메뉴 건너뛰기




Volumn 28, Issue 8, 2012, Pages 843-856

Lubrication and load-bearing properties of human salivary pellicles adsorbed ex vivo on molecularly smooth substrata

Author keywords

film; friction; normal force; saliva; shear force; surface forces

Indexed keywords

ADSORPTION; FILM; FRICTION; LUBRICANT; MICA; MOLECULAR ANALYSIS; SALIVA; SUBSTRATE;

EID: 84865554288     PISSN: 08927014     EISSN: 10292454     Source Type: Journal    
DOI: 10.1080/08927014.2012.714777     Document Type: Article
Times cited : (27)

References (60)
  • 1
    • 0024789499 scopus 로고
    • Characterization of in vivo salivary-derived enamel pellicle
    • Al-Hashimi, I and Levine, MJ. 1989. Characterization of in vivo salivary-derived enamel pellicle. Arch Oral Biol, 34: 289-295.
    • (1989) Arch Oral Biol , vol.34 , pp. 289-295
    • Al-Hashimi, I.1    Levine, M.J.2
  • 3
    • 0014009374 scopus 로고
    • Amino-acid composition of the acquired pellicle of human tooth enamel
    • Armstrong, WG. 1966. Amino-acid composition of the acquired pellicle of human tooth enamel. Nature, 210: 197-198.
    • (1966) Nature , vol.210 , pp. 197-198
    • Armstrong, W.G.1
  • 4
    • 1842431512 scopus 로고    scopus 로고
    • Protein adsorption in the oral environment
    • In: Malmsten M, editors 2nd ed, New York, NY: Marcel Dekker Inc
    • Arnebrant, T. 2003. "Protein adsorption in the oral environment". In Biopolymers at interfaces, 2nd ed, Edited by: Malmsten M. 811-855. New York, NY: Marcel Dekker Inc.
    • (2003) Biopolymers at interfaces , pp. 811-855
    • Arnebrant, T.1
  • 5
    • 0038403243 scopus 로고    scopus 로고
    • New York, NY: John Wiley & Sons 534
    • Bhushan, B. 2002. Introduction to tribology, 213New York, NY: John Wiley & Sons. 534
    • (2002) Introduction to tribology , pp. 213
    • Bhushan, B.1
  • 6
    • 34547173526 scopus 로고    scopus 로고
    • The lubricating properties of human whole saliva
    • Bongaerts, JHH, Rossetti, D and Stokes, JR. 2007. The lubricating properties of human whole saliva. Tribol Lett, 27: 277-287.
    • (2007) Tribol Lett , vol.27 , pp. 277-287
    • Bongaerts, J.H.H.1    Rossetti, D.2    Stokes, J.R.3
  • 10
    • 0024838510 scopus 로고
    • A transmission electron microscopy study of the adsorption patterns of early developing artificial pellicles on human enamel
    • Busscher, HJ, Uyen, HMW, Stokroos, I and Jongebloed, WL. 1989. A transmission electron microscopy study of the adsorption patterns of early developing artificial pellicles on human enamel. Arch Oral Biol, 34: 803-810.
    • (1989) Arch Oral Biol , vol.34 , pp. 803-810
    • Busscher, H.J.1    Uyen, H.M.W.2    Stokroos, I.3    Jongebloed, W.L.4
  • 11
    • 34247576615 scopus 로고    scopus 로고
    • Salivary mucin MUC5B could be an important component of in vitro pellicles of human saliva: an in situ ellipsometry and atomic force microscopy study
    • Cárdenas, M, Elofsson, U and Lindh, L. 2007b. Salivary mucin MUC5B could be an important component of in vitro pellicles of human saliva: an in situ ellipsometry and atomic force microscopy study. Biomacromolecules, 8: 1149-1156.
    • (2007) Biomacromolecules , vol.8 , pp. 1149-1156
    • Cárdenas, M.1    Elofsson, U.2    Lindh, L.3
  • 12
    • 47949131739 scopus 로고    scopus 로고
    • Interactions of hydroxyapatite surfaces: conditioning films of human whole saliva
    • Cárdenas, M, Valle-Delgado, JJ, Hamit, J, Rutland, MW and Arnebrant, T. 2008. Interactions of hydroxyapatite surfaces: conditioning films of human whole saliva. Langmuir, 24: 7262-7268.
