Post-polymerization Treatment Research Articles

Impact of CAD/CAM Material Thickness and Translucency on the Polymerization of Dual-Cure Resin Cement in Endocrowns.

The objective of this study is to evaluate the impact of the thickness and translucency of various computer-aided design/computer-aided manufacturing (CAD/CAM) materials on the polymerization of dual-cure resin cement in endocrown restorations. Three commercially available CAD/CAM materials-lithium disilicate glass (e.max CAD), resin composite (CERASMART), and a polymer-infiltrated ceramic network (ENAMIC)-were cut into plates with five different thicknesses (1.5, 3.5, 5.5, 7.5, and 9.5 mm) in both high-translucency (HT) and low-translucency (LT) grades. Panavia V5, a commercial dual-cure resin cement, was polymerized through each plate by light irradiation. Post-polymerization treatment was performed by aging at 37 °C for 24 h under light-shielding conditions. The degree of conversion and Vickers hardness measurements were used to characterize the polymerization of the cement. The findings revealed a significant decrease in both the degree of conversion and Vickers hardness with increasing thickness across all CAD/CAM materials. Notably, while the differences in the degree of conversion and Vickers hardness between the HT and LT grades of each material were significant immediately after photoirradiation, these differences became smaller after post-polymerization treatment. Significant differences were observed between samples with a 1.5 mm thickness (conventional crowns) and those with a 5.5 mm or greater thickness (endocrowns), even after post-polymerization treatment. These results suggest that dual-cure resin cement in endocrown restorations undergoes insufficient polymerization.

МETHODS OF POST-POLYMERIZATION PROCESSING OF BASES IN REMOVABLE DENTURES IN ORDER TO REDUCE THE QUANTITY OF RESIDUAL MONOMER

The purpose of this study was to assess the effect of post-polymerization treatment on the quantity of methyl methacrylate released into water from polymethyl methacrylate base samples of materials subjected to different procedures.
 Materials and methods. For each technique, 10 samples in the form of a square with a side of 50 mm and a thickness of 5.0 mm were made for the base materials VBPLP, ABPHT, BPHT in accordance with the manufacturers' instructions. Five different procedures for reducing the amount of residual monomer of polished base plastics samples were studied, namely: controlled vacuuming in water at 60-80°C for 10 minutes (A), immersion in an ethanol solution at a temperature of 55°C for 10 minutes (B), ultrasonic treatment at 40 kHz for 5 minutes in distilled water (C), immersion in distilled water for 24 hours (D), boiling in water for 3 hours (E), control samples without post-polymerization treatment (F).
 Following the implementation of procedures for minimizing residual monomer levels in the studied samples, they were placed in individual containers containing 10 ml of distilled water for 12 hours at a temperature of 37°C. The quantification of water-eluted MMA was conducted through liquid chromatography.
 Results. Of the 180 measurements performed, 42 showed values below the limit of detection (MW: 2.0 ppm), 58 below the lower limit of quantification (LMQ: 6.0 ppm), and 80 had average values between 6.4 and 13.2 ppm MMA. The NLQ is the lowest concentration of the analyte that differs from the blank, usually with a confidence level of 99%, while the MV is the lowest concentration of the analyte that can be reliably determined with repeatability and precision. The lower limit of quantification is 6.00 ppm, the detection limit is 2.00 ppm.
 Conclusions. The risk of residual monomer as a primary stimulus for a sensitizing reaction can be minimized by using these regimens. The results of measuring the amount of elution of the MMA monomer in water for two of the three materials tested were below the detection limit in both of these modes.

