Autoclave Polymerization Research Articles

Evaluation of the Effect of Brushing on Vickers Microhardness of Acrylic Denture Base Resins Polymerized by Different Techniques

Objectives: In selecting a denture base material, different polymerization techniques might be considered to avoid adverse effects of brushing on the microhardness of the acrylic resin. The purpose of this study was to evaluate the brushing effect on Vickers microhardness of acrylic denture base resins polymerized by different techniques. Material and Methods: One hundred disk-shaped specimens (15 mm in diameter and 2 mm thick) were fabricated from each acrylic resin (Integra and FuturaJet). Five different polymerization techniques were tested (n=20): conventional water-bath polymerization, short autoclave polymerization (60°C for 30 minutes, then 130°C for 10 minutes), long autoclave polymerization (60°C for 30 minutes, then 130°C for 20 minutes), injection-molding polymerization and auto-polymerization. Half of the specimens were subjected to simulated brushing in an automatic brushing machine using 54 000 brush strokes for each specimen. All specimens were then submitted to Vickers hardness test with a 300-g load for 15 s. Mann Whitney U test and Kruskal-Wallis test followed by Dunn’s post-hoc test were used for results analysis, which were statistically significant at p < 0.05. Results: A statistically significant difference was observed between the control and brushing groups in all polymerization techniques (p < 0.05). Autopolymerized acrylic resin group showed significantly lower microhardness values than water bath, short and long autoclave polymerized resins in control and brushing groups (p < 0.05). Conclusions: Autopolymerization technique might has some disadvantages on avoid adverse effects of brushing on the microhardness, therefore tehniques of polymerization should be considered as microhardness of acrylic denture base resins.

Flexural Properties, Impact Strength, and Hardness of Nanodiamond-Modified PMMA Denture Base Resin.

Purpose Investigate the effect of low nanodiamond (ND) addition and autoclave polymerization on the flexural strength, impact strength, and hardness of polymethylmethacrylate (PMMA) denture base. Methods A total of 240 heat polymerized PMMA were fabricated with low ND concentrations of 0.1%, 0.25%, and 0.5%, and unmodified as control. The specimens were divided equally into group I: conventionally polymerized PMMA by water bath and group II: polymerized by the autoclave. The impact strength, flexural strength, and elastic modulus were tested using the Charpy-type impact-testing machine and three-point bending test, respectively. A scanning electron microscope (SEM) was used to analyze the fractured surfaces. Surface hardness was measured by a hardness tester with a Vickers diamond. The bonding and interaction between the PMMA and ND particles were analyzed by the Fourier-transform infrared (FTIR) spectroscope. ANOVA and post hoc Tukey test were used for data analysis (α = 0.05). Results ND addition significantly increased the flexural strength of groups I and II (p < 0.001, p=0.003); it was highest (128.8 MPa) at 0.25% ND concentration for group I and at 0.1% for group II. Elastic modulus increased at 0.1% ND for both groups (p=0.004, p=0.373), but the increase was statistically significant for group I only. Impact strength showed no significant change with the addition of ND in groups I and II (p=0.227, p=0.273), as well as surface hardness in group I (p=0.143). Hardness decreased significantly with 0.25%ND in group II. Conclusion The addition of ND at low concentration increased the elastic modulus and flexural strength of conventionally and autoclave polymerized denture base resin. Autoclave polymerization significantly increased the flexural strength, impact strength, and hardness of unmodified PMMA and hardness of 0.5% ND group.

Impact of Polymerization Technique and ZrO2 Nanoparticle Addition on the Fracture Load of Interim Implant-Supported Fixed Cantilevered Prostheses in Comparison to CAD/CAM Material.

