Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
  • A61C13/00—Dental prostheses; Making same
  • A61C13/0003—Making bridge-work, inlays, implants or the like
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
  • A61C7/00—Orthodontics, i.e. obtaining or maintaining the desired position of teeth, e.g. by straightening, evening, regulating, separating, or by correcting malocclusions
  • A61C7/12—Brackets; Arch wires; Combinations thereof; Accessories therefor
  • A61C7/20—Arch wires
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
  • A61C13/00—Dental prostheses; Making same
  • A61C13/0003—Making bridge-work, inlays, implants or the like
  • A61C13/0006—Production methods
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
  • A61C13/00—Dental prostheses; Making same
  • A61C13/0003—Making bridge-work, inlays, implants or the like
  • A61C13/0006—Production methods
  • A61C13/001—Electrophoresis coating

Definitions

• the present invention relates to a method of surface treating metal elements intended for odontological use, particularly the metal components of devices for rectifying teeth irregulariti ⁇ es, such as brackets, molar tubes, arches, arch wires and ligatures, and like coated metal elements.
• brackets that are intended to be detachably affixed to teeth intended for treatment, with the aid of an adhesive.
• the brackets mostly include slots or notches that are intended to accommodate pre- shaped dental arches and to fit thereinto with great precision, said arches coacting with several irregular teeth via the brackets.
• the ends of the arches are fixed detachably m position m molar tubes, which are mostly mounted on the molars.
• the position of each tooth in relation to the dental arch is fixed with the aid of fine ligatures.
• the magnitude of the force with which the brackets are clamped to the dental arch is dependent, among other things, on the friction between the bracket material and the dental arch, and will permit a certain amount of movement of the brackets in relation to one another.
• a dental brace In order to achieve the effect intended, it is necessary to wear such teeth rectifying devices, or dental braces, for a long period of time, i.e. months and m certain cases even years. Because a dental brace is intended, in principle, to correct irregularities of growth and position of the teeth, it is fitted on the front side of the teeth and therefore fully visible when the wearer opens his/her mouth.
• stainless 18/8 steel is the best material that can be used, since this material enables the brace elements to be given small dimensions and made with precision and also to be functional and strong. This steel has therefore totally dominated the world market in this respect .
• Brackets have also been produced from ceramic materials. When fitted to the lower jaw, however, these brackets have the drawback of being brittle and of grinding against the teeth in the upper jaw.
• the brackets include sharp, protruding corners and grooves (in which the arch must fit with great precision) .
• the slope of the grooves in these brackets varies by about +22° - -30° according to the shape and position of an individual tooth.
• the molar tubes into which the ends of the arch are inserted must also provide an excellent fit and are very small in size, 0.20 m -0.40 mm, and may be both round and square in shape.
• Square tubes are intended for so-called edge arches (square arches) . It follows from this that it is very important to be able to apply the colouring layer with great precision, both with respect to the brackets and with respect to the molar tubes.
• An object of the present invention is to prevent the brace elements from leaking nickel. It is therefore important that molar tubes, for instance, can be coated on the inner surface that is not visible to the eye with a tolerance of 1-2 ⁇ , and also in the corners of the 90°-angles of the square tube. It shall also be possible to coat the ligatures, which have a thickness of 0.10 mm.
• brackets It is also known to produce the brackets from titanium, with the intention of avoiding alloys in which nickel is present and therewith also avoid associated allergy problems. From an aesthetic point of view, titanium brackets are the worst conceivable option of all types of brackets, since the colours are much darker than that of 18/8 steel. Titanium is difficult to work and has resulted in much sharper bracket edges and corners than with other types of bracket materials.
• US-A 4,050,156 teaches a metal coated dental brace having an aesthetical tooth-coloured surface comprising, e.g., Teflon and Ekonol and T ⁇ 0 2 as the colouring substance.
• the object is to achieve good properties with respect to wear resistance, temperature stability, low friction, shapability and fastening ability.
• US-A 4,722,689 describes metal parts or elements intended for odontological use and coated with a thin layer of tooth- coloured polymer, said layer consisting of nylon, epoxy, polyester, vinyl, rubber or like substances and includes a colouring pigment in an amount corresponding to the colour nuance of the teeth.
• US-A 4,107,844 describes dental braces that include a metal core which is coated with epoxy to give an aesthetic appearance and then laminated with a transparent plastic material.
