Displaying publications 21 - 40 of 198 in total

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  1. Wait S, Kell E, Hamid S, Muljono DH, Sollano J, Mohamed R, et al.
    Lancet Gastroenterol Hepatol, 2016 11;1(3):248-255.
    PMID: 28404097 DOI: 10.1016/S2468-1253(16)30031-0
    In 2015, the Coalition to Eradicate Viral Hepatitis in Asia Pacific gathered leading hepatitis experts from Bangladesh, India, Indonesia, Malaysia, Pakistan, the Philippines, and Thailand to discuss common challenges to the burden posed by hepatitis B virus (HBV) and hepatitis C virus (HCV), to learn from each other's experience, and identify sustainable approaches. In this report, we summarise these discussions. Countries differ in their policy responses to HBV and HCV; however, substantial systemic, cultural, and financial barriers to achievement of elimination of these infections persist in all countries. Common challenges to elimination include limited availability of reliable epidemiological data; insufficient public awareness of risk factors and modes of transmission, leading to underdiagnosis; high rates of transmission through infected blood products, including in medical settings; limited access to care for people who inject drugs; prevailing stigma and discrimination against people infected with viral hepatitis; and financial barriers to treatment and care. Despite these challenges, promising examples of effective programmes, public-private initiatives, and other innovative approaches are evident in all countries we studied in Asia Pacific. The draft WHO Global Health Sector Strategy on Viral Hepatitis 2016-21 provides a solid framework upon which governments can build their local strategies towards viral hepatitis. However, greater recognition by national governments and the international community of the urgency to comprehensively tackle both HBV and HCV are still needed. In all countries, strategic plans and policy goals need to be translated into resources and concrete actions, with national governments at the helm, to enable a sustainable response to the rising burden of hepatitis B and C in all countries.
  2. Ting YW, Kong AS, Zain SM, Chan WK, Tan HL, Mohamed Z, et al.
    Clin Mol Hepatol, 2021 Jul;27(3):486-498.
    PMID: 33618508 DOI: 10.3350/cmh.2020.0162
    BACKGROUND/AIMS: 17β-hydroxysteroid dehydrogenase 13 (HSD17B13) variants were recently reported to have significantly lower odds of non-alcoholic fatty liver disease (NAFLD). This is a two-part study that aimed to evaluate the association of HSD17B13 variants with NAFLD and its histological severity, and to identify the association of the variants with clinical outcomes in a cohort of biopsy-proven NAFLD patients.

    METHODS: Consecutive biopsy-proven NAFLD patients and controls without fatty liver were recruited for this study between 2009 and 2014. Genotyping for HSD17B13 variants was performed using rhAmp assays. A total of 165 patients with NAFLD were monitored up until August 2019. Clinical outcomes were recorded.

    RESULTS: HSD17B13 rs72613567 TA allele and rs6834314 G allele were associated with lower odds of non-alcoholic steatohepatitis (NASH) in the overall cohort and among ethnic Chinese, but not among ethnic Malays or Indians (P<0.05). During a mean follow-up of 89 months, 32 patients (19.4%) experienced at least one clinical outcome (cardiovascular events, n=22; liver-related complications, n=6; extra-hepatic malignancy, n=5; and mortality, n=6). The rs72613567 homozygous TA allele and the rs6834314 homozygous G allele were independently associated with a lower incidence of liver-related complications (hazard ratio [HR], 0.004; 95% confidence interval [CI], 0.00-0.64; P=0.033 and HR, 0.01; 95% CI, 0.00-0.97; P=0.048, respectively) and were associated with lower grade of hepatocyte ballooning among the ethnic Chinese.

    CONCLUSION: HSD17B13 rs72613567 and rs6834314 variants were inversely associated with NAFLD and NASH, and were associated with lower incidence of adverse liver outcomes in a cohort of multi-ethnic Asian patients with NAFLD.

