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`
`[11] Patent Number:
`5,049,074
`UIllted States Patent
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`Otani et al.
`Sep. 17, 1991
`[45] Date of Patent:
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`[19]
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`[54] DENTAL IMPLANT
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`Inventors: Sugio Otani, 2010-2, Kurokawa,
`[75]
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`
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`H‘Shl'maChl: Klrifu'sm: Gumma‘ken;
`
`
`
`Sadakatsu Yanaglsawa: 3-34-4071
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`
`Mita 2-chome, MmatO-ku, TokyO;
`Kunio Niijima, No. 563,
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`Kamiko-machi, Omiya-shi,
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`Saitama_ken; Kazusi Matuura’
`Tokyo; Hirosi Matino, Yokohama;
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`T00,“ Fuse, Tokyo, 311 of Japan
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`[73] Assignees: Sugio Otani, Kiryu; Sadakatsu
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`Yanagisawa, ”TOKYO; KuniO Niijima,
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`Omiya; Mitsubishi Kasei
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`Corporation; Research Development
`
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`
`Corporation of Japan, both of Tokyo,
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`all of Japan
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`[21] Appl.No.: 500,924
`[22] Filed:
`Mar. 29, 1990
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`Foreign Application Priority Data
`Mar. 29, 1989 [JP]
`Japan .................................... 1-77696
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`Mar. 29, 1989 [JP]
`Japan ............ 1-77697
`
`Int. Cl.5 ................................................ A61C 8/00
`[51]
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`[52] US. Cl. .................................. 433/173; 433/201.l
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`[58] Field of Search ..................... 433/2011, 173, 174,
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`433/175, 176; 623/16
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`[30]
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`[56]
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`
`References Cited
`
`
`
`U.S- PATENT DOCUMENTS
`1/1976 Lash et al.
`.......................... 433/173
`3,934,347
`
`
`
`
`
`
`9/1976 Broemer et a1.
`........ 623/16
`3,981,736
`
`
`
`
`
`
`
`4,051,598 10/1977 Sneer ........................ 433/173
`
`
`
`
`
`
`4,424,037
`1/1984 Ogino et al.
`433/2011
`
`
`
`
`
`
`7/1984 Otani et a1.
`.....
`4,457,984
`433/2011
`
`
`
`
`
`7/1986 R1655 Ct 81. ........... 433/173
`4,599,085
`
`3/1987 Grundei .............. 433/175
`4,648,842
`
`
`
`
`
`4,818,559 4/1989 Hama et a1.
`......................... 433/173
`
`
`
`FOREIGN PATENT DOCUMENTS
`4
`2/1987 European Pat. Off.
`............ 433/173
`0211676
`
`
`
`
`
`
`1042834 11/1958 Fed. Rep. of Germany ...... 433/173
`
`
`
`
`
`0249632
`9/1987 Fed. Rep. of Germany ...... 433/173
`
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`
`
`8/1982 United Kingdom .
`2092891
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`
`Primary Examiner—John J. Wilson
`
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`
`Attorney, Agent, or Firm—Oblon, Spivak, McClelland,
`
`
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`
`
`Maier & Neustadt
`
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`
`
`[57]
`
`ABSTRACT
`
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`A dental implant comprising a core material and a po-
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`rous layer formed on the core material, wherein at least
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`a part of the core material coated by the porous layer
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`has a non-circular cross-sectional shape so as not to
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`rotate relative to the porous layer.
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`7 Claims, 2 Drawing Sheets
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`.‘\‘\“\\‘
`9\\\\\\\w
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`Page 1 of7 ,
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`ZIMMER EXHIBIT 1008
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`Page 1 of 7
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`ZIMMER EXHIBIT 1008
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`

`

`US. Patent
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`Sep. 17, 1991
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`Shéet 1 of 2
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`5,049,074
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`NE
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`F\©OmmmaoENmmeE0_0
`0mHEDGEGVumber...mMKDGENmanor.
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`OmmmbwlQ_mmnwi
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`mmmami
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`mm
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`Page 2 0f 7
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`Page 2 of 7
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`US. Patent
`7
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`Sep. 17, 1991
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`Shéet 2 of 2
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`5,049,074
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`FIGURE
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`IO
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`FIGURE
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`FIGURE
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`FIGURE
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`urflldall/'EIQIIQIOO
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`FIGURE
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`Page 3 0f 7
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`1
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`DENTAL IMPLANT
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`5,049,074
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`The present invention relates to a dental implant.