Carbonylative Co- and Terpolymerizations of 10-Undecen-1-ol: A Route to Polyketoesters with Tunable Compositions

A strategy to synthesize branched polyketoesters from the carbonylative polymerization of bifunctional α,ω-alkenols such as 10-undecen-1-ol is presented. This strategy hinges on the competitive application of two related catalytic manifolds, alternating alkene/CO copolymerization, and alkene hydroesterification, which share a common metal acyl intermediate. Small molecule model studies of cationic Pd-catalyzed alkene carbonylation in the presence of alcohols demonstrate that the relative rates of ketone formation (through alternating alkene/CO insertion) and ester formation (through metal acyl alcoholysis) can be tuned across a wide range through judicious bis(phosphine) ligand design. Carbonylative polymerization of 10-undecen-1-ol with a (dppp(3,5-CF3)4)Pd(OTs)2 catalyst (dppp(3,5-CF3)4 = 1,3-bis[bis[3,5-bis(trifluoromethyl)phenyl]-phosphino]propane) led to the formation of high molecular weight polyketoesters with intermediate dispersity (Mn > 20,000 g/mol, D̵ = 2.6) and a ketone/ester microstructure ratio of approximately 1:2. In these polymerization reactions, deploying electron-deficient bis(phosphines) to suppress deleterious alkene isomerization was the key to accessing the high molecular weight polymer. Further, terpolymerization reactions of 1-hexene/10-undecen-1-ol/CO or 1-fluoro-10-undecene/10-undecen-1-ol/CO by (dppp(3,5-CF3)4)Pd(OTs)2 were also successful. This proof of concept polymerization unlocks access to tunable polymer microstructures without extensive postpolymerization treatment.

Protocols of improvements for PMMA denture base resin: An overview

Polymethyl methacrylate (PMMA) is a polymer that is expansively employed in denture base construction due to its low cost, aesthetics, lightweight, reparability, and processability. Nevertheless, this material is not ideal to fulfill the mechanical and physical characteristics of dental restorations. Despite the popularity of the thermal polymerization method, the main shortcoming is the prolonged curing period. Thus, correctly selecting a polymerization cycle and post-polymerization treatment is needed to achieve promising outcomes. In autoclave polymerization, pressure plays a crucial function in accelerating the initial polymerization as well as decreasing the pores and remaining monomer level, thereby improving the flexural strength. Besides, ultrasound can speed up conventional chemical reactions by generating intensive local heating, higher pressures, and very short periods. This article reviews the currently employed protocols for enhancing PMMA denture base polymers and discusses the properties of modified acrylic materials. Moreover, this work explores the effects of the post-polymerization treatment, autoclave process, ultrasonic treatment, and gamma irradiation on the PMMA performance, as well as the positive influence of these treatments on functional properties and clinical longevity.

Surface-mediated twin polymerisation of 2,2′-spirobi[4H-1,3,2-benzodioxasiline] on multi-walled carbon nanotubes, polyacrylonitrile particles and copper particles

Application of twin polymerization by a base-catalysed, surface-mediated coating procedure is shown on different templates. Post-polymerization treatment leads to microporous shells on MWCNTs,N-doped carbon particles, and copper particles.

Application of intrinsically conducting polymers in flexible electronics

AbstractIntrinsically conducting polymers (ICPs), such as polyacetylene, polyaniline, polypyrrole, polythiophene, and poly(3,4‐ethylenedioxythiophene) (PEDOT), can have important application in flexible electronics owing to their unique merits including high conductivity, high mechanical flexibility, low cost, and good biocompatibility. The requirements for their application in flexible electronics include high conductivity and appropriate mechanical properties. The conductivity of some ICPs can be enhanced through a postpolymerization treatment, the so‐called “secondary doping.” A conducting polymer film with high conductivity can be used as flexible electrode and even as flexible transparent electrode of optoelectronic devices. The application of ICPs as stretchable electrode requires high mechanical stretchability. The mechanical stretchability of ICPs can be improved through blending with a soft polymer or plasticization. Because of their good biocompatibility, ICPs can be modified as dry electrode for biopotential monitoring and neural interface. In addition, ICPs can be used as the active material of strain sensors for healthcare monitoring, and they can be adopted to monitor food processing, such as the fermentation, steaming, storage, and refreshing of starch‐based food because of the resistance variation caused by the food volume change. All these applications of ICPs are covered in this review article.

