Displaying publications 61 - 80 of 170 in total

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  1. Ismail NH, Osman K, Zulkefli AF, Mokhtar MH, Ibrahim SF
    Molecules, 2021 Jun 02;26(11).
    PMID: 34199433 DOI: 10.3390/molecules26113346
    Gelam honey (GH) is a prized natural product synthesized from the nectar of flowers from Gelam trees (Melaleuca sp.). Gelam is an evergreen tree species that grows in tropical regions such as Malaysia. GH is a multifloral honey with proven antioxidant and anti-inflammatory properties. However, the beneficial effect of GH on female reproductive tissue has yet to be substantiated. Herein, we investigated the effects of GH administration on the uterine and vaginal epithelial thickness of sexually mature Sprague-Dawley rats. Epithelia thickness could be an indicator of an atrophy manifesting as a symptom of a cardio syndrome. Rats were given oral doses of GH in four groups for 14 days; the lowest dose was 0.2 g GH/kg body weight (bw) rat/day and the highest dose was 8 g GH/kg bw rat/day. The physicochemical characteristics of GH were assessed through hydroxymethylfurfural and moisture content determination and sugar identification. GH attenuated the atrophy of the uterine and vaginal epithelia and increased the thickness of the endometrial stroma and endometrial surface endothelial layer. However, the dissonance observed in the effect of GH administration on the vaginal epithelium requires further investigation. Nevertheless, GH may have a strong potential in attenuating uterine and vaginal atrophies.
  2. Imran S, Taha M, Ismail NH, Fayyaz S, Khan KM, Choudhary MI
    Bioorg Chem, 2016 10;68:90-104.
    PMID: 27474804 DOI: 10.1016/j.bioorg.2016.07.011
    In this study, 45 bisindolylmethanes having sulfonamide moiety had been synthesized through 3 steps. In vitro assay for inhibition of carbonic anhydrase showed that some of the compounds having sulfonamide moiety are capable of inhibiting carbonic anhydrase II. Bisindoles having halogens at fifth position showed better inhibitory activity as compared to unsubstituted bisindoles. The results obtained from in vitro inhibitory activity were subjected through 3D QSAR and docking studies to identify important features contributing to the activity and further improve the structure. Pharmacophore studies suggest that bisindolylmethane moiety is contributing significantly towards the inhibition activity. Docking studies showed that compounds having nitro substituent (5g and 5i) were found to be able interact with Zn(2+) ion, Thr199, His94, His96, and His119, which interferes with the ZnOHThr199Glu106 hydrogen bond network. Bulky nitro substituent at ortho position for compound 5g prevents the compound from interacting with other residues like Thr199 and Thr200. Methyl substituent at ortho position for Compound 5i induces less steric hindrance effect, thus allowing second oxygen atom of sulfonamide to interact with Thr199 (2.51Å). Hydrogen bonding between NH on indole ring with Glu69 might have increased stability of ligand-receptor complex.
  3. Salar U, Taha M, Khan KM, Ismail NH, Imran S, Perveen S, et al.
    Eur J Med Chem, 2016 Oct 21;122:196-204.
    PMID: 27371923 DOI: 10.1016/j.ejmech.2016.06.037
    3-Thiazolylcoumarin derivatives 1-14 were synthesized via one-pot two step reactions, and screened for in vitro α-glucosidase inhibitory activity. All compounds showed inhibitory activity in the range of IC50 = 0.12 ± 0.01-16.20 ± 0.23 μM as compared to standard acarbose (IC50 = 38.25 ± 0.12 μM), and also found to be nontoxic. Molecular docking study was carried out in order to establish the structure-activity relationship (SAR) which demonstrated that electron rich centers at one and electron withdrawing centers at the other end of the molecules showed strong inhibitory activity. All the synthesized compounds were characterized by spectroscopic techniques such as EI-MS, HREI-MS, (1)H NMR and (13)C NMR. CHN analysis was also performed.