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`When a tooth is lost for some reason,
`the cavity
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`formed by the missing tooth will be gradually filled by
`a new bone, but the peripheral portion undergoes bone
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`atrophy since no mastication pressure is exerted thereto,
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`and eventually the jaw bone tends to be slender. A
`10
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`dental implant is intended to supplement such a missing
`tooth and to provide the same mastication function as a
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`natural tooth. The dental implant is required to be com-
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`patible with the bone tissue and free from toxicity and
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`yet have sufficient Strength. As such a dental implant,
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`those made of a metal material such as stainless steel, a
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`cobalt-chromium alloy, titanium or a titanium alloy, a
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`ceramic material such as alumina, hydroxyapatite or
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`bioglass, or a carbon material, have been developed.
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`Some of them have already been practically used.
`Particularly, alumina or a carbon material which is a
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`biologically inactive material, is chemically stable and
`safe with little deterioration of the mechanical proper-
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`ties in a living body and has good compatibility with a
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`living body.
`When a dental implant made of such a material, is to
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`be implanted in a bone tissue, it is known to employ a
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`method wherein the portion of the dental
`implant
`which is in contact with the living body, is provided
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`with a threaded structure as a means to increase the
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`bonding strength between the living body and the den-
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`tal implant, and the dental implant is thereby physically
`fixed, or a method wherein a ceramic porous layer or a
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`carbon porous layer is used to permit the proliferation
`of the bone tissue so that the dental implant is thereby
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`fixed (e.g. Japanese Examined Utility Model Publica-
`tion No. 34731/1981). In particular, some of the present
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`inventors have developed a dental implant having a
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`special porous layer utilizing an excellent affinity of
`carbon to a living body (Japanese Examined Patent
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`4O
`Publication No. 9859/1986). It has been confirmed that
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`when such a dental implant is employed, the bone tissue
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`penetrates and proliferates in the porous layer to estab-
`lish firm bonding between the living body and the den-
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`tal implant. For the bonding of the core material and the
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`porous layer in such an artificial tooth material, it has
`been proposed to employ welding in the case where
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`both materials are made of metal, or bonding with a
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`glass layer or a mechanical fixing method by means of a
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`threaded structure of the core material
`in the case
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`where both materials are made of ceramics (Japanese
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`Examined Utility Model Publication No. 34731/1981).
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`However,
`in the conventional dental implants, no
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`mechanical
`fixing method other than the threaded
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`structure has been used for the bonding of the core
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`material and the porous layer, whereby a deterioration
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`in the interface bonding strength between the core ma-
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`terial and the porous layer, interfacial peeling, loosening
`or rotation of the core material and eventually a possi-
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`bility of falling off of the core material, are likely due to
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`the shock at the time of embedding the dental implant in
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`the jaw bone or due to repeated chewing impacts over
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`a long period of time after the implantation of the dental
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`implant.
`‘Even if the dental implant has a threaded structure,
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`such a structure does not serve to prevent the rotation
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`of the core material.
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`Further, with the conventional dental implants, no
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`interlocking connection to the living body is available
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`immediately after the implantation, whereby the dental
`implants are likely to move, which tend to lead to fail-
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`ures of the dental treatment.
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`implant having a
`On the other hand, a dental
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`threaded structure may be excellent in the initial fixing,
`but has a difficulty that it tends to be loosened from the
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`living body during its use for a long period of time.
`Further, some of dental implants made of alumina
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`have a porous threaded structure. However, the elastic-
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`ity of alumina itself is as high as at least 10,times the
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`elasticity of the bone tissue, and the stress is likely to be
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`locally concentrated, and thusit is likely to lead to
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`loosening of'the dental implant for a long run.
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`Under these circumstances,
`the present
`inventors
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`have conducted extensive researches to solve such con-
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`ventional problems and as a result, have found it possi-
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`ble to solve such problems by improving the previously
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`developed dental
`implant having the special carbon
`porous layer so that it has a special outer shape and the
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`core material has a special shape. The present invention
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`has been accomplished on the basis of this discovery.
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`It 'is an object of the present invention to provide a
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`dental implant whereby the treatment will be easy, a
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`desired function will be provided immediately after the
`treatment, a stabilized fixed state can be maintained for
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`a long period of time, and which is free from falling off
`or rotation of the core material.
