Method for fabricating a dental appliance
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention is related generally to the field of orthodontics. More particularly, the present invention is related to a method and dental appliance for incrementally moving teeth from an initial tooth arrangement to a final tooth arrangement.
Repositioning teeth for aesthetic or other reasons is accomplished conventionally by wearing what are commonly referred to as "braces." Braces comprise a variety of appliances such as brackets, archwires, ligatures, and 0-rings. Attaching the appliances to a patient's teeth is a tedious and time consuming enterprise requiring many meetings with the treating orthodontist. Consequently, conventional orthodontic trcatmcnt limits an orthodontist's paticnt capacity and makes orthodontic treatment quite expensive.
For these reasons, elastic positioners for repositioning teeth are used as an alternative to the bracket method. Such elastic positioners comprise a thin shell of elastic material that generally conforms to a patient's teeth but is slightly out of alignment with the initial tooth configuration. By properly choosing the configuration, placement of the elastic positioner over the teeth will move individual teeth to desired intermediate or final positions over time.
Methods of producing such positioners are for example described in EP 2 226 3599, according to which a positive model of the digital modified tooth arrangement is created on which the dental appliance is then produced, e.g. by deep-drawing, vacuum forming, pressure molding or compressed-air forming of a thermoplastic material.
However, most of the used materials for generating the positive models have little durability, and little thermoresistance (for they often consist of polymeric materials). This strongly affects the forming process of the dental appliance, because due to applied heat in this process the positive model may be deformed, too.
Further, using a positive model directly fabricated, e.g., by a 3D printer bears the risk that due to the used non--porous materials the forming process may suffer in such way that air inclusions may occur between the positive model and the appliance, which affect the quality of the appliance.
For these reasons, it would be desirable to provide alternative methods for generating appliance which do not suffer from the drawbacks mentioned above.
Description of the Background Art
Tooth positioners for finishing orthodontic treatment arc described by Kesling in the Am. J. Orthod. Oral. Surg. 31: 297-304 (1945) and 32: 285-293 (1946). The use of silicone positioners for the comprehensive orthodontic realignment of a patients teeth is described in Warunek et al. (1989) J. Clin. Orthod. 23: 694-700. Clear plastic retainers for finishing and maintaining tooth positions are commercially available from Raintree Essix, Inc., New Orleans, Louisiana 70125, and Tru-Tain Plastics, Rochester, Minncsota 55902. The manufacture of orthodontic positioners is described in EP 2 263 599.
SUMMARY OF THE INVENTION
The present invention provides systems, means and methods for generating dental appliance which arc useful for repositioning teeth from an initial tooth arrangement to a final tooth arrangement.
In particular, the present invention relates to a method for fabricating a dental appliance, said method comprising: * providing a digital data set representing a modified tooth arrangement for a patient * controlling a fabrication machine based on the digital data set to produce a negative model of the modified tooth arrangement which can be used as a mold; * creating a positive model of the modified tooth arrangement by casting said mold with a curable material, and * producing the dental appliance as a negative of the positive model.
In order to provide a dental appliance according to the present invention, first a negative model of the modified tooth position is generated with the help of a fabrication machine. In a preferred embodiment, the fabrication machine is at least one selected from the group of 3D printing, Stereolithography (SL or SLA), CNC (Computer Numerical Control) Milling, Selective Laser Sintering (SLS), Additive Manufacturing (AM) or RTV/Iirethane. 1-lowever, other state of the art technologies or future technologies qualifying as "computer-aided manufacturing" (CAM) or "rapid prototyping" do also fall under this definition, and arc thus encompassed by the scope of the instant invention.
Thereby a negative model of the modified tooth arrangement, or mold, is created, which can then be used for the generation of at least one positive model of the modified tooth arrangement. It is particularly preferred that the negative model, or mold, thus produced is, to a certain extent, elastically deformable. Once east with a curable material, this facilitates the removal of the latter from the negative model, or mold.
Preferably, the elastic modulus of the material forming the negative model, or mold, is in the range of? 0.01 kN mm2 and I kN mm2.
