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Bakelite, a thermosetting plastic, has limited feasibility for thermal recycling processes such as pyrolysis, unlike thermoplastics, due to its inherent tendency to get charred upon heating and difficulty in being converted into valuable fuel and chemical compounds. In this study, the co‐pyrolysis of bakelite and poly methyl methacrylate is explored to improve the thermal degradation and thus recycling feasibility of bakelite by pyrolysis. The kinetics and thermodynamics of the co‐pyrolysis of blended samples are analyzed using different kinetics models. The thermal degradation experiments of the sample are conducted from ambient to 1000 °C at five various heating rates of 5, 10, 20, 30, and 50 °C/min in an inert N2 gas environment. The results showed that adding poly methyl methacrylate to bakelite changes the pyrolytic degradation temperature and weight loss trend. The kinetic analysis reveals that the thermal degradation at 220–345 °C follows an F2.5 order‐based model with an average activation energy of 181 kJ/mol, while the degradation at 345–475 °C follows an F2 order‐based model with an average activation energy of 318 kJ/mol. The enthalpy changes and free energy change associated with thermal degradation exhibit a positive trend while that of entropy change shows a negative trend. With blending the free energy change and entropy change decreased while enthalpy change increased. During batch pyrolysis at 450 °C, the PMMA‐Bakelite blend generates oil (49.17 %), wax (12.36 %), residue (15.36 %), and gas (23.11 %). According to FTIR and GC‐MS analyses, the pyrolytic oil produced by the co‐pyrolysis of the blended sample at 450 °C comprises 32.23 % saturated hydrocarbons (C9–40), 20.97 % unsaturated hydrocarbons (C6–24), and 46.80 % oxygenated material (C5–19). These findings can assist in the optimization of pyrolysis reactor design for the recycling of thermosetting plastics. [ABSTRACT FROM AUTHOR]

This research aimed to develop lead-free polymer composites based on poly-methyl methacrylate (PMMA) and embedded with tungsten carbide (WC) micro and nanoparticles for use in radiation protection applications. PMMA was filled with 20 %, 40 %, and 60 % by weight of WC micro- and nanoparticles. The shielding features of the proposed polymer mixtures were evaluated at different radioactive sources of different energies using the HPGe detector. The results revealed that the investigated composites containing micro and nano-structured WC particles showed superior radiation shielding at 81 keV due to the K-edge of the W element occurring at 69.5 keV. The findings also demonstrated that composites loaded with WC nanoparticles were more effective in shielding gamma radiation than those loaded with WC microparticles, even at the same filler wt.%. Furthermore, the sample containing 60 % by weight of nano-WC, coded as P-60nWC, had superior shielding performance than other polymer-based composites reported in the literature. Thus, the proposed nano-WC/PMMA composites can be effectively employed in radiation facilities as alternative environmentally and lead-free radiation shielding materials to protect people and the environment from the harmful risks of gamma radiation.

Abstract Long-term oral health issues caused by fungi and bacteria are a primary concern for individuals who wear dentures. Denture stomatitis, primarily caused by Candida albicans (C. albicans), is a prevalent condition among denture users. Metal nanoparticles exhibit improved antimicrobial effectiveness and fewer adverse effects. This study aimed to evaluate the antifungal and antibacterial effects of nystatin-coated silver nanoparticles (Nys-coated AgNPs) embedded in acrylic resin as a more biocompatible material for denture resins. AgNPs and Nys-coated AgNPs were synthesized and characterized using UV-Vis, SEM, EDX, and DLS. Specimens of polymethyl methacrylate (PMMA) with three different concentrations of Nys, AgNPs, and Nys-coated AgNPs (0.1%, 1%, 10% w/w) were prepared. The water absorption properties of the disks and drug release were investigated for 14 days and 120 h, respectively. The hydrophilic and hydrophobic properties of the samples and their contact angles were evaluated using the sessile drop technique. The antifungal and antimicrobial activity of the prepared discs was studied against C. albicans and Streptococcus mutans, respectively. Adding Nys-coated AgNPs decreased the contact angle of discs from 67° to 49°. Furthermore, the water absorption rates of the different discs were not significantly different from those of the control groups. Results showed that Nys-coated AgNPs (10% w/w) in PMMA effectively inhibited C. albicans growth better than Nys composites (10% w/w). Additionally, Nys-coated AgNPs composites, as well as AgNPs-containing composites, showed considerable antibacterial activity against S. mutans. Nys-coated AgNPs (10% w/w) had no toxic effect on NIH3T3 cells. In conclusion, Nys-coated AgNPs could be considered a good candidate for incorporation into denture resins to address chronic oral diseases.

Aim: This study aims to evaluate the surface homogeneity of poly methyl methacrylate (PMMA) resin fabricated by two different methods of incorporating titanium dioxide nanoparticles (NPs). Settings and Design: In vitro study; qualitative analysis. Materials and Methods: PMMA resin was divided into two groups with 1% of titanium dioxide NPs were added to each group; Group A contained NPs incorporated in the polymer through magnetic stirring for 60 min and Group B contained NPs incorporated in the monomer through ultrasonic dispersion for 60 min. Ten acrylic block samples were fabricated by standard method for each group and then tested for surface homogeneity by scanning electron microscopy analysis for qualitative analysis. Results: Group A showed NPs as defined pale white dots with a consistent distribution pattern and minimal air entrapment. Group B showed NPs agglomerated forming clusters of white dots with flaky sheet-like structures. Conclusion: Magnetic stirring of NPs into polymer showed better surface homogeneity than the ultrasonic dispersion of NPs in monomer. The NP incorporation method plays a role in modifying the surface homogeneity of the acrylic.

Long-term oral health issues caused by fungi and bacteria are a primary concern for individuals who wear dentures. Denture stomatitis, primarily caused by Candida albicans (C. albicans), is a prevalent condition among denture users. Metal nanoparticles exhibit improved antimicrobial effectiveness and fewer adverse effects. This study aimed to evaluate the antifungal and antibacterial effects of nystatin-coated silver nanoparticles (Nys-coated AgNPs) embedded in acrylic resin as a more biocompatible material for denture resins. AgNPs and Nys-coated AgNPs were synthesized and characterized using UV-Vis, SEM, EDX, and DLS. Specimens of polymethyl methacrylate (PMMA) with three different concentrations of Nys, AgNPs, and Nys-coated AgNPs (0.1%, 1%, 10% w/w) were prepared. The water absorption properties of the disks and drug release were investigated for 14 days and 120 h, respectively. The hydrophilic and hydrophobic properties of the samples and their contact angles were evaluated using the sessile drop technique. The antifungal and antimicrobial activity of the prepared discs was studied against C. albicans and Streptococcus mutans, respectively. Adding Nys-coated AgNPs decreased the contact angle of discs from 67° to 49°. Furthermore, the water absorption rates of the different discs were not significantly different from those of the control groups. Results showed that Nys-coated AgNPs (10% w/w) in PMMA effectively inhibited C. albicans growth better than Nys composites (10% w/w). Additionally, Nys-coated AgNPs composites, as well as AgNPs-containing composites, showed considerable antibacterial activity against S. mutans. Nys-coated AgNPs (10% w/w) had no toxic effect on NIH3T3 cells. In conclusion, Nys-coated AgNPs could be considered a good candidate for incorporation into denture resins to address chronic oral diseases. [ABSTRACT FROM AUTHOR]

