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
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K6/00—Preparations for dentistry
  • A61K6/80—Preparations for artificial teeth, for filling teeth or for capping teeth
  • A61K6/84—Preparations for artificial teeth, for filling teeth or for capping teeth comprising metals or alloys
  • A61K6/844—Noble metals
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/12—Both compacting and sintering
  • B22F3/1208—Containers or coating used therefor
  • B22F3/1258—Container manufacturing
  • B22F3/1283—Container formed as an undeformable model eliminated after consolidation

Definitions

• the present invention relates to a method for obtaining artefacts or metal structures for odontotechny and dentistry, providing for the use of powders of the metals and of the alloys commonly used in the practice of odontotechnical laboratories.
• the lost wax technique consists of numerous successive operations starting with the dentist's taking the impression of the patient's teeth. From this impression, a cast of the teeth is obtained, with the aid of which the dentist builds a wax model of the prosthetic component (crown, bridge or other) to be made of metal.
• This model is incorporated in a refractory material known as coating and which, solidifying, encloses the model in a thermally stable shell.
• a subsequent heat treatment allows to eliminate, through appropriate vents, the wax part and to obtain a case having in its interior a cavity with the shape of the original wax model. This cavity is filled with the molten metal casting and, after the mechanical elimination of the coating, the metallic prosthetic component is obtained, to be used as it is or coated, for aesthetic purposes, with ceramic or resin.
• the paste is modelled on a prepared component, wherefrom it is isolated by means of another metallic layer, also obtained by sintering.
• the powder sintering technique is also used according to U.S. Pat. No. 4,980,124, which provides for the metallic powders to be sintered on a thing sheet of palladium or suitable alloys, adapted to a model of the component to be realised, in such a way as to obtain a metallic structure that is difficult to deform, whereon a ceramic crown is constructed.
• U.S. Pat. No. 5,234,343 discloses a method and a material that allow to obtain prosthetic components starting from metallic powders constituted by a metal with high melting point and a metal with low melting point.
• such alloys contain—in addition to a high percentage of noble metals—also a certain quantity of non noble and easily oxidised metals. The latter make the sintering operation more difficult and not achievable under atmospheric pressure conditions or with the degree of vacuum reachable in common ceramic furnaces.
• Italian Patent No. 1271360 in the name of the same Applicant describes a method for obtaining artefacts starting from alloy powders for metal-ceramic at ambient pressure, providing for the use of graphite containers, under which the sintering process takes place.
• the need to effect the sintering under graphite containers constitutes a limitation to the application of the technique, for the following two reasons.
• the dimension of the work that can be executed is limited by the dimensions of the graphite container.
• the introduction of graphite objects into a ceramic furnace is not viewed favourably by the user, due to the possibility of contamination from the carbon of the graphite containers.
• the carbon may combine with the palladium contained in may alloys used for dentistry, giving rise to compounds that make the alloy considerably more fragile, to the point that it is no longer suitable for normal conditions of use.
• carbon contamination may originate bubbles when the ceramic is cooked and it may promote the formation of discoloration and aesthetic flaws in the ceramic.
• the aim of the present invention is to find a method that allows to achieve, in an easy, precise and economical manner, the production of metallic dental structures for prosthetic uses and it simultaneously enables also to achieve the addition of metallic material for modification, correction, reinforcement or junction purposes, or for any other requirements, eliminating the drawbacks of the aforesaid known methods and above all the need to use vacuum conditions or particular atmospheres as well as graphite containers, and determining a considerable improvement of the work processes used thus far, while it allows fully to exploit the advantages of sintering and to obtain prosthetic structures and to realise additions and corrections in a more convenient manner relative to the prior art.
• the present invention entails the considerable advantage and the peculiarity of working directly on the master model and not on the refractory material, thereby avoiding the duplication step, with consequent time savings and reduced risk of imprecision.
• the present invention provides for the use of common dental alloys such as gold or pure silver.
• the present invention provides a method for obtaining prosthetic metallic structures, corrections, additions, adaptations of details, and the like, characterised in that it comprises the following steps:
• an organic liquid is used for the refractory coating material, whose molecule contains 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms such as, for instance, methyl alcohol, ethyl alcohol, propyl alcohol, acetone, ethyl-methyl-ketone, diethyl-ketone, acrylic acid, metacrylic acid, diethanolamine, diethylamine, and the like. Mixtures of two or more of said liquids can also be used.