    • (2008) Langmuir , vol.24 , pp. 7262-7268
    • Cárdenas, M.1    Valle-Delgado, J.J.2    Hamit, J.3    Rutland, M.W.4    Arnebrant, T.5
  • 14
    • 0016338153 scopus 로고
    • Rhythms in salivary flow rate and composition
    • Dawes, C. 1974. Rhythms in salivary flow rate and composition. Int J Chronobiol, 2: 253-279.
    • (1974) Int J Chronobiol , vol.2 , pp. 253-279
    • Dawes, C.1
  • 15
    • 0002444186 scopus 로고
    • The nomenclature of the integuments of the enamel surface of teeth
    • Dawes, C, Jenkins, GN and Tonge, CH. 1963. The nomenclature of the integuments of the enamel surface of teeth. Br Dent J, 115: 65-68.
    • (1963) Br Dent J , vol.115 , pp. 65-68
    • Dawes, C.1    Jenkins, G.N.2    Tonge, C.H.3
  • 16
    • 0020014037 scopus 로고
    • Contact angle measurements on human enamel - an in vitro study of influence of pellicle and storage period
    • de Jong, HP, van Pelt, AWJ and Arends, J. 1982. Contact angle measurements on human enamel-an in vitro study of influence of pellicle and storage period. J Dent Res, 61: 11-13.
    • (1982) J Dent Res , vol.61 , pp. 11-13
    • de Jong, H.P.1    van Pelt, A.W.J.2    Arends, J.3
  • 17
    • 84985747292 scopus 로고
    • Gel filtration, ion exchange chromatography and chemical analysis of macromolecules present in acquired enamel pellicle (2-hour pellicle)
    • Eggen, KH and Rölla, G. 1982. Gel filtration, ion exchange chromatography and chemical analysis of macromolecules present in acquired enamel pellicle (2-hour pellicle). Eur J Oral Sci, 90: 182-188.
    • (1982) Eur J Oral Sci , vol.90 , pp. 182-188
    • Eggen, K.H.1    Rölla, G.2
  • 18
    • 78650709107 scopus 로고    scopus 로고
    • 2nd ed, Sandy, Beds, UK: Authors Online Ltd
    • Ferguson, DB. 2006. Oral bioscience, 2nd ed, Sandy, Beds, UK: Authors Online Ltd. 340 pp.
    • (2006) Oral bioscience , pp. 340
    • Ferguson, D.B.1
  • 19
    • 33744981406 scopus 로고    scopus 로고
    • Characterization of the human salivary proteome by capillary isoelectric focusing/nanoreversed-phase liquid chromatography coupled with ESI-tandem MS
    • Guo, T, Rudnick, PA, Wang, W, Lee, CS, DeVoe, DL and Balgley, BM. 2006. Characterization of the human salivary proteome by capillary isoelectric focusing/nanoreversed-phase liquid chromatography coupled with ESI-tandem MS. J Proteome Res, 5: 1469-1478.
    • (2006) J Proteome Res , vol.5 , pp. 1469-1478
    • Guo, T.1    Rudnick, P.A.2    Wang, W.3    Lee, C.S.4    DeVoe, D.L.5    Balgley, B.M.6
  • 20
    • 1642565241 scopus 로고    scopus 로고
    • Lubricating properties of the initial salivary pellicle - an AFM study
    • Hahn Berg, I C, Rutland, MW and Arnebrant, T. 2003. Lubricating properties of the initial salivary pellicle-an AFM study. Biofouling, 19: 365-369.
    • (2003) Biofouling , vol.19 , pp. 365-369
    • Hahn Berg, I.C.1    Rutland, M.W.2    Arnebrant, T.3
  • 21
    • 0033139583 scopus 로고    scopus 로고
    • Ultrastructural investigation of pellicle morphogenesis at two different intraoral sites during a 24-h period
    • Hannig, M. 1999. Ultrastructural investigation of pellicle morphogenesis at two different intraoral sites during a 24-h period. Clin Oral Investig, 3: 88-95.
