf BH, Reitemeier BK, Schmidt AE, Richter GH, Duncan G. In vitro testing of the bond between soft materials used for maxillofacial prostheses and cast titanium. J Prosthet Dent 2001; 85:401-8. [PMID: 11319539 DOI: 10.1067/mpr.2001.114511] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
STATEMENT OF PROBLEM The choice of soft materials for maxillofacial prostheses is important for covering extraoral defects after tumor surgery or radiation therapy. The use of cast commercially pure titanium as reinforcement seems to be a suitable option. PURPOSE Making use of the advantages of titanium frameworks for maxillofacial prostheses requires exploring ways of combining it with soft materials. This study investigated such combinations and evaluated discoloration of the soft material to determine whether it was attributable to the titanium reinforcement. MATERIAL AND METHODS Five soft materials used for maxillofacial prostheses and their bond strengths to cast titanium were tested. Different ways of conditioning the titanium surface and different adhesives were used. Plain mechanical retention was also studied. The Gretag SPM 100 was used to determine the potential effects on coloring after 24 hours of radiation in the Suntest rapid exposure unit. RESULTS Suitable material combinations for bonding soft materials to titanium were found for all soft materials studied. Bond strength varied depending on the chemical basis of the soft material. Results indicated that maximal bond strengths were obtained by the combinations Supersoft with Super-Bond, Supersoft with subsequent silicoating, and bonding with Dentacolor connector. Few color shifts attributable to the titanium reinforcement were evident in the 2-mm layers of the soft materials applied. CONCLUSION The results of this study showed that it is possible to combine a titanium framework and soft silicone materials.
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Sfondrini MF, Cacciafesta V, Pistorio A, Sfondrini G. Effects of conventional and high-intensity light-curing on enamel shear bond strength of composite resin and resin-modified glass-ionomer. Am J Orthod Dentofacial Orthop 2001; 119:30-5. [PMID: 11174537 DOI: 10.1067/mod.2001.111399] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The purpose of this study was to evaluate the shear bond strengths of a composite resin (Transbond XT; 3M/Unitek, Monrovia, Calif) and a resin-modified glass ionomer (Fuji Ortho LC; GC America Inc, Alsip, Ill) cured with 2 different light-curing units: a conventional visible light unit (Ortholux XT; 3M Dental Products, St Paul, Minn) and a xenon arc light unit (Plasma Arc Curing [PAC] System; American Dental Technologies, Corpus Christi, Texas). One hundred twenty freshly extracted bovine permanent mandibular incisors were randomly divided into 1 of 8 groups; each group consisted of 15 specimens. Two groups (1 group for each type of adhesive) were exposed to the visible light for 20 seconds (Transbond XT) and 40 seconds (Fuji Ortho LC), respectively, and used as control groups. The remaining 6 groups (3 for each adhesive) were cured with the xenon arc light for 2, 5, and 10 seconds. After bonding, all samples were stored in distilled water at room temperature for 24 hours and subsequently tested in a shear mode on an Instron universal testing machine (Instron Corp, Canton, Mass). For the groups bonded with Transbond XT, no statistically significant differences (P =.868) were found between the shear bond strength of the control group cured with Ortholux XT and those of the groups cured with the PAC System for 2, 5, or 10 seconds. When the shear bond strengths of the groups bonded with Fuji Ortho LC were evaluated, no statistically significant differences (P =.087) were found between the control group that was cured with Ortholux XT and those cured with the PAC System. The bond strength of the composite resin was significantly higher than that of the resin-modified glass ionomer in all the groups tested (P <.0001). The present findings indicate that, compared with visible light-curing, the xenon arc light enables the clinician to significantly reduce the curing time of both bonding agents, without affecting their shear bond strengths. Therefore, xenon arc light sources can be recommended as an advantageous alternative for curing both composite resins and resin-modified glass ionomers.
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Odake T, Tsunoda K, Kitamori T, Sawada T. Highly sensitive and direct detection of DNA fragments using a laser-induced capillary vibration effect. ANAL SCI 2001; 17:95-8. [PMID: 11993684 DOI: 10.2116/analsci.17.95] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A pulsed laser-induced stationary wave capillary vibration detection method was applied to the sensitive detection of capillary gel electrophoresis, and the direct detection of non-labeled nucleic acids, such as DNA sequencing products, was demonstrated. An excimer laser operating at 248 nm was used as a CVL excitation source, and polynucleotides were sensitively detected without derivatization. From an investigation on the endurance of several matrixes to pulsed laser irradiation, a polyacrylamide without a cross-linker (0%C) was found to have adequate endurance, and it exhibited no serious damage during an analysis. A cytosine-terminated sequence reaction product was detected with a sensitivity close to that of laser-induced fluorometry (LIF). These results suggest the feasibility of the highly sensitive detection of ultramicro amounts of biological materials without a pre- or post-column derivatization, which has usually been required in sensitive detection procedures, such as LIF. Furthermore, the feasibility of a novel DNA sequencing method is also suggested.
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Brahmasandra SN, Ugaz VM, Burke DT, Mastroangelo CH, Burns MA. Electrophoresis in microfabricated devices using photopolymerized polyacrylamide gels and electrode-defined sample injection. Electrophoresis 2001; 22:300-11. [PMID: 11288898 DOI: 10.1002/1522-2683(200101)22:2<300::aid-elps300>3.0.co;2-f] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Microfabrication techniques have become increasingly popular in the development of the next generation of DNA analysis systems. While significant progress has been reported by many researchers, complete microfabricated integrated DNA analysis devices are still in the earliest stages of development. Most miniaturized analysis systems have incorporated noncross-linked polymer solutions as the separation medium of choice and the operation of these systems necessitates the use of high electric fields and long separation lengths. In this paper, we present two techniques that may help alleviate this problem and accelerate the development of the so-called 'lab-on-a-chip' systems. We present the use of photodefinable polyacrylamide gels as a sieving medium for DNA electrophoresis. These gels offer the significant advantages of faster curing times, locally controlled gel interface, and simpler handling over chemically polymerized gels. We also introduce an electrode-defined sample compaction and injection technique. This technique helps achieve sample compaction without migration into the gel and offers significant control over the size and application of the sample plug. The use of these technologies for double-stranded DNA separations in microfabricated separation systems is demonstrated.