  4. Taha M, Ismail NH, Ali M, Rashid U, Imran S, Uddin N, et al.
    Bioorg Chem, 2017 04;71:192-200.
    PMID: 28228228 DOI: 10.1016/j.bioorg.2017.02.005
    The high potential of quinoline containing natural products and their derivatives in medicinal chemistry led us to discover a novel series of compounds 6-23 based on the concept of molecular hybridization. Most of the synthesized analogues exhibited potent leishmanicidal potential. The most potent compound (23, IC50=0.10±0.001μM) among the series was found ∼70 times more lethal than the standard drug. The current series 6-23 conceded in the development of fourteen (14) extraordinarily active compounds against leishmaniasis. In silico analysis were also performed to probe the mode of action while all the compounds structure were established by NMR and Mass spectral analysis.
  5. Salar U, Khan KM, Taha M, Ismail NH, Ali B, Qurat-Ul-Ain, et al.
    Eur J Med Chem, 2017 Jan 05;125:1289-1299.
    PMID: 27886546 DOI: 10.1016/j.ejmech.2016.11.031
    Current study is based on the biology-oriented drug synthesis (BIODS) of 2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl aryl carboxylate derivatives 1-26, by treating metronidazole with different aryl and hetero-aryl carboxylic acids in the presence of 1,1'-carbonyl diimidazole (CDI) as a coupling agent. Structures of all synthetic derivatives were confirmed with the help of various spectroscopic techniques such as EI-MS, (1)H -NMR and (13)C NMR. CHN elemental analyses were also found in agreement with the calculated values. Synthetic derivatives were evaluated to check their β-glucuronidase inhibitory activity which revealed that except few derivatives, all demonstrated good inhibition in the range of IC50 = 1.20 ± 0.01-60.30 ± 1.40 μM as compared to the standard d-saccharic acid 1,4-lactone (IC50 = 48.38 ± 1.05 μM). Compounds 1, 3, 4, 6, 9-19, and 21-24 were found to be potent analogs and showed superior activity than standard. Limited structure-activity relationship is suggested that the molecules having electron withdrawing groups like NO2, F, Cl, and Br, were displayed better activity than the compounds with electron donating groups such as Me, OMe and BuO. To verify these interpretations, in silico study was also performed, a good correlation was observed between bioactivities and docking studies.
  6. Imran S, Taha M, Selvaraj M, Ismail NH, Chigurupati S, Mohammad JI
    Bioorg Chem, 2017 08;73:121-127.
    PMID: 28648924 DOI: 10.1016/j.bioorg.2017.06.007
    A series of twenty indole hydrazone analogs (1-21) were synthesized, characterized by different spectroscopic techniques such as 1H NMR and EI-MS, and screened for α-amylase inhibitory activity. All analogs showed a variable degree of α-amylase inhibition with IC50 values ranging between 1.66 and 2.65μM. Nine compounds that are 1 (2.23±0.01μM), 8 (2.44±0.12μM), 10 (1.92±0.12μM), 12 (2.49±0.17μM), 13 (1.66±0.09μM), 17 (2.25±0.1μM), 18 (1.87±0.25μM), 20 (1.83±0.63μM), and 19 (1.97±0.02μM) showed potent α-amylase inhibition when compared with the standard acarbose (1.05±0.29μM). Other analogs showed good to moderate α-amylase inhibition. The structure activity relationship is mainly focusing on difference of substituents on phenyl part. Molecular docking studies were carried out to understand the binding interaction of the most active compounds.
  7. Baharudin MS, Taha M, Imran S, Ismail NH, Rahim F, Javid MT, et al.
    Bioorg Chem, 2017 06;72:323-332.
    PMID: 28505547 DOI: 10.1016/j.bioorg.2017.05.005