    • (1999) Clin Oral Investig , vol.3 , pp. 88-95
    • Hannig, M.1
  • 22
    • 0035013403 scopus 로고    scopus 로고
    • Atomic force microscopy study of salivary pellicles formed on enamel and glass in vivo
    • Hannig, M, Herzog, S, Willigeroth, SF and Zimehl, R. 2001. Atomic force microscopy study of salivary pellicles formed on enamel and glass in vivo. Colloid Polym Sci, 279: 479-483.
    • (2001) Colloid Polym Sci , vol.279 , pp. 479-483
    • Hannig, M.1    Herzog, S.2    Willigeroth, S.F.3    Zimehl, R.4
  • 23
    • 84856368075 scopus 로고    scopus 로고
    • Normal and frictional interactions of purified human statherin adsorbed on molecularly-smooth solid substrata
    • Harvey, NM, Carpenter, GH, Proctor, GB and Klein, J. 2011a. Normal and frictional interactions of purified human statherin adsorbed on molecularly-smooth solid substrata. Biofouling, 27: 823-835.
    • (2011) Biofouling , vol.27 , pp. 823-835
    • Harvey, N.M.1    Carpenter, G.H.2    Proctor, G.B.3    Klein, J.4
  • 24
    • 79953850348 scopus 로고    scopus 로고
    • Normal and shear forces between surfaces bearing porcine gastric mucin, a high molecular weight glycoprotein
    • Harvey, NM, Yakubov, GE, Stokes, JR and Klein, J. 2011b. Normal and shear forces between surfaces bearing porcine gastric mucin, a high molecular weight glycoprotein. Biomacromolecules, 12: 1041-1050.
    • (2011) Biomacromolecules , vol.12 , pp. 1041-1050
    • Harvey, N.M.1    Yakubov, G.E.2    Stokes, J.R.3    Klein, J.4
  • 25
    • 0023225890 scopus 로고
    • Lubrication and viscosity features of human saliva and commercially available saliva substitutes
    • Hatton, MN, Levine, MJ, Margarone, JE and Aguirre, A. 1987. Lubrication and viscosity features of human saliva and commercially available saliva substitutes. J Oral Maxillofac Surg, 45: 496-499.
    • (1987) J Oral Maxillofac Surg , vol.45 , pp. 496-499
    • Hatton, M.N.1    Levine, M.J.2    Margarone, J.E.3    Aguirre, A.4
  • 27
    • 17644448651 scopus 로고
    • Thin film studies using multiple-beam interferometry
    • Israelachvili, JN. 1973. Thin film studies using multiple-beam interferometry. J Colloid Interface Sci, 44: 259-271.
    • (1973) J Colloid Interface Sci , vol.44 , pp. 259-271
    • Israelachvili, J.N.1
  • 29
    • 0000988187 scopus 로고
    • Measurement of forces between two mica surfaces in aqueous electrolyte solutions in the range 1-100nm
    • Israelachvili, JN and Adams, GE. 1978. Measurement of forces between two mica surfaces in aqueous electrolyte solutions in the range 1-100nm. J Chem Soc Faraday Trans, 1(74): 975-1001.
    • (1978) J Chem Soc Faraday Trans , vol.1 , Issue.74 , pp. 975-1001
    • Israelachvili, J.N.1    Adams, G.E.2
  • 30
    • 0019256699 scopus 로고
    • Clinical adhesiveness of selected dental materials - an in vivo study
    • Jendresen, MD and Glantz, P-O. 1981. Clinical adhesiveness of selected dental materials - an in vivo study. Acta Odontol Scand, 39: 39-45.
    • (1981) Acta Odontol Scand , vol.39 , pp. 39-45
    • Jendresen, M.D.1    Glantz, P.-O.2
  • 31
    • 85040956871 scopus 로고
    • 1st ed, Cambridge, UK: Cambridge University Press
    • Johnson, KL. 1985. Contact mechanics, 1st ed, 84-106. Cambridge, UK: Cambridge University Press.
    • (1985) Contact mechanics , pp. 84-106
    • Johnson, K.L.1
  • 32
    • 0027179337 scopus 로고
    • The functions of saliva
    • Kaplan, MD and Baum, BJ. 1993. The functions of saliva. Dysphagia, 8: 225-229.
    • (1993) Dysphagia , vol.8 , pp. 225-229
    • Kaplan, M.D.1    Baum, B.J.2
  • 33
    • 4243177192 scopus 로고
    • Forces between mica surfaces bearing adsorbed macromolecules in liquid media
    • Klein, J. 1983. Forces between mica surfaces bearing adsorbed macromolecules in liquid media. J Chem Soc Faraday Trans, 1(79): 99-118.