Preferred elastic modulus values are 0,01; 0,03; 0,05; 0,07; 0,09; 0,11; 0,13; 0,15; 0,17; 0,19; 0,21; 0,23; 0,25; 0,27; 0,29; 0,31; 0,33; 0,35; 0,37; 0,39; 0,41; 0,43; 0,45; 0,47; 0,49; 0,51; 0,53; 0,55; 0,57; 0,59; 0,61; 0,63; 0,65; 0,67; 0,69; 0,71; 0,73; 0,75; 0,77; 0,79; 0,81; 0,83; 0,85; 0,87; 0,89; 0,91; 0,93; 0,95; 0,97; 0,99; and/or 1 kN mm2 Preferably, the curable material which is cast into the negative model, or mold, is at least one selected from the group consisting of gypsum, synthetic resin, cold-curing synthetic resins, cross-linking two-component silicone materials on polysiloxane base.
It is particularly preferred that the curable material, when cured, is porous in such way that it is pervious to air. In such embodiment, air can escape through the positive model during the forming process of the appliance, and thus the inclusion of air (which can affect the quality of the appliance) can be avoided. Gypsum is for example material which meets these requirements.
It is furthermore preferred that the curable material, when cured, is thermoresistant, in such way that it is not affected by the forming process of the dental appliance, which often involves application of heat.
Finally, it is particularly preferred that the producing step comprises molding the appliance ovcr thc positive model thus produced. This process can, for example, deep-drawing, vacuum forming, pressure molding or compressed-air forming of a thermoplastic material.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. IA illustrates a patient's jaw and provides a general indication of how teeth may be moved by the methods and apparatus of the present invention.
Fig. lB illustrates a single tooth from Fig. 1A and defines how tooth movement distances are determined.
Fig. IC illustrates the jaw of Fig. IA together with an incremental position adjustment appliance which has been configured according to the methods of the present invention.
Fig. 2 illustrates altemative processes for producing one or a plurality of appliances according to the methods of the present invention, utilizing digital data sets representing the intermediate and final appliance designs.
DESCRIPTTON OF SPECIFIC EMBODIMENTS
The present invention provides an alternative method for fabricating a dental appliance comprising providing a first digital data set representing a modified tooth arrangement for a patient. In accordance with the present invention the term "first", "before" or "initial" arc used herein interchangeably and relates to the digitalized information of a tooth arrangement of a patient before the treatment. These digital data set can be obtained by using ultrasonic scanned images, 2D or 3D scanned images, photographs, and 2D or 3D X-rays, MRT, CT images which show the condition of the teeth and of the upper and/or lower jaw of a patient.
Of course non digital images could also be converted into a digital data set by well known techniques. The term a "second", "after" or "modified" digital data set is used herein interchangeably and relates to the digitalized information of a tooth arrangement which has be calculated to reflect a different, i.e. optimized position of the teeth which is produced from the first digital data set, where the second data set represents a negative model of the modified tooth arrangement. Suitable software and programs are well known in the art in the, e.g. EP 2 434 955, US 20120296612 or EP2165672. The contents of these references are incorporated by reference herein.
Once the initial digital data are obtained, the can be used for simulations of the teeth. In these simulations, the teeth of the patient are preferably represented as individual tooth models that are moveable relative to each other. The clinician is provided by the used software with tools to manipulate their position for diagnostic and treatment-planning purposes. Moreover, the tools provide the user the ability to simulate changes in the position or shape of the jaw, tooth or teeth, and the movement of such structures and the skull movement, and to visually observe the effect of such simulated changes on the patient's face and smile. This provides for tools for study of proposed treatments for the patient. Similarly, the patient's desired feature and smile can be simulated on the user interface, and from that desired feature and smile it is possible to automatically back solve for the required jaw, and/or tooth movements or changes needed to provide that desired result, simply by comparing "before" and "after" positions of the jaw, tooth and/or skull positions.