Nerve injuries and neurodegenerative disorders remain serious challenges due to the poor results of nerve cell regeneration. The most promising treatment for such injuries is treatments based on stimulating cells to grow and differentiate stem cells in that area into nerve cells, but there are obstacles in controlling the growth and differentiation into fully functional nerve cells and research is ongoing to overcome these obstacles. In this study, polymethyl methacrylate (PMMA) and its laser modified surfaces were used for cell culture and differentiation into neuron-like cells. In order to show the differentiation of PC12 cells into neuron-like cells, the expression levels of the neuronal markers Map2 and Synapsin-1 were examined. The results showed the growth of PC12 on raw PMMA was increased significantly compared to the control group and micrometric parallel grooves lead to a significant difference in cell growth compared to raw PMMA. Also, the simultaneous irradiation of laser to the cell cultured on PMMA caused more cell adhesion on the surface, faster growth and differentiation of PC12 into neuron-like cells. [ABSTRACT FROM AUTHOR]

Aim: This study aims to evaluate the surface homogeneity of poly methyl methacrylate (PMMA) resin fabricated by two different methods of incorporating titanium dioxide nanoparticles (NPs). Settings and Design: In vitro study; qualitative analysis. Materials and Methods: PMMA resin was divided into two groups with 1% of titanium dioxide NPs were added to each group; Group A contained NPs incorporated in the polymer through magnetic stirring for 60 min and Group B contained NPs incorporated in the monomer through ultrasonic dispersion for 60 min. Ten acrylic block samples were fabricated by standard method for each group and then tested for surface homogeneity by scanning electron microscopy analysis for qualitative analysis. Results: Group A showed NPs as defined pale white dots with a consistent distribution pattern and minimal air entrapment. Group B showed NPs agglomerated forming clusters of white dots with flaky sheet-like structures. Conclusion: Magnetic stirring of NPs into polymer showed better surface homogeneity than the ultrasonic dispersion of NPs in monomer. The NP incorporation method plays a role in modifying the surface homogeneity of the acrylic. [ABSTRACT FROM AUTHOR]

Background: The objective of this research was to explore how the addition of boron nitride (BN) nanoparticles in the concentrations of 1% and 1.5% w/w affect the impact strength and surface roughness of heat-cured poly methyl methacrylate resin (PMMA). Methods: Sixty specimens were made from heat-cured acrylic resin and then divided into control, 1%, and 1.5% w/w BN groups. The impact strength and surface roughness were investigated. One-way ANOVA and Tukey’s post hoc test were used for data analysis. Results: Statistically significant difference is found among the three study groups regarding impact strength (P = 0.011) and surface roughness test (P < 0.001). The post hoc test showed significant differences for all multiple comparisons for the surface roughness test (P < 0.001). Yet, multiple comparisons for the impact strength test revealed only a significant difference between the 1.5% BN and control groups (P = 0.005). Conclusion: The addition of boron BN into PMMA improves impact strength with 1.5% concentration; while adversely increase the surface roughness.

Introduction: This study aimed to find out how exposure to gaseous ozone affected heat-cured acrylic resin’s transverse and impact strengths. Methods: Sixty samples of heat-cured acrylic resin were prepared and divided into three subgroups, control, microwave radiation (positive control), and gaseous ozone. Transverse strength and impact strength were evaluated using testing machines. At a level of significance of 5%, data were assessed using one-way analysis of variance (ANOVA) and Tukey’s post hoc test. Results: Transverse strength analysis showed a significant difference among groups (P < 0.001). Post hoc test revealed significant differences between all multiple groups (P < 0.001). Impact strength analysis results showed a non-significant difference among groups (P = 0.13). Conclusion: Within the limits of this research, it is possible to conclude that gaseous ozone exposure improves the transverse strength of heat-cure acrylic resin.

In radiation dosimetry, achieving electronic equilibrium is vital for accurate dose measurements in radioprotection. This study investigates the effect of Poly Methyl Methacrylate (PMMA) layers, known by its chemical formula C 5 H 8 O 2 and a density of 1.19 g/cm³ (PNNL, 2011), on electronic equilibrium for the calibration of radiation protection instruments, focusing on photon beams of varying energies. Using DOSIMEX 2.0 simulation software, we modeled the influence of PMMA thickness on calibration factors across different X-ray and gamma-ray beam energies. Experimental validation with Cs-137 and Co-60 sources confirmed the reliability of the simulation. Our results highlight that while PMMA layers have a minimal impact on calibration for higher-energy beams, their role becomes significant for energies below 40 keV. For X-ray beams (From 30 to 140 kV), the results show minimal calibration factor deviation (<1.6%), whereas radionuclide beams exhibit more significant variations (4.1%), necessitating customized calibration approaches. This study underscores the importance of adhering to ISO 4037-3 standards in radioprotection, particularly in low-energy scenarios, to ensure the precision of calibration procedures and optimize radiation protection practices. Furthermore, based on the results obtained, the absence of PMMA does not have a dramatic effect on the calibration of X-ray radiation instruments, whereas for gamma-ray beams, it has a significant impact. • First study to verify the impact of not considering this effect: PMMA layers on electronic equilibrium during radioprotection instrument calibration. • Shows minimal calibration factor deviation (<1.6%) for X-ray beams but significant variations (4.1%) for radionuclide beams, requiring customized calibration approaches. • Stresses the importance of adhering to international standards, like those set by the IAEA and ISO, in radiation dosimetry. • Highlights the importance of adding a 3 mm PMMA layer for calibration, especially for energies below 40 keV and with Co-60 sources. [ABSTRACT FROM AUTHOR]

The effect of a novel nano-ceramic coating (TiO2) using an atomic layer deposition (ALD) technique on the surface of polymethyl methacrylate (PMMA) material was investigated. The patients' and clinicians' perception and acceptance of the PMMA color with TiO2 coating were also examined. In vitro color measurement was performed on thirty specimens (light, original, and dark pink) before and after TiO2 coating. Patients' and clinicians' perception and acceptance of color changes on PMMA were measured and compared. Descriptive and analytic statistics were analyzed (a = 0.05). TiO2 films were successfully deposited on the PMMA specimen by the ALD technique. Color changes after TiO2 coating were observed on all three PMMA shades, significantly higher than the established 50:50% perceptibility threshold, but below the established 50:50% acceptability threshold. The percentage of patients that perceived a color difference after TiO2 coating were 83.3%, 63.9%, and 77.8% for light, original, and dark pink, respectively. The percentages of clinicians that were satisfied with the color difference were 96.4%, 80%, and 69.2% for light, original, and dark pink, respectively. Color changes after TiO2 coating were observed, but below the acceptable threshold. The clinical survey demonstrated that a color difference was perceived but was clinically acceptable. In general, laypeople have lower perception and higher acceptance of changes in PMMA color than clinicians. [ABSTRACT FROM AUTHOR]

Statement of the Problem: Composite restoration failures may occur because of different factors. In these situations, the repair of a composite restoration has many advantages over replacement such as saving time, lower cost, and lower risk of excessive removal of sound tooth structure and subsequent pulp exposure. Purpose: The purpose of this in vitro study was to evaluate the effects of two surface treatments on shear bond strength (SBS) of new composite to old composite. Materials and Method: In this in vitro study, 60 composite discs were fabricated using a plexiglass mold measuring 4 mm in thickness and 7 mm in diameter, and were randomly divided into three groups (n=20). In group 1, the bonding procedure was done with no modification. After roughening of one surface in all remaining samples, chloroform (CHCl3) was applied on the surface of samples in group 2 and phosphoric acid 35% was applied on the surface of the samples in group 3. PermaSeal was then applied in all samples and new composites were bonded to the surface. The samples were stored in distilled water for one week and were then subjected to 500 thermal cycles and shear bond strength between two layers of composite and mode of failures were evaluated. Results: The lowest and the highest SBS values of repair composite to old composite were noted in groups 3 and 1, respectively and this difference was statistically significant (p< 0.05).The difference between groups 1 and 2 was not significantly different (p= 0.197). The mode of failure was mixed in all samples of groups 2 and 3 and cohesive in group 1. Conclusion: After grinding, the surface treatment with phosphoric acid did not increase the SBS of new composite to old composite, while chloroform increased the SBS almost to the level of the baseline in control group.

