Browsing by Author "Lizymol, PP"

Now showing 1 - 20 of 37
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    A comparison of efficiency of two photoinitiators for polymerization of light-cure dental composite resins
    (JOURNAL OF APPLIED POLYMER SCIENCE, 2008) Lizymol, PP; Krishnan, VK
    The purpose of the study was to compare the effect of two photoinitiators, (-)camphorquinone (CQ) and 1-phenyl-1,2-propanedione (PPD) on curing performance of light-cure dental composite resins. Bisphenol Aglycidyl methacrylate (BisGMA)/triethylene glycol dimethacrylate (TEGDMA) monomer mixture was used as the resin matrix. The resin matrix was mixed with CQ and/or PPD along with 0.25% of 4-(dimethyl amino) phenethyl alcohol (DMAPEA) catalyst. The effect of photoinitiator on curing performance was evaluated and compared in terms of properties such as depth of cure, diametral tensile strength (DTS), flexural strength (FS),, flexural. modulus (FM), vickers hardness number (VHN), water sorption (WS), and solubility of cured composite. Statistical evaluation using Analysis of Variance (single factor) showed that the photosensitization efficiency of CQ and PPD are comparable. However, their combination showed synergistic effect for properties such as DTS and solubility. (c) 2007 Wiley Periodicals, Inc.
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    A study of the diluent effect on the properties of urethane based dental composites
    (JOURNAL OF POLYMER MATERIALS, 2003) Lizymol, PP; Krishnan, VK
    Low molecular weight monomers such as triethylene glycol dimethacrylate (TEGDMA) and tetraethylene glycol diacrylate (TEGDA) have been conventionally used as diluents in combination with highly viscous dimethacrylate organic resins such as Bisphenol A - Glycidyl methacrylate (bis-GMA) in dental composite formulations to facilitate easier mixing and for providing improved properties. In this study a new low molecular weight dimethacrylate 1,3 bis (methactyloxy) 2-hydroxy propane [MHP] has been synthesized and used in dental composites. Glycidyl methacrylate was reacted with methacrylic acid in presence of a base catalyst, the product of which was subsequently used as a precursor for preparing two urethane tetramethacrylate resins by reacting with hexamethylene diisocyanate [HMDI] and toluene diisocyanate [TDI]. Dental composite pastes prepared using these two urethane resins had MHP or TEGDMA as diluents and dimethyl aminophenethyl alcohol [DMAPEA] or dimethyl p-toluidine [DMPT] as activators and their properties were compared. Comparisons were made in terms of compressive strength (CS), diametral tensile strength (DTS) and Vickers microhardness (MH). Composites containing HMDI showed improved mechanical properties compared to those prepared using TDI. Composites containing MHP showed comparable properties with those incorporated with TEGDMA. SEM studies showed evidence for uniform mixing of the filler in the urethane tetramethacrylate resin thinned with MHP.
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    Aging Effects of Dental Restorative Materials upon Surface Hardness
    (JOURNAL OF POLYMER MATERIALS, 2009) Lizymol, PP; Krishnan, VK
    This study was conducted to compare the effect of one-year storage of one indigenously developed and seven commercially available dental restorative materials on surface microhardness (VHN) and the use of hardness value as an indirect measure of degree of conversion and degradation in aqueous medium. Four composite pastes (Spectrum- TPH, Z-100, P -60 and indigenously developed Ormo 48, one compomer (F- 2000) and three glass ionomers (Fuji II LC, Fuji II CC and Ketac Molar) were either self or light cured and stored in distilled water at 37 +/- 1 degrees C and Vickers microhardness was measured at intervals of 1 hour, 1 and 7 days, 1, 3, 6, 9 and 12 months. A minimum of 6 measurements was carried out on both surfaces. Mean and standard deviations were calculated. Statistical evaluation was done by means of one-way analysis of variance (ANOVA). Degradation and monomer conversion were correlated with the support of Fourier Transform Raman spectra of cured and uncured paste. A significant difference in hardness was noticed for each material over storage time. Among the materials tested, composites exhibited the highest hardness values throughout the study. The values reached a maximum after 24 hours and showed a significant decline over a period of 1 year. Compomer had the maximum hardness after seven days. However in case of FUJI glass ionomers, no significant change in hardness was noticed even after 1 year whereas Ketac Molar showed a significant increase in hardness with time. FT Raman spectra of photo cured organically modified ceramics composite showed residual unsaturation (1610 cm(-1) peak). The results indicate that composites and compomers show significant decrease in hardness with time whereas glass ionomers tend to show either significant (P< 0.05) increase or no change on storage.
