Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
  • A61B17/56—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor
  • A61B17/58—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws, setting implements or the like
  • A61B17/68—Internal fixation devices, including fasteners and spinal fixators, even if a part thereof projects from the skin
  • A61B17/84—Fasteners therefor or fasteners being internal fixation devices
  • A61B17/86—Pins or screws or threaded wires; nuts therefor
  • A61B17/8605—Heads, i.e. proximal ends projecting from bone
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
  • A61C8/00—Means to be fixed to the jaw-bone for consolidating natural teeth or for fixing dental prostheses thereon; Dental implants; Implanting tools
  • A61C8/0048—Connecting the upper structure to the implant, e.g. bridging bars
  • A61C8/005—Connecting devices for joining an upper structure with an implant member, e.g. spacers
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
  • A61C8/00—Means to be fixed to the jaw-bone for consolidating natural teeth or for fixing dental prostheses thereon; Dental implants; Implanting tools
  • A61C8/0048—Connecting the upper structure to the implant, e.g. bridging bars
  • A61C8/005—Connecting devices for joining an upper structure with an implant member, e.g. spacers
  • A61C8/0068—Connecting devices for joining an upper structure with an implant member, e.g. spacers with an additional screw

Definitions

• the invention relates to a breakable fixing screw.
• a screw is intended for the biomedical field, in general. It is particularly suitable for fixing a suprastructure on an intraosseous implant, in particular periodontal. It is more particularly, but not exclusively adapted to the installation of suprastructures on such implants when they are made of a ceramic material, especially zirconia.
• the present invention allows the use of a screw itself made of ceramic, including yttrié zirconia.
• the screw which is the subject of the invention can also be used as an intraosseous implant, definitive or temporary, in particular for fixation of osteosynthesis plates.
• EP-B-1 034 750 discloses a device for attaching a suprastructure to an intraosseous implant comprising an internal thread.
• Such a device known as transfixation, is commonly used, in particular to fix false stumps or abutments on a periodontal implant, which false abutments constitute supports for the crowns.
• the fixing is performed by a transfixation screw comprising a screw head comprising a bearing surface and a thread, the screw head being connected to the thread by a groove.
• the end of the thread on the screw head side comprises two flats.
• the throat in the screw constitutes a fusible zone, the rupture of which makes it possible to limit the force transmitted to the implant, in order to avoid degrading the bone in which it is implanted.
• the flats allow disassembly in said screw after the screw head has been disconnected from the thread following such an event.
• the protection of the implant and the bone tissue in the event of impact or major stress on the suprastructures is of particular importance when said implant is made of a ceramic material whose elastic modulus and hardness are high. Indeed, under these conditions, the difference in elastic modulus between the bone and the implant leads to incompatibility constraints of elastic deformation between the bone and the implant, constraints which are limited in usual life conditions but which can become important in extreme situations and lead to rupture of the tissue and / or implant.
• the hardness of the implant makes the removal of the latter problematic as soon as its osseointegration is achieved, so that it is essential to preserve the integrity of the implant in all circumstances, including these extreme circumstances.
• the coefficient of concentration of stress Kt related to the presence of the groove is between 1, 60 and 2.1 according to the modes of solicitation, that is to say of the same order of magnitude that what differentiates a usual solicitation and vis-à-vis which the screw must resist, especially fatigue, an exceptional solicitation under which it must break.
• the problem is even more critical when the screw is made of a material such as a ceramic that does not have many faculties of accommodation by plastic deformation able to slow or stop the progression of cracks and whose resistance ratio in fatigue compared to the static resistance is low.
• the invention proposes a screw, in particular for fixing a suprastructure on an intraosseous implant, said screw extending along a longitudinal axis and comprising:
• a head comprising a bearing surface capable of cooperating with a bearing surface of the suprastructure for maintaining said superstructure in position;
• a thread capable of cooperating with a tapping for clamping the bearing surfaces of the suprastructure and the screw;
• which screw comprises, between the support surface and the thread, a portion, called security portion, comprising a functional form, called operation, and a fusible section at the connection between said safety portion and the head of the screw so that the form of maneuver remains attached to the thread in case of rupture of the fuse part.