Here, for the first time, a 2D and leaf-like zeolitic imidazolate framework (ZIF-L) is reported for the synthesis of ultrahigh molecular weight (UHMW) poly(methyl methacrylate) (PMMA) with Mn up to 1390 kg mol−1. This synthesis method is a one-step process without any co-catalyst in a solvent-free medium. SEM, PXRD, FT-IR, TGA, and nitrogen sorption measurements confirmed the 2D and leaf-like structure of ZIF-L. The results of PXRD, SEM, TGA demonstrate that the catalyst ZIF-L is remarkably stable even after a long-time polymerization reaction. Zwitterionic Lewis pair polymerization (LPP) has been proposed for the catalytic performance of ZIF-L on methyl methacrylate (MMA) polymerization. This MMA polymerization is consistent with a living system, where ZIF-L could reinitiate the polymerization and propagates the process by gradually growing the polymer chains. [ABSTRACT FROM AUTHOR]

Background and Aims: Poly methyl methacrylate (PMMA) is still the most commonly used material in prosthetic dentistry. However, there are problems with the mechanical properties of this type of material including low flexural strength. Addition of nanoparticles into the polymer is one way to improve the mechanical properties of acrylic resin. In the present study, the effect of silicon dioxide (SiO2) nanoparticles addition into the heat-cured acrylic resin in different concentrations was investigated. Because of the controversy had been observed in previous articles, the aim of this study was to investigate the mechanical properties of PMMA/SiO2 nanoparticle obtained from different percentages of SiO2. Materials and Methods: In this in-vitro study, acrylic resin specimens containing 0, 1, 3 and 5% silicon dioxide (SiO2) were prepared. The specimens were placed inside the gypsum molds and placed under pressure for three times. The mold cured in boiling water for 30 min. A trimmer was used to remove the additives. Sandpapers with 180, 320 and 600 grains of silicon-carbide were used for final finishing and polishing. Finally, the flexural strengths were measured using a universal testing machine. Data were finally analyzed by ANOVA and Tukey tests at a significant level of 5% using SPSS software. Results: The mean flexural strengths and standard deviations of control group, 1% filler, 3% filler, and 5% filler, were 57.24±8.30, 69.98±7.26, 60.16±9.18, and 61.59±9.28 MPa, respectively. After comparing significant values between each group with the control group, a significant difference was observed between the control and 1% filler group (P=0.021). However, no significant difference was observed between 3 and 5% fillers with the control group or each other. The significant differences (P-value) between 3% filler and control group were 0.892 and between 5% filler and control group was 0.975. Conclusion: The results of the present study showed that the use of low percentage of silicone dioxide (SiO2) nanofiller could improve the flexural strength of poly methyl methacrylate acrylic resin.

الملخص: أهداف البحث: على الرغم من توافر مجموعة واسعة من المضادات الحيوية، لا يتم الشفاء من العدوى العضلية الهيكلية بنجاح. إن إزالة الأوشظة، والأنسجة النخرية المصابة والغرسات ضرورية. وقد أجريت هذه الدراسة لتقييم فعالية خرز البولي ميثيل ميثكريلات، ولتحديد المتغيرات التي تؤثر على علاج وتكرار الالتهابات العضلية الهيكلية. طرق البحث: ضمت هذه الدراسة ٨٢ مريضا يعانون من التهاب العظم والنقي المزمن، الذين عولجوا على مدى ست سنوات في مستشفى الرعاية الثالثة. تابعنا ٧١ مريضا لمدة عام. وتم تقييم البيانات السريرية الدوائية لمكافحة العدوى وشفاء العظام في زيارة المتابعة الأخيرة. تم تقييم العلاقة بين حساسية المضادات الحيوية والمقاومة وتكرار العدوى لتركيبات جينتامايسين+ سيفروكسيم، وجينتامايسين+ فانكومايسين. النتائج: كان لدى ٥٣ (٦٥.٤٪) من المرضى طريق خارجي للعدوى، بينما قَدِم ٥٦(٦٨.٥١٪) من المرضى مع إفرازات جيبية وقت المراجعة. تم التحقق عند ٤٢ (٥٩٪) من المرضى من التشخيص مع مزرعة بكتيريا إيجابية. بالإضافة إلى ذلك، استخدمنا خرزات المضادات الحيوية من الجينتامايسين +السيفوروكسيم في ٧٤ (٩٠٪) من المرضى، في حين أن في ٨ (١٠٪) من المرضى استخدمنا الجنتامايسين + الفانكومايسين على أساس المزرعة ونتائج الحساسية. وتم العثور على عودة العدوى عند خمس حالات من الجنتامايسين +السيفوروكسيم واثنين من حالات الجنتامايسين + الفانكومايسين. الاستنتاجات: المضادات الحيوية التي تحتوي على خرز البولي ميثيل ميثكريلات فاعلة في علاج التهاب العظم والنقي المزمن وفي منع تكرار العدوى. ومن الضروري تحديد العوامل المختلفة المسؤولة عن تكرار الإصابة. وهذا قد يساعد الأطباء في التنبؤ بتكهن المرض وتقليل خطر النتائج السلبية. Abstract: Objective: Despite the availability of an extensive array of antibiotics, musculoskeletal infections are not cured successfully. It is necessary to remove sequestra, infected necrotic tissue, and implants. This study was undertaken to assess the efficacy of poly methyl methacrylate (PMMA) beads and identify the variables that influence eradication and recurrence in the treatment of musculoskeletal infections. Methods: This study was conducted on 82 patients with chronic osteomyelitis who were treated over a period of 6 years at our tertiary care hospital. We followed up with 71 patients for one year. Clinicoradiological data for the control of infection and bone healing were assessed at the final follow up visit. The correlation between antibiotic sensitivity/resistance and infection was evaluated for Gentamicin + Cefuroxime and Gentamicin + Vancomycin combinations. Chi-squared testing, using SPSS version 16.0, was used for statistical analysis, and a p-value < 0.05 was considered significant. Results: Fifty-three patients (65.4%) had an exogenous route of infection. Fifty-six patients (68.51%) presented with a discharging sinus on first presentation. In 42 patients (59%), the diagnosis was verified with a positive bacterial culture. In addition, we used antibiotic beads of Gentamicin + Cefuroxime in 74 patients (90%), while in 8 patients (10%), we used Gentamicin + Vancomycin, based on culture and sensitivity results. Recurrence was found in five cases of Gentamicin + Cefuroxime and two cases of Gentamicin + Vancomycin (p = 0.065). Conclusion: Antibiotics containing PMMA beads are effective in the treatment of chronic osteomyelitis and in preventing the recurrence of infection. It is imperative to identify various factors responsible for the recurrence of infection. This may help clinicians predict the prognosis of the disease and minimise the risk of adverse outcomes.