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    Biological evaluation of a new organically modified ceramic-based dental restorative resin
    (JOURNAL OF APPLIED POLYMER SCIENCE, 2012) Lizymol, PP; Mohanan, PV; Sabareeswaran, A; Krishnan, VK
    Material tissue interactions of a newly developed organically modified ceramic (ormocer)-based dental restorative composite based on a resin containing mixture of alkoxides of silicone and calcium with polymerizable methacrylate end groups are discussed in this study. Admira, a commercially available ormocer was used as control. A solgel process has been used to synthesize organically modified ceramic resins from liquid precursors, which allow one to produce inorganicorganic hybrid polymer materials, which can be functionalized to optimize their physical and chemical properties. Besides, the resulting material properties have been significantly modified by further technological processing such as photochemical curing of the materials by incorporating dimethacrylate groups as organically polymerizable units. Intracutaneous (intradermal) irritation test is found not to elicit any gross signs of tissue reaction. The results of maximization test for delayed hypersensitivity also did not show any adverse skin reaction during the induction or challenge period. Histological analysis after 1, 4, and 12 weeks of subcutaneous implantation of restorative composite resin on the dorsal surface on one side of the spinal column of Wister rats is also found not to reveal any inflammatory response after the implantation. Granuloma and material debris is found to be absent in all three periods of implantation in both test and control. No necrosis was observed around the implanted materials, which were found to be encapsulated by fibrous connective tissue consisting of predominantly fibroblasts and inflammatory cells. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
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    Can a mouth wash prevent atherosclerosis and ischemic stroke?
    (Cell Signaling, 2024-04) Lizymol, PP
    Can a mouth wash prevent atherosclerosis and ischemic stroke? Is it a joke/dream/possibility in future? The mini review points to the possibility of controlling atherosclerosis and ischemic stroke through proper oral hygiene, regular dental check-up, removing tooth decay, preventing dental plaque and gum diseases. A systematic and detailed survey/study of oral health conditions among the neuro/cardio patients may be useful in improving their health recovery. Maintaining good oral health with regular brushing, flossing, and dental check-ups are crucial for preventing gum diseases. Moreover, mouthwash can be a helpful component of oral hygiene. Daily use of proven natural materials such as 0.1% turmeric mouthwash or coconut oil can reduce the chance of gum diseases.
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    Capped oligomers of isocyanate of acrylic monomers as potential bioerodible tissue adhesives
    (JOURNAL OF POLYMER MATERIALS, 2000) Jayabalan, M; Lizymol, PP
    Tissue adhesives based on capped-oligomeric resin prepared from isocyanato ethyl methacrylate and acrylic acid monomers are found to bind beef muscle. The cured adhesive undergoes bioerosion. A potential soft tissue adhesive could be formulated from capped isocyanate based oligomer for optimised adhesive strength, bioerosion and shelf life.