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Marks LA, Verbeeck RM, De Maeyer EA, Martens LC. Effect of maturation on the fluoride release of resin-modified glass ionomer and polyacid-modified composite resin cements. Biomaterials 2000; 21:1373-8. [PMID: 10850931 DOI: 10.1016/s0142-9612(00)00026-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The effect of an early water contact on the fluoride release is studied for the resin-modified glass ionomer cements (RM-GIC) GC Lining LC, PhotacBond, Vitremer and Vitrebond and for the polyacid-modified composite resins (PAM-C) Variglass and Dyract. Six months fluoride release profiles were determined in regularly renewed water (37 degrees C), for the products directly after light curing and after 24 h maturation in a humid atmosphere (85% RH). ANOVA shows that both the short-term and the long-term fluoride release of a RM-GIC are influenced by this maturation. This indicates that direct water contact for this material should be avoided. For the RM-GIC a correlation is found between the initial fluoride release process and the long-term process. For the PAM-C materials, no differences in the fluoride release are found as a function of maturation, indicating that early water contact has no effect. The amounts of fluoride released by PAM-C are low compared to RM-GIC, which can affect their caries preventive potential. The results are explained on the basis of the setting reaction of both types of materials.
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Navarro RS, Esteves GV, Oliveira WT, Matos AB, Eduardo CP, Youssef MN, Matson E. Nd:YAG laser effects on the microleakage of composite resin restorations. JOURNAL OF CLINICAL LASER MEDICINE & SURGERY 2000; 18:75-9. [PMID: 11800106 DOI: 10.1089/clm.2000.18.75] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE This study evaluated microleakage of composite restorations submitted to marginal treatment with Nd:YAG laser and surface sealant. BACKGROUND DATA Previous studies have demonstrated that Nd:YAG-lased enamel melted and became recrystallized with a morphologic appearance similar to lava, and has been used clinically in the sealing of enamel pits and fissures. METHODS Class V cavities in enamel of human premolars were restored with composite resin (Z100, 3M) and randomly divided in six groups: G1, control; G2, surface sealant marginal treatment; G3 to G6, were treated with pulsed Nd:YAG laser (1.064 microm) marginal treatment, contact fiberoptic (300 microm), air cooling, for 30 seconds, powers of 1.2-2 W, repetition rates of 20-30 Hz, energies of 40-100 mJ. Teeth were impermeabilized, immersed in a rhodamine dye, sectioned, and evaluated under stereomicroscope microscopy with scores. RESULTS There were significant differences between marginal treatments; there were no differences between groups 1, 2, and 4, and 3,5, and 6; lower values of microleakage were at groups 3, 5, and 6 (Kruskal-Wallis,p = 0.05). CONCLUSION Nd:YAG laser showed improved marginal sealing and decreased microleakage of composite resins restorations.
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Abstract
The failure of the bond between acrylic resin teeth and denture base material remains a considerable problem. Previous research has indicated that the introduction of a bonding agent to the tooth-resin interface significantly increased the tensile bond strength. To further investigate this finding, and to complement the earlier study, a shear strength assessment was carried out. Both a commercial and an experimental bonding agent were evaluated for tooth retention when applied to heat-cured and visible light-cured (VLC) resin. A significant increase in shear bond strength was obtained when bonding agents were applied. The experimental cement gave the greatest increase in strength, although the VLC resin failed to achieve the same degree of tooth attachment as the heat-cured resin.
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162
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Bishara SE, VonWald L, Olsen ME, Laffoon JF, Jakobsen JR. Effect of light-cure time on the initial shear bond strength of a glass-ionomer adhesive. Am J Orthod Dentofacial Orthop 2000; 117:164-8. [PMID: 10672216 DOI: 10.1016/s0889-5406(00)70227-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
With the introduction of photosensitive (light-cured) restorative materials in dentistry, various methods were suggested to enhance the polymerization of these materials including layering and the use of more powerful light-curing devices. The purpose of this study was to determine the effects of increasing the light-cure time on the initial shear bond strength (in the first half hour) of a resin-modified glass-ionomer adhesive. Eighty-six teeth were divided into 4 groups according to either; (1) the adhesive system used, namely resin, reinforced glass ionomer, or composite, and (2) the light-cure time for the glass ionomer adhesive, namely 40, 45, and 50 seconds. The bonding approach followed the manufacturer's instructions unless otherwise specified. The results of the analysis of variance comparing the 4 experimental groups (F = 19.4) indicated the presence of significant differences between the groups (P =. 0001). In general, the shear bond strength was greater for the composite adhesive system (¿x(-) = 5.2 +/- 2.9 MPa), followed by the 2 groups bonded with the resin-reinforced glass-ionomer adhesive and light cured for 50 seconds (¿x(-) = 3.8 +/- 1.1 MPa) and 45 seconds (¿x(-) = 3.4 +/- 2.7 MPa). On the other hand, the shear bond strength was significantly lower for the group bonded with the glass ionomer adhesive and light cured for 40 seconds only (¿x(-) = 0.4 +/- 1.0 MPa). The present findings indicated the following: (1) the resin-reinforced glass-ionomer adhesive has a significantly lower shear bond strength in the first half hour after bonding when compared to a composite resin adhesive; (2) the initial bond strength of the glass-ionomer adhesive was significantly increased by increasing the light-cure time for an additional 5 to 10 seconds; (3) the mean increase in the shear bond strength between 5 and 10 seconds of additional light curing was not significant but the variability was less with the longer cure time.
