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
  • A61C13/0004—Computer-assisted sizing or machining of dental prostheses
• • 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
  • A61C13/08—Artificial teeth; Making same
  • A61C13/082—Cosmetic aspects, e.g. inlays; Determination of the colour
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
  • A61C9/00—Impression cups, i.e. impression trays; Impression methods
  • A61C9/004—Means or methods for taking digitized impressions
  • A61C9/0046—Data acquisition means or methods
  • A61C9/0053—Optical means or methods, e.g. scanning the teeth by a laser or light beam
• • 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
  • A61C13/0019—Production methods using three dimensional printing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y80/00—Products made by additive manufacturing

Definitions

• the present invention relates to a method for manufacturing a dental restoration.
• Ceramic materials have been successfully applied for many years in dental restorations .
• the two most important functions of restorative ceramics are aesthetics and strength.
• most dental ceramics do not fulfil both functions.
• Different porcelains and glass ceramics are used for aesthetic applications. These have a natural tooth colour and translucence but have a relatively low three-point bending strength (50- 200 MPa) .
• Higher-strength materials have been developed as basic core material . These materials have a three-point bending strength of 150 to 500 MPa, but are generally too opaque and must be combined with translucent porcelain veneered thereon. The fracture toughness however remains low compared to metal alloys, whereby these ceramics are susceptible to production errors and stress concentrations, such as occur when there is a less than optimal fit between prepared tooth and the restorative ceramic.
• Y-TZP Medically pure yttrium-stabilized tetragonal zirconium oxide
• Yoshida describes a method of colouring orthodontic zirconium oxide components by adding a mixture of erbium-, praseodymium-, iron- and zinc oxides. Some additives, such as zinc, result in serious degradation of the physical properties of the sintered zirconium oxide.
• DE 19938143 Al erbium-, iron- and manganese oxide are mainly applied as colouring oxides .
• a dental restoration enlarged by the sintering shrinkage factor, is then cut out by means of a CAD/CAM system and the product is sintered to increase density at 1300-1500 °C for 2-4 hours.
• the result is a monochrome coloured restoration.
• the base structure of a crown in the form of a cap, is thus coloured slightly browner at the bottom, the so-called shoulder portion, and lighter yellow in the sections in the cutting edge area.
• a new method for manufacturing a dental restoration is provided according to the present invention, which is distinguished by the combination of measures of claim 1.
• a method according to the invention it is possible to manufacture a restoration with a very natural appearance, in respect of both colour, translucence and so on and the shape thereof.
• a possible embodiment of a method according to the invention can be designated as 3D printing.
• Experimental configurations have recently been constructed, particularly at the Massachusetts Institute of Technology (MIT, Boston, USA) , with which it is possible using software to determine the colours of the STL files (input files for rapid prototyping machines) .
• 3D printing Owing to the development of new materials and machines, the possibilities in the field of 3D printing have recently been greatly expanded, although there is still no application known for using this technology for dental restorations.
• the printer is used to apply an organic binder to a powder compacted using a roller, whereby complex shapes can be produced.
• the principle of 3D printing (3DP) is known. The method was developed by the institute of technology of Boston, MIT. Market developments of the principle have since taken place. Zcorporation for instance has however used starch, which has little environmental impact and is freely available, as binder.
• a drawback to the use of starch as binder is that it increases the shrinkage of the bound ceramic powder and that the shrinkage can moreover not be predicted in all directions. This makes starch less useful for the accuracy desired in dentistry. This in contrast to cold isostatic pressed (more than 2000 bar) ceramic, which after cutting and sintering results in a sufficiently accurate restoration.
• ZP100 was developed as an alternative, with which thin-walled and complex products such as dental restorations can indeed be printed in 3D with sufficient accuracy.
• a method according to the invention has the characteristics of claim 2.
• the production process hereby remains readily manageable and leads to good results. Particularly good results are achieved in respect of the appearance of the restoration to be produced (colour, translucence and so on) , if the measures of claim 3 are herein also applied.
• Colour variations can thus be realized in a three-dimensional direction over the outer surface of the restoration to be produced, while colour variations could only be realized in the direction in which the layers are successively provided on each other when layers to be provided separately have a homogenous composition.
• a variation resulting in colour variation can also be realized in the layers, so that even more natural variations can be obtained.
• the non- cohesive form of the material to be applied can be one of powder form, liquid, thin slices and so on.
• the cohesion can for instance be given by selectively adding binder to the powder or by subjecting the powder to the action of at least one laser.
• an arrangement with two lasers can be used depending on the capacity of this liquid material to transmit laser light, where the intended effect of providing cohesion, for instance solidifying, only occurs where the laser beams coming from the lasers cross each other.
• colour variations can be realized per slice around the periphery thereof, or the slices can be manufactured from homogenous material .
• the material to be applied in the method is for instance ceramic material, porcelain, glass ceramic, and so on, but preferably yttrium-stabilized tetragonal zirconium oxide, to which the invention is however not limited. This has properties which are very advantageous in respect of the invention.
• many materials can be used, such as erbium oxide, iron oxide and praseodymium oxide, manganese oxide and so on. Such materials can be combined well with the materials to be applied in the restoration to be manufactured, particularly zirconium oxide.
• Installation 1 comprises a holder (not shown) in which layers of powder-form yttrium-stabilized tetragonal zirconium oxide (Y-TZP) can be placed one over another.
• the zirconium oxide is in powder form so that a body 2 of this powder is formed as the stacking of said layers onto each other progresses.
• the layers are arranged using a powder holder 3, which in this embodiment is funnel-shaped and adapted to pour a measured quantity.
• Powder holder 3 is provided for this purpose with a flap 4 with which the pouring opening of powder holder 3 can be closed.
• the installation further comprises a laser generator 7 connected to a control 8.
• the focal point 9 of the laser generator acts on the upper surface of body 2 to give the powder-form zirconium oxide cohesion in the upper layer, which has just been poured from powder holder 3 and levelled and compacted by roller 5. Under the influence of the action of the focal point of laser generator 7 there also occurs adhesion to the material lying beneath the last poured layer. Any random shape can thus be generated in a layered structure, precisely this being advantageous in the case of dental restorations because of the usually erratic shapes thereof.
• the figure shows such a dental restoration 10.
• the method for manufacture hereof is being performed, so that the dental restoration 10 is only partly shown.
• a part of the body 2 of loose powder is further cut away in the view in order to show the dental restoration 10.
• the focal point 9 of laser generator 7 follows a pattern in the material of the last spread layer such that, after processing a number of layers in this manner, a desired three-dimensional form of the dental restoration can be obtained.
• the dental restoration 10 material is added to the powder-form zirconium oxide prior to the action of focal point 9.
• This may be for instance iron oxide, erbium oxide or praseodymium oxide. These materials have an effect on the colour, wherein iron oxide produces a brown discolouration and erbium oxide a light violet discolouration, while praseodymium oxide has a deep yellow colouring effect.
• the installation 1 as shown in fig. 1 is also referred to as a colour printer.
• the laser generator 7 shown in fig. 1 it is also possible to work with a binder which gives the non-cohesive powder-form zirconium oxide cohesion locally and where desired. As shown in fig. 1, this can also take place in a structure with layers.
• the binder is active up to a depth to which the binder is able to give cohesion to the powder-form zirconium oxide. In such an application this active depth is of course greater than the thickness of a layer of powder-form zirconium oxide which has been applied or is to be applied, so that the adhesion to underlying parts of the restoration 10 to be formed is also brought about.
• Dental restorations are manufactured with colour printer 1 from a loose, dry zirconium oxide powder with 3% yttrium oxide.
• the geometry for the restorations originates from a scan-design system such as a CAD-CAM system.
• Printer 1 is used to apply an organic binder to powder compacted with the roller, whereby complex shapes can be produced.
• a solution of 4% by weight 4AC (Hercules, USA) is made as binder.
• Three print suspensions are made herefrom by adding respectively 0.05% Pr-oxide, 0.05% Fe-oxide and 0.05% Er-oxide.
• the pigment is added to the binder as micronized powder and mixed in a turbine agitator.
• a bridge is printed with an STL data file, with differentiated colouring, obtained from a CAD system for dental restorations. After construction the bridge is heated to 650 * C at 5°C/min. The restoration is then heated to 1500 "C at lO'C/min and held there for 2 hours. The bridge exhibits the designed local differentiated colouring .