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    Development and evaluation of a single solution bonding agent as a dental adhesive
    (JOURNAL OF POLYMER MATERIALS, 2005) Krishnan, VK; Lizymol, PP; Kumari, TV; Rauf, TA; Thomas, MM
    Development of a dentine bonding agent based on a tetramethacrylate resin with free carboxyl groups and its evaluation are described in this paper. Pyromellitic dianhydride was reacted with glycerol dimethactylate at 42-45 degrees C for 5 h in presence of an amine catalyst to produce a colorless and viscous pyromellitic anhydride-glycerol dimethacrylate adduct [PMGDM]. The resin was characterized using refractive index, infra red and NMR spectroscopy and HPLC chromatographic techniques. The resin was used to formulate a single solution bonding agent [SSBA] using acetone as the solvent, 2-hydroxyethyl methacrylate [HEMA] as the diluent, camphorquinone [CO] as the photoinitiator and dimethylamino phenethyl alcohol [DMAPEA] as the accelerator. Shear and tensile bond strengths of composites polymerized by photoinitiation adhered on dentinal and metallic surfaces using SSBA and an imported control Single Bond were evaluated and compared. Cytotoxicity evaluation by the MTT assay of SSBA and Single Bond on L-929 mammalian cell lines demonstrated metabolic activity of 1.7% of cells in contact with SSBA extract and 1.5% of cells in contact with Single Bond extract compared to 100% for cells alone. Shear and tensile strength evaluation at different intervals of time for the newly developed bonding agent stored at 22 +/- 2 degrees C upto 70 days showed no statistically significant variation in the strength values with time.
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    Development of a new photoinitiator for dental app lications ( Project - 7025 )
    (SCTIMST, 2004-03-05) Lizymol, PP; KalliyanaKrishnan, V
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    Development of bioactive bone cement based on organically modified ceramic resin ( Project 6033 )
    (SCTIMST, 2012-12-31) Lizymol, PP; KalliyanaKrishnan, V
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    Development of bioactive bone cement based on novel inorganic-organic hybrid resin ( Project - 8172 )
    (SCTIMST, 2020-03-31) Lizymol, PP; SATHEESH, R; Kalliyanakrishnan, V
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    Effect of autoclaving sterilization on the stability of polyurethane potting compounds based on caprolactone polyol
    (JOURNAL OF POLYMER MATERIALS, 1997) Jayabalan, M; Lizymol, PP
    Stability of polyurethane potting compounds based on caprolactone polyol and cycloaliphatic diisocyanate in repeated autoclaving and methanol treatment was studied. While methanol treatment alone induces degradation of polyurethane and leaching of fragments, the single cycle autoclaving do not induce degradation. However, the increased cycles of autoclaving and exposure to more hydrophilic reagents like methanol enhances the degradation and leaching of low molecular weight components. There was no evidence of formation of cycloaliphatic diamine product.
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    Effect of dehydrochlorination of PVC on miscibility and phase separation of binary and ternary blends of poly(vinyl chloride), poly(ethylene-co-vinyl acetate) and poly(styrene-co-acrylonitrile)
    (POLYMER INTERNATIONAL, 1997) Lizymol, PP; Thomas, S; Jayabalan, M
    The enhancement of miscibility at the lower critical solution temperature (LOST) of the blends poly(vinyl chloride)/poly(ethylene-co-vinyl acetate) (PVC/EVA), poly(vinyl chloride)/poly(styrene-co-acrylonitrile) (PVC/SAN) and poly(vinyl chloride)/poly(ethylene-co-vinyl acetate)/poly(styrene-co-acrylonitrile) (PVC/EVA/SAN) was observed at the micron level. Such miscibility is attributed to the dehydrochlorination and formation of hydrogen bonds between blend components. However, macrolevel immiscibility of these blends heated to the LCST was observed. Such microdomain compatibility of these blends gives a synergistic character. Brittle-type failure observed for LCST samples testifies to the synergism in treated blends.