In recent years, many researchers used polymethyl methacrylate in dental applications due to good mechanical and physical properties. In this research, the eggshell powder had mixed with polymethyl methacrylate resin for the preparations of new composite materials have good mechanical properties and low cost compared with industrially processed powders. The hand lay-up technique was adopted for the preparation specimens composite materials that made from a polymethyl methacrylate as a matrix with (1%, 3%, 5% and 7%) weight fraction eggshell powder (before and after burning) a reinforcement material. The mechanical properties were analyzed by utilizing (SPSS) according to (One-Way ANOVA). The results showed that the addition of the eggshell (before and after burning) powder at a ratio of (7% weight fraction) improves the values of tensile properties and fracture toughness, while this ratio leads to a decrease in values of elongation percentage at break and impact strength compared with other specimens. Also, the results showed that the Sig value was lower in all mechanical properties of specimens reinforced with eggshell powder after burning than specimens reinforced with eggshell powder before burning with a polymethyl methacrylate resin, where the percentage of improvement was in ultimate tensile strength 64 %, modulus of elasticity 13 %, elongation percentage 6 %, impact strength 75% and 81% fracture toughness.

Introduction: This study aimed to find out how exposure to gaseous ozone affected heat-cured acrylic resin’s transverse and impact strengths. Methods: Sixty samples of heat-cured acrylic resin were prepared and divided into three subgroups, control, microwave radiation (positive control), and gaseous ozone. Transverse strength and impact strength were evaluated using testing machines. At a level of significance of 5%, data were assessed using one-way analysis of variance (ANOVA) and Tukey’s post hoc test. Results: Transverse strength analysis showed a significant difference among groups (P < 0.001). Post hoc test revealed significant differences between all multiple groups (P < 0.001). Impact strength analysis results showed a non-significant difference among groups (P = 0.13). Conclusion: Within the limits of this research, it is possible to conclude that gaseous ozone exposure improves the transverse strength of heat-cure acrylic resin. [ABSTRACT FROM AUTHOR]

Statement of the Problem: Composite restoration failures may occur because of different factors. In these situations, the repair of a composite restoration has many advantages over replacement such as saving time, lower cost, and lower risk of excessive removal of sound tooth structure and subsequent pulp exposure. Purpose: The purpose of this in vitro study was to evaluate the effects of two surface treatments on shear bond strength (SBS) of new composite to old composite. Materials and Method: In this in vitro study, 60 composite discs were fabricated using a plexiglass mold measuring 4 mm in thickness and 7 mm in diameter, and were randomly divided into three groups (n=20). In group 1, the bonding procedure was done with no modification. After roughening of one surface in all remaining samples, chloroform (CHCl3) was applied on the surface of samples in group 2 and phosphoric acid 35% was applied on the surface of the samples in group 3. PermaSeal was then applied in all samples and new composites were bonded to the surface. The samples were stored in distilled water for one week and were then subjected to 500 thermal cycles and shear bond strength between two layers of composite and mode of failures were evaluated. Results: The lowest and the highest SBS values of repair composite to old composite were noted in groups 3 and 1, respectively and this difference was statistically significant (p< 0.05).The difference between groups 1 and 2 was not significantly different (p= 0.197). The mode of failure was mixed in all samples of groups 2 and 3 and cohesive in group 1. Conclusion: After grinding, the surface treatment with phosphoric acid did not increase the SBS of new composite to old composite, while chloroform increased the SBS almost to the level of the baseline in control group. [ABSTRACT FROM AUTHOR]

Background: Occlusal loading of osseointegrated implants is believed to be an essential determining factor in the long-term success of an implant treatment. Numerous studies have been conducted on the evaluation of stress distribution by definitive restoration materials for Implant-supported fixed prosthesis, but very few have evaluated provisional restoration materials for the same. This study aims to evaluate the influence of provisional restoration material – Milled Polymethylmethacrylate (PMMA) and Milled Polyetheretherketone (PEEK), over stress distribution on the peri-implant bone around an implant-supported three-unit, fixed dental prosthesis using finite element analysis method. Materials and Methods: Three-dimensional models of a pair of bone-level implant system and titanium base abutments were created using the standard tessellation language data of original implant components. A bone block representing the mandibular posterior area was created, and the implants were placed in the bone block with 100% osseointegration in the 2nd premolar to 2nd molar region. A superstructure of an implant-supported 3-unit bridge was modeled on top of the abutments, each crown to be 8 mm in height and with an outer diameter of 6 mm in 2nd premolar region and 10 mm in 1st molar and 2nd molar region. Two different models were created according to combinations of provisional restoration materials, namely, Milled PMMA and Milled PEEK based on. In each model, the implants were loaded vertically (300 N) and obliquely (150 N at 30°). The stress distribution in the cortical bone, cancellous bone, and implant was evaluated through the von Mises stress analysis. Results: The results showed no difference in stress distribution due to the different provisional restorations – Milled PMMA and Milled PEEK. In addition, the vertical load resulted in higher stress values in the implant components, cortical bone, and cancellous bone in both PEEK and PMMA models as compared to oblique loading. Conclusion: The new polymer, PEEK was seen to provide comparable stress generation in the current study without exceeding the physiological limits of peri-implant bone. Thus, it can be considered as a good alternative to PMMA resin as a provisional crown material since it provides certain additional benefits.

Purpose: The aim of this study was to compare the differences between the ASTM D790 and ISO 20795.1.2013 standards in evaluating the flexural strength of heat cure poly methyl methacrylate (PMMA) denture base resin. Materials and Methods: 30 heat cure denture base samples were fabricated in accordance to ISO 20795.1.2013 and ASTM D790 Standards. The specimens were finished and stored following the standardized protocol. The flexural strength was determined using universal testing machine at cross head speed of 1.50 mm/min and a span length of 40.00 mm. The mean flexural strength values were calculated in megapascals (MPa), and statistically analyzed. Results: The mean flexural strength of heat cure PMMA found with ISO and ASTM ranged between 60.492 MPa and 61.470 MPa. There was no significant difference between the two methods. Conclusion: The quantitative differences existed in the flexural strength of denture base resin between ISO 20795.1.2013and ASTM 790 protocols but those differences had no statistical and clinical significance.

Purpose The aim of this study was to compare the differences between the ASTM D790 and ISO 20795.1.2013 standards in evaluating the flexural strength of heat cure poly methyl methacrylate (PMMA) denture base resin. Materials and Methods 30 heat cure denture base samples were fabricated in accordance to ISO 20795.1.2013 and ASTM D790 Standards. The specimens were finished and stored following the standardized protocol. The flexural strength was determined using universal testing machine at cross head speed of 1.50 mm/min and a span length of 40.00 mm. The mean flexural strength values were calculated in megapascals (MPa), and statistically analyzed. Results The mean flexural strength of heat cure PMMA found with ISO and ASTM ranged between 60.492 MPa and 61.470 MPa. There was no significant difference between the two methods. Conclusion The quantitative differences existed in the flexural strength of denture base resin between ISO 20795.1.2013 and ASTM 790 protocols but those differences had no statistical and clinical significance.

In the dentures industry, materials must be chosen to have good mechanical properties in order to resist the conditions that may occur in the mouth. A study was conducted to assess tensile strength, elasticity coefficient, elongation, flexural strength, flexural modulus with impact properties of poly methyl methacrylate resin as matrix strengthened with cinnamon powder and also analysing these mechanical properties by using (OriginLab) software program. The samples of Poly Methyl methacrylate bio composites which containing 2%, 4%, 6%, and 8% weight fractions of cinnamon powder and an unfilled as control sample were fabricated using “hand lay up” method. The results indicate that the addition of 8% weight fraction cinnamon powder into Poly Methyl methacrylate resin improved of ultimate tensile strength, modulus elasticity ,flexural strength, flexural modulus (62 MPa, 3.7 GPa, 96 MPa, 6.4 GPa) respectively, compared with the values of pure Poly Methyl methacrylate (51 MPa, 1.5 GPa, 78MPa, 2.0 GPa) respectively. Also can be noted that the elongation at break values decreases with an increase in weight fractions of filler, where the sample (Poly Methyl methacrylate +2% cinnamon) has the best value for elongation compared with samples reinforced (4%, 6% and 8% wt). The impact strength results observe the maximum value was present in the sample (Poly Methyl methacrylate+6% cinnamon). From the results, descriptive, One Way ANOVA statistical analysis and means comparison by used (Scheffe test and Tukey test) for all mechanical properties indicated, turns out if Sig equals 1 shows that the variance in mean is significant at the level of 0.05, whereas Sig is 0 designates that the mean variance is not significant at the level 0.05.