Investigating the effect of diverse structural variation of conjugated polymer electrolytes as the interlayer on photovoltaic properties

The effect of the diverse structural variation of conjugated polymer electrolytes (CPEs) as an interlayer on the photovoltaic properties was investigated. We found that the CPE with a strong electronegative BT group in the backbone and OH salt group in the side chain offers the highest PCEs among CPEs. • Diverse structural variation of conjugated polymer electrolytes (CPEs). • Step-by-step improvement in efficiency of solar cells based on diverse CPEs as interlayer. • Optical simulations of solar cells using transfer matrix formalism. A series of conjugated polymer electrolytes (CPEs) based on dimethylamino propyl fluorene (FN), thiophene (T), benzothiadiazole (BT), and dithienyl benzothiadiazole (TBT) were synthesized by the Suzuki coupling reaction. Quaternarized polyelectrolytes were obtained from the post-polymerization treatment of the amino-terminal group. The incorporation of electron-rich (T), electron-deficient moiety (BT), and their combination (TBT) in the polymer backbone represent the different effects of polarity. Conjugated backbones are substantially strengthened by varying their electron affinity and conjugated planarity. We systematically investigated the effect of applying CPEs with different backbones and functionalities in the side chain. Different backbones produce different molecular dipoles, and the side chain functionality induces an interfacial dipole. Inverted polymer solar cells (iPSCs) based on a bulk heterojunction (BHJ) were fabricated with the ITO/ZnO/CPE/PTB7-Th:PC 71 BM/MoO 3 /Ag structure. The device performance enhancement was achieved by inserting CPEs as the interlayer. Modifying the polymer backbone leads to improved efficiency and modifying the side chain functionality improves the performance compared with that of the interlayered neutral polymer.

Comparison of flexural properties and cytotoxicity of interim materials printed from mono-LCD and DLP 3D printers

Statement of problemBecause few 3D-printing resins have been specifically developed for liquid crystal display (LCD) 3D printers, mono-LCD users may use digital light processing (DLP) 3D-printing resins. However, the suitability of these resins requires evaluation. PurposeThe purpose of this in vitro study was to evaluate whether 3D-printing resins designed for DLP 3D printers can be used successfully in a mono-LCD 3D printer. Material and methods3D printers based on photopolymerization and 3D-printing resin for interim restorations were used in this study. Enlighten AA temp and NextDent C&B MFH were printed from both the MiiCraft Ultra 125 and Phrozen Sonic printers, followed by postpolymerization by using the FormCure and PhrozenCure units for different times. The flexural strength and cytotoxicity of the specimens were evaluated. ResultsAfter postpolymerization treatment, the flexural strength of Enlighten AA temp and NextDent C&B MFH from both 3D printers was over the 50-MPa minimal requirement for the flexural strength of interim resins specified in the International Standards Organization (ISO) 10477 standard. With 15 minutes of FormCure and 1 minute of PhrozenCure postpolymerization, 4 material-printer combinations reached nearly 100% in cell viability. ConclusionsInterim resins designed for DLP 3D printers can be successfully used in mono-LCD 3D printers if the printed specimens are postpolymerized in a more powerful postpolymerization unit or in a less powerful postpolymerization unit for a longer time.

Sulfonated Polyaniline as Zwitterionic and Conductive Interfaces for Anti-Biofouling on Open Electrode Surfaces in Electrodynamic Systems.