• the molecule of the organic liquid used according to the invention to mix the coating material can also contain other elements as well, such as nitrogen, oxygen, sulphur, chlorine, fluorine and all elements that commonly bind with carbon.
• the organic liquid and the coating material react to each other at the time of mixing and/or inside the furnace, to generate conditions suitable for sintering, strengthening also the normal protection against contact with the atmosphere, which protection is determined by the protective shell constituted by the coating material.
• a prosthetic artefact is obtained in the following way.
• the material for obtaining the prosthesis is constituted by a metallic powder which has the same composition as the alloys and the pure metals commonly used in dentistry.
• This powder is employed as such or it is preferably incorporated in an additive that facilitates its deposition and/or modelling.
• a diluting agent can be used to make the paste even more malleable and workable.
• additives are constituted by polyethylene, glycol, glycerine, butylic, isobutylic or natural rubber, natural or synthetic wax, as well as mixtures of one or more of said substances.
• diluting agents are constituted by water, hydrocarbons, alcohols, poly-oils and mixtures thereof.
• the size of the particles of the powders used normally ranges from 0.1 and 1000 ⁇ m. Powder composition is not critical and may correspond to the compositions used in common practice with traditional methods.
• a component of a prosthesis for the metal-ceramic technique can be obtained starting from powders with identical composition to that of the alloy used normally for the same purposes.
• the metallic powder mixture is worked in such a way as to obtain plates of defined thickness. Indicative, but not limiting, values of the thickness of such plates range between 0.15 and 0.40 millimetres.
• the metallic powder may be constituted by pure metal, alloy, or a mixture of pure metal/pure metal or pure metal/alloy or alloy/alloy with a volumetric ratio ranging between 0.5 and 1.5 and preferably equal to 1.
• the plate (or a part thereof) is adapted directly to the plaster model of the component to be obtained. After adapting and modelling this plate, it is coated with a refractory coating material according to the invention, i.e. mixed with an organic liquid, as described above.
• the modelled part is extracted from the plaster model and completely coated with metallic coating as per the present invention.
• the whole set is then moved to a common dentistry furnace, where sintering is performed. It is preferable, but not binding, to keep the prepared item, before sintering, for a certain time interval to a temperature lower than sintering temperature, to obtain the elimination of the excess organic liquid.
• Sintering is performed in a ceramic or pre-heating furnace, at ambient pressure and in normal atmosphere, at a temperature equal to about 80% of the melting temperature of the alloy.
• the metallic artefact thus produced can be ceramic coated and worked as usual.
• the method according to the present invention is particularly advantageous for effecting modifications, corrections of the biting surface, corrections of the general shape of said prostheses, as well as welding different components in order to obtain a single body.
• the welding material (which preferably has the same composition of the alloy constituting the prosthetic artefact) is deposited with extreme precision and ease, thanks to the ease of manipulation of the metal-additive mix.
• the component to be sintered is enclosed in the coating material mixed, according to the invention, with the organic liquid.
• the method according to the present invention moreover, allows the supermelting technique using suitable alloys.
• the elements produced by sintering the metal according to the method of the present invention can thereafter be united and/or modified with:
• a metal crown was manufactured using a quantity of New Ceramit USA 88 alloy (Nobil Metal, Villafranca, AT) with wax added (Industria Zingardi, Novi Ligure, Ala.).
• the composition of the alloy is as follows: Au Pd Cu Ga Ru 2.0% 79.0% 9.9% 9.0% 0.1%
• the mixture was subjected to pressure to increase the consistency of the material, obtaining a plate with a thickness of 0.30 mm.
• a portion cut off from said plate was wound about a plaster model and then pressed, to adapt it to the shape of the model.
• the metal paste was coated with coating material (Sintercast RDM, Nobil Metal).
• the coating material used is characterised by the following composition: Crystalline silica (quartz) 10-30% Crystalline silica (cristobalite) 40-70% Phosphate-based powders 10-30% Metal oxides 3-15%
• the items were sintered in a ceramic furnace (of the kind commercially known as LECTRA, Nobil Metal, Villafranca, AT) at 1050° C. for 10 minutes.
