Diversity and antimicrobial susceptibility patterns of clinical and environmental Salmonella enterica serovars in Western Saudi Arabia.

The diverse environmental distribution of Salmonella makes it a global source of human gastrointestinal infections. This study aimed to detect Salmonella spp. and explore their diversity and antimicrobial susceptibility patterns in clinical and environmental samples. Pre-enrichment, selective enrichment, and selective plating techniques were adopted for the Salmonella detection whereas the API 20E test and Vitek Compact 2 system were used to confirm the identity of isolates. Salmonella serovars were subjected to molecular confirmation by 16S rDNA gene sequencing. Disc diffusion method and Vitek 2 Compact system determined the antibiotic susceptibility of Salmonella serovars. Multiple antibiotic resistance index (MARI) was calculated to explore whether Salmonella serovars originate from areas with heavy antibiotic usage. Results depicted low Salmonella prevalence in clinical and environmental samples (3.5%). The main detected serovars included Salmonella Typhimurium, S. enteritidis, S. Infantis, S. Newlands, S. Heidelberg, S. Indian, S. Reading, and S. paratyphi C. All the detected Salmonella serovars (27) exhibited multidrug resistance to three or more antimicrobial classes. The study concludes that the overall Salmonella serovars prevalence was found to be low in environmental and clinical samples of Western Saudi Arabia (Makkah and Jeddah). However, antimicrobial susceptibility patterns of human and environmental Salmonella serovars revealed that all isolates exhibited multidrug-resistance (MDR) patterns to frequently used antibiotics, which might reflect antibiotic overuse in clinical and veterinary medicine. It would be suitable to apply and enforce rules and regulations from the One Health approach, which aim to prevent antibiotic resistance infections, enhance food safety, and improve human and animal health, given that all Salmonella spp. detected in this investigation were exhibiting MDR patterns.

Utilization of dental care and dentate status in diabetic and nondiabetic patients across US states: An analysis using the 2020 Behavioral Risk Factor Surveillance System.

OBJECTIVE: This study examines the differences, by state, in dental care utilization and tooth retention between adults with and without diabetes mellitus (DM). METHODS: We conducted a secondary analysis of data from the 2020 Behavioral Risk Factor Surveillance System, an annual, state-based, random telephone survey of noninstitutionalized US civilian adults. The predictor variable was DM status. The outcome variables were time since the last dental appointment and tooth loss. We utilized multiple multinomial logistic regression models followed by postestimation procedures to determine state-level adjusted proportions for dental visits within the last year and complete teeth retention among DM and non-DM adults. RESULTS: Among adults with DM, 60.0% reported dentist visits within a year of survey participation, while 53.6% had complete tooth retention. As education and income levels increased, dental attendance and tooth retention increased among adults with DM. Most Southern states had a higher prevalence of DM, a lower proportion of dentist visits, and worse tooth retention among DM adults. Nationally, DM individuals were 4.3 percentage points less likely to visit a dentist and were 7 percent less likely to have complete teeth retention than non-DM adults. Compared with the national average, 25/50 states had greater disparities in dental visits between DM and non-DM adults, and 27/50 states had greater disparities in tooth loss between DM and non-DM adults. CONCLUSION: State-level variations indicate geographical and dental coverage influences on DM and dental outcomes. There is a need for state-specific interventions to improve dental access and outcomes for adults with DM.

The effectiveness of water jet flossing and interdental flossing for oral hygiene in orthodontic patients with fixed appliances: a randomized clinical trial.