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    Effect of gamma-radiation sterilization on the stability of polyurethane potting compounds based on castor oil SMDI and caprolactone polyol SMDI, used for hollow fibre haemodialyzer
    (BULLETIN OF MATERIALS SCIENCE, 1997) Jayabalan, M; Lizymol, PP
    Stability of polyurethane potting compounds based on castor oil/SMDI and caprolactone polyol/SMDI in repeated gamma radiation sterilization was studied. Radiation-induced degradation and leaching of low molecular weight fragments are higher in castor oil based polyurethane than in caprolactone polyol based polyurethane. For castor oil and caprolactone polyol based polyurethanes degradation increases up to 5 Mrad dose of sterilization. Further increase of dose of sterilization decreases leaching in caprolactone polyol based polyurethane which has resulted from secondary reactions leading to crosslinking. In the case of castor oil based polyurethane such crosslinks undergo cleavage at 10 Mrad dose of sterilization.
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    Effects of diluent's concentration upon the properties of organicallv modified ceramics based composites for application in dentistry
    (JOURNAL OF APPLIED POLYMER SCIENCE, 2004) Lizymol, PP
    Organically modified ceramic resin (ormoresin) mixed with triethylene glycol dimethacrylate (TEGDMA) was used as the binder resin for the preparation of visible light cured dental composite. Three different combinations of ormoresin and TEGDMA were used for the preparation of composites, and their properties were compared in terms of depth of cure, diametral tensile strength (DTS), flexural strength (FS), flexural modulus (FM), Vickers micro hardness (VMH), water sorption (WS), and solubility. It is found that an optimum amount of diluent is necessary for better crosslinking and properties of cured composites based on ormoresin. (C) 2004 Wiley Periodicals, Inc.
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    Fabrication and Characterization of Soy Protein/Polyvinyl Alcohol (PVA) Composite Membrane for Guided Tissue Regeneration
    (Regenerative Engineering and Translational Medicine, 2024-10) Saranya, CV; Bridget Jeyatha, W; Deepu, DR; Bhatt, A; Lizymol, PP
    Purpose Periodontitis is an inflammatory disease that damages the periodontal tissue and leads to tooth loss. Guided tissue regeneration (GTR) is a membrane-based method that prevents the down growth of epithelial and fibroblast cells and gradually restores the periodontal tissues. Currently, collagen membranes exist as the top choice in the field of GTR membranes. However, disease transmission, poor mechanical strength and unpredictable degradation limit its use. The main aim of the study is to fabricate a soy protein–based GTR membrane with good mechanical properties, cell barrier function, and cytocompatibility. Methods Soy protein isolate (SPI) was extracted from the seeds of Glycine max, and the membranes (SPG-1, SPG-2, and SPG-3) were fabricated using SPI, polyvinyl alcohol (PVA), and glycerol (Gly) by aqueous solution casting method. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), contact angle, swelling analysis, and degradation studies of the membranes were carried out. Human periodontal ligament (hPDL) cells were used for the direct contact test, MTT assay, live-dead, cell adhesion, and membrane barrier function experiments. Results SPG-1 membrane exhibited a rough surface and significantly (p ≤ 0.05) lower contact angle (68°) than SPG-3. SPG-1 showed a lower swelling (74.03%) and weight loss percentage (42.13%) (p ≤ 0.001) than SPG-2 and SPG-3. SPG-1 membrane exhibited significantly (p ≤ 0.05) higher tensile strength of 5.7 MPa and suture pull-out strength of 9.04 N when compared with SPG-2 and SPG-3. SPG membranes were non-cytotoxic, cyto-compatible, and prevented the down growth of fibroblast cells. Conclusion SPG-1 membranes with 50% SPI stand out as a best candidate than other SPG membranes with better physiochemical properties. It favoured the growth and proliferation of hPDL cells and exhibited barrier properties. Lay Summary Periodontitis is a disease that affects the structure and function of the periodontal tissues, leading to teeth loss. Guided tissue regeneration (GTR) is a widely accepted treatment using a barrier membrane. Three different composite GTR membranes of soy protein, polyvinyl alcohol, and glycerol were fabricated by the solvent casting method by varying the amount of soy protein isolate. Physiochemical characterization and in vitro studies with human periodontal ligament cells and fibroblast cells demonstrated the suitability of the material for periodontal defect management.