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Purpose: The study aimed to compare the effect of different materials, thicknesses, and polymerization methods and cycles, on the surface porosity of acrylic denture base resins. Materials and Methods: Conventional heat-polymerized polymethyl methacrylate (PMMA) and specially designed acrylic resin (Acron MC) were used to make 84 rectangular samples. They were divided into three groups to evaluate and compare the polymerization techniques, curing cycles, and thicknesses of the two denture base materials (28 samples each). Group A contained PMMA samples polymerized using water bath method (control group); Group B contained Acron MC samples polymerized by microwave method, and Group C contained PMMA samples polymerized by microwave method. Each group was further divided based on sample thickness and polymerization cycles. Each sample was scanned for surface porosity and area of each pore was measured using optical microscope. Data was analyzed using ANOVA, Bonferroni, and student t-tests. Unpaired student t-test was performed to compare the means of surface porosity with polymerization cycles and thicknesses among the groups. The power of study was kept at 80%. Results: Group C showed highest mean % of porosity depending on method of polymerization, different polymerization cycles (short and long) and polymerization cycles within the group. Group B showed the highest mean % of porosity depending on thickness and thickness within the groups. Conclusions: Microwavable acrylic resin polymerized by microwave energy exhibited statistically insignificant increase in porosity when compared to conventional heat cured acrylic resin by water bath method. Conventional acrylic resin polymerized by microwave energy exhibited high statistically significant porosity irrespective of sample thickness. There was statistically insignificant increase in porosity depending on sample thickness irrespective of material and method of polymerization.

Background & Objective: Currently selection and use of nanoparticle adjuvant is very important. Due to the lack of effective anti-snakebite serums to treat it and high cost of purchasing external anti-snakebite serums, preparation of suitable internal nanoparticles to produce hyper-immunization plasma has become very important. In order to minimize the disadvantages associated with traditionally used adjuvants in ovines and to produce potent antivenum, a comparison was made between various adjuvants for their immune-potentiation capacity and safety. Material & methods: The present study was conducted in 15 sheep, divided into three groups and hyper-immunized using crude venom of cobra snake (Naja naja oxiana) along with three adjuvants, Montanide, aluminum phosphate and poly methyl methacrylate through subcutaneous route at intervals of a week. Periodic standard safety assessments were done. Results: The neutralization activity (LD50) of pooled sera samples by 9th week, obtained with aluminum phosphate, Montanide and poly methyl methacrylate groups were 1.5, 2.2 and 2 LD50/ml respectively. The sheep of poly methyl methacrylate group showed minimum local reactions at injection site, while sheep from other two groups exhibited moderate reactions. However, these were transient and reabsorbed or healed subsequently. Conclusion: Poly methyl methacrylate nanoparticle adjuvant could be a possible alternative to the emulsion adjuvants for primary phase of immunization in antivenomous preparation considering its acceptable immunopotentiation capacity and safety in donor animals.

Background and Aims: Poly methyl methacrylate (PMMA) is still the most commonly used material in prosthetic dentistry. However, there are problems with the mechanical properties of this type of material including low flexural strength. Addition of nanoparticles into the polymer is one way to improve the mechanical properties of acrylic resin. In the present study, the effect of silicon dioxide (SiO2) nanoparticles addition into the heat-cured acrylic resin in different concentrations was investigated. Because of the controversy had been observed in previous articles, the aim of this study was to investigate the mechanical properties of PMMA/SiO2 nanoparticle obtained from different percentages of SiO2. Materials and Methods: In this in-vitro study, acrylic resin specimens containing 0, 1, 3 and 5% silicon dioxide (SiO2) were prepared. The specimens were placed inside the gypsum molds and placed under pressure for three times. The mold cured in boiling water for 30 min. A trimmer was used to remove the additives. Sandpapers with 180, 320 and 600 grains of silicon-carbide were used for final finishing and polishing. Finally, the flexural strengths were measured using a universal testing machine. Data were finally analyzed by ANOVA and Tukey tests at a significant level of 5% using SPSS software. Results: The mean flexural strengths and standard deviations of control group, 1% filler, 3% filler, and 5% filler, were 57.24±8.30, 69.98±7.26, 60.16±9.18, and 61.59±9.28 MPa, respectively. After comparing significant values between each group with the control group, a significant difference was observed between the control and 1% filler group (P=0.021). However, no significant difference was observed between 3 and 5% fillers with the control group or each other. The significant differences (P-value) between 3% filler and control group were 0.892 and between 5% filler and control group was 0.975. Conclusion: The results of the present study showed that the use of low percentage of silicone dioxide (SiO2) nanofiller could improve the flexural strength of poly methyl methacrylate acrylic resin. [ABSTRACT FROM AUTHOR]

Because of some undesirable properties of polymethyl methacrylate(PMMA) bone cement, it is necessary to adopt a new strategy to improve its function. In this study, after preparing of chitosan (CS) powder and CS/multiwalled carbon nanotubes (MWCNTs) composite powder, they were added to the PMMA bone cement in different percentages with homogeneous distribution. The results showed that by adding CS/MWCNTs to the PMMA, injectability and setting time were increased and maximum temperature and contact angle were decreased, significantly. Mechanical tests showed that by adding 25 wt. % of CS/MWCNTs to the PMMA, the compressive and bending strength were increased, significantly. According to the results obtained from the bioactivity and cellular activity test, by adding 25 wt. % of CS/MWCNTs to the PMMA, apatite like deposition and extra cellular matrix formation were increased, significantly. Accordingly, 25 wt. % PMMA-CS/MWCNTs composite can create a new approach to improve commercial bone cements. [ABSTRACT FROM AUTHOR]

Copyright of Baghdad Science Journal is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Engineering & Sustainable Development is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• The low concentrations of photocatalytic nanoparticles, such as emodin (≤0.5 %), curcumin (≤0.5 %), curcumin nisin (≤5 %), and ulva lactuca (≤1 %), could be incorporated into orthodontic acrylic resins without compromising flexural strength. • The addition of zinc oxide (≤2 %) and titanium dioxide (≤3 %) to acrylic resins improved flexural strength. • Titanium dioxide was found to be the most prevalent photocatalytic nanoparticle. Orthodontic acrylic resins containing antimicrobial photocatalytic nanoparticles aims to reduce oral lesions including denture stomatitis and white spot lesions but they should not imperil its mechanical properties. This systematic review was done to evaluate the effect of various photocatalytic nanoparticles on the flexural strength (FS) of acrylic resins. We systematically searched the PubMed/Medline, Cochrane Library, and Scopus databases from January 2018 to October 2023. The review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, and the quality of the studies was evaluated using the QUIN tool, which is specifically designed to assess the risk of bias in vitro studies. Following screening of 1016 initial records, 23 studies were deemed eligible for inclusion. The addition of photocatalytic nanoparticles, such as emodin (Emo), curcumin (Cur), Cur nisin (CurNis), zeolite/zinc oxide (Zeo/ZnO), and Ulva lactuca (U. lactuca), to acrylic resins resulted in a reduction in FS, with the extent of reduction dependent on the nanoparticle concentration. Specifically, the addition of Emo (≥0.5 %), Cur (≥0.5 %), CurNis (≥5 %), Zeo/ZnO (≥2), and U. lactuca (≥1 %) to acrylic resins significantly decreased FS. Conversely, the inclusion of ZnO and titanium dioxide (TiO 2) in acrylic resins improved FS, but higher concentrations (≥5 % for TiO 2) had a limited positive effect. Our study supports the use of low concentrations of photocatalytic nanoparticles, such as ZnO (≤2 %), TiO 2 (≤3 %), Emo (≤0.5 %), Cur (≤0.5 %), CurNis (≤5 %), and U. lactuca (≤1 %), in orthodontic acrylic resins without compromising FS. [ABSTRACT FROM AUTHOR]

