DENTAL MODELS AND METHODS OF FIXTURING THE SAME

Abstract: A dental model includes a quantity of mold material having portions that represent oral structure, as well as a holder in contact with the mold material. The holder has a textured surface for secure connection with the mold material, and preferably is embedded in the mold material as the mold material is hardened. The dental model is especially suitable for use with computer-aided milling systems, since the holder provides for convenient releasable connection to a fixture during the time that a scanner or other device collects data representing the oral structures of interest.

Description: DENTAL MODELS AND METHODS OF FIXTURING THE SAME Background of the Invention 1. Field of the Invention This invention relates to replicas of oral structures that are used in the course of dental treatment, such as models of a patient's teeth and/or gingival tissue. This invention also relates to methods of holding such replicas as may be useful for other operations such as scanning to obtain a set of electronic data of the replica, use as study models or use in articulators. Description of the Related Art Dental models are widely used for a variety of purposes during the course of dental treatment. As one example, a dentist or prosthodontist may desire to have a model of an area of a patient's oral cavity where one or more teeth are missing or damaged. In that instance, suitable replacement teeth may be made in the laboratory using the model as a guide. As another example, dental practitioners often use models of a patient's teeth to study malformations or malpositions of the teeth and jaws and plan a course of treatment. Sometimes, models of the patient's entire upper and lower dental arch are mounted on a device known as an articulator. The articulator includes a hinged coupling that enables the models of the arches to swing toward and away from each other in a manner that mimics the opening and closing of the patient's jaws. The practitioner can use the articulator to study the opening and closing movements of the patient's jaws from various angles of view in order to better diagnose any problems and plan an appropriate course of treatment. As can be appreciated, use of dental models represents a significant convenience for both the practitioner and the patients. When the model is used to construct restorations such as a dental crown, the trial and error fitting procedure can be carried out in the dental laboratory as long as necessary until a proper size and shape is attained. Consequently, the amount of time that the patient must occupy the dental chair in the operatory is reduced. When dental models are used for purposes of study, the practitioner is able to take as much time as needed to complete the diagnosis and plan an appropriate course of treatment, again without the necessity of keeping the patient in the dental chair. When desired, the models can also be used for educating the patient and explaining various treatment options. Additionally, the models can serve as a permanent record of the patient's oral structures at a particular point in time. Recently, there has been increased interest in the use of dental models for preparation of dental prosthetics using computer automated systems. For example, some systems scan dental models to collect a set of electronic data that is representative of the patient's tooth structure of interest. The data set is then used during the operation of an automated mechanical milling machine (such as a computer-aided milling machine) to fabricate a prosthetic that, when completed, closely matches the shape of natural tooth structure. Examples of computer-aided milling machines used in the field of dentistry include the CEREC 2™, CEREC 3™ and CERECSCAN™ systems available from Sirona Dental Systems of Bensheim, Germany, the VITA CELAY™ machine from Vita Zahnfabrik of Bad Sackingen, Germany, PRO-SCAN™ from Cad-Cam Ventures Incorporated, of Dallas, Texas and PROCERA™ ALLCERAM™ from Nobel Biocare USA of Westmont, Illinois. U.S. Patent Nos. 4,837,732, 4,776,704 and 4,575,805, as well as PCT Patent Application No. WO 96/37163 also disclose systems for making dental prosthetics using computer-aided milling machines. One known method of using dental models with computer-aided milling systems involves placing a plate in contact with mold material for making the model before the mold material has hardened. The plate has dovetail-shaped grooves that couple the resulting model to the plate. The plate is then clamped to a fixture while a scanner traverses the model to collect the electronic data. Other known methods of fixturing dental models include the use of pins that are set into the mold material before the mold material hardens. The pins project outwardly from the resultant model to provide a handle for holding the models during a scanning operation. Clamps or other structures are used to couple the pins to a fixture during the scanning operation. The use of grooved plates and pins in the procedures mentioned above is somewhat unsatisfactory since the plates or pins must be removed from the model and cleaned before subsequent reuse. However, the mold material used to make the model may be difficult to remove from the plates and pins. In some instances, portions of the model that bear the replica surfaces of the patient's oral structures may be damaged when an effort is made to remove the pins or plate such that the model can no longer serve as a record of the patient's oral structures. Additionally, the practitioner's choice of mold material for the model is somewhat restricted