  3. Ting YW, Jalaludin MY, Zaini AA, Mohamed R
    Front Endocrinol (Lausanne), 2022;13:1071350.
    PMID: 36589844 DOI: 10.3389/fendo.2022.1071350
    BACKGROUND: Insulin resistance (IR), one of the key components of the metabolic syndrome, is recognized as the pathophysiological hallmark of non-alcoholic fatty liver disease (NAFLD). This study aims to investigate the relationship between surrogate markers of IR and the severity of NAFLD among overweight or obese children.

    METHODOLOGY: A total of 56 consecutive children aged 6 to 18 years old were recruited from the pediatric obesity and type 2 diabetes mellitus (T2DM) clinic in University Malaya Medical Centre (UMMC) from 2016 to 2019. Data on anthropometric measurements, clinical components of metabolic syndrome and fasting serum insulin were collected. Triglyceride to high-density lipoprotein cholesterol ratio (TG: HDL-C), Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) and Single Point Insulin Sensitivity Estimator (SPISE) were calculated. Transient elastography was performed with hepatic steatosis and liver fibrosis assessed by controlled attenuation parameter (CAP) and liver stiffness measurement (LSM), respectively.

    RESULTS: A total of 44 children (78.6%) had liver steatosis and 35.7% had presence of significant liver fibrosis (stage F≥2). Majority (89.3%) are obese and 24 children (42.9%) were diagnosed with metabolic syndrome. Higher number of children with T2DM and significant liver fibrosis were associated with higher tertiles of TG: HDL-C ratio (p<0.05). Top tertile of TG: HDL-C ratio was an independent predictor of liver fibrosis (OR=8.14, 95%CI: 1.24-53.36, p=0.029). ROC analysis showed that the area under the curve (AUC) of HOMA-IR (0.77) and TG: HDL-C ratio (0.71) were greater than that of metabolic syndrome (0.70), T2DM (0.62) and SPISE (0.22). The optimal cut-off values of HOMA-IR and TG: HDL-C ratio for detecting liver fibrosis among children with NAFLD are 5.20 and 1.58, respectively.

    CONCLUSION: Children with NAFLD and higher TG: HDL-C ratio are more likely to have liver fibrosis. TG: HDL-C ratio is a promising tool to risk stratify those with NAFLD who are at risk of developing advanced liver disease.