• US-A 4,946,387 describes a tooth rectification metal wire which is coated with a first layer of tooth-coloured material, preferably a plastic, such as polyethylene or polyurethane, and a second outer layer of transparent material, preferably a silicone elastomer.
• a first layer of tooth-coloured material preferably a plastic, such as polyethylene or polyurethane
• a second outer layer of transparent material preferably a silicone elastomer
• US-A 4,731,018 describes methods for the co-extrusion of teetn rectifying wire comprising a metal coated with an aesthetically attractive tooth-coloured plastic material or like material.
• US-A 4,180,912 describes a metal dental brace that includes a plastic casing.
• EP-A 393 002 describes a metal dental arch that is coated witn a thin layer of tooth-coloured material having a low coeffici ⁇ ent of friction.
• the layer material is polyamide and is applied to a thickness of 0.02 to 0.2 mm.
• the object of the present invention is to provide a method of applying an outer layer that has very small layer thickness tolerances (1-2 ⁇ ) even on sharp corners and edges, and to prevent the leakage of nickel and to provide an aesthetically attractive surface of low friction.
• Another object of the invention is to provide metal elements that have these properties.
• the surface coating is applied by an electrocoating process to form the colouring layer, it has been possible to achieve a very even layer thickness even on corners of razor blade sharpness, both negative and positive corners, that occur on metal elements of the kinds concerned, and also within the square-section molar tubes of 0.2-0.4 mm in size.
• the layer also obtains a very narrow tnickness tolerance of about 1-2 ⁇ , even on its critical sharp sections, so as to be impervious to nickel ions, even at internal and external corners of the tube
• the colouring solution with which the metal elements are electrocoated is preferably a polya ide/polyurethane based solution.
• the colouring solution includes one or more of the following components: self cross-linking polyacrylate, ammo resins, epoxy esters, epoxy resins and isocyanate pre-polymers .
• an inner electrocoated layer whereafter an outer thin layer is applied using a vacuum coating technique
• This outer layer will preferably have a thickness of 0 2-5 ⁇ and consists of carbon or metal oxides.
• the electrocoated layer will preferably have a thickness of about 10-30 ⁇
• a layer tha preferably consists of carbon or metal oxide This results in a very hard protective outer layer.
• an inner layer of titanium or titanium oxide is applied by means of a vacuum surface coating process prior to applying the colouring sub ⁇ stance. This enhances adhesion of the colouring substances, which may be especially necessary when the metal element is made of stainless steel. Furthermore, the titanium/titanium oxide layer also prevents the leakage of nickel should the colouring layer be damaged.
• Fig. 1 is a perspective view of a dental brace,-
• Fig. 2 is a cross-sectional view of one part of the brace shown in Fig. 1;
• Fig. 3 illustrates schematically one step in the production process
• Fig. 4 is a cross-sectional view of a part similar to Fig. 2 but in a further enlarged view and illustrating an alternative embodiment cf the invention.
• Fig. 5 illustrates schematically an additional treatment stage in the production process according to said alternative embodiment .
• Fig. 1 illustrates one type of dental brace to which tne present invention relates.
• a dental arch 2 that includes brackets 3 s disposed on a row of teeth 1.
• the brackets 3 are affixed to each tooth 7 witr. the aid of cement or some l ⁇ e adhesive.
• One of the brackets 3 is configured as a molar tube 6.
• One end 4 of the arch 2 is removably fastened to the molar tube 6, which is, in turn, fastened to a molar.
• the other end of the arch 2 is similarly attached removably to a similar molar tube.
• the dental arch 2 is shown in cross-section in Fig. 2.
• the arch is comprised of a metal core part 22, for instance comprised of 18/8 steel.
• the surface of the arch 2 is coated with a plastic material that prevents the leakage of nickel and is coloured with a colouring substance that matches the colour of the teeth 7.
• the outer layer 23 is an electrocoated layer applied in accor- dance with a method illustrated schematically in Fig. 3.
• the metal arch 2 is lowered into a bath 10 that contains an appropriate colour solution.
• a fixed electrode 11 is disposed in the bath and the arch 2 forms a counterelectrode .
• a DC voltage is applied between the two electrodes 2, 11 and pigment particles move towards the arch 2, so-called electrophoreses .
• the arch 2 can either constitute the anode or the cathode of the cell, this latter alternative (so-called cataphoreses) being preferred.
• the electrophoretic transportation of pigment particles to the arch 2, functioning as the cathode, and the precipitation of these particles on the arch result in a colouring layer of uniform thickness on the arch.
• the electrophoreses is continued until a layer of desired thickness has been built-up, about 20-30 ⁇ .