when a grooved plate is employed. For example, plates having dovetail-shaped grooves may necessitate the use of a mold material having a rubbery consistency when cured, so that the plate can be detached from the model. However, such mold materials may not be preferred for other reasons such as permanency or resolution. For example, some practitioners prefer to use epoxy-type mold material that cures to a relatively hard mass. Unfortunately, epoxy-type mold material may be deemed too difficult to be removed from the plate with a reasonable amount of effort. Accordingly, there remains a need in the art for new dental models and methods of fixturing dental models that enable the practitioner to use essentially any mold material as desired. Moreover, there is a need to improve existing methods and models in order to reduce the time and effort associated with the dental procedure of interest, so that a cost savings can be realized. Summary of the Invention The present invention is directed toward a dental model and related methods that involve the use of a holder having a textured surface. The textured surface is in contact with the mold material as the mold material hardens. The holder is then used to connect the resulting model to a fixture such as a scanner support, a study table, workbench or an articulator. In more detail, the present invention in one aspect relates to a dental model that comprises a quantity of mold material having an exterior surface. At least a portion of the exterior surface represents oral structure. The dental model also includes a holder having a textured surface. The textured surface is in contact with the mold material. In another aspect, the present invention is directed toward a method of preparing a dental model that comprises the acts of making an impression of oral structure, and placing a quantity of hardenable mold material in the impression. The method also includes the acts of engaging a textured surface of a holder with the mold material before the mold material has hardened, and allowing the mold material to harden and thereby securely couple the holder to the resulting model. Another aspect of the present invention is directed toward a method of connecting a dental model to a fixture. The method comprises the acts of making an impression of oral structure, and placing a quantity of hardenable mold material in the impression. This method also includes the acts of engaging a textured surface of a holder with mold material before the mold material has hardened, and allowing the mold material to harden while the mold material is in engagement with the textured surface of the holder. The method also includes the act of coupling the holder to the fixture. The present invention is also directed to a method of making a negative dental model. This method comprises the acts of placing a holder in contact with a quantity of impression material, and placing the impression material in an impression tray. The method also includes the acts of placing the impression material in contact with oral structure, and allowing the impression material to at least partially harden in the impression tray while the holder is in contact with the oral structure. Additionally, the present invention is directed toward a dental kit. The kit includes a container, a holder having a textured surface in the container and a dental material in the container. Preferably, the holder is made of an inexpensive material that can be disposed of after a single use. As such, the practitioner need not attempt to disengage the holder and/or clean the holder after, for example, a scanning procedure. The holder has structure opposite the textured surface that preferably is especially adapted for quick coupling or uncoupling to the fixture. Further aspects of the invention are defined in the features of the claims. Brief Description of the Drawings Fig. 1 is a side elevational view of a dental model according to the present invention; Fig. 2 is an enlarged end cross-sectional view of the dental model shown in Fig. 1, looking in a direction along its longitudinal axis; Fig. 3 is a reduced schematic illustration showing one example of use of the model illustrated in Figs. 1-2; and Fig. 4 is an end elevational view of a holder of a dental model according to another embodiment of the invention. Detailed Description of the Preferred Embodiments A dental model according to one embodiment of the invention is illustrated in Figs. 1 and 2 and is broadly designated by the numeral 10. The dental model 10 includes a quantity of mold material 12. The mold material 12 includes replica tooth portions 14 having exterior surfaces that match the size and shape of tooth structure, as well as replica gingival portions 16 having exterior surfaces that match the size and shape of gingival tissue. The model 10 that is shown in Fig. 1 has a generally straight elongated configuration with only three tooth portions 14. However, it should be understood that other constructions are also possible, including models having only a single tooth or a portion of a tooth. As another alternative, the model 10 may have a generally, overall "U"-shaped configuration in plan view with a sufficient number of tooth portions 14 to represent all of the teeth in a patient's dental arch, or an overall, generally "J"-shaped configuration with a sufficient number of tooth portions 14 to represent one-half of a patient's dental arch (also known as a quadrant). Models having other quantities of teeth are also possible. The mold material 12 can be any hardenable material that is useful for making a dental model. Examples