  4. Ting YW, Wong SW, Anuar Zaini A, Mohamed R, Jalaludin MY
    Front Pediatr, 2019;7:491.
    PMID: 31850288 DOI: 10.3389/fped.2019.00491
    Background: Non-alcoholic fatty liver disease (NAFLD) among children is a growing concern with potential significant outcome. This study aims to investigate the relationship between hepatic steatosis, metabolic syndrome, and liver fibrosis among children with obesity and diabetes mellitus. Methodology: Children aged 6-18 years old were recruited from pediatric obesity and diabetes clinic in University Malaya Medical Center (UMMC) between year 2016 and 2019. Data on basic demographics, anthropometric measurements and clinical components of metabolic syndrome were collected. Transient elastography was performed with hepatic steatosis and liver fibrosis assessed by controlled attenuation parameter (CAP) and liver stiffness measurement (LSM) respectively. Mild, moderate and severe steatosis were defined as >248, >268, and >280 dB/m respectively, and LSM above 7.0 kPa for fibrosis stage F ≥ 2, 8.7 kPa for F ≥ 3, and 10.3 kPa for F4 (cirrhosis). Results: A total of 57 children (60% male) with median age of 13 years old were recruited. Fifty (87.7%) of the children are obese and 27 (54%) out of 50 are morbidly obese. Among 44 (77.2%) patients with steatosis, 40 (70.2%) had severe steatosis and 18 (40.9%) had developed liver fibrosis of stage 2 and above. Advanced fibrosis or cirrhosis was detected in 8 (18.2%) children with presence of steatosis. Twenty-three out of 57 (40.4%) was diagnosed with metabolic syndrome. Fibrosis is three times more likely to occur in the presence of metabolic syndrome (OR = 3.545, 95% CI: 1.135-11.075, p = 0.026). Waist circumference is a significant predictor of fibrosis after multiple regression analysis. Conclusion: Obese children with metabolic syndrome are more likely to have advanced liver fibrosis compared to those without metabolic syndrome. Waist circumference predicts development of liver fibrosis.
  5. Tan HL, Mohamed R, Mohamed Z, Zain SM
    Pharmacogenet Genomics, 2016 Feb;26(2):88-95.
    PMID: 26636496 DOI: 10.1097/FPC.0000000000000193
    Phosphatidylethanolamine N-methyltransferase (PEMT) governs the secretion of hepatic triglycerides in the form of very low-density lipoprotein and has been implicated in nonalcoholic fatty liver disease (NAFLD). Studies on the role of the PEMT rs7946 polymorphism as a genetic modifier of NAFLD have reported inconsistent results. This meta-analysis was carried out to evaluate and summarize the association of PEMT rs7946 with susceptibility to NAFLD.
  6. Tan HL, Zain SM, Mohamed R, Rampal S, Chin KF, Basu RC, et al.
    J Gastroenterol, 2014 Jun;49(6):1056-64.
    PMID: 23800943 DOI: 10.1007/s00535-013-0850-x
    BACKGROUND: Recent genome-wide association studies demonstrated an association between single nucleotide polymorphisms (SNPs) on the glucokinase regulatory gene (GCKR) with hepatic steatosis. This study attempted to investigate the association of GCKR rs780094 and rs1260326 with susceptibility to non-alcoholic fatty liver disease (NAFLD) and its severity.

    METHODS: The genotypes were assessed on 144 histologically confirmed NAFLD patients and 198 controls using a Sequenom MassARRAY platform.

    RESULTS: The GCKR rs1260326 and rs780094 allele T were associated with susceptibility to NAFLD (OR 1.49, 95 % CI 1.09-2.05, p = 0.012; and OR 1.51, 95 % CI 1.09-2.09, p = 0.013, respectively), non-alcoholic steatohepatitis (NASH) (OR 1.55, 95 % CI 1.10-2.17, p = 0.013; and OR 1.56, 95 % CI 1.10-2.20, p = 0.012, respectively) and NASH with significant fibrosis (OR 1.50, 95 % CI 1.01-2.21, p = 0.044; and OR 1.52, 95 % CI 1.03-2.26, p = 0.038, respectively). Following stratification by ethnicity, significant association was seen in Indian patients between the two SNPs and susceptibility to NAFLD (OR 2.64, 95 % CI 1.28-5.43, p = 0.009; and OR 4.35, 95 % CI 1.93-9.81, p < 0.0001, respectively). The joint effect of GCKR with adiponutrin rs738409 indicated greatly increased the risk of NAFLD (OR 4.14, 95 % CI 1.41-12.18, p = 0.010). Histological data showed significant association of GCKR rs1260326 with high steatosis grade (OR 1.76, 95 % CI 1.08-2.85, p = 0.04).

    CONCLUSION: This study suggests that risk allele T of the GCKR rs780094 and rs1260326 is associated with predisposition to NAFLD and NASH with significant fibrosis. The GCKR and PNPLA3 genes interact to result in increased susceptibility to NAFLD.

  7. Tan HL, Zain SM, Eng HS, Mohamed Z, Mahadeva S, Chan WK, et al.
    PMID: 32410320 DOI: 10.1111/hepr.13525
    AIM: Human leukocyte antigen (HLA) regions were highlighted as important genetic markers for various liver diseases by hepatology-related genome-wide association studies. Replication studies in non-alcoholic fatty liver disease (NAFLD) are limited and none has investigated the association of HLA alleles with non-alcoholic steatohepatitis (NASH) and other histological characteristics. In the current study, we examined the association of HLA-DQA1 and HLA-DQB1 alleles with NAFLD spectrum and its histological characteristics.