BACKGROUND: Orthodontic treatment presents challenges with plaque accumulation around brackets, archwires, and elastics, leading to retained plaque and gingival inflammation. Conventional toothbrushing may not be enough, requiring additional oral hygiene aids like interproximal brushes, dental flosses, and water flossers. Limited research exists on comparing water flossing and interdental flossing in orthodontic patients. Therefore, this study aims to assess their effectiveness in maintaining oral hygiene during active orthodontic treatment. METHODS: A single-blind, randomized, parallel clinical study recruited orthodontic patients with full-mouth brackets and archwires. Thirty participants were randomly assigned to either water jet flossing or interdental flossing groups. All participants were instructed to brush twice daily with a provided toothbrush and toothpaste and use the assigned intervention once daily at night. Clinical measures, including the Gingival Bleeding Index (BI), Plaque Index (PI), and Gingival Index (GI), were recorded at baseline and day 14. Descriptive statistics and statistical tests were performed using SPSS software. RESULTS: The water jet flossing group demonstrated a slightly higher, albeit non-significant, benefit in plaque removal (median difference of 6.79%%, P = 0.279) and bleeding reduction (median difference of 5.21%%, P = 0.172) compared to the interdental flossing group after two weeks. Both groups showed significant reductions in gingival bleeding index and plaque index from baseline to the 2-week follow-up. The interdental flossing group had median mean percentage differences of 16.13%% (plaque index) and 23.57% (gingival bleeding index), while the water jet flossing group had median percentage differences of 21.87% (plaque index) and 32.29% (gingival bleeding index). No significant changes in gingival index grades were observed in either group. CONCLUSION: Both water jet flossing and interdental flossing were effective in reducing plaque accumulation and gingival bleeding among orthodontic patients. While no significant differences were found between the two methods, water jet flossing showed a potential advantage. Further research is needed to validate its effectiveness, assess long-term impact, and understand its benefits for orthodontic patients.

Influence of gingival display on smile attractiveness assessed by Saudi Arabian laypersons and dental professionals.

This study was undertaken to evaluate the influence of changes in the gingival display of the maxillary teeth on smile attractiveness assessed by Saudi Arabian dental professionals and laypeople. A total of 138 dental professional and 182 laypeople rated the attractiveness of male and female smiles in a computerized survey. A smiling photograph of a male and a female dental students were selected and digitally manipulated to create changes the amount of gingival display from 4 mm of gingival display to 4mm of gingival covered by the upper lip in 1 mm increments. Each photo was accompanied by a visual analog scale (VAS) for rating. Among dental professionals, 61% rated the female photo with a 1-mm low lip line as the most attractive smile (VAS score ± SE, 7.3 ± 3.18), while 52.7% of laypeople considered the smile with a 2-mm low lip line as the most attractive (6.7 ± 3.4). Regarding male smile photos, 61.6% of dental professionals found the 1-mm low lip line the most attractive (7.3 ± 3.18). The same rating was given by 48.3% of laypeople (6.1 ± 3.6) (p ≤ 0.009). The least attractive smile photo was the smile showing 4 mm of gingiva for male and female smiles. More than half of the laypeople believed that an attractive smile highly affects social life and communication. The Saudi Arabian population appears to be sensitive to the amount of gingival display. The difference in female smile assessment between dental professionals and laypeople highlights the importance of dentist-patient consensus regarding decisions for esthetic treatments. Esthetic treatment is of a major concern for both dentist and patient. The careful assessment of smile pillars including gingival display must be tailored to each patient.

Consanguinity as a Risk Factor for Autism.

PURPOSE: Genetic and environmental risk factors associated with Autism Spectrum Disorders (ASD) continue to be a focus of research worldwide. Consanguinity, the cultural practice of marrying within a family, is common in cultures and societies of the Middle East, North Africa and parts of Asia. Consanguinity has been investigated as a risk factor for ASD in a limited number of studies, with mixed results. We employed registry and survey data from Qatar to evaluate the role of consanguinity as a risk factor for ASD. METHODS: Data were sourced from a national registry and a population-based survey of autism recently conducted in Qatar. We selected a sample of 891 children (mean age: 8.3 years) with (N = 361) or without (N = 530) ASD. Data on consanguinity and covariates were collected through questionnaires and interviews. RESULTS: The prevalence of consanguinity in the overall sample was 41.2% with no significant difference between cases and controls (42.1% vs 41.3%; p = .836). In adjusted multiple logistic regression analyses, consanguinity was not associated with risk of ASD (aOR = 1.065; 95% CI: .751-1.509; NS). CONCLUSION: Parental consanguinity was not associated with autism risk in our study. Replication in other populations with high rates of consanguineous unions is recommended.