    • (1983) J Chem Soc Faraday Trans , vol.1 , Issue.79 , pp. 99-118
    • Klein, J.1
  • 34
    • 0022078136 scopus 로고
    • Surface interactions with adsorbed macromolecules
    • Klein, J. 1986. Surface interactions with adsorbed macromolecules. J Colloid Interface Sci, 111: 305-313.
    • (1986) J Colloid Interface Sci , vol.111 , pp. 305-313
    • Klein, J.1
  • 35
    • 0000358239 scopus 로고
    • Long-range attractive forces between two mica surfaces in an aqueous polymer solution
    • Klein, J and Luckham, PF. 1984. Long-range attractive forces between two mica surfaces in an aqueous polymer solution. Nature, 308: 836-837.
    • (1984) Nature , vol.308 , pp. 836-837
    • Klein, J.1    Luckham, P.F.2
  • 36
    • 0343754431 scopus 로고    scopus 로고
    • Simple liquids confined to molecularly thin layers. I. Confinement-induced liquid-to-solid phase transitions
    • Klein, J and Kumacheva, E. 1998. Simple liquids confined to molecularly thin layers. I. Confinement-induced liquid-to-solid phase transitions. J Chem Phys, 108: 6996-7009.
    • (1998) J Chem Phys , vol.108 , pp. 6996-7009
    • Klein, J.1    Kumacheva, E.2
  • 37
    • 0028485116 scopus 로고
    • Reduction of frictional forces between solid surfaces bearing polymer brushes
    • Klein, J, Kumacheva, E, Mahalu, D, Perahia, D and Fetters, LJ. 1994. Reduction of frictional forces between solid surfaces bearing polymer brushes. Nature, 370: 634-636.
    • (1994) Nature , vol.370 , pp. 634-636
    • Klein, J.1    Kumacheva, E.2    Mahalu, D.3    Perahia, D.4    Fetters, L.J.5
  • 38
    • 9744261733 scopus 로고    scopus 로고
    • Fluidity of water and of hydrated ions confined between solid surfaces to molecularly thin films
    • Klein, J, Raviv, U, Perkin, S, Kampf, N, Chai, L and Giasson, S. 2004. Fluidity of water and of hydrated ions confined between solid surfaces to molecularly thin films. J Phys: Condens Matter, 16: S5437-S5448.
    • (2004) J Phys: Condens Matter , vol.16
    • Klein, J.1    Raviv, U.2    Perkin, S.3    Kampf, N.4    Chai, L.5    Giasson, S.6
  • 39
    • 0016764243 scopus 로고
    • Pellicle formation on hydroxyapatite splints attached to the human dentition: morphologic confirmation of the concept of adsorption
    • Lie, T. 1975. Pellicle formation on hydroxyapatite splints attached to the human dentition: morphologic confirmation of the concept of adsorption. Arch Oral Biol, 20: 739-742.
    • (1975) Arch Oral Biol , vol.20 , pp. 739-742
    • Lie, T.1
  • 40
    • 84984416973 scopus 로고
    • Scanning and transmission electron microscope study of pellicle morphogenesis
    • Lie, T. 1977. Scanning and transmission electron microscope study of pellicle morphogenesis. Eur J Oral Sci, 85: 217-231.
    • (1977) Eur J Oral Sci , vol.85 , pp. 217-231
    • Lie, T.1
  • 41
    • 0035651934 scopus 로고    scopus 로고
    • An in vitro study of initial adsorption from human parotid and submandibular/sublingual resting saliva at solid/liquid interfaces
    • Lindh, L, Glantz, P-O, Isberg, P-E and Arnebrant, T. 2001. An in vitro study of initial adsorption from human parotid and submandibular/sublingual resting saliva at solid/liquid interfaces. Biofouling, 17: 227-239.
    • (2001) Biofouling , vol.17 , pp. 227-239
    • Lindh, L.1    Glantz, P.-O.2    Isberg, P.-E.3    Arnebrant, T.4
  • 42
    • 77549084128 scopus 로고    scopus 로고
    • Influence of ionic strength changes on the structure of pre-adsorbed salivary films. A response of a natural multi-component layer
    • Macakova, L, Yakubov, GE, Plunkett, MA and Stokes, JR. 2010. Influence of ionic strength changes on the structure of pre-adsorbed salivary films. A response of a natural multi-component layer. Colloids Surf B Biointerfaces, 77: 31-39.