In one possible example, the three-dimensional jaw model obtained from the intra-oral scan, 3D data from CT scan, and/or 2 dimensional X-rays to create a virtual patient tooth arrangement model and displayed on the workstation user interface. The workstation exhibit in one possible example a computing platform having a graphical user interface, a processor and a computer storage medium containing digitized records pertaining to a patient including image data (3D image data and/or 2D image data). The workstation further includes a set of software instructions providing graphical user interface tools by which the user can create a proposed treatment plan (proposed position of the teeth at the end of treatment) in three dimensions. To facilitate such modeling and simulations, teeth may be modeled as independent, individually moveable three dimensional virtual objects, using the techniques described in the above-referenced OraMetrix published PCT application, WO 01/8076 or for ifirther guidance US 20040197727 Al. Thus, a skilled person is provided with tools for simulating movement or repositioning of craniofaeial structures of the virtual patient, and the computer animates such movement or repositioning and shows the effect of such movement or repositioning on the external visual appearance of the patient.
In particular, the present invention relates to a method for fabricating a dental appliance, said method comprising: providing a digital data set representing a modified tooth arrangement for a patient; controlling a fabrication machine based on the digital data set to produce a negative model of the modified tooth arrangement which can be used as a mold; creating a positive model of the modified tooth arrangement by casting said mold with a curable material, and producing the dental appliance as a negative of the positive model.
In one aspect, methods according to the present invention provide for fabricating one and/or a plurality of dental incremental position adjustment appliances. Said methods comprise providing an initial or first digital data set, a final or modified digital data set, and producing a plurality of successive digital data sets representing the target successive tooth arrangements, generally as just described.
The dental appliances are then fabricated based on at least some of the digital data sets representing the successive tooth arrangements, the final data sets, i.e. the treatment plan calculated with the software described above. Preferably, the fabricating step comprises controlling a fabrication machine based on the successive digital data sets or modified data set to produce one or successive (physical) negative models of the desired tooth arrangements.
Subsequently one or more positive models made of different materials are produced. The dental appliances are then produced as negatives of the positive models using conventional positive pressure or vacuum fabrication techniques.
One advantages of the present invention is the provision of method, wherein contrary to most methods for fabricating dental appliances first a negative model is manufactured by 3D printing. Thereby, a high precision negative model can be generated, which can be used for generating more than one positive models which are used for the generation of a dental appliance. It is well-known that during the fabrication of dental application the positive model gets damaged or destroyed and thus cannot be reused. Hence, a further cost-expensive positive model must be fabricated for the patient files or in case the old appliance gets lost or broken. Generating first a negative model avoids these problems, since a plurality of positive models can be generated from one single negative model.
Based on this negative model, which can be used as a mold, a positive model is provided which is preferably made of a porous material, thus allowing a fast, cost-effective fabrication of the dental appliance with pressure or vacuum fabrication techniques.
Usually, 3D printing is used for the generation of the physical positive model. However, materials in 3D printers result in non-porous models, for which reason air during the pressure or vacuum fabrication cannot escape. This leads to the inclsuon of air in the process, and thus the generated dental appliances may have suboptimal fit.
As an alternative, instead of using a porous material such as plaster, or gypsum, the positive model can have little holes on its back, i.e. the flat site, through which air can escape during the molding process.
Once the intermediate and final data sets have been created, the modified data set representing a negative model can be calculated. Based on these digital negative model the physical negative model may be fabricated. Preferably, fabrication methods will employ a rapid prototyping device such as a stereolithography machine. The rapid prototyping machine 200 will selectively harden a liquid or other non-hardened resin into a three-dimensional structure which can be separated from the remaining non-hardened resin, washed, and used as a mold for producing the positive model. The prototyping machine 200 will receive the individual digital data sets and produce one structure corresponding to each of the desired negative models. Other fabrication machines which could be utilized in the methods of the present invention include tooling machines and wax deposition machines.
In a preferred embodiment, the fabrication machine is at least one selected from the group of 3D printing, Stereolithography (SL or SLA), CNC (Computer Numerical Control), Selective Laser Sintering (SLS), Additive Manufacturing (AIVI) or RTV/Urethane.