    METHODS: Consecutive biopsy-proven NAFLD patients (n = 191) and healthy controls (n = 188) were enrolled and genotyped for HLA-DQA1 and HLA-DQB1 alleles using the sequence-specific oligonucleotide-polymerase chain reaction method.

    RESULTS: No association was found between the HLA alleles and NAFLD or NASH in a case-control setting. Nevertheless, among NAFLD patients, the frequency of HLA-DQB1*06 allele was significantly the lowest in NASH with significant fibrosis (10.4%) and approximately similar for NASH without significant fibrosis (22.9%) and NAFL (22.5%) (P = 0.004). It is noteworthy that the association remains significant after correction for multiple comparisons (Pc  = 0.04). Multivariate analysis revealed that HLA-DQB1*06 allele is also associated with fibrosis score (P = 0.001); the result remains significant after correction for multiple comparisons.

    CONCLUSION: These findings suggest that HLA-DQB1*06 is associated with lower fibrosis score in NAFLD patients.

  8. Syazwan SA, Lee SY, Sajap AS, Lau WH, Omar D, Mohamed R
    Biology (Basel), 2021 Mar 25;10(4).
    PMID: 33806225 DOI: 10.3390/biology10040263
    Metarhizium anisopliae (Metchnikoff) Sorokin, a pathogenic fungus to insects, infects the subterranean termite, Coptotermes curvignathus Holmgren, a devastating pest of plantation trees in the tropics. Electron microscopy and proteomics were used to investigate the infection and developmental process of M. anisopliae in C. curvignathus. Fungal infection was initiated by germ tube penetration through the host's cuticle as observed at 6 h post-inoculation (PI), after which it elongated into the host's integumental tissue. The colonization process continued as seen from dissemination of blastospores in the hemocoel at 96 h PI. At this time point, the emergent mycelia had mummified the host and forty-eight hours later, new conidia were dispersed on the termites' body surface. Meanwhile, hyphal bodies were observed in abundance in the intercellular space in the host's body. The proteomes of the pathogen and host were isolated separately using inoculated termite samples withdrawn at each PI-time point and analyzed in two-dimensional electrophoresis (2-DE) gels. Proteins expressed in termites showed evidence of being related to cell regulation and the immune response, while those expressed in M. anisopliae, to transportation and fungal virulence. This study provides new information on the interaction between termites and its entomopathogen, with potential utilization for developing future biopesticide to control the termite population.
  9. Su YC, Wan KL, Mohamed R, Nathan S
    Vaccine, 2010 Jul 12;28(31):5005-11.
    PMID: 20546831 DOI: 10.1016/j.vaccine.2010.05.022
    Burkholderia pseudomallei is resistant to a wide range of antibiotics, leading to relapse and recrudescence of melioidosis after cessation of antibiotic therapy. More effective immunotherapies are needed for better management of melioidosis. We evaluated the prophylactic potential of the immunogenic outer membrane protein Omp85 as a vaccine against murine melioidosis. Immunization of BALB/c mice with recombinant Omp85 (rOmp85) triggered a Th2-type immune response. Up to 70% of the immunized animals were protected against infectious challenge of B. pseudomallei with reduced bacterial load in extrapulmonary organs. Mouse anti-rOmp85 promoted complement-mediated killing and opsonophagocytosis of B. pseudomallei by human polymorphonuclear cells. In conclusion, we demonstrated that B. pseudomallei Omp85 is potentially able to induce protective immunity against melioidosis.
  10. Su YC, Wan KL, Mohamed R, Nathan S
    Microbes Infect., 2008 Oct;10(12-13):1335-45.
    PMID: 18761419 DOI: 10.1016/j.micinf.2008.07.034