ZrO2 nanoparticles (ZNPs) have excellent physical properties. This study investigated the fracture load of implant-supported, fixed cantilevered prosthesis materials, reinforced with ZNPs and various polymerization techniques, compared with conventional and CAD/CAM materials. Sixty specimens were made from two CAD/CAM; milled (MIL) (Ceramill TEMP); and 3D-printed (NextDent Denture 3D+). Conventional heat-polymerized acrylic resin was used to fabricate the other specimens, which were grouped according to their polymerization technique: conventionally (HP) and autoclave-polymerized (AP); conventionally cured and reinforced with 5 wt% ZNPs (HPZNP); and autoclave reinforced with 5 wt% ZNPs (APZNP). The specimens were thermocycled (5000 cycles/30 s dwell time). Each specimen was subjected to static vertical loading (1 mm/min) using a universal Instron testing machine until fracture. Scanning electron microscopy was used for fracture surface analyses. The ANOVA showed significant fracture load differences between all the tested groups (p = 0.001). The Tukey post hoc tests indicated a significant difference in fracture load between all tested groups (p ˂ 0.001) except HP vs. HPZNP and AP vs. MIL. APZNP had the lowest mean fracture load value (380.7 ± 52.8 N), while MIL had the highest (926.6 ± 82.8 N). The CAD/CAM materials exhibited the highest fracture load values, indicating that they could be used in long-term interim prostheses. Autoclave polymerization improved fracture load performance, whereas ZrO2 nanoparticles decreased the fracture load performance of cantilevered prostheses.

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.

Effect of Low Nanodiamond Concentrations and Polymerization Techniques on Physical Properties and Antifungal Activities of Denture Base Resin.

Background: Denture base resin has some drawbacks. This study investigated the impact of nanodiamonds (ND) and autoclave polymerization on the surface characteristics, translucency, and Candida albicans adherence in polymethyl methacrylate (PMMA) denture base resin after thermocycling. Methods: Heat-polymerized PMMA discs (15 × 2 mm) with a total sample size n = 160 were studied. Specimens were categorized into two main groups (N = 80): conventional water-bath-polymerized PMMA (CP/PMMA) and autoclave-polymerized PMMA (AP/PMMA). Each group was subdivided according to the ND concentration into four groups (n = 20): unmodified PMMA as a control, and 0.1%, 0.25%, and 0.5% ND–PMMA. Scanning electron microscopy (SEM) was used to inspect the morphology of the ND and the ND–PMMA mixtures before heat polymerization. The specimens were exposed to thermal cycling (5000 cycles at 5 and 55 °C), then surface roughness was measured with a non-contact optical interferometric profilometer, contact angle with an automated goniometer, and translucency using a spectrophotometer. Colony-forming units (CFU) were used to determine the adherence of Candida albicans cells to the specimens. ANOVA and Tukey post hoc tests for pairwise comparison were utilized for the statistical analysis (α = 0.05). Results: Surface roughness was significantly reduced with ND addition to CP/PMMA (p ˂ 0.001), while the reduction was not statistically significant in AP/PMMA (p = 0.831). The addition of ND significantly reduced the contact angle, translucency, and Candida albicans count of CP/PMMA and AP/PMMA (p ˂ 0.001). The incorporation of ND in conjunction with autoclave polymerization of PMMA showed significant reduction in all tested properties (surface roughness, contact angle and Candida albicans adherence) except translucency (p = 0.726). Conclusions: ND addition to PMMA and autoclave polymerization improved the surface properties with respect to antifungal activities, while the translucency was adversely affected.

THE EFFECT OF AUTOCLAVE POLYMERIZATION ON THE TENSILE STRENGTH OF VARIOUS DENTURE BASE MATERIALS

Objectives: The aim of this in vitro study was to evaluate the effect of autoclave polymerization method on the tensile strength of the polymethylmethacrylate (PMMA) acrylic denture base resins. Materials and Methods: Total of 60 specimens were fabricated from four different denture base materials such as three heat polymerized dental resins Meliodent, Paladent, and QC-20 and one microwave polymerized resin Acron MC. The tensile strength tests were performed. Results: Acron-MC showed the highest tensile strength value, QC-20, Paladent and Meliodent were followed in order for the control group. Acron MC was significantly different than the other acrylic resins for the control and autoclave polymerization 10 minutes groups (p&amp;lt;0.01). Autoclave polymerized acrylic resin specimens showed higher tensile strength values than the control groups (p&amp;lt;0.01). There was no significant difference between the increasing time of autoclave polymerization methods 10 minutes and 20 minutes (p&amp;gt;0.01) Conclusion: Within the limitations of the study, autoclave polymerization method may provide a stronger alternative to conventional polymerization methods. Autoclave polymerization method provides high temperature that the activation ratio of cross-linking agents (glycoldimethacrylate) can be increased.

