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Publication numberWO2002019940 A1
Publication typeApplication
Application numberPCT/SE2001/001889
Publication date14 Mar 2002
Filing date5 Sep 2001
Priority date8 Sep 2000
Publication numberPCT/2001/1889, PCT/SE/1/001889, PCT/SE/1/01889, PCT/SE/2001/001889, PCT/SE/2001/01889, PCT/SE1/001889, PCT/SE1/01889, PCT/SE1001889, PCT/SE101889, PCT/SE2001/001889, PCT/SE2001/01889, PCT/SE2001001889, PCT/SE200101889, WO 0219940 A1, WO 0219940A1, WO 2002/019940 A1, WO 2002019940 A1, WO 2002019940A1, WO-A1-0219940, WO-A1-2002019940, WO0219940 A1, WO0219940A1, WO2002/019940A1, WO2002019940 A1, WO2002019940A1
InventorsAnders Sundh, Michael OŽBrian, Derrick Luksch
ApplicantDecim Ab
Export CitationBiBTeX, EndNote, RefMan
External Links: Patentscope, Espacenet
A method for a dental restoration
WO 2002019940 A1
Abstract
The present invention relates to a method for producing a dental restoration of at least part of at least one tooth. The method comprises measuring the surface of a preparation replica (1) of a preparation, for which the dental restoration is intended, and storing information about the topology of the preparation replica (1) in a data storage means (3), and creating a computer model (4) of the dental restoration, whereby at least some of the information stored in the previous step is used and/or user inputs from a computer operator is registered. At least one tool path is generated for the control of a machining equipment (5), using the computer model (4), and a restoration replica (6) is machined in a restoration replica material, using the at least one tool path. Finally a mould (7) is formed, using the restoration replica (6), and the dental restoration is cast, using the mould (7).
Claims  (OCR text may contain errors)
1. A method for producing a dental restoration of at least part of at least one tooth, the method comprising the steps of
• measuring the surface of a preparation replica (1) of a preparation, for which the dental restoration is intended, and storing information about the topology of the preparation replica (1) in a data storage means (3),
• creating a computer model (4) of the dental restoration, whereby at least some of the information stored in the previous step is used and/or user inputs from a computer operator is registered,
• generating at least one tool path for the control of a machining equipment (5), using the computer model (4),
• machining a restoration replica (6) in a restoration replica material, using the at least one tool path,
• forming a mould (7), using the restoration replica (6), and
• casting the dental restoration, using the mould (7).
2. A method according to claim 1, wherein the machining equipment (5) is a CNC- machine (5).
3. A method according to any of the preceding claims, wherein the restoration replica material has a melting point below the melting point of a mould material, used for forming the mould (7).
4. A method according to any of the preceding claims, wherein the restoration replica material has a evaporation temperature below the melting point of a mould material, used for forming the mould (7), and wherein the step of forming a mould is succeeded by removing the restoration replica by letting it evaporate, by subjecting the mould to a temperature above the evaporation temperature of the restoration replica.
5. A method according to any of the preceding claims, wherein the restoration rep- lica material is a wax material.
6. A method according to any of the preceding claims, wherein the step of measuring comprises measuring at least one tooth, or part thereof, adjacent to the preparation, and storing information about the topology of said at least one tooth in the data storage means (3).
7. A method according to any of the preceding claims, wherein the restoration replica is machined from a blank, provided with a protrusion (9), for fixing the blank in the maclώτing equipment (5) during macliining of the restoration rep- lica, and the protrusion (9) is used to form a channel in the mould (7), for entering restoration material during casting.
Description  (OCR text may contain errors)

A METHOD FOR A DENTAL RESTORATION

TECHNICAL FIELD

The present invention relates to a method for producing a dental restoration.

RELATED ART

The so called Lost Wax technique is a standard method within dental laboratories, to manufacture parts of, or complete restorations in various materials, e.g. gold alloys, titanium, ceramics, etc. The Lost Wax technique includes producing a replica of the prepared tooth, often in a plaster material, with the aid of a bite impression. With the plaster die as base, a dental technician sculptures and designs a restoration in a wax or similar material. The wax-restoration is embedded in a material that will form a mould with the shape of the wax-restoration. The wax is removed from the mould by placing it in an oven, whereby the wax evaporates and disappears. The restoration is cast by letting a metal or some other material in a liquid, or semi- liquid, form enter into the mould through a special channel. The technique used for making the liquid metal reach all parts of the mould is, for example, by rotation us- ing centrifugal force, or by using vacuum/pressure.

A major problem with this traditional casting method is that it is labour intensive, especially concerning the wax model design part. For each restoration, a trained dental technician must design the restoration by hand in order to achieve a wax model of the restoration for use in subsequent casting steps. The actual casting step may however be done in a quite efficient manner.