    Burkholderia pseudomallei is the etiological agent of melioidosis, a severe infectious disease of humans and animals. The role of the bacterium's proteins expressed in vivo during human melioidosis continues to remain an enigma. This study's aim was to identify B. pseudomallei target proteins that elicit the humoral immune response in infected humans. A small insert genomic expression library was constructed and immunoscreened to identify peptides that reacted exclusively with melioidosis patients' sera. Sero-positive clones expressing immunogenic peptides were sequenced and annotated, and shown to represent 109 proteins involved in bacterial cell envelope biogenesis, cell motility and secretion, transcription, amino acid, ion and protein metabolism, energy production, DNA repair and unknown hypothetical proteins. Western blot analysis of three randomly selected full-length immunogenic polypeptides with patients' sera verified the findings of the immunome screening. The patients' humoral immune response to the 109 proteins suggests the induction or significant upregulation of these proteins in vivo during human infection and thus may play a role in the pathogenesis of B. pseudomallei. Identification of B. pseudomallei immunogens has shed new light on the elucidation of the bacterium's pathogenesis mechanism and disease severity. These immunogens can be further evaluated as prophylactic and serodiagnostic candidates as well as drug targets.
  11. Shee YG, Mahdi MA, Al-Mansoori MH, Yaakob S, Mohamed R, Zamzuri AK, et al.
    Opt Lett, 2010 May 1;35(9):1461-3.
    PMID: 20436603 DOI: 10.1364/OL.35.001461
    An all-optical generation of a microwave carrier at 21 GHz that incorporates a double-Brillouin frequency shifter is presented. The frequency shift of approximately 21 GHz is achieved by generating the second-order Brillouin Stokes signal from the Brillouin pump. This is accomplished through the circulation and isolation of its first-order Stokes signal in the optical fiber. The Brillouin pump signal is heterodyned with its second-order Brillouin Stokes signal at a high-speed photodetector, and the output beating frequency is equal to the offset between these two signals. The generated microwave carrier is measured at 21.3968 GHz, and the carrier phase noise as low as -58.67 dBc/Hz is achieved.
  12. Shaibullah S, Shuhaimi N, Ker DS, Mohd-Sharif N, Ho KL, Teh AH, et al.
    Commun Biol, 2023 Sep 08;6(1):920.
    PMID: 37684342 DOI: 10.1038/s42003-023-05265-4
    Burkholderia pseudomallei is a highly versatile pathogen with ~25% of its genome annotated to encode hypothetical proteins. One such hypothetical protein, BPSL1038, is conserved across seven bacterial genera and 654 Burkholderia spp. Here, we present a 1.55 Å resolution crystal structure of BPSL1038. The overall structure folded into a modified βαββαβα ferredoxin fold similar to known Cas2 nucleases. The Cas2 equivalent catalytic aspartate (D11) pairs are conserved in BPSL1038 although B. pseudomallei has no known CRISPR associated system. Functional analysis revealed that BPSL1038 is a nuclease with endonuclease activity towards double-stranded DNA. The DNase activity is divalent ion independent and optimum at pH 6. The concentration of monovalent ions (Na+ and K+) is crucial for nuclease activity. An active site with a unique D11(X20)SST motif was identified and proposed for BPSL1038 and its orthologs. Structure modelling indicates the catalytic role of the D11(X20)SST motif and that the arginine residues R10 and R30 may interact with the nucleic acid backbone. The structural similarity of BPSL1038 to Cas2 proteins suggests that BPSL1038 may represent a sub-family of nucleases that share a common ancestor with Cas2.
  13. Shaibullah S, Mohd-Sharif N, Ho KL, Firdaus-Raih M, Nathan S, Mohamed R, et al.
    Acta Crystallogr F Struct Biol Commun, 2014 Dec 01;70(Pt 12):1697-700.
    PMID: 25484229 DOI: 10.1107/S2053230X14025278
    Melioidosis is an infectious disease caused by the pathogenic bacterium Burkholderia pseudomallei. Whole-genome sequencing revealed that the B. pseudomallei genome includes 5855 coding DNA sequences (CDSs), of which ∼25% encode hypothetical proteins. A pathogen-associated hypothetical protein, BPSL1038, was overexpressed in Escherichia coli, purified and crystallized using vapour-diffusion methods. A BPSL1038 protein crystal that grew using sodium formate as precipitant diffracted to 1.55 Å resolution. It belonged to space group C2221, with unit-cell parameters a = 85.36, b = 115.63, c = 46.73 Å. The calculated Matthews coefficient (VM) suggests that there are two molecules per asymmetric unit, with a solvent content of 48.8%.