    Natural products are the main source of motivation to design and synthesize new molecules for drug development. Designing new molecules against β-glucuronidase inhibitory is utmost essential. In this study indole analogs (1-35) were synthesized, characterized using various spectroscopic techniques including 1H NMR and EI-MS and evaluated for their β-glucuronidase inhibitory activity. Most compounds were identified as potent inhibitors for the enzyme with IC50 values ranging between 0.50 and 53.40μM, with reference to standard d-saccharic acid 1,4-lactone (IC50=48.4±1.25μM). Structure-activity relationship had been also established. The results obtained from docking studies for the most active compound 10 showed that hydrogen bond donor features as well as hydrogen bonding with (Oε1) of nucleophilic residue Glu540 is believed to be the most importance interaction in the inhibition activity. It was also observed that hydroxyl at fourth position of benzylidene ring acts as a hydrogen bond donor and interacts with hydroxyl (OH) on the side chain of catalysis residue Tyr508. The enzyme-ligand complexed were being stabilized through electrostatic π-anion interaction with acid-base catalyst Glu451 (3.96Å) and thus preventing Glu451 from functioning as proton donor residue.
  8. Taha M, Baharudin MS, Ismail NH, Selvaraj M, Salar U, Alkadi KA, et al.
    Bioorg Chem, 2017 04;71:86-96.
    PMID: 28160943 DOI: 10.1016/j.bioorg.2017.01.015
    Novel sulfonamides having oxadiazole ring were synthesized by multistep reaction and evaluated to check in vitro β-glucuronidase inhibitory activity. Luckily, except compound 13, all compounds were found to demonstrate good inhibitory activity in the range of IC50=2.40±0.01-58.06±1.60μM when compared to the standard d-saccharic acid 1,4-lactone (IC50=48.4±1.25μM). Structure activity relationship was also presented. However, in order to ensure the SAR as well as the molecular interactions of compounds with the active site of enzyme, molecular docking studies on most active compounds 19, 16, 4 and 6 was carried out. All derivatives were fully characterized by 1H NMR, 13C NMR and EI-MS spectroscopic techniques. CHN analysis was also presented.
  9. Zawawi NK, Taha M, Ahmat N, Ismail NH, Wadood A, Rahim F
    Bioorg Chem, 2017 02;70:184-191.
    PMID: 28043716 DOI: 10.1016/j.bioorg.2016.12.009
    Thiourea derivatives having benzimidazole 1-17 have been synthesized, characterized by 1H NMR, 13C NMR and EI-MS and evaluated for α-glucosidase inhibition. Identification of potential α-glucosidase inhibitors were done by in vitro screening of 17 thiourea bearing benzimidazole derivatives using Baker's yeast α-glucosidase enzyme. Compounds 1-17 exhibited a varying degree of α-glucosidase inhibitory activity with IC50 values between 35.83±0.66 and 297.99±1.20μM which are more better than the standard acarbose (IC50=774.5±1.94μM). Compound 10 and 14 showed significant inhibitory effects with IC50 value 50.57±0.81 and 35.83±0.66μM, respectively better than the rest of the series. Structure activity relationships were established. Molecular docking studies were performed to understand the binding interaction of the compounds.
  10. Afzan A, Kasim N, Ismail NH, Azmi N, Ali AM, Mat N, et al.
    Metabolomics, 2019 Mar 04;15(3):35.
    PMID: 30830457 DOI: 10.1007/s11306-019-1489-2
    BACKGROUND: Ficus deltoidea Jack (Moraceae) is a plant used in Malaysia for various diseases including as a supplement in diabetes management. Morphology distinction of the 7 main varieties (var. angustifolia, var. bilobata, var. deltoidea, var. intermedia, var. kunstleri, var. motleyana and var. trengganuensis) is challenging due to the extreme leaf heterophylly and unclear varietal boundaries, making it difficult for quality control of F. deltoidea products.