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`Such an object can readily be accomplished by a
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`dental implant of the present invention which comprises
`a core material and a porous layer formed on the core
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`'material, wherein at least a part of the core material
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`coated by the porous layer has a non-circular cross-sec-
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`tional shape so as not to rotate relative to the porous
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`layer.
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`In the accompanying drawings:
`FIGS. 1 to 8 illustrate different embodiments of the
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`non-circular cross-sectional shape of the core material
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`of the dental implant of the present invention.
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`FIG. 9 illustrates the dental implant used in Example
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`1.
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`FIGS. 10, 11 and 12 illustrate embodiments of the
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`core material, the crown base and the cap of the dental
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`implant of the present invention.
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`FIG. 13 is a cross-sectional view illustrating the den-
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`tal implant of the present invention after mounting the
`crown.
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`FIG. 14 is a cross-sectional view illustrating the
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`threaded portion of the dental implant.
`Now, the present invention will be described in de-
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`tail. The dental implant of the present invention com-
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`prises a core material and a porous layer. More particu-
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`larly, the porous layer is formed on the surface of the
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`core material. Here, the shape of the core material is a
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`rod shape. Its material is not particularly limited. How-
`ever, usually various carbon fiber-reinforced carbon
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`materials, sintered carbon or glass-like carbon material,
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`or a metal such as platinum, titanium, tantalum or tung-
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`sten, or ceramics such as alumina, zirconia, calcium
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`phosphate, titania or biologically active glass, may be
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`mentioned. It is preferred to use a carbon fiber-rein-
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`forced carbon material, titanium or alumina, which is
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`biologically inactive and has high strength.
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`The porous layer is not particularly restricted so long
`as it can‘be formed on the above-mentioned core mate-
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`rial, and when the dental implant is implanted in a living
`body, the vital tissue can penetrate into pores of the
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`porous layer, and a firmly bonded tissue can be formed
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`by the steric structure of the pores and the penetrated
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`Page 4 of 7
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`5,049,074
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`3
`vital tissue, and the bonded tissue can undergo calcifica-
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`tion to form a bone tissue. Specifically, a porous layer of
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`alumina or a carbon-type porous layer obtained by de-
`positing pyrolytic carbon on a non-woven fabric such as
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`carbon fiber, may be mentioned. As the porous layer
`made of alumina, the one disclosed in Japanese Exam-
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`ined Utility Model Publication No. 34731/ 1981 can be
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`employed. For example, an organic material (e.g. a
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`spherical product or chopped fibers of PVA or polyeth-
`ylene) is mixed to e.g. A1203 powder, and then the
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`organic material is burned off and evaporated until the
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`sintering or semi-sintering temperature of ceramics is
`reached, to obtain a porous layer having continuous
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`pores. above core material. When the woven fabric,
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`non-woven fabric, felt or paper is employed, such a
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`material is cut into a proper size and attached by means
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`of an organic adhesive, as the case requires, and if neces-
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`sary, it is further wound and fixed by long fibers. When
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`chopped strands are employed, an organic adhesive is
`20
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`coated on the necessary portion of the surface of the
`substrate, and chopped strands are sprinkled and fixed
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`thereto. Then, pyrolytic carbon is precipitated and inte-
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`grated to the material
`thereby obtained (hereinafter
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`referred to as a piling carbon material). This pyrolytic
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`carbon treatment
`is preferably conducted in such a
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`manner that pyrolytic carbon is precipitated under such
`a condition that the temperature of the substrate is from
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`600° to 2300° C., preferably from 700° to 1100° C., with
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`a negative temperature gradient from the substrate to
`the surface, whereby an excellent carbon porous layer is
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`formed.
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`Namely, the above-mentioned conditions are suitable
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`so that the core material and the fiber material on the
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`surface are firmly bonded to each other, and at the same
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`time a porous layer having a pore distribution such that
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`the interior of the fiber material i.e. the core material
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`side, is most dense and the porosity gradually increases
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`towards the external surface layer.
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`The dental implant of the present invention comprises
`such a porous layer and the core material. It is impor-
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`tant in the present invention that at least a part of the
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`core material has a non-circular cross-sectional shape,
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`and the core material will not rotate. Here, the non-cir-
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`cular cross section is not particularly limited so long as
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`it is a shape whereby the core material will not rotate.