  14. Shahzad F, Jamshed W, Eid MR, Safdar R, Putri Mohamed Isa SS, El Din SM, et al.
    Sci Rep, 2022 Nov 17;12(1):19817.
    PMID: 36396776 DOI: 10.1038/s41598-022-24294-3
    Solar radiation, which is emitted by the sun, is required to properly operate photovoltaic cells and solar water pumps (SWP). A parabolic trough surface collector (PTSC) installation model was created to investigate the efficacy of SWP. The thermal transfer performance in SWP is evaluated thru the presence of warmth radiation and heat cause besides viscid dissipation. This evaluation is performed by measuring the thermal transmission proportion of the selected warmth transmission liquid in the PTSC, known as a hybrid nano-fluid. Entropy analysis of Oldroyd-B hybrid nano-fluid via modified Buongiorno's model was also tested. The functions of regulating parameters are quantitatively observed by using the Keller-box approach in MATLAB coding. Short terms define various parameters for tables in velocity, shear pressure and temperature, gravity, and Nusselt numbers. In the condition of thermal radiation and thermal conductivity at room temperature, the competence of SWP is proven to be enhanced. Unlike basic nano-fluids, hybrid nano-fluids are an excellent source of heat transfer. Additionally, with at least 22.56% and 35.01% magnitude, the thermal efficiency of AA7075-Ti-6Al-4 V/EO is higher than AA7075-EO.
  15. Schröeder SE, Pedrana A, Scott N, Wilson D, Kuschel C, Aufegger L, et al.
    Liver Int, 2019 10;39(10):1818-1836.
    PMID: 31433902 DOI: 10.1111/liv.14222
    Viral hepatitis is a leading cause of morbidity and mortality worldwide, but has long been neglected by national and international policymakers. Recent modelling studies suggest that investing in the global elimination of viral hepatitis is feasible and cost-effective. In 2016, all 194 member states of the World Health Organization endorsed the goal to eliminate viral hepatitis as a public health threat by 2030, but complex systemic and social realities hamper implementation efforts. This paper presents eight case studies from a diverse range of countries that have invested in responses to viral hepatitis and adopted innovative approaches to tackle their respective epidemics. Based on an investment framework developed to build a global investment case for the elimination of viral hepatitis by 2030, national activities and key enablers are highlighted that showcase the feasibility and impact of concerted hepatitis responses across a range of settings, with different levels of available resources and infrastructural development. These case studies demonstrate the utility of taking a multipronged, public health approach to: (a) evidence-gathering and planning; (b) implementation; and (c) integration of viral hepatitis services into the Agenda for Sustainable Development. They provide models for planning, investment and implementation strategies for other countries facing similar challenges and resource constraints.
  16. Sarker MR, Mohamed A, Mohamed R
    Micromachines (Basel), 2016 Sep 23;7(10).
    PMID: 30404344 DOI: 10.3390/mi7100171
    This paper presents a new method for a vibration-based piezoelectric energy harvesting system using a backtracking search algorithm (BSA)-based proportional-integral (PI) voltage controller. This technique eliminates the exhaustive conventional trial-and-error procedure for obtaining optimized parameter values of proportional gain (Kp), and integral gain (Ki) for PI voltage controllers. The generated estimate values of Kp and Ki are executed in the PI voltage controller that is developed through the BSA optimization technique. In this study, mean absolute error (MAE) is used as an objective function to minimize output error for a piezoelectric energy harvesting system (PEHS). The model for the PEHS is designed and analyzed using the BSA optimization technique. The BSA-based PI voltage controller of the PEHS produces a significant improvement in minimizing the output error of the converter and a robust, regulated pulse-width modulation (PWM) signal to convert a MOSFET switch, with the best response in terms of rise time and settling time under various load conditions.