• the screw in question comprises a preferred rupture zone, or fuse, under the screw head, which allows to keep intact a functional form called maneuver in case of rupture of this fusible zone.
• maneuver in case of rupture of this fusible zone.
• the functional form is said to maneuver because in most applications this form is able to manipulate the screw to achieve its loosening.
• said shape can also be used in other objectives in particular to serve as a centering, support or sealing to a superstructure without departing from the scope of the invention.
• the invention can be implemented according to the advantageous embodiments described below, which can be considered individually or in any technically operative combination.
• the security portion is conical with respect to the longitudinal axis, the smallest section of said portion being on the side of the bearing surface of the head and the large section of said portion being less than or equal to the bottom thread section of the thread, the smallest section being the fuse section.
• the security portion comprises an internal recess adapted to create a fusible zone at the connection between the security portion and the head.
• This embodiment simplifies the shape of the screw and keeps a constant perimeter maneuvering shape over its entire height when this form of maneuver is prominent with respect to the implantation of the thread. Both embodiments can be combined.
• the screw comprises a connection of progressive section between the small section of the maneuvering form and the screw head.
• This progressive connection makes it possible to reduce the coefficient of concentration of stress between the fuse section and the screw head.
• the form of maneuver is prominent with respect to the implantation of the thread.
• This embodiment is more particularly advantageous when the screw is used as a transfixation element, the threading of said screw being implanted in the tapping of an intraosseous implant.
• the maneuvering form remains easily accessible for disassembly of the screw in case of rupture while the implant is implanted in vivo.
• the form of maneuver is a polygonal shape. This can be easily maneuvered using a key. Unlike the prior art represented by the European patent EP-B 1 034 750 and where the flats on the threaded portion allow only two angular positions of the key at the initiation of loosening in case of rupture, the polygonal shape allows at least four positions of the operating key and more depending on the number of sides of the polygon, which is advantageous when the implant is in a place difficult to access, for example in the case of a periodontal implant.
• the taper angle of the maneuvering form is between 5 ° and 6 °. This taper value provides a particularly advantageous compromise between the length of the maneuver shape and the section reduction effect.
• the ratio of the surfaces of the small section and the large section of the conical portion is between 0.75 and 0.9. This ratio range makes it possible to find the best compromise between static resistance and fatigue resistance regardless of the material, in particular the metal or ceramic constituting the screw.
• the maneuvering shape of the security portion comprises conical sections according to a polygonal base in section and protruding lugs from said panels, said ears extending without conicity in the axial direction of the screw.
• said recess constitutes a form of maneuver.
• the screw can be shorter with equivalent functionality.
• the recess is an internal thread.
• This variant embodiment is more particularly adapted to cases where the screw itself is implanted in the connective tissue. It is thus possible, in case of accidental or deliberate breakage of the screw head, on the one hand, to precisely locate the rupture zone on the fusible zone, and on the other hand, to use the recess thus discovered to reinstall a fastener, or as a sealing base.
• the screw object of the invention consists of a stainless steel. This material offers maximum safety against fatigue stresses.
• the screw object of the invention consists of yttrié zirconia.
• the addition of Yttrium makes it possible to increase the fatigue strength of zirconia, the particular design of the screw makes this material suitable for this type of use and thus to create an intraosseous implantation device associated with suprastructures the whole being free of metal.
• the invention also relates to a method of manufacturing a screw according to embodiments of the invention comprising a recess which method comprises a step of obtaining a blank of said screw by an additive machining method.
• This type of method is advantageously used, by constructing the volume in successive layers to achieve any form of recess.
• the invention also relates to a key comprising a conical recess complementary to the form of operation of a screw according to any one of the preceding claims adapted to maneuver said screw in rotation about the longitudinal axis when the connection between the screw head and the form of maneuver is broken.