Evaluation of Mechanical Properties of Different Thermoplastic Orthodontic Retainer Materials after Thermoforming and Thermocycling.

While the durability of thermoplastic aligners has been the subject of numerous studies, the durability of thermoplastic retainers has received significantly less attention. Patients are often advised to wear their thermoplastic retainers indefinitely, so the durability of the materials used in their fabrication is crucial to determining whether they are worth the cost. Limited studies have evaluated the properties of thermoplastic retainer materials and the effects of thermocycling on their mechanical properties. Thus, this study aimed to examine six thermoplastic retainer materials after thermoforming with and without thermocycling. The materials' flexural modulus, hardness, and surface roughness values were measured after thermoforming (Group 1) and after thermoforming with subsequent thermocycling for 10,000 cycles (Group 2). After thermoforming, there was a significant difference in flexural modulus and hardness values between most of the materials. However, their surface roughness was not significantly different (p < 0.05). After thermocycling, the flexural modulus and hardness increased significantly for most tested materials (p < 0.05) compared to Group 1. Concerning the surface roughness, only two materials showed significantly higher values after thermocycling than Group 1. Thus, all the mechanical properties of the evaluated materials differed after thermoforming, except the surface roughness. Moreover, while thermocycling made the materials stiffer and harder in general, it also made some of them rougher.

Juvenile Dermatomyositis Presenting As Generalized Poikiloderma: A Case Report.

Juvenile dermatomyositis (JDM) is a chronic autoimmune inflammatory disorder and is considered the most common form of idiopathic inflammatory myopathies. JDM primarily affects the skin and the skeletal muscles. Characteristic signs and symptoms include Gottron papules, heliotrope rash, calcinosis cutis, and symmetrical proximal muscle weakness. However, JDM presenting with generalized scaly poikeloderma is an unfamiliar presentation. Herein we report a 14-month-old female toddler presented with generalized progressive asymptomatic scaly mottled violaceous patches (poikilodermatous) that started when she was seven months old. Her lab results were unremarkable. She was diagnosed with poikilodermatous skin rash with a differential diagnosis of Amyopathic dermatomyositis, poikilodermatous genodermatosis, and patch-stage mycosis fungoides. She was prescribed moisturizer creams only. A year later, during a follow-up, she presented with a full picture of JDM, with a history of scaly poikilodermatous skin patches that became more widespread, frequent choking during oral intake, and not being able to stand and sit unsupported. Laboratory workup was significant for low WBC and hemoglobin counts, along with elevated CPK, LDH, ferritin, CRP, and ESR levels. MRI revealed the right anterior thigh and vastus lateralis subcutaneous edema. Therefore, the child was diagnosed and treated as a case of JDM.

Antimicrobial Resistance, Virulence Factor-Encoding Genes, and Biofilm-Forming Ability of Community-Associated Uropathogenic Escherichia coli in Western Saudi Arabia.