    OBJECTIVE: We aimed to compare the phytochemical composition of 7 varieties growing in different conditions at various geographical locations. We also aimed to establish the quality control markers for the authentication of these varieties.

    METHODS: We applied untargeted UHPLC-TOFMS metabolomics to discriminate 100 leaf samples of F. deltoidea collected from 6 locations in Malaysia. A genetic analysis on 21 leaf samples was also performed to validate the chemotaxonomy differentiation.

    RESULTS: The PCA and HCA analysis revealed the existence of 3 chemotypes based on the differentiation in the flavonoid content. The PLS-DA analysis identified 15 glycosylated flavone markers together with 1 furanocoumarin. These markers were always consistent for the respective varieties, regardless of the geographical locations and growing conditions. The chemotaxonomy differentiation was in agreement with the DNA sequencing. In particular, var. bilobata accession which showed divergent morphology was also differentiated by the chemical fingerprints and genotype.

    CONCLUSION: Chemotype differentiation based on the flavonoid fingerprints along with the proposed markers provide a powerful identification tool to complement morphology and genetic analyses for the quality control of raw materials and products from F. deltoidea.

  11. Abdul Somat N, Osman CP, Ismail NH, Yusoff Z, Md Yusof Y
    Science Letters, 2019;13(1):23-32.
    MyJurnal
    In a search for new potential AChE inhibitors, 31 selected medicinal plants from Perlis were collected gathered, air dried and successively extracted using hexane, dichloromethane, and alcohol. The dichloromethane and alcoholic extracts were screened for AChE inhibitory activity using Ellman's method. Out of 31 plant species, the methanol extracts of Rhapis excelsa leaves (97.03 ± 3.71 %), Diospyros blancoi leaves (95.80 ± 1.57 %) and Phyllantus elegans root (83.22 ± 3.08 %) showed the highest AChE inhibitory activity at the concentration of 100 μg/mL.
  12. Lin GSS, Cher CY, Cheah KK, Noorani TY, Ismail NH, Ghani NRNA
    J Esthet Restor Dent, 2021 Oct 30.
    PMID: 34716755 DOI: 10.1111/jerd.12831
    OBJECTIVES: This review aimed to summarize contemporary evidence related to dental composite resin derived from rice husk biowaste and its potential future advancement. This review paper included the techniques for synthesis, characterization, and preparation of rice husk composite resin. Focus was also given to the flexural strength and modulus, compressive strength, wear rate, hardness, surface roughness, color stability, polymerization shrinkage, degree of conversion, and their application onto root canal treated teeth.

    MATERIAL AND METHODS: A search of English peer-reviewed literature (January 1960-February 2021) was conducted from electronic databases (PubMed Central, Cochrane, LILACS, Science Direct, Web of Science, SIGLE, EMBASE, EBSCO, Medline, and Google Scholar).

    RESULTS: 11 articles and a book section were finally selected for qualitative analysis. Studies concluded that the physicomechanical properties and the color stability of rice husk dental composites showed comparable results to conventional dental composites. Incorporation of zirconia nanopowder into rice husk dental composite increased the compressive strength and hardness values, associated with lower shrinkage, a high degree of conversion, and improved fracture strength when applied on root canal treated teeth.

    CONCLUSIONS: Due to its low cost, eco-friendliness, and acceptable clinical performances, rice husk dental composite resin can be considered as an alternative to conventional composites.

    CLINICAL SIGNIFICANCE: Dental composite resin derived from rice husk silica demonstrated excellent performance, which could potentially substitute currently available composite resins. This review will give new insight to clinicians and researchers on the usage of natural biowaste mass in the field of dental restorative materials.