  17. Sarin SK, Kumar M, Lau GK, Abbas Z, Chan HL, Chen CJ, et al.
    Hepatol Int, 2016 Jan;10(1):1-98.
    PMID: 26563120 DOI: 10.1007/s12072-015-9675-4
    Worldwide, some 240 million people have chronic hepatitis B virus (HBV), with the highest rates of infection in Africa and Asia. Our understanding of the natural history of HBV infection and the potential for therapy of the resultant disease is continuously improving. New data have become available since the previous APASL guidelines for management of HBV infection were published in 2012. The objective of this manuscript is to update the recommendations for the optimal management of chronic HBV infection. The 2015 guidelines were developed by a panel of Asian experts chosen by the APASL. The clinical practice guidelines are based on evidence from existing publications or, if evidence was unavailable, on the experts' personal experience and opinion after deliberations. Manuscripts and abstracts of important meetings published through January 2015 have been evaluated. This guideline covers the full spectrum of care of patients infected with hepatitis B, including new terminology, natural history, screening, vaccination, counseling, diagnosis, assessment of the stage of liver disease, the indications, timing, choice and duration of single or combination of antiviral drugs, screening for HCC, management in special situations like childhood, pregnancy, coinfections, renal impairment and pre- and post-liver transplant, and policy guidelines. However, areas of uncertainty still exist, and clinicians, patients, and public health authorities must therefore continue to make choices on the basis of the evolving evidence. The final clinical practice guidelines and recommendations are presented here, along with the relevant background information.
  18. Rose S, Aravindakshan S, Mohamed Usman JA, Mohamed R, Menon S, Shafiullah RS, et al.
    J Pharm Bioallied Sci, 2021 Jun;13(Suppl 1):S851-S856.
    PMID: 34447214 DOI: 10.4103/jpbs.JPBS_819_20
    Introduction: Impression making is an integral part of prosthetic dentistry. Development of material science has allowed integrating qualities of hydrophilic polyether and hydrophobic polyvinyl siloxane into a newer hybrid material, vinyl polysiloxane (VPS) ether. This study was aimed to compare the VPS ether with the polyether and polyvinyl siloxane in terms of accuracy and dimensional stability.

    Materials and Methods: Stainless steel dies with the American Dental Association specification 19 were made. Die has three horizontal and two vertical lines which are used for taking the impression. Two cross-points at the junction of the vertical lines with line 2 were marked as x and x' and served as beginning and end points of measurements for dimensional accuracy. Accuracy was evaluated 30 min after making each impression. If at least two of the three horizontal lines were reproduced continuously between cross-points, this impression was considered satisfactory. The specimens are poured with Type IV gypsum product and allowed to set completely for 24 h. Then, dimensional stability was measured in the model by measuring the distance between the two lines and comparing the distance with the measurement of line on metal die, which was used to make the impression.

    Results: The mean value obtained for light- and medium-bodied VPS ether was 0.05370 and 0.05330 and for light and medium-bodied polyvinyl siloxane was 0.06370 and 0.07150, respectively. The mean value for polyether monophase was 0.06430. Two-way ANOVA and post hoc test showed statistical significance.

    Conclusion: The newer VPS ether material showed good surface detail reproduction and dimensional stability when compared with polyvinyl siloxane and polyether.

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