Electrodynamic systems for bioanalytical applications constantly suffer from biofouling due to electrical field-induced nonspecific bioadsorption on electrode surfaces. To minimize this issue, surface modification using anti-biofouling and conductive materials is necessary to not only protect the electrode surface from nonspecific bioadsorption but also maintain desired electrodynamic properties for electrode operation. In this study, we designed and prepared a conductive, zwitterionic, and self-doped sulfonated polyaniline (SPANI) coating on Au electrode surfaces for anti-biofouling applications. The zwitterionic coating was fabricated by electrochemical polymerization of aniline on the Au electrode surface functionalized with cysteamine (HS-CH2CH2-NH2) and then a post-polymerization treatment with fuming sulfuric acid. We found that the SPANI-coated electrodes exhibited an excellent anti-biofouling ability in dielectrophoresis (DEP) capturing-and-releasing processes, with a very low average residual mass rate of 1.44% for the SPANI-5s electrode, whereas electrodes modified with poly(ethylene glycol) (PEG) gave an average residual mass rate of 14.30%. Even under continuous operation for more than 1 h, the SPANI-5s electrode still showed stable anti-biofouling ability for an 11-cycle E. coli capturing-and-releasing DEP process, with the residual mass rate for all 11 cycles being kept at or below 2.18% to give an average residual mass rate of 1.62% with a standard deviation of 0.40%. This study demonstrates that electrodynamic systems with zwitterionic SPANI coated on open electrode surfaces can excellently function with decent conductance and anti-biofouling performance.

Synthesis and Self-Assembly of Block Polyelectrolyte Membranes through a Mild, 2-in-1 Postpolymerization Treatment

Block polymer systems containing spatially separated positive and negative charges are desirable for a number of applications, including biomedical devices, membrane separations, and coatings. Unfo...

Fabrication of Crystalline Gel Fibers By Electrospinning

The purpose of this research is to develop a new material with a combination of functions of gel and fiber using electrospinning. Gel has a three-dimensional network structure that is usually synthesized by crosslinking the monomers in various ways. It is widely used in hygiene, cosmetic, fragrance, medicine and many others fields. Multi-functions like water absorbability, biocompatibility and flexibility, can be designed and given depending on the chemical structure of monomers and crosslinkers. We developed crystalline gels with high performance via introducing crystalline side chains into the three-dimensional network structure. There are many kinds of crosslinks to form three-dimensional network structure, such as covalent bonds, Coulomb force, hydrogen bonds, coordination bonds, bonds through entanglements, etc. Among these crosslinks, covalent bonds are most suitable for preparing high performance gels. We use photopolymerization to synthesize crystalline gels because it offers advantages including rapid curing rate, minimal heat production and temperature independence, compared to other polymerization techniques. Photopolymerization is a light-based technique that uses to initiate and propagate a polymerization reaction. To create crosslinked gels, at least three reactive components are required: photoinitiator, monomer and crosslinking agent. A photoinitiator creates free radicals upon exposure to specific wavelengths of light, and then initiates polymerization of monomer and crosslinking agent through a photolytic mechanism. In this research, our aim is to develop a novel gel fiber with a combination of functions of gel and fiber, and ultimately to develop gel nonwoven fabric. The gel nonwoven fabric is expected to have the properties such as water absorbability, biocompatibility, flexibility, and also air permeability, filtration and heat retention. The gel nonwoven fabric could be a promising material for the application in medical treatment due to its air and moisture adjustment function to prevent soaking of wound. Gel has a three-dimensional network structure, it does not dissolve in an organic solvent to make gel solution, and it is also difficult to be heated to make gel melt. Before gelation, only the droplets but no fibers can be formed via electrospinning because of the too low viscosity of reactive solution. On the other hand, after full gelation, fibers cannot be formed either due to their insolubility and infusibility deriving from three-dimensional network structure. Therefore, the manufacture of gel fibers is difficult. In this study, electrospinning with pre and post polymerization treatment is used to make gel nonwoven fabric. We propose to use prepolymerized solution with appropriate viscosity to undergo electrospinning. Electrospinning is a method capable of relatively easily preparing nanofibers under a high voltage. An electrospinning device generally consists of a high voltage power supply, a cylinder, and a substrate. The principle of the electrospinning method is that when a positive high voltage is applied to the polymer solution, charges are collected on the droplet surface at the tip of the nozzle and repel each other, and the droplets coming out of the nozzle gradually become conical. When the repulsive force of charge exceeds the surface tension, the solution is jetted straight from the tip of the cone, gradually heading toward the grounded or negatively charged substrate while drawing a spiral. As the ejected solution stream becomes thinner, the surface charge density increases, so the charge repulsion increases and the solution flow is further elongated. Prepolymerized gel solution is set in cylinder, distance between substrate and nozzle is determined, extrusion amount is set, and voltage is given. We run experiments with the procedure of sticking aluminum foil to the metal plate and then spraying the prepolymerizted gel solution onto the board, finally taking aluminum foil off the board and applying postpolymeriation under UV light. SEM observation indicated the fiber diameter is about 400 nm.

