This study investigated the effect of intermittent polymerization on the rate of polymerization shrinkage and cuspal deflection in composite resins. The linear polymerization shrinkage of each composite was measured using the custom-made linometer along with the light shutter specially devised to block the light at the previously determined interval. Samples were divided into 4 groups by light curing method; Group 1) continuous light (60s with light on); Group 2) intermittent light (cycles of 3s with 2s light on & 1s with light off for 90s); Group 3) intermittent light (cycles of 2s with 1s light on & 1s with light off for 120s); Group 4) intermittent light (cycles of 3s with 1s light on & 2s with light off for 180s). The amount of linear polymerization shrinkage was measured and its maximum rate (Rmax) and peak time (PT) in the first 15 seconds were calculated. For the measurement of cuspal deflection of teeth, MOD cavities were prepared in 10 extracted maxillary premolars. Reduction in the intercuspal distance was measured by the custom-made cuspal deflection measuring machine. ANOVA analysis was used for the comparison of the light curing groups and t-test was used to determine significant difference between the composite resins. Pyramid showed the greater amount of polymerization shrinkage than Heliomolar (p < 0.05). There was no significant difference in the linear polymerization shrinkage among the groups. The Rmax was group 4 < 3, 2 < 1 in Heliomolar and group 3 < 4 < 2, 1 in Pyramid (p < 0.05). Pyramid demonstrated greater cuspal deflection than Heliomolar. The cuspal deflection in Heliomolar was group 4 < 3 < 2, 1 and group 4, 3 < 2, 1 in Pyramid (p < 0.05). It was concluded that the reduced rate of polymerization shrinkage by intermittent polymerization can help to decrease the cuspal deflection.
Acrylic Resins ; Bicuspid ; Composite Resins ; Light ; Polymerization ; Polymers ; Polyurethanes ; Tooth

Dental composite resin is a kind of material which has been widely used in dental restoration. Research has found that the influence of residual monomer on the material mechanical, chemical and biological properties cannot be ignored. This paper elaborates these harms of residual monomers. The effects of resin matrix, inorganic filler and initiating system, illumination, secondarily treatment on the degree of conversion were also analyzed. The paper also discusses the effective measures to increase the conversion, and offers theoretical basis for the clinical application and development of composite resin.
Acrylic Resins ; Composite Resins ; Humans ; Light ; Polymers ; Polyurethanes

The purpose of this study was to evaluate the effect of thickness, filling methods and curing methods on the polymerization of dual cured core materials by means of microhardness test. Two dual cured core materials, MultiCore Flow (Ivoclar Vivadent AG, Schaan, Liechtenstein) and Bis-Core (Bisco Inc., Schaumburg, IL, USA) were used in this study. 2 mm (bulky filled), 4 mm (bulky filled), 6 mm (bulky and incrementally filled) and 8 mm (bulky and incrementally filled)-thickness specimens were prepared with light cure or self cure mode. After storage at 37degrees C for 24 hours, the Knoop hardness values (KHN) of top and bottom surfaces were measured and the microhardness ratio of top and bottom surfaces was calculated. The data were analyzed using one-way ANOVA and Scheffe multiple comparison test, with alpha = 0.05. The effect of thickness on the polymerization of dual cured composites showed material specific results. In 2, 4 and 6 mm groups, the KHN of two materials were not affected by thickness. However, in 8 mm group of MultiCore Flow, the KHN of the bottom surface was lower than those of other groups (p < 0.05). The effect of filling methods on the polymerization of dual cured composites was different by their thickness or materials. In 6 mm thickness, there was no significant difference between bulk and incremental filling groups. In 8 mm thickness, Bis-Core showed no significant difference between groups. However, in MultiCore Flow, the microhardness ratio of bulk filling group was lower than that of incremental filling group (p < 0.05). The effect of curing methods on the polymerization of dual cured composites showed material specific results. In Bis-Core, the KHN of dual cured group were higher than those of self cured group at both surfaces (p < 0.05). However, in MultiCore Flow, the results were not similar at both surfaces. At the top surface, dual cured group showed higher KHN than that of self cured group (p < 0.05). However, in the bottom surface, dual cured group showed lower value than that of self cured group (p < 0.05).
Acrylic Resins ; Composite Resins ; Hardness ; Light ; Methacrylates ; Polymerization ; Polymers ; Polyurethanes