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`Specifically, it may be any one of the shapes as shown in
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`FIGS. 1 to 9. Accordingly, it is required to be not a
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`threaded structure. The core material may have such a
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`, non-circular cross sectional shape in its entirety or a
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`part thereof. The porous layer of the present invention
`is formed on such a core material, so that the interfacial
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`peeling and rotation between the 'core material and the
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`porous layer will be prevented.
`Preferably, the core material has a shape as shown in
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`FIG. 8 (1: pore material, 2: porous layer) so that it is
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`effective not only against the rotation but also against
`the shearing in the longitudinal direction of the core
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`material and the porous layer. More preferably, in addi-
`tion to the non-circular cross section, a surface rough-
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`ness with the maximum height (Rmax) of at least 10 pm
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`is provided on the surface of the core material by e.g.
`blast treatment. The blast treatment may be conducted,
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`for example, in such a manner that an abrasive sand such
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`as alumina (#100) or SiC is blasted against the surface of
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`65
`the core material by means of compressed air to form
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`the roughness on the surface of the core material.
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`In the present invention,
`the core material of the
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`dental implant has a non-circular cross section, whereby
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`4
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`the shock to the jaw bone at the time of implanting the
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`dental implant and the shear stress at the interface be-
`tween the core material and the porous layer due to the
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`chewing for a long period of time after the implantation
`of the dental implant, can be reduced. Thus, substantial
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`effects against the rotation or falling off of the core
`material can be expected.
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`Further, in the present invention, the porous layer has
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`a porosity (void rate) of at least 10% and preferably has
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`an average porosity of from 30 to 40%. Typically, for
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`example, it has a structure in which fibers are randomly
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`piled and mutually firmly bonded. The pores thus
`formed preferably have pore sizes of at least 100 um,
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`preferably at least 200 um, and such pore sizes prefera-
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`bly gradually decrease towards the interior.
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`In general, a dental implant is required to have ade-
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`quate elasticity and strength to be durable against sub-
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`stantial
`impacts or force. To such requirements,
`the
`implant of the present invention provides an
`dental
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`extremely effective performance by virtue of the pres-
`ence of the porous layer, the vapor phase pyrolytic
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`carbon precipitated thereon and the threaded structure
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`provided to the surface of the dental implant at a posi-
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`tion where the surface of the dental implant and the
`bone tissue are in contact. Namely, the dental implant is
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`covered by the vapor phase pyrolytic carbon and is
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`extremely strong by itself, and when implanted in a
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`living body, the vital tissue penetrates into pores of the
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`porous layer, and the penetrated connective tissue un-
`dergoes calcification and is converted to a bone tissue
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`by the bone-inducing action of the carbon and the steric
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`structure of pores. Thus, the carbon fibers and the vital
`tissue will form a mutually intertwined double network
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`structure, whereby the dental implant is firmly bonded
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`and fixed to the living body.
`Further, the threaded portion is located at a position
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`which is in contact with the bone tissue without having
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`the above porous layer. In other words, the dental im-
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`‘plant of the present invention is bonded and fixed to the
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`bone tissue by means of the threaded portion and the
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`porous portion. By the threaded portion,
`the initial
`fixing after the implantation of the dental implant is
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`ensured, and by the porous layer, semi-permanent bond-
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`ing and fixing will be ensured by the calcification and
`conversion to the bone tissue of the periphery of the
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`dental implant.
`If necessary, the dental implant after the formation of
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`the porous layer is shaped into the final form by means
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`of e.g. a grinder. When the dental implant of the present
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`invention is to be used for the dental treatment, it is
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`subjected to sterilizing treatment and then implanted
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`into a living body. In order to facilitate the penetration
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`of the vital tissue into the porous layer, a biologically
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`active ceramics such as apatite or bioglass, or a cell-
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`proliferation promoting substance such as a bone-induc-
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`ing factor, may be impregnated or coated to the porous
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`layer. To apply a ceramics, a method such as dipping in
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`a slurry having the ceramics dispersed therein, flame
`spraying or CVD (chemical vapor deposition) may be
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`employed. The application of the cell-proliferation pro-
`moting substance may be conducted by the method
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`disclosed in Japanese Examined Patent Publication No.
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`125260/1988.