Purpose: The study aimed to compare the effect of different materials, thicknesses, and polymerization methods and cycles, on the surface porosity of acrylic denture base resins.Materials and Methods: Conventional heat-polymerized polymethyl methacrylate (PMMA) and specially designed acrylic resin (Acron MC) were used to make 84 rectangular samples. They were divided into three groups to evaluate and compare the polymerization techniques, curing cycles, and thicknesses of the two denture base materials (28 samples each). Group A contained PMMA samples polymerized using water bath method (control group); Group B contained Acron MC samples polymerized by microwave method, and Group C contained PMMA samples polymerized by microwave method. Each group was further divided based on sample thickness and polymerization cycles. Each sample was scanned for surface porosity and area of each pore was measured using optical microscope. Data was analyzed using ANOVA, Bonferroni, and student t-tests. Unpaired student t-test was performed to compare the means of surface porosity with polymerization cycles and thicknesses among the groups. The power of study was kept at 80%.Results: Group C showed highest mean % of porosity depending on method of polymerization, different polymerization cycles (short and long) and polymerization cycles within the group. Group B showed the highest mean % of porosity depending on thickness and thickness within the groups.Conclusions: Microwavable acrylic resin polymerized by microwave energy exhibited statistically insignificant increase in porosity when compared to conventional heat cured acrylic resin by water bath method. Conventional acrylic resin polymerized by microwave energy exhibited high statistically significant porosity irrespective of sample thickness. There was statistically insignificant increase in porosity depending on sample thickness irrespective of material and method of polymerization. [ABSTRACT FROM AUTHOR]

In this study, we synthesized cross-linked poly methyl methacrylate beads and cross-linked fluorinated poly methacryalte copolymer (F-cPMMA) beads by the dispersion polymerization method with methyl methacrylate monomer, ethylene glycol dimethacrylate, and 2,2,2-trifuloroethyl methacrylate. The size of cross-linked PMMA and F-cPMMA beads was about 100 nm. Then we developed a new geometrical high-hydrophobic film by embedding the F-cPMMA nanobeads on polyurethane (PU) film. The PU film containing fluorinated poly methacryalte copolymer beads showed a greater hydrophobic property than the non-fluorinated one in the range of 1–10 wt.%. For the purpose of industrial application of the PU films, we applied 0.1–1 wt.% of beads on the fabric by the laminating method. The PU film containing 1 wt.% of fluorinated poly methacryalte copolymer beads, which was laminated onto nylon fabric, showed the best performance of hydrophobic property (water contact angle, 79°) and moisture vapor transmission rate (8797 g·m–2·24 h). [ABSTRACT FROM AUTHOR]

Bioactive scaffolds with polymer and nanostructured bioactive glass-based composites are promising materials for regenerative applications in consequence of close mimics of natural bone composition. Poly methyl methacrylate (PMMA) is a highly preferred thermoplastic polymer for orthopedic applications as it has good biocompatibility. Different kinds of bioactive, biodegradable as well as biocompatible biomaterial composites such as Bioglass (BG), Hydroxyapatite (Hap), and Tricalcium phosphate (TCP) can be integrated with PMMA, so as to augment the bioactivity, porosity as well as regeneration of hard tissues in human body. Among the bioactive glass, 60S BG (Bioactive glass with 60 percentage of Silica without Sodium ions) is better materials among aforementioned systems owning to mechanical stability as well as controlled bioactive material. In this work, the fabrication of PMMA-CaP (calcium phosphate)-based scaffolds were carried out by Thermal Induced Phase Separation method (TIPS). X-ray diffractogram analysis (XRD) is used to examine the physiochemical properties of the scaffolds that evidently reveal the presence of calcium phosphate besides calcium phosphate silicate phases. The Field Emission Scanning Electron Microscopy (FESEM) studies obviously exhibited the microstructure of the scaffolds as well as their interconnected porous morphology. The PMMA/60S BG/TCP (C50) scaffold has the maximum pore size, measuring 77 ± 23 μm, while the average pore size ranges from 50 ± 20 to 80 ± 23 μm. By performing a liquid displacement method, the C50 scaffold is found to have the largest porosity of 50%, high hydrophilicity of 118.16°, and a compression test reveals the scaffolds to have a maximum compressive strength of 0.16 MPa. The emergence of bone-like apatite on the scaffold surface after 1st and 21st days of SBF immersion is further supported by in vitro bioactivity studies. Cytocompatibility and hemocompatibility analyses undoubtedly confirmed the biocompatibility behavior of PMMA-based bioactive scaffolds. Nano-CT investigation demonstrates that PMMA-CaP scaffolds provide more or less alike morphologies of composites that resemble the natural bone. Therefore, this combination of scaffolds could be considered as potential biomaterials for bone regeneration application. This detailed study promisingly demonstrates the eminence of the unique scaffolds in the direction of regenerative medicines. [ABSTRACT FROM AUTHOR]

Loss of the lower limb can cause loss of mobility.At all places and at all times, efforts have always been made to make up for such a loss.In this work polymer composite materialshad been used to manufacture prosthetic foot. Polymer composite materialsPMMA:SR/PURreinforced by carbon fibers (CF) were prepared as suitable material for prosthetic foot then, tensile characteristics were measured and determined. Numerical work included Finite element method (ANSYS-15) was used to analyze and evaluate deformation, stress and strain characteristics of a new designed prosthetic foot, which was treated as three-dimensional structure composite polymer material. The experimental and theoretical results were improvedthat polymer composite material can be used for this application

The main goal of this paper was to investigate transparency and mechano-acoustic properties of poly methyl methacrylate (PMMA)/polycarbonate (PC) based nanocomposites, reinforced with silica (SiO2), zinc dioxide (ZnO), and titanium dioxide (TiO2) nanoparticles. For this purpose, morphological, transparency, acoustical and mechanical tests were carried out on the specimens, prepared by melt-compounding method in a twin-screw extruder. The morphological test results confirmed uniform dispersion of the nanoparticles in the polymer matrix. The results also revealed that transparency of the PC and PMMA nanocomposites, characterized by the degree of light transmittance, was decreased by adding 0.3 wt% of the nanoparticles. Also, tensile modulus of the nanocomposite specimens was higher than that of neat PC and PMMA. Unlike the neat PC specimens, tensile strength showed a decrease in PMMA specimens. The presence of nanoparticles in the composites decreased mobility of polymer chains and consequently, reduced elongation at break in the specimens. After surface roughening process, noise absorption coefficient in PC/PMMA nanocomposite specimens (PCSI3-R, PMSI3-R, and PMZN3-R) showed a higher absorption coefficient than the other specimens in the dominant frequency of traffic noise (500 Hz). As conclusion, roughening the surface of materials would be one of the most important factors enhancing the absorption coefficient of some of the nanocomposites in the middle frequency. The rough surface of particles in the base matrix increases the absorption coefficient of the materials, especially in the frequency of 500 Hz, as the dominant frequency of noise traffic. The suggested materials are predestinated to be appropriate in building industry, particularly in the structure of noise barriers. [ABSTRACT FROM AUTHOR]