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Lalani N, Foley TF, Voth R, Banting D, Mamandras A. Polymerization with the argon laser: curing time and shear bond strength. Angle Orthod 2000; 70:28-33. [PMID: 10730673 DOI: 10.1043/0003-3219(2000)070<0028:pwtalc>2.0.co;2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
The objective of this study was to determine the efficiency of an argon laser in polymerizing a light-cured orthodontic adhesive. Metal brackets were bonded to 185 premolars, divided into 5 different protocol groups of 37 each as follows: light 40-second buccal, light 40-second lingual, laser 5-second lingual, laser 10-second lingual, and laser 15-second lingual. All bonded specimens were placed in distilled water for 30 days at 37 degrees C followed by thermal cycling for 24 hours. Brackets were detached using a shearpeel load delivered by an Instron machine. The site of bond failure was examined under 10x magnification. The difference in the shear-peel bond strength between the light 40-second buccal (13.31 MPa) and the light 40-second lingual (11.95 MPa) groups was not statistically significant. The mean shear-peel bond strengths for the laser cured groups were quite similar for the 5-, 10- and 15-second laser groups (10.86, 11.32, and 10.80 MPa). The difference in mean lingual bond strength between the light 40-second and laser 5-second groups was not statistically significant (t = 1.26; P = .212). The adhesive remnant index analysis revealed principally cohesive bond failures. An increased frequency of enamel fractures at debond was noted in the lingual light-cured and 10-second laser-cured groups, at 35.1% (13/37) and 21.6% (8/ 37), respectively. All other groups displayed enamel fractures of 16.2% (6/37). A 5-second cure using an argon laser produced bond failure loads comparable to those obtained after 40 seconds of conventional light cure, with less than half the frequency of enamel fracture at debond.
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Gupte A, D'Souza SF. Stabilization of alginate beads using radiation polymerized polyacrylamide. JOURNAL OF BIOCHEMICAL AND BIOPHYSICAL METHODS 1999; 40:39-44. [PMID: 10481950 DOI: 10.1016/s0165-022x(99)00015-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
A technique has been described for the stabilization of calcium alginate beads using radiation polymerized acrylamide. The technique involved dropping a mixture containing the cells (20%), sodium alginate (2%), acrylamide (2.5%) and N-N'-methylene-bis-acrylamide (0.1%) through a syringe needle into cold (-75 degrees C) toluene. The frozen beads obtained were exposed to 60Co gamma-rays (0.5 KGy) and were then thawed in 0.1 M CaCl2 solution. Unlike the calcium alginate beads the conjugate beads were not found to be dissolved when incubated in 3% trisodium citrate solution. Stabilized beads containing entrapped yeast cells could be reused for over 15 batches for the inversion of sucrose without loss in activity or chemical integrity of the beads.
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Yang JM, Huang MJ, Yeh TS. Preparation of poly(acrylic acid) modified polyurethane membrane for biomaterial by UV radiation without degassing. JOURNAL OF BIOMEDICAL MATERIALS RESEARCH 1999; 45:133-9. [PMID: 10397967 DOI: 10.1002/(sici)1097-4636(199905)45:2<133::aid-jbm8>3.0.co;2-d] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Poly(acrylic acid) modified polyurethane (AA/PU) membranes were prepared by UV radiation without degassing. The chemical composition of the AA/PU membrane was studied by IR spectroscopy. In addition to those absorption peaks associated with pure PU, the absorption peak at 2400 cm-1 of poly(AA) was also found. The morphology of AA/PU membrane was studied by optical polarizing microscopy. We also measured the glass transition temperature and the decomposition temperature of the AA/PU membrane by differential scanning calorimetry and thermogravimetric analysis. A significant domain was found in the AA/PU membrane, which resulted in different glass transition temperature and decomposition temperature between AA/PU and pure PU membrane. The effect of AA content on the contact angle and water absorption of the AA/PU membrane was determined. It was found that the water content of AA/PU membrane increased with increasing AA content, whereas the contact angle decreased. By using Kaeble's equation and the contact angle data, the surface free energy of AA/PU membrane was determined. The increase of surface free energy resulted from the increase of the dispersion (gammad) term and polar (gammap) term. In order to evaluate the biocompatibility of these membranes, a cytotoxicity test and a cell adhesion and proliferation assay were conducted in cell culture. Immortal cells and primary lymphocytes were both used in this study. The results showed that these AA/PU membranes exhibited very low cytotoxicity and could support cell adhesion and growth. An animal primary test was also done in this study. It was found that the AA/PU membrane could possibly be employed in the treatment of bowel defect.
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Waaler T, Sande SA, Müller BW, Schüller Lisether G. Influence of neutron irradiation on Eudragit coated tablets: validation of neutron activation II. Eur J Pharm Sci 1999; 7:287-93. [PMID: 9971911 DOI: 10.1016/s0928-0987(98)00045-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The in vitro characteristics of enteric coated acetylsalicylic acid tablets and cores were compared before and after irradiation with thermal neutrons, 2, 4, 7 or 15 min at 1.1.1013 neutrons cm-2s-I. The irradiation procedure affected the coated formulation to a greater extent than the cores. Drug release from tablets was already affected after 2 min of exposure, whereas the cores showed no significant inhibition of release until after 15 min of irradiation, leading to the conclusion that the effects of irradiation were caused by a combination of changes both in the core and the coating. Both tablets and cores showed an increase in the disintegration time following irradiation. Scanning electron micrographs (SEM) of non-irradiated cores/tablets and cores/tablets irradiated for 15 min, showed clear differences in the structure of the surface. SEM of the tablets irradiated for 15 min, showed that the irradiation had caused the film to loosen from the core in several places. SEM of the cross-sections of both irradiated tablets and cores showed a partially melted surface above stacked layers with reduced porosity.