To explore the prevalence of multidrug-resistant community-associated uropathogenic Escherichia coli (UPEC) and their virulence factors in Western Saudi Arabia. A total of 1,000 urine samples were examined for the presence of E. coli by selective plating on MacConkey, CLED, and sheep blood agar. Antimicrobial susceptibility patterns were determined using Vitek® 2 Compact (MIC) and the disc diffusion method with Mueller-Hinton agar. Genes encoding virulence factors (kpsMTII, traT, sat, csgA, vat, and iutA) were detected by PCR. The overall prevalence of UTI-associated E. coli was low, and a higher prevalence was detected in samples of female origin. Many of the isolates exhibited resistance to norfloxacin, and 60% of the isolates showed resistance to ampicillin. No resistance to imipenem, meropenem, or ertapenem was detected. In general, half of the isolates showed multiple resistance patterns. UPEC exhibited a weak ability to form biofilms, where no correlation was observed between multidrug resistance and biofilm-forming ability. All uropathogenic E. coli isolates carried the kpsMTII, iutA, traT, and csgA genes, whereas the low number of the isolates harbored the sat and vat genes. The diversity of virulence factors harbored by community-associated UPEC may render them more virulent and further explain the recurrence/relapse cases among community-associated UITs. To the best of our knowledge, this study constitutes the first exploration of virulence, biofilm-forming ability, and its association with multidrug resistance among UPEC isolates in Saudi Arabia. Further investigations are needed to elucidate the epidemiology of community-associated UPEC in Saudi Arabia.

Diabetes mellitus and its association with dental caries, missing teeth and dental services utilization in the US adult population: Results from the 2015-2018 National Health and Nutrition Examination Survey.

AIMS: This study aimed to evaluate the associations of self-reported diabetic status with clinically assessed dental end points, including teeth with untreated coronal and root caries, missing teeth, complete tooth retention, edentulism and routine dental services utilization among adults aged ≥20 years in the United States. METHODS: We pooled data from the 2015-2016 and 2017-2018 cycles of the National Health and Nutrition Examination Survey (NHANES), a nationally representative, cross-sectional, continuous survey of noninstitutionalized US population. The analysed data included all adult participants aged ≥20 years who completed the dental examination and reported their diabetic status. We estimated the prevalence and average outcomes of dental end points by diabetic status. Regression analyses were employed to evaluate the associations between diabetic status and dental outcomes. RESULTS: Of 10,249 participants, 1,562 reported having diabetes mellitus, which translates to 11.3% of US adults aged ≥20 years (25.7 million). Compared to non-diabetic individuals, adults with diabetes had 1.49 (95%CI = 1.1-2.0) and 1.46 (95%CI = 1.2-1.8) times higher odds of developing coronal and root caries respectively. Adults with diabetes were 32% less likely to be fully dentate (OR = 0.68; 95%CI = 0.55-0.83) and had a higher average number of missing teeth (mean ratio = 1.35; 95%CI = 1.18-1.55). There was no association between diabetic status and routine dental services utilization. CONCLUSIONS: Adults with diabetes exhibited worse dental health; nonetheless, there was no difference in dental services utilization. Multidisciplinary efforts from both medical and dental service providers are required to proactively address the well-being of adults with diabetes in terms of oral health.

Dental Magnification Loupes: An Update of the Evidence.

AIM: To overview dental magnification loupes and to present the updated scientific evidence supporting its use. BACKGROUND: The practice of dentistry places considerable stress on the operators' visual acuity and musculoskeletal system. The use of magnification loupes has spanned many decades with claims of supporting visual and postural capacities of dental professionals and enhancing diagnostic and procedural accuracy. REVIEW RESULTS: Galilean and prismatic loupes both provide lightweight and clinically appropriate magnifications between 2.5× and 5.0×, with beneficial features such as a fixed working distance and downward lens inclinations. Studies have found significantly increased detection and diagnostic abilities due to enhanced visibility and improved treatment outcomes for some investigated procedures. Postural studies have found improved positioning of the upper body when using loupes as compared to the positioning when using the naked eye, with practitioners experiencing reductions in musculoskeletal symptoms when using magnification loupes. CONCLUSION: The current evidence supports the presence of some visual advantages of loupe magnification in diagnosis and treatment delivery. However, more clinical trials are needed to investigate different procedure outcomes over the long term. Further, there is robust scientific evidence advocating the use of loupe magnification for postural and musculoskeletal support. CLINICAL SIGNIFICANCE: Dentistry is a visually and physically demanding profession with a high prevalence of musculoskeletal disorders among dental professionals. The use of loupe magnification potentially benefits both the dental healthcare provider and patients. Therefore, there is reason to consider the use of loupe magnification as an integral part of dental education and training, as well as a tool in the dental clinician's armamentarium.