Stereolithography is an additive manufacturing process which employs a vat of liquid ultraviolet curable photopolymer "resin" and an ultraviolet laser to build parts' layers one at a time. Under the term Rapid Prototyping different 3D printing techniques such as SLA, a powerful additive manufacturing method that can jet one or multiple materials in a single print run. This means that you can selectively position multiple materials in one printed prototype and even combine two materials to create composite digital materials with distinct, predictable material properties.
For further reading regarding suitable polymeric resins see Osswald, Tim A.; Menges, Georg (2003). Materials science of polymers for engineers. Flanser Verlag. pp. 334-335. ISBN 978- 1-56990-348-3 or Glockncr, Patrick (2009). Radiation Curing. Vinccntz Network. pp. 11-16.
ISBN 978-3-86630-907-4.
RTV/tirethane, also known as Direct Digital Manufacturing, or any fabrication machine which is capable of generating a physical model using computer programs such as CAD/CAM. Various materials can be used which arc well known to the person skilled in the art.
RTVRircthanc castings arc made from a wide varicty of simulated engineered plastics including ABS-like, PE-like, elastomers, PP-like, glass-filled, high strength, transparent, and high temp. A silicone RTV mold is made from an SLA master pattern. After curing, the mold is cut, separated, and the SLA pattern is removed. The RTV mold is reassembled and urethane resin is poured into the mold. After curing in a vacuum chamber, the mold is disassembled and the completed part is removed.
A wide variety of engineered plastics and metals can be used in Computer Numerical Control (CNC). A subtractive manufacturing process, CNC provides flexible, versatile, and precise control over advanced high-speed machining centers using a variety of machine tools to mill plastics or metals into parts representing the original CAD design. CNC machines are for example distributed by Scicon Technologies Valcncia, California US.
SLS technology directs a focused CO2 laser beam on to a bed of thermoplastic powder sintering (fusing together) thin two-dimensional cross-sections layer-upon-layer producing a solid engineered-plastic or metal part.
SLA technology directs a focused UV (ultra-violet) laser beam on to a basin of liquid resin solidifying and curing thin two-dimensional cross-sections layer-upon-layer producing a solid part. The part is created in layers from the bottom up, each layer only thousandths of an inch thick. The result is a precise physical replication of the CAD model. Various materials can be used such as tough, flexible nylon, strong, stiff nyloniglass composite, or other such as steels.
Thereby a negative model is created, preferably which is also very durably in order to be used for the generation of at least one positive model.
Hence, in accordance with the present invention, this negative model is used as a mold in order to produce the positive model.
In accordancc with thc prcscnt invcntion any synthctic rcsin can be uscd. Gypsum is the dihydrate form of calciunisulfate, CaSO42H2O, found in a compact mass in nature. Dental gypsum products are manufactured by driving off part of the water of the calcium sulfated ihydrate to form calcium sulfate hemihydrate. This process is referred to as calcination. When calcium sulfate hemihydratc (dental plaster, stone, etc.) is mixed with water, the reverse reaction takes place, and the hemihydrate is converted back to the dihydrate. The gypsum components of these materials are identical chemically; differences in these materials is attributed to calcination Dental StoncType Ill -dental stone (diagnostic casts) Type IV -high strength dental stone (working models) Type V -high-strength, high-expansion dental stone.
Also polymerizable resins such as described in US US4288472 etc. can be used. Suitable materials for the production of working casts are, in particular, the various grades of gypsum, such as plaster of Paris or special plaster of Paris; however, synthetic resins, cements or low-melting dental alloys may also be used to advantage. Any molding material is suited which is adapted to adsorb the first catalyst on its surface without reacting with it. The adhesion of the first catalyst to the working cast may be improved by the addition of a bonding agent to the catalyst solution.