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Dixon DL, Breeding LC, Faler TA. Microwave disinfection of denture base materials colonized with Candida albicans. J Prosthet Dent 1999; 81:207-14. [PMID: 9922435 DOI: 10.1016/s0022-3913(99)70250-7] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
STATEMENT OF PROBLEM Infection of denture materials with Candida albicans is common and contributes to denture stomatitis. PURPOSE This 3-phase investigation examined: (1) the efficacy of microwave irradiation against C albicans colonized on 3 soft denture liners and 1 heat-polymerized denture base resin, and (2) the effect of this irradiation on the hardness of the materials tested. MATERIAL AND METHODS In phase 1, an experimental protocol was developed. Sterilized specimens from 2 denture base soft liners and 1 heat-polymerized acrylic resin denture base material (n = 45 each) were inoculated with C albicans. Two thirds of the specimens were irradiated in a 60 Hz microwave oven for 5 minutes (dry). C albicans growth was then assessed with streaked blood agar plates and thioglycollate broth. One third of the specimens were not irradiated and served as controls. Pretest and posttest Shore A hardness values were obtained and compared. For phase 2, 15 specimens from each material group were subjected to irradiation (while immersed in water) for 5 minutes; and, 15 from each material were subjected to 10- and 15-minute irradiation (dry), with subsequent sterility and change in hardness assessments completed as described in phase 1. In phase 3, 15 specimens from each material group were subjected to repeated 5-minute irradiation cycles (while immersed in water), and changes in hardness were examined. RESULTS Only the 5-minute irradiated specimens immersed in water were effectively sterilized, as verified by the thioglycollate assay. The effect of repeated 5-minute irradiation cycles resulted in a significant change in hardness of the PermaSoft specimens. CONCLUSIONS Five-minute irradiation, while immersed in water, killed all C albicans present on the materials tested; and, repeated 5-minute irradiation significantly affected the hardness of only the PermaSoft material.
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Baldock C, Rintoul L, Keevil SF, Pope JM, George GA. Fourier transform Raman spectroscopy of polyacrylamide gels (PAGs) for radiation dosimetry. Phys Med Biol 1998; 43:3617-27. [PMID: 9869036 DOI: 10.1088/0031-9155/43/12/017] [Citation(s) in RCA: 102] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Polyacrylamide gels (PAGs) are used for magnetic resonance imaging radiation dosimetry. Fourier transform (FT) Raman spectroscopy studies were undertaken to investigate cross-linking changes during the copolymerization of polyacrylamide gels in the spectral range of 200-3500 cm(-1). Vibrational bands of 1285 cm(-1) and 1256 cm(-1) were assigned to acrylamide and bis-acrylamide single CH2 deltaCH2 binding modes. Bands were found to decrease in amplitude with increasing absorbed radiation dose as a result of copolymerization. Principal component regression was performed on FT-Raman spectra of PAG samples irradiated to 50 Gy. Two components were found to be sufficient to account for 98.7% of the variance in the data. Cross validation was used to establish the absorbed radiation dose of an unknown PAG sample from the FT-Raman spectra. The calculated correlation coefficient between measured and predictive samples was 0.997 with a standard error of estimate of 0.976 and a standard error of prediction of 1.140. Results demonstrate the potential of FT-Raman spectroscopy for ionizing radiation dosimetry using polyacrylamide gels.
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169
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CARRINGTON A, STEIN G. Free radical formation and oxygen effect in irradiated polymethylmethacrylate. Nature 1998; 193:976. [PMID: 13876878 DOI: 10.1038/193976a0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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170
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Skotnicki S, Pratt MD. Occupational dermatitis to ultraviolet-cured acrylic-based inks in computer hard disc manufacturing. AMERICAN JOURNAL OF CONTACT DERMATITIS : OFFICIAL JOURNAL OF THE AMERICAN CONTACT DERMATITIS SOCIETY 1998; 9:179-81. [PMID: 9744912] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
OBJECTIVE Ultraviolet-cured acrylates and their various components and applications are reviewed in this report. METHODS A 26-year-old woman involved in silk screening computer discs with ultraviolet-cured inks developed an acute allergic contact dermatitis on her hands and forearms. Patch testing revealed a number of strong reactions to epoxy resin and many multifunctional acrylates. RESULTS The only one listed on the material safety data sheet to which she reacted was tripropyleneglycol diacrylate (TRPGDA). The other positive reactions likely represent cross-reactions. The positive reaction to epoxy is possibly relevant and attributable to nonhardened epoxy resin contaminant in the epoxy prepolymer. CONCLUSION This case report shows a new application for ultraviolet-cured acrylate based inks in computer hard disc manufacturing.