of suitable materials include gypsum, acrylate-based and methacrylate-based resins and composites, epoxy-based resins and composites, phosphate- bound refractory materials and silicones. Preferably, the mold material 12 has a relatively short hardening time and begins to cure once components of the material are mixed together. Alternatively, the mold material 12 is made of a material that can be hardened upon command (for example, by the use of a curing light that initiates a photopolymerization reaction in the mold material 12). The dental model 10 also includes a holder 18. In the embodiment shown in the drawings, the holder 18 has an elongated shape with a rectangular configuration in plan view, although other shapes are also possible. For example, the holder 18 could have a square, circular or oval configuration in plan view, which might be especially suitable for use with a model having only a single tooth portion. As another alternative, the holder 18 may have an overall, generally "U"-shaped configuration or an overall, generally "J"- shaped configuration in plan view to match the shape of a model having sufficient tooth portions to represent an entire dental arch or a quadrant respectively. Preferably, the holder 18 has a somewhat planar configuration with two sides. One side (i.e., a first side) of the holder 18 has a textured surface 20 that is embedded in the mold material 18. Preferably, the textured surface 20 is in contact with the mold material 12 before the mold material 12 has hardened, and remains in contact with the mold material 12 as the latter hardens so that the holder 18 is ultimately securely connected to the mold material 12. The textured surface 20 may have a variety of shapes and/or be constructed according to any one of a variety of methods. As used herein, a "textured surface" means a surface having a fibrous, grainy and/or dimensional quality. The textured surface preferably has at least 3 more preferably at least 12 and most preferably at least 20 projections or pores per square centimeter. For example, the textured surface 20 may have a number of projections in the form of small fibers, filaments, threads or strands that project outwardly and into the mold material 12. The fibers, filaments, threads or strands may have loose ends or alternatively be connected to one another, similar to melt-blown fabrics. As another alternative, the textured surface 20 may include projections having geometric shapes in cross-section other than cylindrical or fiber-shaped. Examples of suitable shapes include cones, truncated cones, square rods, pyramids, truncated pyramids, cubes, gum drops, cylinders, nail heads or mushroomed-shaped heads. Outer ends of the projections may be flat, rounded, pointed or have other shapes as desired. In the example shown in the drawings, the textured surface 20 comprises a number of mushroom-shaped projections. As another option, the textured surface has a number of pores such as cells, or recesses. The pores may be separated and spaced from each other in non-communicating relationship. Alternatively, the pores may be in communication with each other, either in a reference plane extending along the outermost portion of the textured surface 20, or in one or more reference planes extending below such outermost portion, or in any combination of such planes. The textured surface 20 may be a micro-replicated surface if desired. Examples of micro-replicated surfaces and methods of manufacturing such surfaces are disclosed in U.S. Patent Nos. 5,152,917 and 5,500,273. As another option, the textured surface 20 has a roughened or granular configuration. For example, the textured surface 20 may comprise a number of particles that project outwardly from a middle portion or backing layer. Preferably, the textured surface 20 includes a number of undercut regions. The holder 18 also has a second side with an exterior surface 22 that is opposite the textured surface 20. The exterior surface 22 includes structure for securely connecting the model 10 to a fixture. Preferably, but not necessarily, the exterior surface 22 has structure for releasable connection to such fixture. The fixture may serve as a support for the model 10 for use in any one or more of a variety of operations. A number of constructions for the exterior surface 22 are possible. As one example, the exterior surface 22 may include an adhesive such as a pressure sensitive adhesive. Optionally, the adhesive may be a high-strength removable adhesive, such as "COMMAND" brand adhesive from 3M. Preferably, a release liner initially extends over the adhesive to protect the adhesive from contamination and wear before use. As another option, the exterior surface 22 may include mechanical fastener structure that is releasably connected to the fixture. Examples of suitable mechanical fasteners include one component of a hook and loop fastener such as "VELCRO" brand mechanical fastener form DuPont and "SCOTCH-MATE" brand or "DUAL-LOCK" brand mechanical fastener from 3M. Another suitable mechanical fastener structure is "HOOKIT" brand fastener from 3M. Optionally, the exterior surface 22 may be an array of upstanding, headed stems or other projections. As another alternative, the exterior surface 22 may include magnetic structure for releasable connection to the fixture. The magnetic structure may be a permanent magnet or made of an alloy that is attracted to a permanent magnet or an electromagnet. Optionally, the magnetic structure is flexible and can assume a non-planar configuration if desired. An example of a suitable holder 18 is the "SCOTCH-MATE" brand hook and loop