Evaluation of the Transverse Strength and Elastic Modulus of High Impact Denture Base Material

Introduction: High fracture resistance of prostheses are well accepted by both patients and dentists to have a proper restoration of the dentition. The research designated assess polymerization time effect distinct and complete temperatures on mechanical properties (denture base resin) of a high strength. The research purpose is to assess and compare the procedure used in polymerization distinct effect autoclave on the elastic modulus and transverse strength of a high strength acrylic resin to the conventional heat polymerizing. Methods: Rectangular sample of ninety-one polymarised high heat strength denture base resin were created. Polymerized sample done by hot water regarded as control group and the other groups were polymerized in autoclave at different temperatures and time lenghts. After deflasking of sample before procedure it was kept forty eight hours in water. Three parameters were used when conducting transverse strength test bending using calibrated universal testing machine with a load of 500 kg cell and a crosshead speed of 5 mm/min. One-way ANOVA was used in assessing transverse strength and elastic modulus data. And for comparison of the groups application of Tukey HSD trial has been seen appropriate (p <0.05). Results: Specimens that polymerized by autoclave at 130oC for 20 and 30 minutes showed significantly better characteristics compared to the other groups. Conclusion: Upgrading of base resins transverse strength is required because the research indicated autoclave polymerization at 130°C for 20 and 30 minutes may be an alternative polymerization method.

The Impact of Polymerization Technique and Glass-Fiber Reinforcement on the Flexural Properties of Denture Base Resin Material.

Objective Different polymerization and reinforcement techniques have been tested to enhance the mechanical characteristics of denture base acrylic resins. The goal of the present study was to evaluate the influence of autoclave polymerization techniques with glass fiber reinforcement on the flexural strength and elastic modulus of polymethyl methacrylate denture base resins. Materials and Methods Ninety specimens were fabricated from heat-polymerized acrylic resin and randomly distributed depending on the polymerization technique into three groups ( n = 30): water bath polymerization, short-cycle autoclave polymerization, and long-cycle autoclave polymerization. Each group was further divided into three subgroups ( n = 10) based on the concentration of glass fiber 0, 2.5, and 5wt%. The flexural strength and elastic modulus were investigated using a universal testing machine. One-way ANOVA and Tukey’s post hoc test were performed to analyze the results ( α = 0.05). Results The flexural strength and elastic modulus values were significantly higher in 5wt% glass fiber reinforced long-cycle autoclave group in comparison with the other test groups ( p < 0.05). Conclusions The long-cycle autoclave polymerization technique with the glass fiber reinforcement significantly increased the flexural strength and elastic modulus of the denture base resin material.

Experimental research regarding carbon fiber/epoxy material manufactured by autoclave process

The fiber reinforced polymers (FRP) represent a group of materials with a very impressive development in the last time. There are used in different applications from aerospace to sports or medicine. Carbon fiber reinforced polymer (CFRP) has special properties and tend to replace traditional materials like steel, aluminum alloys or wood. Different procedures were developed to manufacture the CFRP. Autoclave processing can be considered the most important way to obtain the best mechanical properties of this kind of material. In this paper it is presented the autoclave manufacturing process to obtain theCFRP plates. The autoclave polymerization process steps are indicated for the CFRP made of Twill textile prepreg material. The stacking sequence of the layers is [0/90]. To determine the mechanical properties of the material tensile test on standardized specimens was employed. The obtained mechanical material’s properties are comparable with steel but its density was reduced 5.5 times.

Effect of polymerization technique and glass fiber addition on the surface roughness and hardness of PMMA denture base material.