• FIGS. 1 to 4 show a front view of an embodiment of a transfixation screw according to the invention
• FIG. 2 is a front view in a section C-C defined in Figure 1 of an embodiment of a screw according to the invention having an internal recess connection to the security portion and the screw head;
• FIG. 3 shows in a perspective view and a section B-B defined on the same view, an embodiment of a screw according to the invention comprising a safety portion with a form of wing maneuver;
• FIG. 4 is a longitudinal sectional view (CC) of a screw according to an embodiment of the invention in which the internal recess also fulfills the function of operating form, FIG. 4A in the form of a tapered tapping; and FIG. 4B in the form of a polygonal imprint according to a partial view Z, defined in FIG. 4A.
• CC longitudinal sectional view
• the fixing screw (100) object of the invention comprises a screw head (120) and a threaded portion (130) coaxial along a longitudinal axis (1 10).
• the screw head (120) comprises a form of maneuver (121) for example in the form of a hexagonal imprint.
• the other end of the head (120), thread side (130) comprises a bearing surface (122) which is, according to this embodiment, a flat surface, but which may be a conical surface, spherical or any other shape adapted to provide a contact surface for producing a clamp on a complementary surface fitted to a superstructure.
• the threaded portion (130) of the screw is housed in the tapping of an intraosseous implant, after said implant has been implanted in the recipient tissue.
• the bearing surface (122) of the screw head (120) and the thread (130) thus cooperate to maintain in position by clamping a suprastructure such as a false abutment or abutment on said implant.
• a safety portion (140) comprises a form of maneuver (142) for example polygonal.
• this safety portion (140) is of conical shape, the small section is on the screw head side, the polygonal maneuver shape following the taper of said security portion .
• section AA the polygon is a square.
• the taper (141) of this safety zone is advantageously between 5 ° and 6 °. Due to this taper, there is a reduced section (143) between the thread and the screw head, the area of this section being between 0.75 and 0.9 times the cross-sectional area of the connecting portion. safety (140) and threading.
• the end of the security portion comprises a progressive connection, for example in the form of a connection radius (144).
• a progressive connection for example in the form of a connection radius (144).
• the fuse zone (143) is obtained by practicing a recess (243) inside the portion (140) of security, said safety portion not being conical according to this embodiment.
• This recess is made by machining or during the molding operation of the screw (200).
• the recess is obtained by inserting a core or insert into the injection mold.
• said core is of calcinable type and disappears during sintering of the screw.
• this machining is performed when the ceramic is in the green state, before sintering, when the screw is made of such a material.
• this machining uses a so-called “recessing” tool, that is to say a rotating tool comprising a body supporting radially extending machining grains, the eccentricity of said grains with respect to the body being able to be modified during processing. 'machining.
• a rotating tool comprising a body supporting radially extending machining grains, the eccentricity of said grains with respect to the body being able to be modified during processing. 'machining.
• Such a tool makes it possible to drill a first bore (223) of diameter substantially smaller than that of the recess (243) and then to make said recess by off-centering the boring grains.
• such a recess (243) can be combined with a tapered safety portion (140) to provide the fuse section (143).
• the rupture of the fusible zone (143) discovers the recess.
• said recess can also used for functional purposes after breaking the fuse box.
• the recess (243) and the protruding security portion (140) cooperate to install a superstructure, said superstructure being centered on the protruding portion and sealed thereon, for example, by means of cement or resin poured into the recess (243).
• the portion (140) of security is advantageously tapered to facilitate the centering of the suprastructure thereon during installation after rupture of the fuse zone.
• the section of the safety portion (140) is not limited to a polygonal shape and may be any section adapted to a maneuver shape function.
• the section of the portion (140) of security may be of multi-lobed shape, or describe a curvilinear polygon.
• the form (340) for maneuvering the portion (140) of safety comprises conical panels (341) according to a polygonal base in section and ears ( 342) protruding from said flaps (341), said flanges extending without taper in the axial direction (1 10).