    • (2010) Colloids Surf B Biointerfaces , vol.77 , pp. 31-39
    • Macakova, L.1    Yakubov, G.E.2    Plunkett, M.A.3    Stokes, J.R.4
  • 43
    • 79957879886 scopus 로고    scopus 로고
    • Influence of ionic strength on the tribological properties of pre-adsorbed salivary films
    • Macakova, L, Yakubov, GE, Plunkett, MA and Stokes, JR. 2011. Influence of ionic strength on the tribological properties of pre-adsorbed salivary films. Tribol Int, 44: 956-962.
    • (2011) Tribol Int , vol.44 , pp. 956-962
    • Macakova, L.1    Yakubov, G.E.2    Plunkett, M.A.3    Stokes, J.R.4
  • 44
    • 0013785893 scopus 로고
    • The formation and properties of organic films on teeth
    • Meckel, AH. 1965. The formation and properties of organic films on teeth. Arch Oral Biol, 10: 585-597.
    • (1965) Arch Oral Biol , vol.10 , pp. 585-597
    • Meckel, A.H.1
  • 45
    • 0031592185 scopus 로고    scopus 로고
    • Interactions between salivary films adsorbed on mica surfaces
    • Nylander, T, Arnebrant, T and Glantz, P-O. 1997. Interactions between salivary films adsorbed on mica surfaces. Colloids Surf A, 129-130: 339-344.
    • (1997) Colloids Surf A , vol.129-130 , pp. 339-344
    • Nylander, T.1    Arnebrant, T.2    Glantz, P.-O.3
  • 46
    • 0013444854 scopus 로고
    • + electrolyte solutions: a correlation of double-layer and hydration forces with surface cation exchange properties
    • + electrolyte solutions: a correlation of double-layer and hydration forces with surface cation exchange properties. J Colloid Interface Sci, 83: 531-546.
    • (1981) J Colloid Interface Sci , vol.83 , pp. 531-546
    • Pashley, R.M.1
  • 47
    • 33746552211 scopus 로고    scopus 로고
    • Forces between mica surfaces, prepared in different ways, across aqueous and nonaqueous liquids confined to molecularly thin films
    • Perkin, S, Chai, L, Kampf, N, Raviv, U, Briscoe, W, Dunlop, I, Titmuss, S, Seo, M, Kumacheva, E and Klein, J. 2006. Forces between mica surfaces, prepared in different ways, across aqueous and nonaqueous liquids confined to molecularly thin films. Langmuir, 22: 6142-6152.
    • (2006) Langmuir , vol.22 , pp. 6142-6152
    • Perkin, S.1    Chai, L.2    Kampf, N.3    Raviv, U.4    Briscoe, W.5    Dunlop, I.6    Titmuss, S.7    Seo, M.8    Kumacheva, E.9    Klein, J.10
  • 49
    • 16644372363 scopus 로고    scopus 로고
    • Salivary proteins interact with dietary constituents to modulate tooth staining
    • Proctor, GB, Pramanik, R, Carpenter, GH and Rees, GD. 2005. Salivary proteins interact with dietary constituents to modulate tooth staining. J Dent Res, 84: 73-78.
    • (2005) J Dent Res , vol.84 , pp. 73-78
    • Proctor, G.B.1    Pramanik, R.2    Carpenter, G.H.3    Rees, G.D.4
  • 50
    • 0028547354 scopus 로고
    • Evidence for presence of micelle-like protein globules in human saliva
    • Rølla, G and Rykke, M. 1994. Evidence for presence of micelle-like protein globules in human saliva. Colloids Surf B Biointerfaces, 3: 177-182.
    • (1994) Colloids Surf B Biointerfaces , vol.3 , pp. 177-182
    • Rølla, G.1    Rykke, M.2
  • 51
    • 78751514680 scopus 로고    scopus 로고
    • Adsorption from saliva to silica and hydroxyapatite surfaces and elution of salivary films by SDS and delmopinol
    • Santos, O, Lindh, L, Halthur, T and Arnebrant, T. 2010. Adsorption from saliva to silica and hydroxyapatite surfaces and elution of salivary films by SDS and delmopinol. Biofouling, 26: 697-710.