`
`Further,
`in order to improve the adhesion to the
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`gingival epithelium and the vital tissue in contact with
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`the threaded portion, the surface of the core material
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`may be coated with a biologically active ceramics such
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`35
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`45
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`50
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`55
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`Page 5 0f 7
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`Page 5 of 7
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`

`

`5
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`as apatite or bioglass. As the coating technique, flame
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`spraying or glass firing may be employed.
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`When the dental implant of the present invention is
`used for the dental treatment, the dental implant and the
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`crown base may be unified or may be separable. In the
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`unified case, a crown is mounted after the dental im-
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`plant is sufficiently bonded and fixed upon expiration of
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`from 2 to 3 months after the implantation in the bone
`tissue.
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`In the separable case, the center portion of the core
`material is made hollow, and a cap is preferably pro-
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`vided to the hollow portion to prevent the penetration
`of the vital tissue. If necessary for the fixing of the cap,
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`an adhesive such as a bone cement may be employed.
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`The material for the cap is not limited to a polymer, a
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`metal, a ceramics or carbon so long as it is stable in the
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`living body. However, a cap made of a polymer with
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`high precision requires no adhesive. Therefore, a poly-
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`mer such as a polysulfone resin is preferred. After plac-
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`ing the cap, the epithelium is once sutured. Upon expi-
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`ration of from 2 to 3 months, the epithelium is again
`incised, and the cap is withdrawn, and a crown base is
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`inserted into the hole 4 (FIG. 10) of the tooth root and
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`fixed with a bone cement. And then the epithelium is
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`again sutured. A few days later, a crown is attached to
`the crown base so that the mastication pressure will be
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`exerted. Thedental implant may be implanted in either
`method. However, the latter method is preferred, since
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`the consistency of the period until the vital tissue suffi-
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`ciently penetrates, is better in the latter method.
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`Now, the present invention will be described in fur-
`ther detail with reference to Examples. ”However,
`it
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`should be understood that the present invention is by no
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`means restricted to such specific Examples.
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`
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`EXAMPLE 1
`
`In a titanium metal having a diameter of 2 mm, a
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`groove of 150 um was formed as shown in FIG. 9 to
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`obtain a core material 1 having a non-circular cross
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`section. To this core material, a non-woven fabric of
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`carbon fibers having a thickness of 0.5 mm was wound,
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`and vapor phase pyrolytic carbon was deposited under
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`the following conditions by means of a high frequency
`
`
`
`induction heating furnace:
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`Starting material organic substance: Dichloroethyl-
`ene
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`Carrier gasf Argon
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`Pyrolytic temperature: 900" C.
`
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`Deposition period: 1.5 hours.
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`The deposited sample was subjected to surface treat-
`ment to obtain a cylindrical dental implant having a
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`porous layer 2 having a thickness of 1300 pm with a
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`porosity gradient and a pore size gradient from the
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`surface of the porous layer towards the core material
`side.
`
`A core material having a circular cross section of
`
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`6O
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`Comparative Example 1 was subjected to the same
`treatment to obtain a cylindrical dental implant (not
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`shown).
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`Then, the bottom portion of each cylindrical dental
`implant was removed, and a punching test of the core
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`material and the porous layer was conducted simulating
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`the shearing force at the time of embedding the dental ,
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`implant to the jaw bone.
`The results are shown in Table 1.
`
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`40
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`45
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`50
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`55
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`65
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`Page 6 of 7
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`5,049,074
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`
`
`TABLE 1
`
`
`
`Example 1
`
`
`Shape of
`
`Punching State of
`the core
`Surface
`
`
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`
`
`material
`roughness
`fracture
`load
`
`
`
`
`100 kg
`Fracture of
`non-
`
`
`
`the porous
`circular
`
`
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`layer
`cross section
`
`
`
`Interfacial
`30 kg
`10 um
`Comparative Circular
`
`
`
`
`
`cross sectionExample 1 fracture
`
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`10 pm
`
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`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`With the core material having a non-circular cross
`
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`section (Example 1), the dental implant was durable
`
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`until the porous layer broke. Whereas, with the circular
`
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`cross section (Comparative Example 1), the interface
`broke. From the foregoing, it is evident that with the
`
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`non-circular cross section, the shearing stress between ..
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`the pore material and the porous layer can be reduced
`over the circular cross section, whereby substantial
`
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`
`
`effects against the rotation or falling off of the pore
`material can be expected.