• the key used to maneuver this form acts on the protruding ears, so that it is not necessary that the operating footprint of said key is tapered.
• the screw (100, 200, 300) consists of a stainless steel, for example an AISI 316L steel in a so-called super-hardened state.
• austenitic stainless steel typically comprising 18% chromium and 10% nickel and a carbon content of less than 0.03%. Because of the low carbon content, this steel can not be hardened by heat treatment and hardening can greatly increase the mechanical properties.
• a ferritic stainless steel type F16PH can also be used for its corrosion resistance and mechanical properties.
• said screw (100, 200, 300) is made of a ceramic, especially a yttria-type zirconia. (Zr0 2 , 3Y 2 O 3 ). While not equalizing the fatigue strength characteristics of metallic materials, the presence of yttrium oxide slows crack propagation. The combination of this characteristic intrinsic to the material with the The structural features of the screw according to the invention makes it possible to produce an implant, suprastructure and transfixation screw assembly in ceramic, more particularly in zirconia, with a high degree of safety with respect to the risks of rupture of the implant, protected by the fusible area of the screw and take full advantage of the bio-compatibility, longevity and the advantageous color of this material for this type of applications.
• the safety portion (140) is prominent with respect to the implant when the screw (100, 200, 300) is screwed into the internal thread of said implant.
• the suprastructure is released and the form of maneuver protrudes. It is then easy to extract said screw from the implant simply by unscrewing with a wrench, of the pipe-type type, comprising a cavity of complementary shape, recessed, that of the security portion (140).
• Figure 4 according to another embodiment of the security portion is of reduced height, the fuse zone (143) being placed close to the birth of the thread (130).
• the recess (443, 444) has the function of both creating the fusible zone and constituting a form of maneuver remaining linked to the threading after rupture of said fusible zone (143).
• the recess (444) is of polygonal shape. This embodiment makes it possible to reduce the height of the screw (400) in particular for transfixation applications.
• the recess (443) is a tapping, for example a tapered tapping.
• This last embodiment is more particularly adapted to a screw (400) used in direct implantation in a connective tissue, in particular for fixing a prosthesis or an osteosynthesis plate.
• the presence of the fusible zone can be advantageously used to deliberately break the screw head. The recess, discovered during this rupture, makes it possible to fix suprastructures on the portion of screw bio-integrated to the fabric.
• FIG. 4, of the screw (400) which is the subject of the invention is advantageously manufactured by an additive machining method.
• Such a method uses a construction of the screw (400) in successive layers and thus allows any form of non-opening recess to be made.
• Processes such as laser sintering or laser projection-melting are particularly suitable for this embodiment, whether the screw is made of a metallic material or a ceramic.
• the screw object of the invention defines a zone (143) fuse capable of breaking under predefined solicitations retaining functionality to the broken part not released by this break.

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• Health & Medical Sciences (AREA)
• Orthopedic Medicine & Surgery (AREA)
• Life Sciences & Earth Sciences (AREA)
• Animal Behavior & Ethology (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• Oral & Maxillofacial Surgery (AREA)
• Dentistry (AREA)
• Epidemiology (AREA)
• Surgery (AREA)
• Neurology (AREA)
• Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
• Engineering & Computer Science (AREA)
• Biomedical Technology (AREA)
• Heart & Thoracic Surgery (AREA)
• Medical Informatics (AREA)
• Molecular Biology (AREA)
• Prostheses (AREA)
• Dental Prosthetics (AREA)

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• 2011
  • 2011-01-18 FR FR1100145A patent/FR2970409B1/fr not_active Expired - Fee Related
  • 2011-12-30 US US13/980,042 patent/US20130304136A1/en not_active Abandoned
  • 2011-12-30 WO PCT/EP2011/074331 patent/WO2012097955A1/fr active Application Filing
  • 2011-12-30 EP EP11807957.3A patent/EP2665438A1/de not_active Withdrawn

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