PURPOSE: The aim of this in vitro study was to examine the curing efficiency of various resin-based materials polymerized through ceramic restorations with 3 different thicknesses. Curing efficiency was evaluated by determining the surface microhardness (VHN) of the resin specimens. MATERIALS AND METHODS: Four kinds of resin materials were used. Z350 (3M ESPE Filtek(TM) Z350: A2 Shade), Z250 (3M ESPE Filtek(TM) Z250: A2 Shade) and Variolink(R) II (VL: Ivoclar vivadent, base: transparent) either with or without a self-curing catalyst (VLC: Ivoclar vivadent, catalyst: low viscosity/transparent) were filled into the silicone mold (10 mm diameter, 1 mm thick). They were cured through ceramic discs (IPS e.max Press MO-0 ingot ivoclar vivadent, 10 mm diameter, 0.5, 1 and 2 mm thicknesses) by LED light-curing units for 20 and 40 seconds. Vicker's microhardness numbers (VHNs) were measured on the bottom surfaces by a microhardness tester. Data were analyzed using a 3- way analysis of variance (ANOVA) at a significance level of 0.05. RESULTS: The thickness of ceramic disc increased, the VHNs of all four resin types were decreased (P<.05). The mean VHN values of the resins light cured for 40 seconds were significantly higher than that of LED for 20 seconds in all four resin materials (P<.05). VLC showed significantly higher VHN values than VL regardless of other conditions (P<.05). Z350 and Z250 showed higher values than VL or VLC (P<.01). CONCLUSION: Thinner ceramic disc with increased curing time resulted higher VHN values of all resin materials. The use of a catalyst produced a greater hardness with all polymerization methods. Restorative resin materials (Z350, Z250) showed higher VHN values than resin cement materials (VL, VLC).
Acrylic Resins ; Ceramics ; Composite Resins ; Fungi ; Hardness ; Light ; Polymerization ; Polymers ; Polyurethanes ; Resin Cements ; Silicones ; Waxes

Linear polymers have been commonly used as dental composite. However the aim of this work is to use hyperbranched polymer in an attempt to produce dental composite. The reason is because the dendritic molecules have shown low viscosity at higher molecular weight compared to the linear counterparts. Therefore, this work attempts to substitute the linear polymer with as much of hyperbranched polymer in the dental composite that would pass the required ISO 4049:1998(E) "Dentistry - Resin-based filling material". Several formulations of dental composites were used, i.e. combinations of linear-linear and linear-hyperbranched polymers for comparison. Following this, physical and mechanical characterisation were conducted based on the ISO standards such as water sorption and water solubility. Other characterisation such as polymerisation shrinkage and Vickers hardness were also evaluated. It was found that different types of resins give different physical and mechanical properties. The maximum achievable hyperbranched polymer, which passes the required ISO standard, that can be incorporated in the linear polymer to form dental composite is 43% wt.
Acrylic Resins/*standards ; Biomechanics ; Composite Resins/*standards ; *Materials Testing ; Polymers/*standards ; Polyurethanes/*standards ; Reference Standards

Membrane separation, as an efficient and green technology, has found more and more research and development reports in the separation and purification of the effective parts and components of traditional Chinese medicine. The basic principle and mechanism was first described in this paper, and the applicability and technological advantage was analyzed accordingly. Then, the separation performance of commonly employed membrane materials including polymeric materials such as polysulfones, cellulose acetate, polyacrylonitrile as well as inorganic materials was compared out and the application examples were presented. Finally, the major considerations in choosing the membrane materials were tentatively listed, including the physical and chemical stability, the flux and selectivity, membrane fouling, and pretreatment of membrane surface.
Acrylic Resins ; Cellulose ; analogs & derivatives ; Drugs, Chinese Herbal ; isolation & purification ; Membranes, Artificial ; Polymers ; Technology, Pharmaceutical ; instrumentation ; methods

BACKGROUND/AIMS: Endoscopic variceal ligation(EVL) is a method to manage esophageal varices bleeding and induces mechanical ligation and strangulation of varices by using elastic O-rings. The lower complication rate seen with EVL compared to sclerotherapy can be explained by the more limited degree of local tissue injury induced by EVL. Only the mucosal and submucosal layers are aspirated into cylinder attachment of the ligating devices, thus limiting injury to these layers. But, sometimes band induced ulcer shows massive bleeding. In these cases, endoscopic therapy is very difficult. This study was performed in order to find out the effectiveness of Histoacryl ingection for band-induced esophageal ulcer bleeding, METHODS: We tried to control band-induced bleeding by injecting Histoacryl in 8 cases of band-induced ulcer bleeding. RESULTS: This therapeutic trials show exellent control of bleeding in all cases without rebleeding. CONCLUSIONS: The cyanoacrylate tissue adhesive Histoacryl(N-butyl-2-cyanoacrylate) is a remarkable substance that transforms from its original liquid state into a solid state when mixed with a physiologic medium such as blood. Histoacryl undergoes an instantaneous polymerization reaction and hardens, thereby plugging the varix or bleeding vessel lumen. Rapid hemostasis of an active bleeding occurs and rebleeding of the treated lesion is prevented. We found out that Histoacryl injection is a safe and effective treatment for band-induced ulcer bleeding.
Cyanoacrylates ; Enbucrilate* ; Esophageal and Gastric Varices ; Esophagus* ; Hemorrhage* ; Hemostasis ; Intestines* ; Ligation ; Polymerization ; Polymers ; Sclerotherapy ; Stomach* ; Tissue Adhesives ; Ulcer* ; Varicose Veins