reclosable fastener from 3M that includes a layer of pressure sensitive adhesive that is initially covered by a release liner. In that instance, the hook or loop component is embedded in the mold material 12, while the pressure sensitive adhesive faces outwardly and represents the exterior surface 20. Moreover, in that instance, the hook or loop component is integrally connected to a backing layer that also provides a surface for receiving the layer of the pressure sensitive adhesive. The dental model 10 may be made according to any one of a number of techniques. For example, to obtain a positive dental model, an impression of desired areas of the patient's oral cavity is first obtained. To prepare an impression, a quantity of curable dental impression material is placed in an impression tray, and the tray is then positioned in the patient's oral cavity such that the impression material fills and surrounds the selected area of interest. Once the impression material has cured or at least partially cured, the impression material along with the tray is removed from the oral cavity. To make the dental model 10 from the impression described above, the mold material 12 is poured or otherwise placed in the recesses of the cured impression material. Next, the holder 18 is brought into contact with the mold material 12 such that the textured surface 20 is in engagement with the mold material 12 before the mold material 12 has hardened. Once the mold material 12 has hardened, the impression material is removed from the resulting model 10. When made properly, the tooth portions 14 and gingival portions 16 provide an accurate physical replica of corresponding tooth portions and gingival portions of the patient's oral cavity. A variety of dental impression materials are commercially available and may be used in accordance with the methods of the present invention. Elastomeric impression materials are generally preferred because the flexibility of the elastomeric material when cured enables the material to be readily removed from the oral cavity even when undercut areas, recesses and the like are present in the tooth structure. However, non-elastomeric impression material (such as plaster of Paris) may also be used to a limited extent. Elastomeric dental impression materials are often considered to fall in one of five major classes: reversible hydrocolloids, irreversible hydrocolloids, polysulfides, silicones and polyethers, of which the last four are thermosetting. An example of an irreversible hydrocolloid impression material is "UNLTEL-2" brand alginate impression material from 3M Unitek Corporation. An example of a silicone dental impression material is "EXPRESS" brand impression material from 3M Company. The mold material 12 is allowed to harden while the textured surface 20 is in contact with the mold material 12. Optionally, the mold material 12 includes a photoinitiator so that a curing light may be used to harden the material. As another option, the mold material 12 self-hardens over a period of time, and begins to harden when exposed to the atmosphere or when two components of the mold material are initially mixed together. If desired, the holder 18 may be temporarily coupled to a support to retain the holder 18 in a precise location or orientation relative to the tooth portions 14 as the mold material 12 hardens. Once the mold material 12 is hardened, the textured surface 20 provides a secure connection between the holder 18 and the mold material 12. The holder 18 then serves as a convenient gripping structure for holding the model 10 during a subsequent operation as desired. Preferably, the exterior surface 22 has one or more of the coupling features described above in order to releasably couple the model 10 to the fixture or other support. Fig. 3 is an illustration of one example of use of the dental model 10. In Fig. 3, the exterior surface 22 of the holder 18 is provided with a layer of adhesive. The adhesive layer is brought into contact with a support 24 of a fixture 26. Consequently, the holder 18 serves to securely couple the dental model 10 to the fixture 26. As electronic data set is then collected from the model 10. In the example shown in Fig. 3, a laser scanner 28 is brought into proximity with the dental model 10 in order to collect electronic data regarding the spatial characteristics of the tooth portions 14 and the gingival portions 16. As the data set is collected, the dental model 10 and the laser scanner 28 are relatively moved so that all of the surfaces of interest of the tooth portions 14 and the gingival portions 16 are scanned. For example, the scanner 28 may be held stationary while the fixture 26 moves along a path to enable the laser beam to scan the entire areas of interest. Alternatively, the fixture 26 is held stationary while the laser scanner 28 moves about the dental model 10. As yet another option, both the laser scanner 28 and the fixture 26 are moved during collection of the data set. Other methods of collecting electronic data includes mechanical profilometry, optical imaging (e.g., a camera) and other types of scanning procedures. Once the scanning operation has been completed, the dental model 10 is removed from the support 24. Advantageously, the holder 18 need not be removed from the mold material 12 for reuse. Instead, the holder 18 is made of an inexpensive material that can be disposed of with the mold material 12 when desired. Fig. 4 is an illustration of an alternative holder 18a that can be optionally used in place of the holder 18 described above. The holder 18a has a backing 19a with a textured surface 20a. The