  13. Abid O, Imran S, Taha M, Ismail NH, Jamil W, Kashif SM, et al.
    Mol Divers, 2021 May;25(2):995-1009.
    PMID: 32301032 DOI: 10.1007/s11030-020-10084-4
    The β-glucuronidase, a lysosomal enzyme, catalyzes the cleavage of glucuronosyl-O-bonds. Its inhibitors play a significant role in different medicinal therapies as they cause a decrease in carcinogen-induced colonic tumors by reducing the level of toxic substances present in the intestine. Among those inhibitors, bisindole derivatives had displayed promising β-glucuronidase inhibition activity. In the current study, hydrazone derivatives of bisindolymethane (1-30) were synthesized and evaluated for in vitro β-glucuronidase inhibitory activity. Twenty-eight analogs demonstrated better activity (IC50 = 0.50-46.5 µM) than standard D-saccharic acid 1,4-lactone (IC50 = 48.4 ± 1.25 µM). Compounds with hydroxyl group like 6 (0.60 ± 0.01 µM), 20 (1.50 ± 0.10 µM) and 25 (0.50 ± 0.01 µM) exhibited the most potent inhibitory activity, followed by analogs with fluorine 21 (3.50 ± 0.10 µM) and chlorine 23 (8.20 ± 0.20 µM) substituents. The presence of hydroxyl group at the aromatic side chain was observed as the main contributing factor in the inhibitory potential. From the docking studies, it was predicted that the active compounds can fit properly in the binding groove of the β-glucuronidase and displayed significant binding interactions with essential residues.
  14. Bano B, Arshia, Khan KM, Kanwal, Fatima B, Taha M, et al.
    Eur J Med Chem, 2017 Oct 20;139:849-864.
    PMID: 28865280 DOI: 10.1016/j.ejmech.2017.08.052
    In this study synthesis and β-glucuronidase inhibitory potential of 3/5/8 sulfonamide and 8-sulfonate derivatives of quinoline (1-40) are discussed. Studies reveal that all the synthetic compounds were found to have good inhibitory activity against β-glucuronidase. Nonetheless, compounds 1, 2, 5, 13, and 22-24 having IC50 values in the range of 1.60-8.40 μM showed superior activity than the standard saccharic acid 1,4-lactone (IC50 = 48.4 ± 1.25 μM). Moreover, molecular docking studies of selected compounds were also performed to see interactions between active compounds and binding sites. Structures of all the synthetic compounds were confirmed through (1)H NMR, EI-MS and HREI-MS spectroscopic techniques.
  15. Abd Aziz NAS, Teng NIMF, Abdul Hamid MR, Ismail NH
    Clin Interv Aging, 2017;12:1615-1625.
    PMID: 29042762 DOI: 10.2147/CIA.S140859
    PURPOSE: The increasing number of elderly people worldwide throughout the years is concerning due to the health problems often faced by this population. This review aims to summarize the nutritional status among hospitalized elderly and the role of the nutritional assessment tools in this issue.

    METHODS: A literature search was performed on six databases using the terms "malnutrition", "hospitalised elderly", "nutritional assessment", "Mini Nutritional Assessment (MNA)", "Geriatric Nutrition Risk Index (GNRI)", and "Subjective Global Assessment (SGA)".

    RESULTS: According to the previous studies, the prevalence of malnutrition among hospitalized elderly shows an increasing trend not only locally but also across the world. Under-recognition of malnutrition causes the number of malnourished hospitalized elderly to remain high throughout the years. Thus, the development of nutritional screening and assessment tools has been widely studied, and these tools are readily available nowadays. SGA, MNA, and GNRI are the nutritional assessment tools developed specifically for the elderly and are well validated in most countries. However, to date, there is no single tool that can be considered as the universal gold standard for the diagnosis of nutritional status in hospitalized patients.

    CONCLUSION: It is important to identify which nutritional assessment tool is suitable to be used in this group to ensure that a structured assessment and documentation of nutritional status can be established. An early and accurate identification of the appropriate treatment of malnutrition can be done as soon as possible, and thus, the malnutrition rate among this group can be minimized in the future.