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171
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Baldock C, Burford RP, Billingham N, Wagner GS, Patval S, Badawi RD, Keevil SF. Experimental procedure for the manufacture and calibration of polyacrylamide gel (PAG) for magnetic resonance imaging (MRI) radiation dosimetry. Phys Med Biol 1998; 43:695-702. [PMID: 9533146 DOI: 10.1088/0031-9155/43/3/019] [Citation(s) in RCA: 181] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
A simple methodology for the manufacture and calibration of polyacrylamide gel (PAG) for magnetic resonance imaging (MRI) radiation dosimetry is presented to enable individuals to undertake such work in a routine clinical environment. Samples of PAG were irradiated using a linear accelerator and imaged using a 0.5 T (22 MHz) Philips Gyroscan MRI scanner. The mean spin-lattice relaxation rate was measured using a 'turbo-mixed' sequence, consisting of a series of 90 degrees pulses, each followed by acquisition of a train of spin echoes. The mean sensitivity for five different batches of PAG in the range up to 10 Gy was calculated to be 0.0285 s-1 Gy-1 for the mean spin-lattice relaxation rate with a percentage standard deviation of 1.25%. The overall reproducibility between batches was calculated to be 2.69%. This methodology, which introduces the novel use of pre-filled nitrogen vials for calibration, has been used to develop techniques for filling anatomically shaped anthropomorphic phantoms.
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172
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Phoenix RD. Introduction of a denture injection system for use with microwaveable acrylic resins. J Prosthodont 1997; 6:286-91. [PMID: 9563329 DOI: 10.1111/j.1532-849x.1997.tb00109.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Recently, an injection system for use with microwaveable denture base resins was introduced. Preliminary evaluation of this system was performed a university-based dental laboratory. This article provides a description of the complete denture fabrication technique, as well as observations regarding its design and practicality.
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173
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Gore JC, Maryanski MJ, Schulz RJ. Test objects for MRI quality assurance based on polymer gels. Med Phys 1997; 24:1405-8. [PMID: 9304568 DOI: 10.1118/1.598029] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Radiation-sensitive polymer gels have been adapted for making test objects that can be used to assess the imaging characteristics of magnetic resonance imaging (MRI) systems. The polymer gels contain acrylic monomers within a gel matrix, and when irradiated with x rays the constituents polymerize to produce highly cross-linked microparticles that dramatically affect water NMR relaxation rates where they form. The size of these effects depends on the radiation dose and composition of the mixture irradiated, while the spatial pattern of relaxation time changes can be precisely controlled by spatial modulation of the x-ray exposure. This permits the manufacture of complex test patterns free of susceptibility or edge effects, and overall image performance can be assessed by constructing contrast-detail diagrams using a singly irradiated gel containing areas of different sizes and contrasts. Polymer gels are stable and a variety of different tests objects can be constructed inexpensively. Such materials and test phantoms may find widespread application in diagnostic MRI quality assurance and testing programs.
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174
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Ewoldsen NO, Sheridan PJ, Koka S. Microwave pressure chamber processing of a denture repair polymer. J Prosthodont 1997; 6:221-4. [PMID: 9497781 DOI: 10.1111/j.1532-849x.1997.tb00096.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Most denture base repairs are made using a chemically activated acrylic resin polymer for reasons of cost and expediency. Heat-activated polymers are not typically used because they require a custom split cast gypsum mold, longer polymerization time, and higher laboratory fees. Repairs made using a chemically activated polymer compared with a heat-activated polymer generally have reduced transverse strength, poorer color stability, increased water sorption, and weak bond strength to existing acrylic resin. A method of utilizing a microwave polymer in a commercially available microwave flask is described. This technique allows denture base repairs to be made with a heat-activated polymer in a manner similar to that of chemically activated repairs.
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175
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Kurchak M, DeSantos B, Powers J, Turner D. Argon laser for light-curing adhesives. JOURNAL OF CLINICAL ORTHODONTICS : JCO 1997; 31:371-4. [PMID: 9511570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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176
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Hemmer W, Focke M, Wantke F, Götz M, Jarisch R. Allergic contact dermatitis to artificial fingernails prepared from UV light-cured acrylates. J Am Acad Dermatol 1996; 35:377-80. [PMID: 8784272 DOI: 10.1016/s0190-9622(96)90600-3] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
BACKGROUND Contact dermatitis from artificial nails made from self-curing acrylic resins is occasionally reported. Recently, UV light-cured products introducing new acrylics have become available. OBJECTIVE Our purpose was to identify relevant allergens in commercial light-curing products by patch tests and to evaluate the efficacy of "hypoallergenic" products by inclusion into the test series. METHODS Patients wearing photobonded acrylic nails who had perionychial and subonychial eczema were patch tested with an acrylate battery and "hypoallergenic" commercial products. RESULTS Triethyleneglycol dimethacrylate, hydroxyfunctional methacrylates, and (meth)-acrylated urethanes proved to be relevant allergens in photobonded nail preparations. Methacrylated epoxy resin sensitization was not observed. All "hypoallergenic" products provoked positive reactions. CONCLUSION The omission of irritant methacrylic acid in UV-curable products does not reduce the high sensitizing potential of new acrylates. In contrast to the manufacturers' declarations, all "hypoallergenic" products continue to include acrylate functional monomers and therefore continue to cause allergic sensitization.
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177
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Liberman R, Combe EC, Piddock V, Watts DC. Colour changes in acrylic teeth--comparison of an objective and subjective method. J Oral Rehabil 1996; 23:464-9. [PMID: 8814561 DOI: 10.1111/j.1365-2842.1996.tb00880.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Colour changes in four currently used brands of acrylic dental teeth were measured objectively and assessed subjectively following the application of heat, acrylic monomer and light. The data indicated that no clear correlation existed between the results of visual inspection and opto-electronic measurements. It is suggested that visual assessment is an unreliable method of detecting colour change, and an objective colorimetric method is therefore recommended.