Occupational Stress among Orthodontists in Saudi Arabia.

AIM: The aim of this study was to identify potential occupational stressors among orthodontists practicing in Saudi Arabia, and to evaluate their relationship to personal and professional characteristics. MATERIALS AND METHODS: Using a validated occupational stress assessment (OSA) questionnaire, demographic information and data pertaining to potential occupational stressors and professional characteristics of the participants were collected. The OSA questionnaire was adopted and modified based on Cooper et al. classification of potential stressors. To assure anonymity of the protocol, the respondents were given the OSA questionnaire at their clinical settings or scientific meetings and requested to return the filled copy of the questionnaire without any personal disclosures. The severity of stressors was assessed using a five-point Likert scale, and individual scores were summed to obtain the overall severity score. The collected data were coded, tabulated, and analyzed using statistical software. RESULTS: Samples of 253 orthodontists were evaluated with a response rate of 82.6% (209) and a higher proportion of male participants (75.1%). The mean severity score for stress was higher among orthodontists of age less than 30 years when compared with those more than 50 years of age (F = 3.486; P = 0.017). Similarly, the mean severity score was higher among orthodontists who had completed their residency program in Saudi Arabia, Arab countries, and Asian countries (F = 5.425; P < 0.0001). Further categorization of the stressors based on patient-, time-, staff-, work-, referral-, and income-related factors were carried out. Although patient-related factors (mean = 3.38) were considered the most stressful, referral- and income-related factors (mean = 2.39) were considered the least stressful. CONCLUSION: Pronounced variation was evident in assessing the potential stressors among orthodontists. Nevertheless, time management and proper patient education can address the most concerning stressors among orthodontists in Saudi Arabia.

Evaluation of the airway space changes after extraction of four second premolars and orthodontic space closure in adult female patients with bimaxillary protrusion - A retrospective study.

BACKGROUND & OBJECTIVES: Previous studies have found that first premolar extractions during orthodontic treatment may alter the upper airway dimensions. The objective of this study is to investigate the effects of second premolar extraction during orthodontic treatment on the dimensions of the upper airway in a sample of female adults. METHODS: Twenty-nine female adult patients with ages between 18 and 30 years old and incisor bimaxillary protrusion were included in this study. They were treated with comprehensive orthodontic treatment which included the extraction of four second premolars. Pre and post cephalometric radiographs were analyzed using Dolphin imaging software for changes in tongue length and height, soft palate thickness and length, the superior, middle, and inferior airway space, and vertical airway length. Descriptive statistics were used to characterize measurements. Student's paired t-test was preformed to compare the pre- and post-test mean values of the dimensions. RESULTS: A significant increase in the vertical airway length was observed after the extraction of the second premolars (p = 0.02). The soft palate length showed a tendency towards an increase that did not reach statistical significance (p = 0.053). No other significant changes in the airway soft tissue measurements were observed. The proclination and protrusion of the upper and lower incisors were significantly decreased compared to pre-treatment measurements.Interpretation & conclusions.Orthodontic treatment involving the extraction of all four second premolars in females with bimaxillary protrusion increases the vertical airway length, which is the amount of distance between base of the tongue and posterior nasal spine. No other significant alterations in the upper airway measurements were observed.

Qualitative Evaluation of the Bracket-Adhesive-Enamel Junction of Metal Orthodontic Brackets: A Preliminary Report.