CAD/CAM based systems from the manufacturing of dental restorations are known in the art, for example: • Duret: "Vers unit prothese informatisee" Tonus Dentaire No 73, 1985pp. 55-57, • Duret et al: "CAD-CAM in dentistry", JADA, Vol. 117, November 1988, pp. 715-720,

• Williams: "Dentistry and CAD/CAM: Another French Revolution", Journal of Dental Practice Administration, January/March 1987, • Sjόlin, Sundh, Bergman: "The Decim System for Production of Dental restorations", International Journal of computerised Dentistry 1999: 3. [1].

Thus, the first CAD/CAM systems for manufacturing of dental restorations appeared in the 1980's. I-n a dental CAD/CAM system a method is used which in- eludes measuring the surface of the plaster model, produced in the same manner as in the Lost Wax technique, described above. Data about the topology of the prepared tooth and possibly also the surrounding teeth are stored in a computer. An operator interacts with the CAD part of the system in order to design the restoration on the scanned surface and to create a computer model of the desired restoration. The computer model is transferred to the CAM part of the system, where tool paths are generated for machining of the restoration out of a given blank, made out of, e.g. ceramics or metal, hi the last step the tool paths are transferred to a CNC-machine for machining.

The CAD/CAM systems use the possibilities that computers and software give in order to design the restoration more or less automaticly in a cost effective way. However, in the manufacturing step, there are some costs that are difficult to avoid: 1. When machining in ceramics or in metal, there will always be a significant cost for tool wear. 2. When a CNC-machine is used for manufacturing, there will always be a significant capital cost. 3. When machining in expensive material such as gold alloys or similar, there is a need for a cost-effective re-cycling system for the cutting chips and excess material. 3 u w ./ ««- w ι f u i! o

4. When expensive material such as gold alloys or similar is to be machined out of a solid block, instead of being cast, a lot more of said material need to be present, say ten times more. Even if most of it could be re-cycled at low cost, just the presence of an expensive material may cause problems and costs related to secu- rity.

SE 470 346 B discloses a method for producing artificial ceramic dental restorations. The method comprises the steps of

- registering the surface of a prepared tooth using a three-dimensional optical method on a plaster model of the preparation,

- reproducing the registered surface (of the preparation) on a first body, using a computer controlled mill,

- forming a second body by expanding the registered surface and milling an outer surface corresponding to the expanded surface, or by applying wax onto the first body,

- generating an imprint of the second body in an elastic material,

- using the first body and the imprint for a pressing tool, and

- forming a coping using the pressing tool in a press casting process.

The method in SE 470 346 B is adapted to an industrial process, involving heavy and expensive equipment, not easily made available in a dental technician laboratory. Further, the method in SE 470 346 B cannot be easily used in the existing casting method presently used in laboratories.

OBJECT OF THE INVENTION

The object of the present invention is to provide a method for producing a dental restoration, which method reduces or avoids the problems mentioned above.

It is a further object of the invention to provide a method for producing a dental restoration, that is more time effective than traditional casting methods, and which can be easily implemented in facilities, where traditional casting methods are employed.

SUMMARY OF THE INVENTION

The object of the invention is obtained by a method according to claim 1.

By creating a computer model for the design of the restoration, instead of, as is the case in the Lost Wax technique, sculpting by hand in wax material, the labour cost is reduced. The tool cost for machining in wax will be significantly lower compared to machining in ceramics or metals. As the machining time per restoration will be lower when machining in wax compared to other materials, the capital cost per restoration will be lower. Since the method according to the invention does not give rise to the need of a re-cycling system for any material presently used for restora- lions, there is also no need for an expensive filtering system for the capturing of contamination in the re-cycled restoration materials. There is no need for logistics and a security system for handling of large amount of gold.

DESCRIPTION OF THE FIGURES

The invention will now be described closer with reference to the accompanying drawings, in which figures 1-4 are schematic perspective views of items used in stages in a method described here below. Fig. 5 is a schematic perspective view of an item used in a method according to an alternative embodiment of the present n- vention.

DETAILED DESCRIPTION

In the following description the term preparation includes a prepared tooth, a pre- pared plurality of teeth or a prepared part of a tooth. To produce a restoration for a preparation, the first step is to create a replica of the preparation, here called a preparation replica. This is done, in a known manner, by creating a bite impression of the preparation, using an appropriate material, usually silicone. The preparation replica, often made in plaster material, is formed by engaging the silicone with plaster material.

Fig. 1 illustrates a step in the method according to the present invention, whereby the surface of the plaster model, i.e. the preparation replica 1 is measured, using a measuring device 2. Data about the topology of the prepared tooth are stored in a data storage means 3, for example a computer 3. The measuring could also include surrounding teeth, whereby the data of the topology of these would be stored as well.

Referring to fig. 2, using a suitable software, such as a CAD/CAM system, a computer model 4 of the desired restoration is created, using data acquired in the step depicted in fig. 1. An operator may interact with the design part, e.g. the CAD part of the system in order to design the restoration on the scanned surface, whereby various types of software tools may be present in order to make the design job easier and quicker.

The computer model 4 is transferred to the manufacturing part of the software, e.g. the CAM part, where tool paths for the control of a machining equipment, such as a CNC-machine, are generated.