This study presents the preparation of poly vinylidene fluoride (PVDF) based polymethyl methacrylate (PMMA), Poly(bis(4-Aminophenoxy)phosphazene)(PPZ) and lithium tantalate (LT) composites films using solution blending process. The fabricated PVDF/PMMA/PPZ/LT composite films were evaluated using Fourier transformed infrared spectroscopy, Scanning electron microscopy, Differential scanning calorimetry and Thermo gravimetric analyses. The changes in microstructure, dielectric, morphological and thermal properties of these films with change in composition of PVDF/PMMA/PPZ/LT have been investigated. The high PMMA content and incorporation of LT favored the PVDF phase transition from ‘α’ to ‘β’ phase as shown by FT-IR analysis. The LT particles were properly dispersed in PVDF/PMMA/PPZ matrix as confirmed by scanning electron micrograph images. The dielectric properties of the PVDF/PMMA/PPZ improved with increasing the concentration of LT. The dielectric constant of the films increased with increase in LT content in the blends. The values of dielectric properties observed were higher at lower frequency at room temperature. The composites having 10, 20, 30 & 40% LT in blend samples showed regular increase in Tons, Tmax and corresponding char yield with increase in the filler content. All the composites demonstrated two steps decomposition due to the interaction of filler with polymers at high temperature leading to oxidative decomposition of polymeric chains. [ABSTRACT FROM AUTHOR]

Background & Objective: Currently selection and use of nanoparticle adjuvant is very important. Due to the lack of effective anti-snakebite serums to treat it and high cost of purchasing external antisnakebite serums, preparation of suitable internal nanoparticles to produce hyper-immunization plasma has become very important. In order to minimize the disadvantages associated with traditionally used adjuvants in ovines and to produce potent antivenum, a comparison was made between various adjuvants for their immune-potentiation capacity and safety. Material & Methods: The present study was conducted in 15 sheep, divided into three groups and hyper-immunized using crude venom of cobra snake (Naja naja oxiana) along with three adjuvants, Montanide, aluminum phosphate and poly methyl methacrylate through subcutaneous route at intervals of a week. Periodic standard safety assessments were done. Results: The neutralization activity (LD50) of pooled sera samples by 9th week, obtained with aluminum phosphate, Montanide and poly methyl methacrylate groups were 1.5, 2.2 and 2 LD50/ml respectively. The sheep of poly methyl methacrylate group showed minimum local reactions at injection site, while sheep from other two groups exhibited moderate reactions. However, these were transient and reabsorbed or healed subsequently. Conclusion: Poly methyl methacrylate nanoparticle adjuvant could be a possible alternative to the emulsion adjuvants for primary phase of immunization in antivenomous preparation considering its acceptable immunopotentiation capacity and safety in donor animals. [ABSTRACT FROM AUTHOR]

Background: Acquired facial defects caused by extirpation of neoplasms, congenital malformations or traumatic injury results in a huge functional, cosmetic and psychological handicap in those patients. These defects can be restored by facial prosthesis using different materials and retention methods to achieve a life-like appearance and function. This clinical report describes a treatment schedule using mechanically retained poly methyl methacrylate (PMMA) resin nasal prosthesis for a patient who has undergone a partial rhinectomy due to squamous cell carcinoma of the nose. The prosthesis was made to restore the esthetic appearance of patient with mechanically retained spectacle glass frame prosthesis without any prosthetic adhesives so that the patient is more comfortable and confident to resume daily activities.

The suspension-like polymerization method is used to obtain poly methyl methacrylate ( PMMA)/paraffin wax microcapsules and micro/nanocapsules with high core content. Particle size distribution ( PSD) analysis indicates that the average particle size of microcapsules is 94 µm, and the size of micro/nanocapsules ranges in 0.1-19 µm. Differential scanning calorimetry ( DSC) and thermalgravimetric analysis ( TGA) results show that the fabricated paraffin contents in microcapsules and micro/nanocapsules are as high as 89.5 wt% and 80.2 wt%, respectively with good thermal stability. Thermal cycling tests justify that both the microcapsules and micro/ nanocapsules have good thermal reliability with respect to the changes in their thermal properties after 1000 thermal cycling. This work provides a novel method to prepare microcapsules and micro/nanocapsules with high core content which may benefit further study on thermal energy storage. [ABSTRACT FROM AUTHOR]

Introduction : Keloids are frequent finding after physical trauma. Keloids of ear lobe are common complication of ear piercing, although its incidence remains unknown. The use of intrakeloid resection and a form pressure device to treat pinna keloids. The recommendation of this therapy is to maintain constant pressure and duration of pressure therapy was about 25 weeks. Clinical innovation : This article will present inexpensive custom made pressure clips of various designs. The dimensions of polymethylmethacrylate (PMMA) plates in ear lobe clip presented by us though they esthetically not so good, but colored PMMA has been used to make it decorative and acceptable by most of the patients. This has been an encouraging experience to use the different designs. Discussion : Ear clip prosthesis has been developed for maintaining pressure on ear lobe keloids before and after surgical removal. The prosthesis includes an ear clip to which heat-polymerized acrylic resin is attached, which covers the keloid area. Pressure therapy is widely used to help in the early maturation of scar tissue and to prevent the recurrence of keloid. The preliminary report by Brent revealed that constant light pressure was an effective means of preventing post excision recurrence of ear lobe keloids using a decorative, spring-pressure earring.

Background: Conventional heat cure poly methyl methacrylate (PMMA) is the most commonly used denture base resin despite having some short comings. Lengthy polymerization time being one of them and in order to overcome this fact microwave curing method was recommended. Unavailability of specially designed microwavable acrylic resin made it unpopular. Therefore, in this study, conventional heat cure PMMA was polymerized by microwave energy. Aim and Objectives: This study was designed to evaluate the surface porosities in PMMA cured by conventional water bath and microwave energy and compare it with microwavable acrylic resin cured by microwave energy. Materials and Methods: Wax samples were obtained by pouring molten wax into a metal mold of 25 mm × 12 mm × 3 mm dimensions. These samples were divided into three groups namely C, CM, and M. Group C denotes conventional heat cure PMMA cured by water bath method, CM denotes conventional heat cure PMMA cured by microwave energy, M denotes specially designed microwavable acrylic denture base resin cured by microwave energy. After polymerization, each sample was scanned in three pre-marked areas for surface porosities using the optical microscope. As per the literature available, this instrument is being used for the first time to measure the porosity in acrylic resin. It is a reliable method of measuring area of surface pores. Portion of the sample being scanned is displayed on the computer and with the help of software area of each pore was measured and data were analyzed. Results: Conventional heat cure PMMA samples cured by microwave energy showed maximum porosities than the samples cured by conventional water bath method and microwavable acrylic resin cured by microwave energy. Higher percentage of porosities was statistically significant, but well within the range to be clinically acceptable. Conclusion: Within the limitations of this in-vitro study, conventional heat cure PMMA can be cured by microwave energy without compromising on its property such as surface porosity.