OBJECTIVES: The purpose of this in vitro investigation was to evaluate qualitatively the surface topography at the bracket-adhesive-enamel junction, bonded to the buccal and lingual surfaces of premolars with composite resin and resin-modified glass-ionomer orthodontic adhesives, using two methods of adhesive removal: a dental explorer and a micro brush. METHODS: Forty premolar surfaces were allocated to four groups of 10/ each, 20/buccal and 20/lingual surfaces. The brackets were bonded to the surface of the enamel and any extra adhesive was removed with a dental explorer or a micro brush. Specimens were evaluated and scored by two calibrated independent raters, at the bracketadhesive-enamel junction, for adhesive overlap on the bracket, the smoothness of the surface, as well as the presence of projections and depressions, using a digital microscope. The Fisher-exact statistical test was conducted to compare the different groups. RESULTS: Regardless of the method used to remove the adhe sives, all groups showed partial or complete overlap of the adhesive on the bracket. No statistical difference was found between the groups for adhesive overlap (P=1.0). However, resin-modified glass-ionomer was found to be statistically significantly (P<0.05) better than composite resin in both smoothness and the lack of projections or depressions, regardless of the instrument of removal. CONCLUSION: Removing excess adhesive with a dental explorer or a micro brush is not an ideal method for adhesive removal, as partial or complete overlap of the adhesive on the bracket existed in all groups. On the other hand, resin-modified glassionomer was a superior material to composite resin for better smoothness and surface topography at the bracket-adhesive-enamel junction.

Elementary school staff knowledge about management of traumatic dental injuries.

AIM: This study investigated the knowledge of elementary school staff regarding the management of traumatic dental injuries (TDIs) in children. METHODS: The present cross-sectional study analyzed data collected between September 2016 and April 2017. The sample consisted of 2,027 elementary school staff members in Riyadh, Saudi Arabia. A stratified cluster random sampling technique was used to select the required sample. Those who agreed to participate in the study completed a 4-part self-administered questionnaire comprising questions regarding demographic data, knowledge on management of tooth fracture, and avulsion using photographs of TDI cases. RESULTS: The majority of the school staff showed inadequate basic knowledge regarding the importance of saving the broken piece of the tooth and identifying the tooth involved in the trauma (67% and 66.3%, respectively), P<0.05. However, they had a significantly high number of correct responses regarding the immediate management of TDIs for the 2 case scenarios presented in the questionnaire (P<0.05), and the majority (41%) reported normal saline as a suitable storage medium (P<0.01). CONCLUSION: This study revealed a lack of knowledge in certain aspects of TDIs among elementary school staff.

Learning style preferences of dental students at a single institution in Riyadh, Saudi Arabia, evaluated using the VARK questionnaire.

BACKGROUND: Students differ in their preferred methods of acquiring, processing, and recalling new information. The aim of this study was to investigate the learning style preferences of undergraduate dental students and examine the influence of gender, Grade Point Average (GPA), and academic year levels on these preferences. METHODS: The Arabic version of the visual, aural, read/write, and kinesthetic (VARK) questionnaire was administered to 491 students from the first- to the fifth-year academic classes at the College of Dentistry, King Saud University. Descriptive statistics were used to characterize the learning styles of the students, and Chi-square test and Fisher's test were used to compare the learning preferences between genders and among academic years. Significance was set at a p-value of <0.05. RESULTS: A total of 368 dental students completed the questionnaire. The multimodal learning style was preferred by 63.04% of the respondents, with the remaining 36% having a unimodal style preference. The aural (A) and the kinesthetic (K) styles were the most preferred unimodal styles. The most common style overall was the quadmodal (VARK) style with 23.64% having this preference. These differences did not reach statistical significance (p>0.05). Females were more likely to prefer a bimodal learning style over a unimodal style (relative risk =2.37). Students with a GPA of "C" were less likely to have a bimodal or a quadmodal style preference compared to students with a GPA of "A" (relative risk =0.34 and 0.36, respectively). Second-year students were less likely to prefer a bimodal over a unimodal style compared to first-year students (relative risk =0.34). CONCLUSION: The quadmodal VARK style is the preferred learning method chosen by dental students, followed by unimodal aural and kinesthetic styles. Gender was found to influence learning style preferences. Students with a "C" GPA tend to prefer unimodal learning style preferences. The VARK questionnaire is a relatively quick and simple tool to reveal the learning style preferences on an individual or a group level. Dental educators should adjust their delivery methods to approximate the learning preferences of their students. Dental students are encouraged to adapt a multimodal style of learning to improve their academic results.