Poly (1,8 Octanediol-co-Citrate) Hydroxyapatite Composite as Antibacterial Biodegradable Bone Screw

The high bone fracture rates reaching up to 300-400 cases per month have been treated with surgical procedure of internal fixation. Nevertheless, the commonly used metal screw has shown several weaknesses. Therefore, it is required bone screw of which primary characteristics include being biocompatible, bio-functional, biodegradable, and anticorrosive. The study aimed to synthesize Antibacterial Poly 1,8-Octanediol-co-Citrate (POC) and investigated the effect of chitosan on the antibacterial and compatibility characteristics of POC-HA composite as antibacterial biodegradable bone screw. The characterization were conducted on POC-HA composite to assess its functional cluster, antibacterial activity, cytotoxicity, degradation capacity, and morphology. Pre-polymer POC was composited with 62% nano-HA, followed by post-polymerization treatment. The sample then coated by chitosan with composition variations of 1%, 3%, and 5%. The nano-HA marked with the appearance of phosphate cluster on the wavenumber of 872.17 cm-1 and 559.51 cm-1, while the chitosan marked with C=O stretch cluster of esther at 1729 cm-1 from Fourier Transform Infra-Red (FTIR) measurement. The best result was obtained with 3% chitosan coating. The POC-HA composites showed bacterial inhibiting ability of 16.92 mm with non-toxic characteristics. These results indicated that chitosan coating Poly 1,8-Octanediol-co-Citrate (POC)-Nano Hydroxyapatite composite is a potential candidate for an antibacterial biodegradable bone screw.

Effect of ethanol solutions as post-polymerization treatment on the properties of acrylic reline resins

ObjectivesTo evaluate the effect of ethanol solutions as post-polymerization treatment on the shear bond strength and the surface free energy of acrylic reline resins. MethodsThree reline resins (Kooliner, Ufi Gel Hard and Probase Cold) were manipulated and attached to 150 parallelepipeds denture base resin previously aged. Constructed specimens of each resin were randomly divided into control group (left untreated) or experimental groups subjected to different treatments: immersion in water or ethanol solutions 20, 50 or 70% at 55°C for 10min (n=10). Shear bond strength was tested and the failure mode was assessed. Surface free energy was calculated by determining the contact angle and estimated by the Wilhelmy plaque technique (n=5). Data were analyzed using Kruskal–Wallis and Mann–Whitney tests with Bonferroni correction (alfa=0.05). ResultsProbase Cold showed higher values (p<0.001) in shear bond strength than other resins. There were no statistically significant differences (p=0.378) in shear bond strength between post-polymerization treatments. Kooliner showed lower values (p<0.001) in surface free energy than other resins. Considering the post-polymerization treatment groups, there were no statistically significant differences (p>0.05) in surface energy. ConclusionsEthanol solutions as post-polymerization treatments did not deteriorate the bond strength of acrylic reline resins to denture base and neither their wettability.