In dentistry, so-called redox systems are employed for the polymerization of cold-curing synthetic resins. The polymerization catalysts used arc mainly organic peroxides. Rapid decomposition of the peroxide is brought about by the use of a second catalyst, the activator, which results in the formation of free radicals which initiate the polymerization. The most common peroxide catalysts are benzoylperoxide, 2,4-dichlorobenzoyl peroxide, 4-ch lorobenzoyl peroxide, lauroylpcroxidc, 6-butyl peroxide, methyl cthylkctone peroxide and cyclohexanone peroxide. Other catalysts consist of a combination of peroxide, a sulfinicacid or sulfinicacid derivative, and traces of copper salts. These catalysts are preferably used in amounts of not more than about 20 weight percent. The preferred range is 10 to 20 weight percent, and more particularly 1 to 10 weight percent, based on the weight of the particular vehicle (solvent or dispersant). In accordance with the present invention, the curable material is at least one selected from the group consisting of gypsum, synthetic resin, cold-curing synthetic resins, cross-linking two-component silicone materials on polysiloxane base.
In one embodiment the present invention relates to a method as outlined above, wherein the negative model consists of a thermoplastic material_Thermoplastic materials arc those that take the hardened form of plastic when cool but arc converted to liquid when heated. This proccss of heating and melting can usually be completed many timcs. Each timc, a new shape or form is possible. Materials that fall into this category include polystyrene, polyvinylchloride, and ethylene-vinyl acetate.
Polystyrene is a material produced from an oily liquid that tends to have a distinct odor. When in its hardened form, polystyrene is generally colorless. A good example of the substance in this state is a CD case. Color is often added to make other items such as plastic cups, DVD cases, and razors. Polystyrene is also used to make foam products such as plates, egg cartons, and packing insulation.
Polyvinyl chloride (PVC) is one of the most common thermoplastic materials Chlorine is an important component in its production. It is usually produced in sheets that are later formed into a wide range of products. Additives known as plasticizers arc used to make PVC more pliable and flexible. It is used to make hoses, pipes, and inflatable toys.
Ethylenevinylacetate (EVA) is a material composed of ethylene, a mass produced chemical compound, and vinyl acetate, a colorless liquid. When hereto substances are combined, a flexible material is made that can easily be formed into a number of products. EVA is used in plastic wraps to make medical gloves and coverings for electrical wires.
Polyurethanes are thermoplastic materials who se characteristics can vary greatly. It can be very elastic and it can also be very tough. Rubber products are often replaced by those made of polyurethane because this matcrial is more resistant to oils, greases, and to tearing. This material can also be used to produce foam, which is often used inside of seats. Other it ems made of polyurethane include gaskets, belts, and surf boards.
Liquid crystal polymcrs (LPC5) arc considered a special class of polyesters. These material shave a strong ability to resist chemical and heat damage. In the liquid form, these thermoplastic material scan produce the liquid crystal displays (LCD5) found in clocks and other electronics. In the hardened form, LPCs are used for the production of printer parts, electrical parts, and cooking wares.
Polycarbonate is a material that is generally light weight but strong. It is considered more environmentally friendly than many other thermoplastic materials. Polycarbonate also tends to have exceptional optical properties, which makes it popular in the production of eyeglasses.
This material is also used to make bullet proof glass, DYDs, and bottles.
In accordance with the present invention, the inventors of the present invention surprisingly found out, that when contrary to the state of the art techniques, a negative model instead of a positive model is fabricated made of an elastic material, various positive models can be generated made of any material, also of those materials which are not suitable for CAM technologies. Thus, positive models can be generated which arc more stable than conventionally positive models generated by CAM technologies. Due to the elastic material the negative model can be easy removed once any suitable resin is poured into the negative model in order to form the positive model. The negative model does not have to be elastic the whole time, also materials which are elastic merely under specific circumstances such as a certain pH, temperature, presence of a certain catalysator.
Based on the negative fabricated model a positive model of the modified tooth arrangement can be generated by casting said mold with a curable material made of a more porous material which allows fabricating a dental appliance by pressure molding techniques.
It is particularly preferred in accordance with the present invention that the producing step comprises molding the appliance over the positive model. Molding the appliance can be generated according to well-known techniques. RTV/Urethane.
The method for fabricating a removable incremental tooth position adjustment appliance is provided by forming a shell of at least one layer of a polymeric material with a teeth mold.