The current study evaluated the effects of autoclave polymerization both with and without glass fiber (GF) reinforcement on the surface roughness and hardness of acrylic denture base material. Ninety disc specimens (30×2.5 mm) were prepared from Vertex resin and divided according to polymerization techniques into a water bath, short and long autoclave polymerization groups. Tested groups were divided into three subgroups according to the GF concentration (0, 2.5, and 5 wt%). Profilometer and Vickers hardness tests were performed to measure surface roughness and hardness. ANOVA and Tukey-Kramer multiple comparison tests analyzed the results, and p≤0.05 was considered statistically significant. Autoclave polymerization significantly decreased the surface roughness and increased the hardness of acrylic resin without GF reinforcement (p<0.05). However, 5 wt% GF addition significantly increased surface roughness and decreased hardness of the autoclave polymerized denture base resin (p<0.05). Surface properties of Polymethyl methacrylate (PMMA) denture base material improved with autoclave polymerization and negatively affected with GFs addition.

Comparison of mechanical and dynamic mechanical behaviors of different dental resins polymerized by different polymerization techniques.

The aim of the present investigation was to evaluate the effect of autoclave polymerization method on the mechanical and dynamic mechanical properties of different polymethylmethacrylate denture base materials. Three different denture materials were used during the study, two of them were heat polymerizable denture base material (Meliodent and Paladent) and one was microwave polymerizable denture base material (Acron MC). Duncan test was used for the statistical analysis. Statistical analyses were completed using a two-way analysis of variance. Statistical analysis of test results was carried out with a 95% confidence level. Tensile strength was increased with autoclave polymerization regardless of the denture base material type. Paladent specimens with autoclave polymerization (30 min at 60°C and 10 min at 130°C) have the highest average impact strength value. Acron MC specimens have the highest average flexural strength and modulus. Flexural strength improved with autoclave polymerization for both of 10 and 20 min polymerizations for each of Meliodent and Paladent specimens. Autoclave polymerization provided higher polymerization temperatures compared with the conventional heat polymerization. Autoclave-polymerized acrylic resin specimens showed higher tensile strength values; however, this was not the case for the impact test results. Flexural strength of specimens was improved with autoclave polymerization. Glass transition temperature was increased with autoclave polymerization.

Comparative Effect of Different Polymerization Techniques on the Flexural and Surface Properties of Acrylic Denture Bases.

Polymerization techniques have been modified to improve physical and mechanical properties of polymethylmethacrylate (PMMA) denture base, as have the laboratory procedures that facilitate denture construction techniques. The purpose of the present study was to investigate the effect of autoclave polymerization on flexural strength, elastic modulus, surface roughness, and the hardness of PMMA denture base resins. Major Base and Vertex Implacryl heat-polymerized acrylic resins were used to fabricate 180 specimens. According to the polymerization technique, tested groups were divided into: group I (water-bath polymerization), group II (short autoclave polymerization cycle, 60°C for 30 minutes, then 130°C for 10 minutes), and group III (long autoclave polymerization cycle, 60°C for 30 minutes, then 130°C for 20 minutes). Each group was divided into two subgroups based on the materials used. Flexural strength and elastic modulus were determined by a three-point bending test. Surface roughness and hardness were evaluated with a profilometer and Vickers hardness (VH) test, respectively. One-way ANOVA and the Tukey-Kramer multiple-comparison test were used for results analysis, which were statistically significant at p ≤ 0.05. Autoclave polymerization showed a significant increase in flexural strength and hardness of the two resins (p < 0.05). The elastic modulus showed a significant increase in the major base resin, while a significant decrease was seen for Vertex Implacryl in all groups (p < 0.05); however, there was no significant difference in surface roughness between autoclave polymerization and water-bath polymerization (p > 0.05). Autoclave polymerization significantly increased the flexural properties and hardness of PMMA denture bases, while the surface roughness was within acceptable clinical limits. For a long autoclave polymerization cycle, it could be used as an alternative to water-bath polymerization.

Some Factors Affecting the Molecular Weight Distribution (MWD) in Low Density Polyethylene Multizone Autoclave Polymerization Reactors

Due to its complexity, free‐radical polymerization of ethylene at high pressure still remains to be fully understood. This paper investigates factors that contribute to shape the MWD, one of the main features of LDPE, such as the structure of primary chains and the reactor operation in one/two phases. Using plant data and different models, it is found that chain transfer to small species is the controlling chain termination step and it is explained why one‐phase operation leads to more branched polymer. Simulations with the Polyred software package provide a set of kinetic parameters that reproduce the observed trends in number average molecular weight and MWD dispersity in the reactor.