  16. Taha M, Irshad M, Imran S, Chigurupati S, Selvaraj M, Rahim F, et al.
    Eur J Med Chem, 2017 Dec 01;141:530-537.
    PMID: 29102178 DOI: 10.1016/j.ejmech.2017.10.028
    Piperazine Sulfonamide analogs (1-19) have been synthesized, characterized by different spectroscopic techniques and evaluated for α-amylase Inhibition. Analogs 1-19 exhibited a varying degree of α-amylase inhibitory activity with IC50 values ranging in between 1.571 ± 0.05 to 3.98 ± 0.397 μM when compared with the standard acarbose (IC50 = 1.353 ± 0.232 μM). Compound 1, 2, 3 and 7 showed significant inhibitory effects with IC50 value 2.348 ± 0.444, 2.064 ± 0.04, 1.571 ± 0.05 and 2.118 ± 0.204 μM, respectively better than the rest of the series. Structure activity relationships were established. Molecular docking studies were performed to understand the binding interaction of the compounds.
  17. Ali F, Khan KM, Salar U, Taha M, Ismail NH, Wadood A, et al.
    Eur J Med Chem, 2017 Sep 29;138:255-272.
    PMID: 28672278 DOI: 10.1016/j.ejmech.2017.06.041
    Acarbose, miglitol, and voglibose are the inhibitors of α-glucosidase enzyme and being clinically used for the management of type-II diabetes mellitus. However, many adverse effects are also associated with them. So, the development of new therapeutic agents is an utmost interest in medicinal chemistry research. Current study is based on the identification of new α-glucosidase inhibitors. For that purpose, hydrazinyl arylthiazole based pyridine derivatives 1-39 were synthesized via two step reaction and fully characterized by spectroscopic techniques EI-MS, HREI-MS, (1)H-, and (13)C NMR. However, stereochemistry of the iminic bond was confirmed by NOESY. All compounds were subjected to in vitro α-glucosidase inhibitory activity and found many folds active (IC50 = 1.40 ± 0.01-236.10 ± 2.20 μM) as compared to the standard acarbose having IC50 value of 856.45 ± 5.60 μM. A limited structure-activity relationship was carried out in order to make a presumption about the substituent's effect on inhibitory activity which predicted that substituents of more negative inductive effect played important role in the activity as compared to the substituents of less negative inductive effect. However, in order to have a good understanding of ligand enzyme interactions, molecular docking study was also conducted. In silico study was confirmed that substituents like halogens (Cl) and nitro (NO2) which have negative inductive effect were found to make important interactions with active site residues.
  18. Salahuddin L, Ismail Z, Hashim UR, Raja Ikram RR, Ismail NH, Naim Mohayat MH
    Health Informatics J, 2019 12;25(4):1358-1372.
    PMID: 29521162 DOI: 10.1177/1460458218759698
    The objective of this study is to identify factors influencing unsafe use of hospital information systems in Malaysian government hospitals. Semi-structured interviews with 31 medical doctors in three Malaysian government hospitals implementing total hospital information systems were conducted between March and May 2015. A thematic qualitative analysis was performed on the resultant data to deduce the relevant themes. A total of five themes emerged as the factors influencing unsafe use of a hospital information system: (1) knowledge, (2) system quality, (3) task stressor, (4) organization resources, and (5) teamwork. These qualitative findings highlight that factors influencing unsafe use of a hospital information system originate from multidimensional sociotechnical aspects. Unsafe use of a hospital information system could possibly lead to the incidence of errors and thus raises safety risks to the patients. Hence, multiple interventions (e.g. technology systems and teamwork) are required in shaping high-quality hospital information system use.
  19. Kasim N, Afzan A, Mediani A, Low KH, Ali AM, Mat N, et al.
    Phytochem Anal, 2022 Dec;33(8):1235-1245.
    PMID: 36192845 DOI: 10.1002/pca.3175
    INTRODUCTION: Ficus deltoidea Jack (Moraceae) is a plant used in Malaysia to treat various ailments, including diabetes. The presence of several varieties raises essential questions regarding which is the potential bioactive variety and what are the bioactive metabolites.

    OBJECTIVES: Here, we explored the phytochemical diversity of the seven varieties from Peninsular Malaysia using Nuclear Magnetic Resonance (NMR) and Liquid Chromatography-Mass Spectrometry (LC-MS) analyses and correlated it with the α-glucosidase inhibitory activity.

    METHODOLOGY: The Nuclear Overhauser Effect Spectroscopy (NOESY) One-Dimensional (1D)-NMR and LC-MS data were processed, annotated, and correlated with in vitro α-glucosidase inhibitory using multivariate data analysis.