The shell is formed with cavities shaped to receive and resiliently reposition teeth from one arrangcment to a succcssive arrangemcnt. Thc shcll transforms from a first state, whcre the appliance is held onto the teeth, to a secoild state, where the appliance may be released from the teeth. Preferably, at least four geometries will be determined in the outset, often at least ten geometries, frequently at least twenty-five geometries, and sometimes forty or more geometries. Usually, the tooth positions defined by the cavities in each successive geometry differ from those defined by the prior geometry by no more than 2 nim, preferably no more than 1 mm, and often no more than 0.5 mm, as defined above.
Each individual appliance will be configured so that its tooth-rccciving cavity has a geometry corresponding to an intermediate or end tooth arrangement intended for that appliallce. That is, when an appliance is first worn by the patient, certain of the teeth will be misaligned relative to an undeformed geometry of the appliance cavity. The appliance, however, is sufficicntly resilicnt to accommodate or conform to the misaligncd teeth, and will apply sufficient resilient force against such misaligned teeth in order to reposition the teeth to the intermcdiatc or end arrangcmcnt desired for that treatmcnt step.
These appliances can be made by using foils such as DURAN® foil (0.5, 0.625, 0.75 mm) or any suitable foils well known by the skilled person.
Modern thermofbrrning machines are bsica1Iy categorized as either pressure systems or the rapid vacuum designs, both of which producc good results. Pressure machines operate from an external compressed air suppLy at pressures of up to 5 atmospheres. These machines are renowned. for having the advantage of very high thermoforming power but require more attention io rnodd quality and bocking out procedures. a dean compressed air supi1y and because the thermoforming operation takes place in a dosed chamber, the model is not accessibk during the forming process. The newer type rapid vacuum machines have become increasingly popular in both labs and the dental practiccs Thcy operate y creating a vacuum in an internal reservolr using a seft'contained nump. When the heated foil is placed over the model, the vacuum charrther is automatically released, pulling the fbii rapidly down overthe modeL it is this rapid forming action that allows the creation of the detail and fit which is chnically equva1ent to prcssurc forming. Ibis differentiates the ncwcr Referring now to Fig. IA, a representative jaw 100 includes sixteen teeth 102. The present invention is intended to move at least some of these teeth from an initial tooth arrangement to a final tooth arrangement. To understand how the teeth may be moved, an arbitrary centerline (CL) is drawn through one of the teeth 102. With reference to this centerline (CL), the teeth may be moved in the orthogonal directions represented by axes 104, 106, and 108 (where 104 is the centerline). The centerline may be rotated about the axis 108 (root angulation) and 104 (torque) as indicated by arrows 110 and 112, respectively. Additionally, the tooth may be rotated about the centerline, as represented by arrow 114. Thus, all possible free-form motions of the tooth can be performed. Referring now to Fig. I B, the magnitude of any tooth movement achieved by the methods and devices of the present invention will be defined in terms of the maximum linear translation of any point P on a tooth 102. Each point Pi will undergo a cumulative translation as that tooth is moved in any of the orthogonal or rotational directions defined in Fig. IA. That is, while the point will usually follow a non-linear path, there will be a linear distance between any point in the tooth when determined at any two times during the treatment. Thus, an arbitrary point P1 may in fact undergo a true side-to-side translation as indicated by arrow dl, while a second arbitrary point P2 may travel along an arcuate path, resulting in a final translation d2. Many aspects of the present invention are defined in terms of the maximum permissible movement of a point Pi induced by the methods in any particular tooth. Such maximum tooth movement, in turn, is defined as the maximum linear translation of that point Pi on the tooth which undergoes the maximum movement for that tooth in any treatment step.
The appliances arc intended to effect incremental repositioning of individual tccth in the jaw as described generally above. In a broadest sense, the methods of the present invention can employ any of the known positioners, retainers, or other removable appliances which are known for finishing and maintaining teeth positions in connection with conventional orthodontic treatment. The polymeric appliance 100 of Fig. IC is preferably formed from a thin sheet of a suitable elastomeric polymeric, such as Tru-Tain 0.03 in thermal forming dental material, Tru-Tain Plastics, Rochester, Minnesota 55902. Usually, no wires or other means will be provided for holding the appliance in place over the teeth. In some cases, however, it will be desirable or necessary to provide individual anchors on teeth with corresponding receptacles or apertures in the appliance 100 so that the appliance can apply an upward force on the tooth which would not be possible in the absence of such an anchor.