Introduction: Provisional restorations serve a key role as a functional and esthetic try-in for the design of the final prosthesis. During selection of materials for this restoration, clinicians must consider physical properties, ease of handling, cost and patient satisfaction and approval. Aim: To evaluate and compare the flexural strength of provisional crown and bridge materials available commercially. Materials and Methods: This in-vitro study was done to compare the flexural strength of six temporary crown and bridge materials available commercially at 24 hours, 8 days and after repair. Three poly methyl methacrylate based materials (DPI, SC10 and Trulon) and three bis-acrylic based composite resins (Protemp, Cooltemp and Luxatemp) were selected. A total of 72 specimens of dimensions 64mm×10mm×2.5mm were prepared from these materials (12 from each material) and divided into two groups (n=36). Specimens were stored in artificial saliva and were fractured after 24 hours and 8 days using Universal Testing Machine. The fractured samples from the 8 days study were then subjected to repair. A uniform space of 2mm and a 450 bevel was maintained for all the repaired samples for better distribution of forces. Flexural strength of these repaired samples was recorded using the same machine. Results were recorded and statistically analysed by one-way Anova and Post hoc tests. Result: Results revealed that there was decrease in flexural strength for all the materials tested from 24 hours to 8 days, though flexural strength between poly methyl methacrylate and bis-acrylic resins was similar at 24 hours and 8 days time interval. A substantial decrease was noticed in the strength of bis-acrylic composite resins after repair. Conclusion: From the current study it can be suggested that though there is decrease in flexural strength for all the materials from 24 hours to 8 days, both can be used to fabricate the provisional restorations. However, in the event of a fracture of a bis-acrylic provisional restoration, it may be more advantageous to make a new provisional restoration than to repair the fractured one.

Background: Occlusal loading of osseointegrated implants is believed to be an essential determining factor in the long-term success of an implant treatment. Numerous studies have been conducted on the evaluation of stress distribution by definitive restoration materials for Implant-supported fixed prosthesis, but very few have evaluated provisional restoration materials for the same. This study aims to evaluate the influence of provisional restoration material – Milled Polymethylmethacrylate (PMMA) and Milled Polyetheretherketone (PEEK), over stress distribution on the peri-implant bone around an implant-supported three-unit, fixed dental prosthesis using finite element analysis method. Materials and Methods: Three-dimensional models of a pair of bone-level implant system and titanium base abutments were created using the standard tessellation language data of original implant components. A bone block representing the mandibular posterior area was created, and the implants were placed in the bone block with 100% osseointegration in the 2nd premolar to 2nd molar region. A superstructure of an implant-supported 3-unit bridge was modeled on top of the abutments, each crown to be 8 mm in height and with an outer diameter of 6 mm in 2nd premolar region and 10 mm in 1st molar and 2nd molar region. Two different models were created according to combinations of provisional restoration materials, namely, Milled PMMA and Milled PEEK based on. In each model, the implants were loaded vertically (300 N) and obliquely (150 N at 30°). The stress distribution in the cortical bone, cancellous bone, and implant was evaluated through the von Mises stress analysis. Results: The results showed no difference in stress distribution due to the different provisional restorations – Milled PMMA and Milled PEEK. In addition, the vertical load resulted in higher stress values in the implant components, cortical bone, and cancellous bone in both PEEK and PMMA models as compared to oblique loading. Conclusion: The new polymer, PEEK was seen to provide comparable stress generation in the current study without exceeding the physiological limits of peri-implant bone. Thus, it can be considered as a good alternative to PMMA resin as a provisional crown material since it provides certain additional benefits. [ABSTRACT FROM AUTHOR]

Aim: The aim of this in vitro study was to compare the flexural strength, the flexural modulus and compressive strength of the acrylic polymer reinforced with glass, carbon, polyethylene and Kevlar fibres with that of plain unfilled resin. Materials and Methods: A total of 50 specimens were prepared and divided into 10 specimens each under 5 groups namely group 1- control group without any fibres, group 2 – carbon fibres, group 3- glass fibres, group 4 – polyethylene, group 5- Kevlar. Universal testing machine (Tinius olsen, USA) was used for the testing of these specimens. Out of each group, 5 specimens were randomly selected and testing was done for flexural strength using a three point deflection test and three point bending test for compressive strength and the modulus was plotted using a graphical method. Statistical analysis was done using statistical software. Results: The respective mean values for samples in regard to their flexural strength for PMMA plain, PMMA+ glass fibre, PMMA+ carbon, PMMA+ polyethylene and PMMA+ Kevlar were 90.64, 100.79, 102.58, 94.13 and 96.43 respectively. Scheffes post hoc test clearly indicated that only mean flexural strength values of PMMA + Carbon, has the highest mean value. One-way ANOVA revealed a non-significant difference among the groups in regard to their compressive strength. Conclusion: The study concludes that carbon fibre reinforced samples has the greatest flexural strength and greatest flexural modulus, however the compressive strength remains unchanged.

Eu(DBM) 3 and Eu(DBM) 3 Phen were introduced into poly methyl methacrylate (PMMA) in comparative, and the differential luminescence behaviors were revealed under ultraviolet (UV) radiation. The comparison of excitation behavior between Eu(DBM) 3 and Eu(DBM) 3 Phen doped PMMAs indicates that the introduction of Phen ligand largely enhances the excitation intensity of europium in the entire UV region. The total quantum yield of Eu(DBM) 3 Phen doped PMMA was derived to be (9.34 ± 0.14)%, and it is about 8 times higher than that of the Eu(DBM) 3 doped PMMA under 373 nm UVA light emitting diode (UVA-LED) excitation, which confirms the effective utilization of UVA radiation by introducing Phen ligand. Similar results on absolute spectral parameters of the bi-ligand under the excitation of 308 nm UVB light emitting diode (UVB-LED) further support the availability for photon conversion. The brilliant red fluorescence of Eu(DBM) 3 Phen doped PMMA under direct sunlight demonstrates the contribution of Phen to modify the solar spectrum and enhance the UV radiation conversion efficiency, which make the Eu(DBM) 3 Phen doped PMMA an attractive UV radiation conversion layer for solar cell. [ABSTRACT FROM AUTHOR]

Introduction: Provisional restorations serve a key role as a functional and esthetic try-in for the design of the final prosthesis. During selection of materials for this restoration, clinicians must consider physical properties, ease of handling, cost and patient satisfaction and approval. Aim: To evaluate and compare the flexural strength of provisional crown and bridge materials available commercially. Materials and Methods: This in-vitro study was done to compare the flexural strength of six temporary crown and bridge materials available commercially at 24 hours, 8 days and after repair. Three poly methyl methacrylate based materials (DPI, SC10 and Trulon) and three bis-acrylic based composite resins (Protemp, Cooltemp and Luxatemp) were selected. A total of 72 specimens of dimensions 64mm×10mm×2.5mm were prepared from these materials (12 from each material) and divided into two groups (n=36). Specimens were stored in artificial saliva and were fractured after 24 hours and 8 days using Universal Testing Machine. The fractured samples from the 8 days study were then subjected to repair. A uniform space of 2mm and a 450 bevel was maintained for all the repaired samples for better distribution of forces. Flexural strength of these repaired samples was recorded using the same machine. Results were recorded and statistically analysed by one-way Anova and Post hoc tests. Result: Results revealed that there was decrease in flexural strength for all the materials tested from 24 hours to 8 days, though flexural strength between poly methyl methacrylate and bis-acrylic resins was similar at 24 hours and 8 days time interval. A substantial decrease was noticed in the strength of bis-acrylic composite resins after repair. Conclusion: From the current study it can be suggested that though there is decrease in flexural strength for all the materials from 24 hours to 8 days, both can be used to fabricate the provisional restorations. However, in the event of a fracture of a bis-acrylic provisional restoration, it may be more advantageous to make a new provisional restoration than to repair the fractured one. [ABSTRACT FROM AUTHOR]