• the binding agent used in the bath 10 will have a composition that will ensure that the binder has no negative effect on human tissue when cured. It shall also be ensured that the pigments and other components of the colouring substance will not induce negative reactions with living tissue.
• Binding agents of different chemical composition can be chosen on the basis of these requirements. For instance, there may be used self cross-linking polyacrylates, particular aminoplastic resins, epoxy esters, combinations of epoxy resins and iso ⁇ cyanate pre-polymers, etc. There is preferably used a com ⁇ bination that comprises diglycidyl ether of bisphenol A having a molecular weight suitable for the purpose, and a pre-polymer of toluene dusocyanate, where the isocyanate groups have been blocked chemically with appropriate hydroxyl-containing chemical compounds.
• Pigments used in the aforedesc ⁇ bed binding agent combination will preferably be inert pigments, which may be inorganic pigments, e.g titanium dioxide, other oxide pigments, carbon black and the like. Inert substances, such as kaolin, are also chosen as filler.
• a small catalyst addition e.g. dibutyltin oxide, in order to achieve a sufficiently high reaction rate in a subsequent oven drying process.
• the coating is allowed to harden on the dental elements subse ⁇ quent to the electrocoating process.
• Fig 4 is a cross-sectional view of part of an arch 2 according to another embodiment of the invention.
• a further layer is applied on the electrocoated layer 23
• This outer layer 24 is applied to a thickness of about 0.2-10 ⁇ with the aid of a vacuum surface treatment process and consists of transparent carbon.
• PVD physical vacuum surface treatment
• CVD chemical vacuum surface treatment
• the carbon layer is very thin and obtains good adhesion and will be transparent or have a very weak in ⁇ terference colour
• the layer obtains a structure of so-called diamond-like carbon (DLC)
• DLC diamond-like carbon
• a metal oxide, such as aluminium oxide, can De applied in the aforesaid manner as an alternative to carbon.
• a vacuum surface coating process will be described briefly hereinafter m accordance with the PVD method in which carbon is used as the coatin ⁇ material
• the surface-coated arch 2 is placed in a vacuum chamber 12.
• the material 13 to be applied to the arch 2 is disposed in a holder element 14 in the chamber 12.
• the chamber 12 is connected to a vacuum pump 15 and a vacuum of about 10 2 to 10 4 pascal is generated in the container.
• the vapou ⁇ zed material is transported directly to the arch 2, or via atom/molecule impacts, and condenses on the arch. Condensation of the material can be promoted by applying an electric potential to the arch 2.
• the arch 2 is mounted on a shaft 16 which passes sealingly through the chamber wall and which is rotated to achieve uniform condensation on the arch 2 and therewith an even surface coating.
• the material used is carbon and the coating process is continued until the required thickness of 0.2-10 ⁇ has been obtained. The result is a surface layer of extreme hardness, about 6,000 Vickers, and high wear resistance.
• the chamber is placed under a powerful vacuum with the intention of avoiding air molecules present from inhibiting free mobility of the carbon atoms m the container and of avoiding chemical reactions between the carbon atoms and the air molecules
• the material can be vapourized with the aid of an electron gun.
• atoms can be loosened from the carbon 13 in the holder element by sputtering, with the aid of gas ion bombard ⁇ ment, preferably argon ion bombardment
• gas ion bombard ⁇ ment preferably argon ion bombardment
• the carbon atoms are therewith stripped from the carbon 13 and released for movement towards the arch 2
• Electrode coating and vacuum surface coating are both well known and established techniques and do not in themselves constitute a subject of the present invention. On the other hand, neither of these techniques has earlier been applied in the fabrication of elements intended for odontological use

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• Health & Medical Sciences (AREA)
• Oral & Maxillofacial Surgery (AREA)
• Dentistry (AREA)
• Epidemiology (AREA)
• Life Sciences & Earth Sciences (AREA)
• Animal Behavior & Ethology (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• Dental Tools And Instruments Or Auxiliary Dental Instruments (AREA)
• Chemically Coating (AREA)

Priority Applications (3)

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Publications (1)

Family

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Family Applications (1)

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Cited By (7)

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Citations (3)

• 1996
  • 1996-02-15 SE SE9600559A patent/SE505952C2/sv not_active IP Right Cessation
• 1997
  • 1997-02-14 JP JP9529273A patent/JP2000506028A/ja active Pending
  • 1997-02-14 WO PCT/SE1997/000230 patent/WO1997029712A1/en not_active Application Discontinuation
  • 1997-02-14 AU AU18178/97A patent/AU1817897A/en not_active Abandoned

Patent Citations (3)

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