Specific methods for producing the appliances 100 are described hereinafter.
Methods for digitizing such conventional images to produce data sets useful in the present invention are well known and described in the patent and medical literature. Usually, however, the present invention will rely on first obtaining a plaster cast of the patient's teeth by well known techniques, such as those described in Graber, Orthodontics: Principle and Practice, Second Edition, Saunders, Philadelphia, 1969, pp. 401-415.
In a preferred embodiment, a wax bite is also obtained from a patient. The wax bite enables scanning of the relative positions of the upper and lower dentition in centric occlusion. This is usually accomplished by fir st placing the lower cast in front of the scanner, with the teeth facing upwards, then placing the wax bite on top of the lower cast, and finally by placing the upper cast on top of the lower cast, with the teeth downwards, resting on the wax bite. A cylindrical scan is then acquired for the lower and upper casts in their relative positions. The scanned data provides a digital model of medium resolution representing an object which is the combination of the patient's arches positioned in the same relative configuration as in the mouth.
The digital model acts as a template guiding the placement of the two individual digital models (one per arch). More precisely, using software, for example the CyberWare alignment software, each digital arch is in turn aligned to the pair scan. The individual models are then positioned relative to each other corresponding to the arches in the patient's mouth.
Referring again to Fig. 2, after the initial digital data set UDDS) has been obtained, the digital information will be introduced to the computer or other workstation for manipulation. In the preferred approach, individual teeth and other components will be "cut" to permit their individual repositioning or removal from the digital data. After thus "freeing" the components, the user will often follow a prescription or other written specification provided by the treating professional. Alternatively, the user may reposition them based on the visual appearance or using rules and algorithms programmed into the computer. Once the user is satisfied with the final arrangement, the fmal tooth arrangement is incorporated into a final digital data set (FDDS).
Based on both the IDDS and the FDDS, a plurality of intermediate digital data sets (INTDDS's) are generated to correspond to successive intermediate tooth arrangements. The system of incremental position adjustment appliances can then be fabricated based on the INTDDS's, as described in more detail below.
Once the teeth have been separated, the FDDS can be created from the IDDS. The FDDS is created by following the orthodontists prescription, moving the teeth into their final prescription. In one embodiment, the prescription is entered into a computer, which algorithmically computes the final position of the teeth. In alternate embodiments, a user may move the teeth into their final positions by independently manipulating one or more teeth while satisfying the constraints of the prescription. It should be appreciated that various combinations of the above described techniques may also be used to arrive at the final teeth position.
In the manufacturing process, which relies on generation of positive models to produce the repositioning appliance, adding a wax patch to the graphic model will generate a positive mold that has the same added wax patch geometry. Because the mold is a positive of the teeth and the appliance is a negative of the teeth, when the appliance is formed over the positive model, the appliance will also form around the wax patch that has been added to the mold.
When placed in the patient's mouth, the appliance will thus allow for a space between the inner cavity surface of the appliance and the patient's teeth or gums. Additionally, the wax patch may be used to form a recess or aperture within the appliance which engages an anchor placed on the teeth in order to move the tooth in directions which could not otherwise be accomplished.
In addition to such wax patches, an individual component, usually a tooth, can be scaled to a smaller or larger size which will result in a manufactured appliance having a tighter or looser fit, respectively.
After the positive models are prepared, a conventional pressure or vacuum molding machine may be used to produce the appliances from a more suitable material, such as 0.03 inch thermal forming dental material, available from Tru-Tain Plastics, Rochester, Minnesota 55902. Suitable pressure molding equipment is available under the tradename BIOSTAR from Great Lakes Orthodontics, Ltd., Tonawanda, New York 14150. The molding machine 250 produces each of the appliances directly from the positive tooth model and the desired material. Suitable vacuum molding machines are available from RaintreeEssix, Inc.