With reference to fig. 3, the tool paths are transferred to a CNC-machine 5 for ma- clmiing of a restoration replica 6 of the dental restoration. The CNC-machine could be of the type commonly used in dental laboratories for machiriing of a restoration out of ceramics or metal. Preferably, a material with a relatively low evaporation temperature is used for the restoration replica 6. The material could be wax of the type commonly used in dental laboratories, for the Lost Wax technique, known to the person skilled in the art. Alternatively plastic or any other suitable material could be used for the restoration replica 6. With reference to fig. 4, the wax-restoration, i.e. the restoration replica 6 is embedded in a material that will form a mould 7, that will obtain an inner surface, essentially complementary to the outer surface of the restoration replica 6. The material for the mould could be one commonly used in dental laboratories.

Preferably, by elevating the temperature of the mould, the restoration replica material is removed by letting it evaporate. For this, an oven equipment commonly used for the Lost Wax technique can be utilised. Alternatively, the restoration replica material 6 can be removed by letting it melt.

Subsequently, the restoration is cast by letting a metal or other material in a liquid, or semi-liquid, form enter into the mould through a special channel 8. A technique that could be used during casting, in order to make the liquid or semi-liquid material reach all parts of the mould, is either rotation, generating centrifugal force, or the use of vacuum/pressure, in the same manner as is done in the Lost Wax technique.

Fig. 5 shows an alternative machining step in the method according to the invention. A restoration replica blank, preferably in wax material, used to machine the restora- tion replica 6, can be provided with a protrusion 9. The protrusion can serve as a fastening device in the CNC-machine, whereby it is engaged with a holding device in the machine, to fix the blank during machining. Subsequently, during mould preparation, the protrusion 9 can be used as a channel plug 9. When the restoration replica material is removed, e.g. by evaporation, as described above, the channel plug 9, being made out of the same material as the rest of the restoration replica 6, will be removed too. Thereby a channel is provided in the mould, which can be used for entering the restoration material into the mould during casting.

In the method described, a CAD/CAM system is used in order to let the computers do the time consuming design work, while an efficient cast process is used in order to avoid the drawbacks with machining the restoration directly.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US5452219 *29 Mar 199419 Sep 1995Dentsply Research & Development Corp.Method of making a tooth mold
Referenced by
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WO2004098443A1 *29 Apr 200418 Nov 2004Geodigm CorporationMethod and apparatus for constructing crows, bridges and implants for dental use
WO2006089717A2 *21 Feb 200631 Aug 2006Wolfgang SokallaMethod for producing metallic dental restoration elements
WO2006089717A3 *21 Feb 200630 Nov 2006Wolfgang SokallaMethod for producing metallic dental restoration elements
EP1568335A3 *24 Feb 200528 Dec 2005Cadent Ltd.Method and system for designing and producing dental prostheses and appliances
EP3130311A1 *24 Feb 200515 Feb 2017Align Technology, Inc.Method and system for designing and producing dental prostheses and appliances
US72281912 May 20035 Jun 2007Geodigm CorporationMethod and apparatus for constructing crowns, bridges and implants for dental use
US733387423 Feb 200519 Feb 2008Cadent Ltd.Method and system for designing and producing dental prostheses and appliances
US746394225 Apr 20059 Dec 2008Geodigm CorporationDental prosthesis manufacturing process, dental prosthesis pattern & dental prosthesis made thereby
US773554218 Dec 200715 Jun 2010Geodigm CorporationSupport structure for a printed model in multi-component dental appliances
US77389894 Jan 200815 Jun 2010Cadent Ltd.Method and system for designing and producing dental prostheses and appliances
US781966220 Jul 200526 Oct 2010Geodigm CorporationMulti-component dental appliances and a method for constructing the same
US787716031 Oct 200825 Jan 2011Geodigm CorporationDental prosthesis manufacturing process, dental prosthesis pattern and dental prosthesis made thereby
US79463347 Nov 200724 May 2011Geodigm CorporationSprue formers
US814534028 May 201027 Mar 2012Cadent Ltd.Method and system for designing and producing dental prostheses and appliances
US820046211 Jan 200812 Jun 2012Geodigm CorporationDental appliances
US828054230 Nov 20102 Oct 2012Geodigm CorporationDental prosthesis manufacturing process, dental prosthesis pattern and dental prosthesis made thereby
US857749317 Feb 20125 Nov 2013Align Technology, Inc.Method and system for designing and producing dental prostheses and appliances
US953907123 Oct 201310 Jan 2017Align Technology, Inc.Method and system for designing and producing dental prostheses and appliances
Classifications
International ClassificationA61C13/20, G05B19/4099, A61C13/00, G05B19/42, A61C9/00
Cooperative ClassificationA61C13/0004, G05B19/4099, G05B2219/45167, A61C13/20, G05B19/4207, G05B2219/49008, A61C9/0046, G05B2219/49007, G05B2219/37572
European ClassificationG05B19/4099, G05B19/42B2, A61C13/00C1
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