OBJECTIVE: To determine the bonding strength of 2-octyl cyanoacrylate (Dermabond) compared with N-Butyl-2-cyanoacrylate (Histoacryl) and nylon 10-0 (Alcon,) in sealing experimentally induced corneal perforations in cadaver porcine eyes. METHODS: This is a single-blind, randomized, physical experimental study involving 78 freshly enucleated porcine eyes in which perforations of 3.0 and 5.1 mm were made in the cornea and randomly sealed with either interrupted nylon 10-0 (n=13), Dermabond (n=13), or Histoacryl (n=13). Intraocular pressures were raised by injecting normal saline into the anterior chamber and postsealing leaking pressures were measured using a precalibrated manometer attached to the anterior chamber maintainer. Fishers Exact Test was used to determine the difference in proportion of eyes that leaked, and Wilcoxon signed ranked test to compare the mean leaking pressures. RESULTS: In the 3.0 mm group, the proportion of eyes that leaked in Dermabond (2/13, 15.4 percent) and Histoacryl (1/13, 7.7 percent) were comparable (p=1.00). Proportion of leak in nylon 10-0 (13/13, 100 percent) was significantly higher (p0.001). Mean leaking pressures of Dermabond (79.5 mm Hg) and Histoacryl (88.0 mm Hg) were higher compared with that of nylon 10-0 (61.44 mm Hg) (p 0.05). In the 5.1 mm group, proportion of eyes that leaked in Dermabond (4/13, 30.8 percent) and Histoacryl (2/13, 15.4 percent) were comparable (p=0.07 AND P=0.10). CONCLUSION: The bonding strengths of Dermabond and Histoacryl are comparable and greater than that of nylon 10-0. Both are effective for 3.0 mm and 5.1 mm corneal perforations.
Animal ; CYANOACRYLATES ; ENBUCRILATE ; CORNEAL PERFORATION

The purpose of this study was to investigate the physical effect of tissue conditioner on polymerized acrylic resins. Surface hardness and transverse strength were measured for evaluating physical effect of tissue conditioner on polymerized acrylic resins. 1) To measured surface hardness, the resin specimens(65x10x10mm size) of each resin material were made, applied tissue conditioner, stored in 37degrees C water for 1week, and changed tissue conditioner every week for 3 weeks. Surface hardness was measured every week with Shore hardness tester for 4 weeks. 2) To measured transverse strength, the resin specimens(65x10x3mm size & 65x10x1.5mm) of each resin material were made. The specimens were divided into four groups, and measured by universial testing machine. Group I (control group) : The resin specimens were stored in 37degrees C water for 5 weeks. Group II : The resin specimens were stored in 37degrees C water for 5 weeks, and relined in 1.5mm thickness with same resin. Group III : The resin specimens were stored in 37degrees C water for 1 week, applied tissue conditioner in 1.5mm thickness, stored in 37degrees C water for 1 week, changed tissue conditioner and water every week for 3 weeks, removed tissue conditioner, reduced 1.5mm thickness from resin surface which was applied tissue conditioner, and relined in 1.5mm thickness with same resin. The following conclusions were obtained : 1. Surface hardness changes of Vertex RS and Vertex SC were not different significantly (p>0.01). 2. Surface hardness of K-33, Tokuso rebase, and Kooliner were decreased (p<0.01). 3. With the exception of Kooliner, transverse strength of all resin materials between control group and groups which applied with tissue conditioner were not different significantly (p>0.01).
Acrylic Resins* ; Hardness ; Hardness Tests ; Polymers* ; Water

Five kinds of pore-forming agents, including PEG-400, chitosan, the polymer of chitosan and glutin, CaCO3 and NazCO3, were used in this experiment to prepare fast responsive and pH sensitive Polyacrylic acid (PAAc) gel which could be used as the material of punctum plug. The mechanism and effects of pore-forming agents on PAAc gel were studied; besides, the experiment also assessed the effects of the three most effective pore-forming agents on gel's water retention and swelling rate. The results showed that the most suitable dose levels of PEG-400, the polymer and Na2CO3 were 1 ml, 0.8 ml and 1 ml respectively, and PEG-400 was most effective with the same dosage; the gel with PEG-400 as pore-forming agent could finish more than 95% of the swelling process in just 5 minutes, it is suitable for use as punctum plug material.
Acrylic Resins ; chemistry ; Carbonates ; chemistry ; Chitosan ; chemistry ; Hydrogels ; chemical synthesis ; chemistry ; Hydrogen-Ion Concentration ; Ophthalmic Solutions ; chemical synthesis ; chemistry ; Polyethylene Glycols ; chemistry ; Polymers ; Porosity