Synthesis and Characterization of Composite Poly(1.8 Octanediol-co-Citrate) (POC)/Nano-Hydroxyapatite as Candidate Biodegradable Bone Screw

The high number of bone fractures, around 300-400 cases per month, are treated with orthopedic surgery method using internal fixation by bone screw which is aimed at accelerating patients’ mobilization. There is a necessity to invent biomaterial which possesses two main characteristics: biocompatible and biofunctional, as well as having an important element of biodegradable without conducting reoperation. A research focused on the various composition of nano-hydroxyapatite (HA) derived from extracted snapper fish scales on Poly (1,8-octanediol-Co-Citrate (POC) as Biodegradable Bone screw. This research is purported to synthesize Poly (1,8-Octanediol-co-Citrate (POC) and characterize the influence of HA compositions against mechanical properties and compatibility of POC-HA composite that enable it to be used as Biodegradable Bone screw material. The condensation polymerization method is applied in synthesizing POC to produce POC pre-polymer by the formation of an ester bond group C=O stretch at 1731 cm-1 through a test of functional groups (FTIR). POC pre-polymer is composited with nano-HA compositions of 62%, 65%, 68% and 71% and followed by post-polymerization treatment. POC-HA composites formed were tested on hardness and biodegradability. The results obtained indicate that the composition of HA nanoparticles influences the mechanical properties and biocompatibility of the material. Best results were from 62% HA composition in which the hardness value was of 885.57 MPa, close to that of bone hardness which is 150-664 MPa. Results also showed that the rate of biodegradation reached 3.42% (4 weeks) which is in accordance to fracture bone grafting period of 21 months. Based on the characteristics result indicated in this study, the composite of Poly (1,8-Octanediol-co-Citrate) (POC)-Nano Hydroxyapatite is a potential candidate for biodegradable bone screw material.

Diketopyrrolopyrrole-Based Low-Bandgap Conjugated Polymers with Siloxane Side Chains for Electrochromic Applications

A series of conjugated copolymers P1–P3 were synthesized from 3,6-bis(5-bromothiophen-2-yl)-2,5-bis(6-(1,1,1,3,5,5,5-heptamethyltrisiloxan-3-yl)hexyl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione and 2,5-bis(trimethylstannyl)-3,4-dialkoxythiophene or its analogue via Stille coupling reactions, with molecular weights in the range of 13000–18000 g mol–1 and polydispersity indexes of 1.4–1.7. This new type of donor–acceptor polymers demonstrated reasonable switching speed, promising redox stability, together with high optical contrast and coloration efficiency. Although, at the current stage, the hybrid siloxane-terminated side chain did not significantly improve the overall performance of the resultant polymers, the unique chemical properties of the siloxane group would offer possibilities for crosslink after suitable post-polymerization treatment, and thus pave the way for future fine-tuning of the morphology of electrochromic films.

Effect of Post-Polymerization Heat Treatment on a Denture Base Acrylic Resin: Histopathological Analysis in Rats

Aims: This work examined the histological effects, on the rat palatal mucosa, of a denture base acrylic resin, submitted or not to a post-polymerization heat-treatment. Methods: Fifteen adult female Wistar rats, with sixty days old, weighting 150 g - 250 g were divided in G1: animals being maintained under the same conditions as the experimental groups following described, but without the use acrylic palatal plates (control group); G2: use of heat-polymerized acrylic resin palatal plates made of Lucitone 550; G3: use of palatal plates identical to G2, but subjected to a post-polymerization treatment in a water bath at 55 0 C for 60 min. The plates covered all the palate and were fixed in the molar region with light-cured resin, thus being kept there for 14 days. After the sacrifice, the palate was removed, fixed in formaldehyde 10% and decalcified with EDTA. Sections were stained using haematoxylin and eosin. Images in duplicate were made from the central region of the cuts, to measure the thickness (μm) of the keratin layers (TKC), epithelium total (TET) and connective tissue (TCC). Statistical analyses were carried out by one-way ANOVA and Tukey post-tests (α=0.05). Results: According to the results there was significant difference in the thickness of keratin between G2 and G3, with G1 having the intermediate value and similar to the other groups. There was a significant difference in the connective tissue with G3 <G1 <G2 (p <0.0001). Conclusion: Regarding the total epithelium, group G3 presented a statistically significant difference with both G1 and with G2 (p <0.0001), which were similar to each other. When using the proposed heat treatment it was found to be effec- tive, from the viewpoint of biocompatibility, for the acrylic resin denture base investigated.