    • (2010) Biofouling , vol.26 , pp. 697-710
    • Santos, O.1    Lindh, L.2    Halthur, T.3    Arnebrant, T.4
  • 52
    • 0035290537 scopus 로고    scopus 로고
    • The effect of acquired salivary pellicle on the surface free energy and wettability of different denture base materials
    • Sipahi, C, Anil, N and Bayramli, E. 2001. The effect of acquired salivary pellicle on the surface free energy and wettability of different denture base materials. J Dent, 29: 197-204.
    • (2001) J Dent , vol.29 , pp. 197-204
    • Sipahi, C.1    Anil, N.2    Bayramli, E.3
  • 54
    • 0016703842 scopus 로고
    • Chemical composition of salivary integuments formed in vivo on solids with some established surface characteristics
    • Sönju, T and Glantz, P-O. 1975. Chemical composition of salivary integuments formed in vivo on solids with some established surface characteristics. Arch Oral Biol, 20: 687-691.
    • (1975) Arch Oral Biol , vol.20 , pp. 687-691
    • Sönju, T.1    Glantz, P.-O.2
  • 55
    • 80755125960 scopus 로고    scopus 로고
    • Friction force spectroscopy as a tool to study the strength and structure of salivary films
    • Sotres, J, Lindh, L and Arnebrant, T. 2011. Friction force spectroscopy as a tool to study the strength and structure of salivary films. Langmuir, 27: 13692-13700.
    • (2011) Langmuir , vol.27 , pp. 13692-13700
    • Sotres, J.1    Lindh, L.2    Arnebrant, T.3
  • 56
    • 36148996837 scopus 로고    scopus 로고
    • Viscoelasticity of human whole saliva collected after acid and mechanical stimulation
    • Biorheology
    • Stokes, JR and Davies, GA. Viscoelasticity of human whole saliva collected after acid and mechanical stimulation. Biorheology. pp.141-160.
    • Stokes, J.R.1    Davies, G.A.2
  • 57
    • 0014641524 scopus 로고
    • The direct measurement of normal and retarded van der Waals forces
    • Tabor, D and Winterton, RHS. 1969. The direct measurement of normal and retarded van der Waals forces. P Roy Soc A Mat, 312: 435-450.
    • (1969) P Roy Soc A Mat , vol.312 , pp. 435-450
    • Tabor, D.1    Winterton, R.H.S.2
  • 58
    • 84989591440 scopus 로고
    • Adsorption of whole saliva onto hydrophilic and hydrophobic solid surfaces: influence of concentration, ionic strength and pH
    • Vassilakos, N, Arnebrant, T and Glantz, P-O. 1992. Adsorption of whole saliva onto hydrophilic and hydrophobic solid surfaces: influence of concentration, ionic strength and pH. Eur J Oral Sci, 100: 346-353.
    • (1992) Eur J Oral Sci , vol.100 , pp. 346-353
    • Vassilakos, N.1    Arnebrant, T.2    Glantz, P.-O.3
  • 59
    • 84989565795 scopus 로고
    • An in vitro study of salivary film formation at solid/liquid interfaces
    • Vassilakos, N, Arnebrant, T and Glantz, P-O. 1993. An in vitro study of salivary film formation at solid/liquid interfaces. Eur J Oral Sci, 101: 133-137.
    • (1993) Eur J Oral Sci , vol.101 , pp. 133-137
    • Vassilakos, N.1    Arnebrant, T.2    Glantz, P.-O.3
  • 60
    • 0037512404 scopus 로고    scopus 로고
    • Identification of protein components in human acquired enamel pellicle and whole saliva using novel proteomics approaches
    • Yao, Y, Berg, EA, Costello, CE, Troxler, RF and Oppenheim, FG. 2003. Identification of protein components in human acquired enamel pellicle and whole saliva using novel proteomics approaches. J Biol Chem, 278: 5300-5308.
    • (2003) J Biol Chem , vol.278 , pp. 5300-5308
    • Yao, Y.1    Berg, E.A.2    Costello, C.E.3    Troxler, R.F.4    Oppenheim, F.G.5


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.