    RESULTS: The α-glucosidase results demonstrated that different varieties have varying inhibitory effects, with the highest inhibition rate being F. deltoidea var. trengganuensis and var. kunstleri. Furthermore, diverse habitats and plant ages could also influence the inhibitory rate. The heat map from NMR and LC-MS profiles showed unique patterns according to varying levels of α-glucosidase inhibition rate. The Partial Least Squares (PLS) model constructed from both NMR and LC-MS further confirmed the correlation between the α-glucosidase inhibition rate of F. deltoidea varieties and its metabolite profiles. The Variable Influence on Projection (VIP) and correlation coefficient (p(corr)) values values were used to determine the highly relevant metabolites for explaining the anticipated inhibitory action.

    CONCLUSION: NMR and LC-MS annotations allow the identification of flavan-3-ols and proanthocyanidins as the key bioactive factors. Our current results demonstrated the value of multivariate data analysis to predict the quality of herbal materials from both biological and chemical aspects.

  20. Lin GS, Ghani NR, Ismail NH, Singbal K, Murugeshappa DG, Mamat N
    J Clin Exp Dent, 2020 Aug;12(8):e762-e770.
    PMID: 32913574 DOI: 10.4317/jced.56864
    Background: This study aimed to compare the fracture strength, fracture pattern and type of fracture of endodontically treated maxillary lateral incisors restored with new zirconia reinforced rice husk nanohybrid composite.

    Material and Methods: Eighty mature permanent maxillary lateral incisors from patients age range of 30-60 years with single canal were selected and randomly divided into: Group 1 - RCT + nanofilled composite (Filtek), Group 2 - RCT + microhybrid composite (Zmack), Group 3 - RCT + new nanohybrid composite (Zr-Hybrid) and Group 4 - Intact teeth (control). Standardized mesio-palatal-distal cavity was prepared, and endodontic treatment was carried out using crown-down technique until size 30, tapered 0.04. Obturation was completed using single cone technique with gutta-percha and AH plus sealer. Cavity access was restored with respective composite resins. Next, teeth were stored in incubator for 24 hours and subdivided into aged and unaged subgroups. Teeth in aged subgroups were subjected to 2500 thermal cycles for 5ºC, 37ºC and 55ºC with 30 seconds dwell time and 5 seconds transfer time. After that, root surfaces of teeth were covered with silicone-based material and placed in boxes filled with acrylic until the cemento-enamel-junction (CEJ) level. They were then tested under Universal Testing Machine until fracture occurred. Samples were then viewed under Leica microscope to determine the fracture pattern and type of fracture. Data analyzed using One-way ANOVA complimented by post hoc Tukey HSD and paired sample T test for fracture strength. Fracture pattern and type of fracture were analyzed using Chi-square test. Level of significance was set at p<0.05.

    Results: Significant differences were observed (p<0.05) with Group 3 demonstrating the highest fracture strength followed by Group 4, Group 1 and lastly Group 2 in both aged and unaged subgroups respectively. A significant decreased in fracture strength was noted in Group 1 and Group 2 (p<0.05) as number of thermocycle increased but no significant differences were noted in Group 3 and Group 4 (p>0.05). Besides, Group 3 and Group 4 showed higher rate of favorable fracture pattern, followed by Group 1 and lastly Group 2. Most favorable fracture pattern was noted to exhibit horizontal fracture type (86.36%), whereas most unfavorable fracture pattern exhibited vertical fracture type (77.78%).

    Conclusions: Endodontically treated teeth restored with new zirconia reinforced rice husk nanohybrid composite (Zr-Hybrid) demonstrated higher fracture strength than commercialized composite resins especially after artificial ageing. Zr-Hybrid showed similar fracture pattern to those of intact teeth with higher rate of horizontal fracture type. Key words:Fracture strength, fracture pattern, composite resin, rice husk, Zirconia.

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