MİKRODALGA VE OTOKLAV POST-POLİMERİZASYON UYGULAMALARININ SERT BESLEME AKRİLİKLERİNİN BÜKÜLME DİRENCİNE ETKİSİNİN KARŞILAŞTIRILMASI

Purpose: To compare the effect of autoclave and microwave post-polymerization treatments on flexural strength of hard reline and heat-polymerized acrylic resins.Material and Methods: Hard chairside reline and heat-polymerized acrylic resin specimens (64x10x3.3 mm) were fabricated. 80 specimens with 4 subgroups for each acrylic (n=20) received post-polymerization treatment by microwave irradiation and two autoclave post-polymerization modalities (short and long). Specimens were subjected to flexural strength testing using 3-point bending with a crosshead speed of 5 mm/min. Two-way, one-way ANOVA and Tukey’s HSD tests were used for statistical analysis of data. Results: The microwave post-polymerization significantly increased the strength of heat polymerized acrylic resin and hard chairside reline resin specimens where its effect was significantly higher than the autoclave and control groups (p 0.05). Conclusion: Using autoclave, may be considered as a viable post-polymerization treatment alternative in order to increase the flexural strength of relined dentures.

Synthesis of comb polyphenylenes by Suzuki coupling from AB macromonomers

A series of soluble comb polyphenylenes (PPs) were synthesized by Suzuki coupling polycondensation from AB macromonomers. After post-polymerization treatment, the comb PPs have a good symmetric single-peak shape in the GPC curves with reasonable polydispersity indexes ranging from 1.15 to 1.74.

Residual monomer content of repair autopolymerizing resin after microwave postpolymerization treatment

Purpose: Acrylic resins are one of the extensively used materials in removable prosthodontics however; complete dentures are highly vulnerable to fracture after long periods of clinical use. The repair of fractured prosthesis can be accomplished using acrylic resins that are light polymerized, autopolymerized, heat polymerized or microwave polymerized. Aim: To evaluate the residual monomer content of three different repair autoploymerising resins processed by two different polymerization techniques after microwave postpolymerization treatment. Materials and Methods: The study was executed with fabrication of a metal die and sixty test specimens of three different materials. The specimens were cured with conventional method and using pressure pot. After this the specimens were tested for residual monomer content using Fourier transform infrared spectroscopy. Results and Conclusion: Results confirmd that their residual monomer content decreased by subjecting them to another cycle of polymerization in microwave at 550 watts for 3 minutes.

Ethanol Postpolymerization Treatment for Improving the Biocompatibility of Acrylic Reline Resins

Objective. To evaluate the effect of postpolymerization treatment based on ethanol-aqueous solutions on the residual monomer (RM) content, flexural strength, microhardness, and cytotoxicity of hard chairside reline resins (Kooliner, Ufi Gel Hard). Methods. After polymerization, specimens were immersed in water, 20%, 50%, or 70% ethanol solutions at 23°C or 55°C for 10 minutes. Controls were left untreated. HPLC was used for the determination of RM content. Specimens were submitted to Vickers microhardness and 3-point loading flexural strength tests. Cytotoxicity of resin eluates was determined on human fibroblasts by assessing cellular mitochondrial function and lactate dehydrogenase release. Results. Higher concentrations of ethanol promoted lower RM content at 55°C in both materials. The mechanical properties were maintained after 50% and 20% ethanol treatments in Kooliner and Ufi Gel Hard, respectively. Specimens submitted to those treatments showed significant reduction on cytotoxicity compared to immersion in hot water, the treatment of choice in the recent literature. Significance. Immersion of relined dentures in specific ethanol solutions at 55°C for 10 minutes can be considered an effective postpolymerization treatment contributing to increase materials biocompatibility. The proposed protocol is expeditious and easy to achieve with simple equipment in a dental office.