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178
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Kuzuya M, Ishikawa M, Noguchi T, Niwa J, Kondo S. A new drug delivery system using plasma-irradiated pharmaceutical aids. VI. Controlled release of theophylline from plasma-irradiated double-compressed tablet composed of water-soluble polymers as a wall material. Chem Pharm Bull (Tokyo) 1996; 44:192-5. [PMID: 8582038 DOI: 10.1248/cpb.44.192] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The rapid drug release from a double-compressed tablet containing theophylline with the water-soluble polymer polymethacrylic acid (PMAA) or polyacrylamide (PAAm) used as a wall material can be suppressed by argon plasma irradiation and changed into the slow release due to a decrease in the solubility of water-soluble polymers used as the outer layer. This report is the first to deal with an attempt to control the release of drugs by controlling polymer solubility, and to fabricate a completely soluble controlled release type of drug delivery system (DDS) making use of plasma processing.
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179
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Abstract
The quality of visible-light-cured composites depends on the capability of the light source to properly polymerize the material within a specified exposure time. In this study, the degree of conversion of different composite materials (hybrid and microfilled) of light and dark shades was compared after illumination by a standard curing unit and pulsed laser (lambda=468) respectively. The degree of conversion was measured by Fourier transform infrared spectroscopy. Results obtained by the analysis of the pulsed laser-induced polymerization were significantly higher for all the materials and shades observed. All values of the degree of conversion were lower for dark shades of all types of composites, regardless of the photopolymerization technique used. Besides the surface, better polymerization was recorded also at depths of 1.0, 2.0 and 3.0 mm, respectively. These values varied from 59.7%+/-2.14 to 84.5%+/-0.33 for pulsed laser (including all depths) caused by the saturation effect induced by high power laser pulses and from 42.7%+/-1.48 to 74.7%+/-0.99 for standard polymerization.
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180
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Eliades T, Eliades G, Brantley WA, Johnston WM. Polymerization efficiency of chemically cured and visible light-cured orthodontic adhesives: degree of cure. Am J Orthod Dentofacial Orthop 1995; 108:294-301. [PMID: 7661147 DOI: 10.1016/s0889-5406(95)70024-2] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The use of light-cured orthodontic adhesives in combination with the new generation of ceramic brackets has become popular from an esthetic standpoint. The purpose of this article was to evaluate the degree of cure (DC) of selected light-cured and chemically cured adhesives bonded to ceramic and stainless steel brackets. The optical properties of eight types of brackets (single-crystal alumina, polycrystalline alumina, polycrystalline allumina with polycarbonate base, and stainless steel) were evaluated by diffuse visible light transmittance spectroscopic analysis. The degree of cure (DC) of a visible light-cured orthodontic adhesive bonded to these brackets under direct (20 seconds through the bracket) and indirect (2 x 10 seconds from the incisal and cervical edges of the bracket) irradiation was measured by micro-MIR FTIR spectroscopy. Brackets bonded to a chemically cured, two-paste orthodontic adhesive were used as a control group. According to the results the single-crystal alumina brackets showed the highest diffuse transmittance values at 468 nm followed by polycrystalline alumina and polycarbonate-base alumina types. Direct irradiation resulted in low DC values that were strongly correlated to the diffuse transmittance measurements at 468 nm (r = 0.73, p < 0.05). Indirect irradiation manifested significantly higher DC values than direct irradiation in the stainless steel bracket group, which yielded values comparable to those found in some indirectly irradiated polycrystalline bracket groups.
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181
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Thomas CJ, Webb BC. Microwaving of acrylic resin dentures. THE EUROPEAN JOURNAL OF PROSTHODONTICS AND RESTORATIVE DENTISTRY 1995; 3:179-82. [PMID: 8601161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Denture hygiene is an important factor in the treatment of denture stomatitis. Sterilization of dentures by microwaves has been recommended, but using specialized equipment not available to the average person. This study tests the effect of microwaving on the dimensional stability of dentures (in an unmodified domestic microwave oven). After microwaving (10 mins at 604 W) some measurements showed significant contraction or expansion but reduced exposure (6 mins at 331 W) caused much smaller changes. The dimensional changes are inexplicable but at lower radiation are considered to be harmless.
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182
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Williamson DL, Boyer DB, Aquilino SA, Leary JM. Effect of polyethylene fiber reinforcement on the strength of denture base resins polymerized by microwave energy. J Prosthet Dent 1994; 72:635-8. [PMID: 7853261 DOI: 10.1016/0022-3913(94)90296-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
This study investigated the effect of addition of polyethylene fibers on the transverse strength, deflection, and elastic modulus of two denture base acrylic resins polymerized by microwave irradiation. Specimens of each resin, Lucitone 199 and Acron MC, were fabricated with 0.0%, 0.5%, 1.5%, and 3.0% fiber loading. Specimens were tested with use of a three-point flexure apparatus with an Instron universal testing machine after storage in water for 10 days at 37 degrees C. The results showed that polyethylene fibers significantly decreased the transverse strength of Acron MC resin and slightly increased the transverse strength of Lucitone 199 resin at a loading of 0.5% by weight. Fiber loading did not significantly affect the deflection and the elastic modulus of either material.
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183
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Pilo R, Brosh T, Lugassy H, Baharav H, Helft M. The effect of irradiation time on the shear strength of composites. Dent Mater 1994; 10:338-42. [PMID: 7498596 DOI: 10.1016/0109-5641(94)90056-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
OBJECTIVES The purpose of this study was to determine the shear strength of composites at a specific depth by a double shear test and to relate it to irradiation time. METHODS Aluminum molds filled with three different composites were irradiated for the manufacturer's recommended time, as well as for three longer and two shorter times. Fifteen cylindrical specimens were prepared for each combination of material and exposure time and subjected to a double shear test based on the principle of rivets connecting various structural members. The shear planes were symmetrically located 1.5 mm from both outer surfaces. RESULTS Shear strength vs. irradiation time was directly but nonlinearly related. All test materials attained a maximum shear strength value which was not exceeded by a further increase of the exposure time. Maximum values obtained were 42.5 MPa for Heliomolar (Vivadent) and Durafill (Kulzer) and 66.9 MPa for P-50 (3M). Only the shear strengths using the shortest light activation time were significantly different for each product. SIGNIFICANCE Shear strength of composites at a specific depth is a function of the combination of light energy and the attenuating power of the specific material. A double shear test might serve as an adjunct to microhardness in determining the extent of cure of composites at a specific depth. The advantage of this testing is the extra information to be gathered regarding the ability of composites to withstand internal stresses at a predetermined distance.