Evaluation of Shear Bond Strength of Artificial Teeth to Heat Cure Acrylic and High Impact Heat Cure Acrylic Using Autoclave Processing Method

Debonding and fracture of artificial teeth from denture bases are common clinical problem, bonding of artificial teeth to heat cure acrylic and high impact heat cure acrylic denture base materials with autoclave processing method is not well known. The aim of this study was to evaluate the effect of autoclave processing method on shear bond of artificial teeth to heat cure denture base material and high impact heat cure denture base material. Materials and methods: Heat polymerized (Vertex) and high impact acrylic (Vertex) acrylic resins were used. Teeth were processed to each of the denture base materials after the application of different surface treatments. The sample (which consist of artificial tooth attached to the denture base at 45 degree) are consist of (80) artificial teeth from the same model of central incisor, they were prepared , treated and bonded to the conventional heat cured and high impact acrylic denture base material then processed. Control group (Group A 40 samples) in which acrylic resins PMMA cured by conventional water- bath processing technique (74°C for 1.5 hours then boil for 30 minutes),the group was subdivided to 20 samples heat cure acrylic and 20 samples high impact acrylic. Experimentalgroups (Group B 40 samples) in which acrylic resins was cured by autoclave at 121°C, 210KPa. For 30min.the group subdivided to 20 samples heat cure acrylic and 20 samples high impact acrylic. For each subgroup, the 20 samples were subdivided according to surface treatment into: 1-Five acrylic teeth without any surface treatment (control). 2- Five acrylic teeth with diatoric preparation (retention grooves). 3- Five acrylic teeth conditioned with thinner. 4- Five acrylic teeth with retention grooves and thinner. Results: Statistical analysis revealed that chemical and mechanical treatment of acrylic teeth improved the shear bond with heat cure and high impact acrylicalsoautoclave processing improvedthe shear bond with acrylic teeth in high impact acrylic. Conclusion: Autoclave polymerization is suggested as alternative method for processing denture base resins. Autoclave polymerization can be easily performed in laboratory conditions. In High Impact Acrylic, there were highly significant differences of autoclave processing technique compared with water bath regarding the shear bond

Determination of Acrylic Denture Resin Surface Roughness by Different Processing Techniques

Background: Poly (methyl methacrylate) (PMMA) seems to be the most commonly used material in the construction of denture base due to its advantages. However, it is still far from being ideal in fulfilling the physical and mechanical properties. Therefore, attempts to improve the properties of PMMA were taken by the researcher through many ways The purpose of this study was to estimate the effect of different processing techniques on surface roughness of acrylic base denture resin. Materials and Methods: A total sample of (50) specimens were prepared; these specimens were divided into 3 main processing techniques, and 5 experimental sub-groups (n=10): Group (A), acrylic denture base material processed by conventional water bath technique (74C for 1 and half hours then boiled for 30 min; Group (B), acrylic resins processed by microwave oven at (500 Watts) for 3 min; Group (C) samples processed by autoclave device with 3 different timing set up : (C1) for l0 min, (C2) for 20 min and (C3) for 30 min. This is done to make a comparison of different autoclave polymerization conditions on the surface roughness of denture base resin. Results: Statistically, there was no significant difference between the traditional water bath group technique and an autoclave system when the specimen processed at (121C/210Kpa) for 30 min. However, there was a statistically significant difference compared to other experimental groups. Conclusion: The autoclave processing technique could be the new alternative system to process the acrylic resin base material alongside the conventional methods. The experimental group prepared by autoclave system at (121C/21Kpa) for 30 min showed an improvement in the surface roughness compared to microwave and water bath techniques.