`
`
`
`EXAMPLE 2
`
`
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`
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`
`
`
`In FIG. 10, a dental implant of the present invention
`is shown. A titanium rod was ground to form a neck
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`portion 14 having a diameter of 4 mm and a length of 4
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`mm'and a porous layer base portion 13 having a diame-
`ter of 2 mm and a length of 8 mm. Three threads 3 with
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`a pitch of 0.8 mm were provided from 1 mm from the
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`upper end of the neck portion downwardly. Then, a
`hexagonal hole (a hole 4 for fixing a crown base) was
`
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`formed in the neck portion to receive a crown base 5
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`(FIG. 11). This Example shows a case where the dental
`
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`
`
`implant and the crown base 5 are separable. However,
`
`
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`
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`they may be formed integrally (6: connecting portion to
`the hole 4).
`
`
`
`Then, a felt of carbon fibers was wound on the porous
`
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`layer base portion, and carbon was deposited among the
`carbon fibers under the following conditions by means
`
`
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`
`
`of a high frequency induction heater, to form a porous
`
`
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`
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`layer.
`
`
`
`CVD conditions
`
`
`
`
`Starting material: Dichloroethylene
`Carrier gas: Argon
`
`
`
`
`
`Temperature: 900° C.
`Time: 90 minutes
`
`
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`
`
`After shaping by a grinder, the porous layer had a sur-
`face pore size of 200 um and a porosity of 60% and a
`
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`
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`thickness of about 1 mm, whereby the porosity and the
`
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`
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`pore diameter were found to increase towards the sur-
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`
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`face.
`
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`
`The dental implant thus prepared was screwed into
`
`
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`
`
`the lower jaw bone of a monkey having a body weight
`
`
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`
`
`of about 4 kg while threading the bone by the threaded
`portion. A cap made of a polysulfone resin (FIG. 3, 7:
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`connecting portion to the hole 4) was inserted to the
`hole 4 of the dental implant, and the the epithelium was
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`sutured. After expiration of 2 months, the epithelium
`was incised again, and the resin cap was withdrawn
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`from the dental
`implant, and the crown base 5 was
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`inserted into the hole 4 of the dental implant and fixed
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`with a bone cement. Then, the epithelium was again
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`sutured. A few days later, a crown 9 was attached to the
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`crown base 5 so that the mastication pressure would be
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`exerted.
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`In FIG. 13, reference numeral 8 indicates the porous
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`layer, numeral 10 indicates a sponge bone, numeral 11
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`Page 6 of 7
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`7
`indicates a dense bone, and numeral 12 indicates the
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`gingival epithelium.
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`Upon expiration of 3 months, the treatment was con-
`firmed to be successful.
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`According to the present invention, at least a part of
`the core material of the'dental implant having a porous
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`layer is made to have a non-circular cross section,
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`whereby the shearing stress at the interface between the
`core material and the porous layer can be reduced, and
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`substantial effects against the rotation or falling off of
`the core material can be expected, and a constant use of
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`the dental implant for a long period of time after the
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`implantation will be possible.
`Further, since it has a porous layer, the vital tissue
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`penetrates into pores, and due to the steric structure of
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`pores, the penetrated connective tissue will be calcified
`and converted to a bone tissue, whereby a dental im-
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`plant firmly bonded and fixed to the living body is ob-
`tainable.
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`Furthermore, by the threaded structure provided at a
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`portion of the core material, the dental implant and the
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`jaw bone are mechanical bonded immediately after the
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`implantation, whereby the movement of the implanted
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`dental implant will be prevented until the interlocking
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`with the living body is established. Thus, the success
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`rate in the dental operation will be increased, and the
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`period until the crown can be attached, will be short-
`ened.
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`What is claimed is:
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`5
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`10
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`15
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`20
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`8
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`1. A dental implant comprising a core material and a
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`porous layer formed on the core material, wherein at
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`least a part of the core material coated by the porous
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`layer has a non-circular cross-sectional shape, said po-
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`rous layer covering the non-circular cross-sectional
`area of said core material so as not to rotate relative to
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`the porous layer, and wherein said porous layer has a
`thickness of at least 0.1 mm, and the pore size is at least
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`100 pm, at the surface of the porous layer and gradually
`decreases from the surface towards the core material
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`side.
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`2. The dental implant according to claim 1, wherein
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`the porous layer has a porosity of at least 10%.
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`3. The dental implant according to claim 1, wherein
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`the porous layer is composed essentially of a carbon
`material.
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`4. The dental implant according to claim 1, wherein
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