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184
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Tsuchiya H, Yamada K, Akagiri M, Tajima K, Miyazaki T, Takagi N, Itoh U, Sato M. Effect of an ultraviolet light-activated coating material on reduction of the leaching of methyl methacrylate and formaldehyde from denture acrylic resins. Dent Mater J 1993; 12:253-8. [PMID: 8004921 DOI: 10.4012/dmj.12.253] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Effect of glazing with an ultraviolet light-activated coating material on reduction of the leaching of methyl methacrylate and formaldehyde from denture acrylic resins was quantitatively evaluated. Disks prepared from auto-polymerized resins were painted with the material and radiated with ultraviolet light. The disks were immersed in artificial saliva and the concentrations of methyl methacrylate and formaldehyde leached were determined by high-performance liquid chromatography and flow injection analysis. Compared to untreated controls, the glaze significantly decreased concentrations of both leachable substances. Treatment with an ultraviolet light-activated coating material is effective in suppressing the leaching of methyl methacrylate and formaldehyde from acrylic resins as well as in smoothing the denture surfaces.
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185
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Curtis PM, Farman AG, von Fraunhofer JA. Effects of gamma radiation on the in vitro wear of composite restorative materials. J Dent 1991; 19:241-4. [PMID: 1838557 DOI: 10.1016/0300-5712(91)90126-j] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The effects of gamma radiation at therapeutic dosage levels on the wear of three anterior (two light-cured and one autocured) composites and a light-cured posterior composite were studied in vitro. Specimens were subjected to successive sets of 100 abrades to a maximum of 500 abrades on a reciprocating arm abrader, with the dimensional change being recorded between the sets of abrades. The data showed that there were no significant effects on the wear rates of any of the materials tested. The rate of height loss was similar for the two hybrid composites tested (P less than 0.05), as was that for the microfilled and conventional material (P less than 0.05). There was, however, a significant difference (P greater than 0.001) in the wear behaviour between the two groups.
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186
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Brugmans MJ, Kemper J, Gijsbers GH, van der Meulen FW, van Gemert MJ. Temperature response of biological materials to pulsed non-ablative CO2 laser irradiation. Lasers Surg Med Suppl 1991; 11:587-94. [PMID: 1753852 DOI: 10.1002/lsm.1900110614] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
This paper presents surface temperature responses of various tissue phantoms and in vitro and in vivo biological materials in air to non-ablative pulsed CO2 laser irradiation, measured with a thermocamera. We studied cooling off behavior of the materials after a laser pulse, to come to an understanding of heat accumulation and related thermal damage during (super) pulsed CO2 laser irradiation. The experiments show a very slow decay of temperatures in the longer time regime. This behavior is well predicted by a simple model for one-dimensional heat flow that considers the CO2 laser radiation as producing a heat flux on the material surface. The critical pulse repetition frequency for which temperature accumulation is sufficiently low is estimated at about 5 Hz. Although we have not investigated the ablative situation, our results suggest that very low pulse frequencies in microsurgical procedures may be recommended.
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187
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Tanzi MC, Sket I, Gatti AM, Monari E. Physical characterization of acrylic bone cement cured with new accelerator systems. CLINICAL MATERIALS 1990; 8:131-6. [PMID: 10149162 DOI: 10.1016/0267-6605(91)90021-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
In the attempt to substitute dimethyl-p-toluidine (DMPT), a toxic tertiary aryl-amine accelerator, into the formulation of acrylic cements, less toxic accelerator systems are developed. These systems consist of benzoyl peroxide (BPO) and unsaturated tertiary-aryl-amines, such as acryloyl- (ANP) and methacryloyl-(MNP) N-phenylpiperazine, which can be chemically incorporated in the polymerizing resin or, at least, result in less leaching from cured materials. In this work compressive mechanical properties and ageing tests for colour stability of acrylic cement cured with BPO and ANP or MNP have been considered. For compressive tests, cylindrical specimens were cured with BPO and equivalent molecular amounts of DMPT, ANP and MNP. Compressive yield stress (sigma y), strain at yield (epsilon y, %) and elastic modulus (E) gave very similar results for samples cured with DMPT and ANP, and slightly lower results for samples cured with MNP. In colour stability tests, the samples (disks of 1.5 cm diameter) were exposed to UV light at different irradiation times (up to 42 h). The evaluation of the colour change was performed with a digital analyser for images, and observed under scanning electron microscopy. From the obtained results, ANP appeared to be the best candidate as accelerator in the preparation of biomedical acrylic resins and composites.
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188
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Ryl'tsev VV, Virnik RV, Plekhanova NI, Filatov VN. [The action of gamma irradiation on trypsin immobilized on a modified polypropylene textile material]. RADIOBIOLOGIIA 1989; 29:425-7. [PMID: 2548228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
In studying the proteolytic activity and ESR spectra of gamma-irradiated samples of trypsin immobilized at an inoculated copolymer of polypropylene with polyacrylic acid it was established that the carrier of a modified polypropylene increases the radioresistance of trypsin immobilized on it.