• a ceramic furnace of the kind commercially known as LECTRA, Nobil Metal, Villafranca, AT
• Example 1 The experiment of Example 1 was repeated with powders of the Pal Keramit (Nobil Metal, Villafranca, AT) alloy.
• the composition of the alloy is as follows: Ag Pd Sn Ga In Ru 32.0% 57.5% 8.0% 1.5% 1.0% 0.1%
• a metal crown was obtained with the lost wax technique, using the Pal Keramit alloy as a model.
• the thickness of the part destined to cover the stump was measured with a micrometer and a maximum value of 0.8 mm was recorded.
• the item was uniformly coated with a plate of Pal Keramit alloy powder, with wax added.
• the sintering process was conducted with the times and in the ways of cases b) and d) of Example 2. Thickness was measured again and a uniform increase of 0.5 mm was recorded in case d), whilst the added powder was not found to have been sintered in case b).
• a mixture of pure gold powder was obtained by combining gold powder and wax in the proportions of 3.5 g of wax per 100 g of gold. The mixture thus obtained was pressed to obtain a platelet with a thickness of 0.30 mm. A cut-off portion of said plate was wound about a plaster model and then pressed, to adapt it to the shape of the model.
• the metal paste was coated with coating material (Sintercast RDM, Nobil Metal) mixed with acetone.
• the items were sintered in a ceramic furnace (LECTRA, Nobil Metal, Villafranca, AT) a 1030° C. for 4 minutes.
• a mixture of pure silver powder was obtained by combining silver powder and wax in the proportions of 6.5 g of wax per 100 g of silver.
• the mixture thus obtained was worked to obtain a platelet with a thickness of 0.30 mm.
• a cut-off portion of this platelet is wound about a plaster model and then pressed, to adapt it to the shape of the model.
• the metallic paste was coated with coating material (Sintercast RDM, Nobil Metal) mixed with acetone.
• the items were sintered in a ceramic furnace (LECTRA, Nobil Metal, Villafranca, AT) at 920° C. for 4 minutes.
• a plate with a thickness of 0.35 mm was obtained by homogeneously mixing pure gold powder and pure silver powder.
• the final plate had a volumetric ratio of 1 to 1.
• a portion of said plate was wound about a plaster model and the pressed, to adapt it to the shape of the model.
• the metal paste was coated with coating material (Sintercast RDM, Nobil Metal) mixed with acetone.
• the items were sintered in a ceramic furnace (LECTRA, Nobil Metal, Villafranca, AT) at 990° C. for 4 minutes.
• a portion of the plate was wound about a plaster model and then pressed, to adapt it to the shape of the model.
• the metal plate was coated with coating material (Sintercast RDM, Nobil Metal) mixed with acetone.
• the items were sintered in a ceramic furnace (LECTRA, Nobil Metal, Villafranca, AT) at 1086° C. for 8 minutes.
• a plate with a thickness of 0.33 mm was obtained by homogeneously mixing pure gold powder and powder of an alloy characterised by a content of Au+PGM of 84.0%.
• a portion of the plate was wound about a plaster model and then pressed, to adapt it to the shape of the model.
• the metal plate was coated with coating material (SINTERCAST RDM, Nobil Metal) mixed with acetone.
• the items were sintered in a ceramic furnace (LECTRA, Nobil Metal, Villafranca, AT) at 1080° C. for 8 minutes.
• a portion of the plate was wound about a plaster model and then pressed, to adapt it to the shape of the model.
• the metal plate was coated with coating material (Sintercast RDM, Nobil Metal) mixed with acetone.
• the items were sintered in a ceramic furnace (LECTRA, Nobil Metal, Villafranca, AT) at 1095° C. for 8 minutes.
• a series of prosthetic elements obtained as described in the previous examples (1 ⁇ 13) was welded using portions of a plate having the same chemical composition as the prosthetic element.
• the metallic paste was adapted in the point of interest joining two single crowns, then proceeding with the sintering process in a ceramic furnace (LECTRA, Nobil Metal, Villafranca, AT) with the same parameters used for sintering the initial artefact, except for the sintering temperature, lower by 5-10° C. than the initial one.
• the results of the sintering process were assessed through the visual observation of the product and by means of mechanical stressing, as described in Example 1. The result obtained, according to the scale described in Example 1, was assigned a value of 5.