Evaluation of shear bond strength of artificial teeth to heat cure acrylic and high impact heat cure acrylic using autoclave processing method

Background: Debonding and fracture of artificial teeth from denture bases are common clinical problem, bonding of artificial teeth to heat cure acrylic and high impact heat cure acrylic denture base materials with autoclave processing method is not well known. The aim of this study was to evaluate the effect of autoclave processing method on shear bond of artificial teeth to heat cure denture base material and high impact heat cure denture base material. Materials and methods: Heat polymerized (Vertex) and high impact acrylic (Vertex) acrylic resins were used. Teeth were processed to each of the denture base materials after the application of different surface treatments. The sample (which consist of artificial tooth attached to the denture base at 45 degree) are consist of (80) artificial teeth from the same model of central incisor, they were prepared , treated and bonded to the conventional heat cured and high impact acrylic denture base material then processed. Control group (Group A 40 samples) in which acrylic resins PMMA cured by conventional water- bath processing technique (74°C for 1.5 hours then boil for 30 minutes),the group was subdivided to 20 samples heat cure acrylic and 20 samples high impact acrylic. Experimentalgroups (Group B 40 samples) in which acrylic resins was cured by autoclave at 121°C, 210KPa. For 30min.the group subdivided to 20 samples heat cure acrylic and 20 samples high impact acrylic. For each subgroup, the 20 samples were subdivided according to surface treatment into: 1-Five acrylic teeth without any surface treatment (control). 2- Five acrylic teeth with diatoric preparation (retention grooves). 3- Five acrylic teeth conditioned with thinner. 4- Five acrylic teeth with retention grooves and thinner. Results: Statistical analysis revealed that chemical and mechanical treatment of acrylic teeth improved the shear bond with heat cure and high impact acrylicalsoautoclave processing improvedthe shear bond with acrylic teeth in high impact acrylic. Conclusion: Autoclave polymerization is suggested as alternative method for processing denture base resins. Autoclave polymerization can be easily performed in laboratory conditions. In High Impact Acrylic, there were highly significant differences of autoclave processing technique compared with water bath regarding the shear bond strength with acrylic teeth.

Study on the Frontal Polymerization of Polyurethane/Hollow Glass Microsphere Hybrid Material

In this article, we use propylene glycol (PPG), Chain expansion agent 1, 4-Butylene Glycol (BG), toluene diisocyanate (TDI) and hollow glass microsphere Sol as raw materials to prepare polyurethane/hollow glass microsphere hybrid materials by frontal polymerization. Here we studies how the front position varies with time and how the polymer viscosity influences the reaction rate in the frontal polymerization process, and through the comparisons with autoclave polymerization, draw to a conclusion that we can also get polyurethane/hollow glass microsphere hybrid materials by this new preparation and processing method.

In vitro Comparison of Autoclave Polymerization on the Transverse Strength of Denture Base Resins

The aim of this study was to determine the effect of autoclave polymerization on the transverse strength of denture base polymers. To this end, 30 rectangular test specimens were fabricated of two heat-polymerized denture base polymers. The test groups were: (I) control, i.e., conventional water bath to polymerize resins by heat at 100 degrees C for 30 minutes; (II) autoclave polymerization at 60 degrees C for 30 minutes followed by 130 degrees C for 10 minutes; and (III) autoclave polymerization at 60 degrees C for 30 minutes followed by 130 degrees C for 20 minutes. The specimens were tested with three-point bending test at a crosshead speed of 5 mm/min. It was revealed that the transverse strength of specimens increased with statistical significance when the autoclave was used for polymerization.

Modeling of molecular weights in industrial autoclave reactors for high pressure polymerization of ethylene and ethylene‐vinyl acetate

AbstractWe have incorporated mass balances of monomer, radical and polymer species to a previously developed mixing model for high pressure autoclave polymerization reactors. The customary quasi steady state approximation is not used, and the method of moments is used to simplify the mass balance calculations. The resulting moment model is able to calculate conversions, average molecular weights, long chain branching and melt flow indexes at any point in the reactor. It may also calculate concentration and temperature profiles along the reactor. Results for two base cases are presented in detail. Model predictions were compared with experimental data obtained at the industrial reactor; excellent agreement was obtained. The moment balance equations are presented in a modular way so that they may be easily adapted to be used with any other mixing model for this type of reactor.