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• Health & Medical Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Dentistry (AREA)
• Epidemiology (AREA)
• Life Sciences & Earth Sciences (AREA)
• Animal Behavior & Ethology (AREA)
• Oral & Maxillofacial Surgery (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Dental Preparations (AREA)
• Dental Prosthetics (AREA)
• Treatment Of Sludge (AREA)

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Citations (5)

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• 2001
  • 2001-04-23 NL NL1017907A patent/NL1017907C2/nl not_active IP Right Cessation
• 2002
  • 2002-04-19 AU AU2002306555A patent/AU2002306555B2/en not_active Ceased
  • 2002-04-19 CA CA002444875A patent/CA2444875C/en not_active Expired - Fee Related
  • 2002-04-19 JP JP2002582823A patent/JP4371659B2/ja not_active Expired - Fee Related
  • 2002-04-19 DE DE60226966T patent/DE60226966D1/de not_active Expired - Lifetime
  • 2002-04-19 US US10/474,605 patent/US7686989B2/en not_active Expired - Fee Related
  • 2002-04-19 WO PCT/NL2002/000259 patent/WO2002085242A1/en not_active Ceased
  • 2002-04-19 AT AT02733585T patent/ATE397421T1/de active
  • 2002-04-19 EP EP02733585A patent/EP1383442B1/en not_active Expired - Lifetime
  • 2002-04-19 ES ES02733585T patent/ES2307756T3/es not_active Expired - Lifetime
  • 2002-04-19 BR BRPI0209109-7A patent/BR0209109B1/pt not_active IP Right Cessation

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