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189
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al Doori D, Huggett R, Bates JF, Brooks SC. A comparison of denture base acrylic resins polymerised by microwave irradiation and by conventional water bath curing systems. Dent Mater 1988; 4:25-32. [PMID: 3267600 DOI: 10.1016/s0109-5641(88)80084-8] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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190
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Shterenberg AK, Pavlenko AV. [Causes of structural and color changes in acrylic plastics used in fixed dentures]. STOMATOLOGIIA 1988; 67:54-6. [PMID: 3163198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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191
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Szabó G, Stafford GD, Huggett R. Some mechanical properties of denture-base polymers treated with an ultraviolet light-activated coating material. J Dent 1987; 15:261-5. [PMID: 3480909 DOI: 10.1016/0300-5712(87)90051-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
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192
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Szabó G, Stafford D, Huggett R. Effect of an ultraviolet light-activated coating on the indentation resistance of some denture base polymers. QUINTESSENCE OF DENTAL TECHNOLOGY 1986; 10:523-7. [PMID: 3464045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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193
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Rietschel RL. Contact allergens in ultraviolet-cured acrylic resin systems. OCCUPATIONAL MEDICINE (PHILADELPHIA, PA.) 1986; 1:301-6. [PMID: 2956711] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Ultraviolet-cured acrylic resin systems expose the worker to an ultraviolet reactive prepolymer, multifunctional acrylate esters, and a photoinitiator system. Irritation occurs primarily with exposure to the acrylate compounds and increases with an increased number of acrylic double bonds, decreased viscosity, and the presence of hydrophilic groups. It is recommended that sensitive individuals handle these materials with nitrile gloves, but acrylics have been known to penetrate even this form of protection.
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194
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Cook WD, Chong MP. Colour stability and visual perception of dimethacrylate based dental composite resins. Biomaterials 1985; 6:257-64. [PMID: 4052538 DOI: 10.1016/0142-9612(85)90022-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The spectrophotometric method of colour measurement was applied to an investigation of the colour stability of dimethacrylate based composite resins exposed to thermal and photochemical aging. A good correlation was observed between visual perception of colour change and the spectrophotometric colour difference [delta E (FMC-2)] of unexposed and aged specimens, but 50% of the observers considered the colour match of two specimens to be clinically unacceptable when the colour difference exceeded 10.6. Kinetic studies of thermally and photochemically induced colour change showed a sigmoidal dependence of colour change on the logarithm of exposure time. Because the direction and magnitude of the colour change differed for the two procedures, it would appear that different mechanisms are involved.
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195
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Ziomek E, Martin WG, Williams RE. Immobilization of isolated and cellular hydrogenase of D. desulfuricans in radiation-polymerized polyacrylamides. Appl Biochem Biotechnol 1984; 9:57-64. [PMID: 6383215 DOI: 10.1007/bf02798374] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Purified hydrogenase from Desulfovibrio desulfuricans was immobilized either by entrapment or absorption onto porous neutral and charged acrylamide beads. Surface absorption and crosslinking on the beads resulted in a high hydrogenase activity and a good immobilization coefficient compared to the enzyme and whole cells entrapped in the same matrix. Maximum enzyme activity (citrate-phosphate buffer) was shifted to pH 6.5 upon immobilization in contrast to 6.0 for the free enzyme and the range of 6-7 for whole cells. Both the purified enzyme and whole cells were most active when held in neutral matrices. Immobilization improved the temperature stability (65 degrees C) and long term storage (4 degrees C) of the hydrogenase activity of both the purified enzyme and whole cells.
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196
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Kimura H, Teraoka F, Ohnishi H, Saito T, Yato M. Applications of microwave for dental technique (part 1). Dough-forming and curing of acrylic resins. THE JOURNAL OF OSAKA UNIVERSITY DENTAL SCHOOL 1983; 23:43-49. [PMID: 6374082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
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197
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Dzhalilov KR, Kilichev S, Karimov A, Zufarov SA, Musaev UN. [Effect of gamma radiation on the properties of polymeric base materials used in stomatology]. STOMATOLOGIIA 1980; 59:87-8. [PMID: 6931446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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198
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Reinhardt KJ, Vahl J. [Residual monomer content and water absorption of UV-polymerizable adhesives and filling polymers]. DEUTSCHE ZAHNARZTLICHE ZEITSCHRIFT 1980; 35:564-70. [PMID: 6935028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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199
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Yoshida M, Kumakura M, Kaetsu I. Controlled drug dissolution by radiation-induced polymerization in the presence of dimethylaminoethyl methacrylate-methyl methacrylate copolymer or methacrylic acid-methyl acrylate copolymer. J Pharm Sci 1979; 68:860-2. [PMID: 458603 DOI: 10.1002/jps.2600680719] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Polymer-containing tablet preparation was studied using radiation-induced polymerization of glass-forming monomers at low temperatures in the presence of dimethylaminoethyl methacrylate-methyl methacrylate copolymer or methyl acrylate-methacrylic acid copolymer. Drug dissolution from tablets was in the pH 3.0-8.0 range. A copolymer contained in the tablets dissolved in the dissolution medium at a specific pH. Drug dissolution from tablets took place rapidly at pH greater than 6.0 in the presence of methyl acrylate-methacrylic acid copolymer and at pH less than 5.0 in the presence of dimethylaminoethyl methacrylate-methyl methacrylate copolymer. The polymers had fibrous or capillary pore structures in contrast to the spherical pore structures formed in the presence of polyethylene glycol 600.
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200
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Salako NO, Cruickshanks-Boyd DW. Curing depths of materials polymerised by ultra-violet light. Br Dent J 1979; 146:375-9. [PMID: 287491 DOI: 10.1038/sj.bdj.4804262] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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