IMPORTED MALARIA TO MAKKAH DISTRICT, SAUDI ARABIA: IS THERE ANY RISK OF LOCAL TRANSMISSION?

In Makkah, Saudi Arabia, there is an impending risk of imported malaria. This risk comes from the fact that millions of people, in majority from tropical and subtropical countries where malaria is endemic, visit the country to perform Hajj and Umrah every year. Moreover, millions of expatriates from endemic countries come to Makkah for work. Likewise, many Saudi citizens travel to endemic areas overseas for business and pleasure. We performed a retrospective analysis of all reported malaria cases in Makkah region, Saudi Arabia for years 2014 and 2015. In addition, sorting of mosquito populations in Makkah region was undertaken. Based on national data regarding reported malaria cases, 235 malaria cases were recorded in years 2014 and 2015. Of the reported cases 232 were non-Saudi and only 3 cases were Saudi. Those recorded Saudi cases were just returning from a travel to an endemic area. Most of the cases (79.6%) were P. falciprum and the remaining was P. vivax. Infected male represent 62% and female represent 38%. Age of the majority of reported cases (71.5%) lie between 31 and 50 years. Most of reported cases were from Chad, Pakistan, Nigeria and Sudan. Sorting of mosquito populations revealed the absence of malaria vectors in Makkah District.

Microwave Irradiation Effect on the Dispersion and Thermal Stability of RGO Nanosheets within a Polystyrene Matrix.

Polystyrene-reduced graphene oxide (PSTY/RGO) composites were prepared via the in situ bulk polymerization method using two different preparation techniques. The general approach is to use microwave irradiation (MWI) to enhance the exfoliation and the dispersion of RGO nanosheets within the PSTY matrix. In the first approach, a mixture of GO and styrene monomers (STY) were polymerized using a bulk polymerization method facilitated by microwave irradiation (MWI) to obtain R-(GO-PSTY) composites. In the second approach, a mixture of RGO and STY monomers were polymerized using a bulk polymerization method to obtain RGO-(PSTY) composites. The two composites were characterized by FTIR, ¹H-NMR, XRD, SEM, HRTEM, TGA and DSC. The results indicate that the composite obtained using the first approach, which involved MWI, had a better morphology and dispersion with enhanced thermal stability, compared with the composites prepared without MWI. Moreover, DSC results showed that the Tg value of the composites after loading the RGO significantly increased by 24.6 °C compared to the neat polystyrene.

Synthesis and characterization of the in situ bulk polymerization of PMMA containing graphene sheets using microwave irradiation.

Polymethylmethacrylate-graphene (PMMA/RGO) nanocomposites were prepared via in situ bulk polymerization using two different preparation techniques. In the first approach, a mixture of graphite oxide (GO) and methylmethacrylate monomers (MMA) were polymerized using a bulk polymerization method with a free radical initiator. After the addition of the reducing agent hydrazine hydrate (HH), the product was reduced via microwave irradiation (MWI) to obtain R-(GO-PMMA) composites. In the second approach, a mixture of graphite sheets (RGO) and MMA monomers were polymerized using a bulk polymerization method with a free radical initiator to obtain RGO-(PMMA) composites. The composites were characterized by FTIR, (1)H-NMR and Raman spectroscopy and XRD, SEM, TEM, TGA and DSC. The results indicate that the composite obtained using the first approach, which involved MWI, had a better morphology and dispersion with enhanced thermal stability compared with the composites prepared without MWI.