• a series of prosthetic elements obtained as described in Examples 1 ⁇ 13 was modified adding and modelling portions of a plate having the same chemical composition as the prosthetic element.
• the metallic paste was added in the area of interest, modifying the anatomic profile of the prosthesis and then proceeding with the sintering process in a ceramic furnace (LECTRA, Nobil Metal, Villafranca, AT) with the same parameters used for sintering the initial artefact, with the exception of the sintering temperature, 5-10° C. lower than the usual one.
• the results of the sintering process were assessed through the visual observation of the product and by means of is mechanical stressing, as described in Example 1.
• the result obtained, according to the scale described in Example 1, was assigned a value of 5.
• a series of prosthetic elements obtained as described in Examples 1 ⁇ 13 was welded using the classic blowpipe welding method. Two single crowns, after incorporation in the refractory material and subsequent pre-heating in the furnace were welded with the aid of the blowpipe, according to the technique widely known as blowpipe welding, with appropriate welding material. The success of the welding process was assessed through the visual observation of the product and by means of mechanical stressing, as described in Example 1. The result obtained, according to the scale described in Example 1, was assigned a value of 5.
• a series of prosthetic elements obtained as described in Examples 1 ⁇ 13 was modified adding metal (welding material) with the traditional blowpipe welding technique.
• the welding material used characterised by a working temperature that is 50° C. lower than the sintering temperature, flowed perfectly on the surface to be modified, thereby demonstrating an excellent ability to wet said surface.
• the results of the sintering process were assessed through the visual observation of the product and by means of mechanical stressing, as described in Example 1.
• the result obtained, according to the scale described in Example 1, was assigned a value of 5.
• a series of prosthetic elements obtained as described in Examples 1 ⁇ 13 was joined using the supermelting technique (lost wax method). Two crowns were joined modelling an intermediate element with wax. The bridge structure thereby obtained (crowns plus wax structure) was then placed in a smelting coating (Proper Vest Fast Nobil Metal, AT) and incorporated in a smelting cylinder. The pre-heating and smelting operations were then carried out, using an alloy having a suitable casting temperature (Keramit Bio Uno Nobil Metal), close to the sintering temperature. The success of the supermelting process was assessed through the visual observation of the product and by means of mechanical stressing, as described in Example 1. The result obtained, according to the scale described in Example 1, was assigned a value of 5.
• a series of prosthetic elements obtained as described in Examples 1 ⁇ 13 was modified adding metal with the traditional lost wax technique. Some crowns were modelled adding wax and thereby modifying the anatomical profile. The structure thus obtained (crown plus wax addition) was then placed in a smelting coating (Proper Vest Fast Nobil Metal) and incorporated in a smelting cylinder. The pre-heating and smelting processes were then performed, using an alloy with a suitable casting temperature (Keramit Bio Uno Nobil Metal), close to the sintering temperature. The success of the supermelting process was assessed through the visual observation of the product and by means of mechanical stressing, as described in Example 1. The result obtained, according to the scale described in Example 1, was assigned a value of 5.

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• Health & Medical Sciences (AREA)
• Oral & Maxillofacial Surgery (AREA)
• Veterinary Medicine (AREA)
• Epidemiology (AREA)
• Life Sciences & Earth Sciences (AREA)
• Animal Behavior & Ethology (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Dentistry (AREA)
• Plastic & Reconstructive Surgery (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Mechanical Engineering (AREA)
• Dental Preparations (AREA)
• Powder Metallurgy (AREA)
• Materials For Medical Uses (AREA)
• Dental Prosthetics (AREA)

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  • 2000-09-13 IT IT000007A patent/ITAL20000007A1/it unknown
• 2001
  • 2001-09-13 AU AU2001295871A patent/AU2001295871A1/en not_active Abandoned
  • 2001-09-13 ES ES01976608T patent/ES2261482T3/es not_active Expired - Lifetime
  • 2001-09-13 WO PCT/IT2001/000476 patent/WO2002022041A1/fr active IP Right Grant
  • 2001-09-13 DE DE60118584T patent/DE60118584T2/de not_active Expired - Lifetime
  • 2001-09-13 EP EP01976608A patent/EP1317222B1/fr not_active Expired - Lifetime
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