textured surface 20a may have any one or more of the aspects describe above in connection with the textured surface 20. In the embodiment shown, the textured surface 20a includes a number of mushroom-shaped projections, although other shapes are also possible. The holder 18a also has a protrusion 21a that is connected to the backing 19a. The protrusion 21a extends away from the textured surface 20a and has a shape that is adapted to fit into coupling structure of a fixture (not shown). For example, the protrusion 21a could have a threaded portion that is complemental in configuration to a mating, threaded portion of the fixture. As another option, the protrusion could be received in a mating recess of a fixture that includes a clamp for securing the holder 18a to the fixture. In that instance, the protrusion 21a may have a cylindrical, conical, rectangular or any other shape as needed. Preferably, but not necessarily, the holder 18a is integrally made of an inexpensive synthetic resinous material. An example of a suitable synthetic resinous material is polyethylene or polycarbonate. Preferably, the backing 19a is integrally connected to the protrusion 21a as well as to the exterior surface 18a. The model 10 as set out above for exemplary purposes has been described as a positive representation of the oral structure of interest. However, the model 10 alternatively may be a negative representation of the oral structure. In that instance, a holder such as the holder 18 is placed in contact with a quantity of impression material as the impression material hardens. The holder is located in the impression tray before the impression material is placed in the tray. The resulting negative model may then be used as desired. For example, a scanner or camera (such as the "RAINBOW" brand 3D camera from Genex Technologies, Inc.) may be employed to collect an electronic set of data from the negative model. Components for making the model 10 or for use in the methods described above may be supplied in the form of a dental kit. The dental kit is not shown in the drawings, but includes a container and a holder such as the holder 18 or 18 a. The container also includes one or more of the following items: a dental restorative material, a dental prosthetic material, instructions, dental cements, dental adhesives, impression materials, shade guides, temporary dental restorative materials, abrasives, tools, instruments and impression trays. An example of a suitable dental prosthetic material is a dental mill blank such as disclosed in pending U.S. Patent Application Serial No. 09/441,577. Moreover, the set of electronic data may be used for other dental procedures as well. Examples of such procedures include use as a patient record, use for patient education, use for insurance authorization or verification, for fabrication of a prosthetic, for diagnosis, for treatment planning and for transmittal to third parties (e.g., a dental laboratory remote from the dental office). A variety of other constructions and methods of use are also possible. For example, the models and methods described above can be used in other fields of dentistry such as orthodontics. Accordingly, the invention should not be deemed limited to the detailed description that is set out above, but instead only by a fair scope of the claims that follow along with their equivalents.

Claims: Claims: 1. A dental model comprising: a quantity of mold material having an exterior surface, wherein at least a portion of the exterior surface represents oral structure; and a holder having a textured surface, wherein the textured surface is in contact with the mold material. 2. A dental model according to claim 1 wherein the textured surface is fibrous. 3. A dental model according to claim 2 wherein the textured surface includes fibers having free ends. 4. A dental model according to claim 1 wherein at least a portion of the textured surface has a granular configuration. 5. A dental model according to claim 1 wherein the textured surface includes undercut regions. 6. A dental model according to claim 1 wherein the textured surface includes projections. 7. A dental model according to claim 6 wherein at least some of the projections have outer ends with heads presenting undercut regions. 8. A dental model according to claim 7 wherein at least some of the projections have a mushroom-shaped configuration. 9. A dental model according to claim 1 wherein the textured surface includes a number of pores. 10. A dental model according to claim 1 wherein the textured surface is one component of a hook and loop fastener assembly. 11. A dental model according to claim 1 wherein the holder includes a magnetic surface opposite the textured surface. 12. A dental model according to claim 1 wherein the holder includes an exterior surface opposite the textured surface, and wherein the exterior surface includes a quantity of adhesive. 13. A dental model according to claim 12 wherein the holder includes a release liner extending over the adhesive. 14. A dental model according to claim 1 wherein the holder includes a protrusion extending away from the textured surface for coupling the model to a fixture. 15. A dental model according to claim 1 wherein the holder includes an exterior surface opposite the textured surface, and wherein the exterior surface includes one component of a hook and loop fastener assembly. 16. A dental model according to claim 1 wherein the portion of the exterior surface that represents oral structure is a positive representation of the oral structure. 17. A dental model according to claim 1 wherein the portion of the exterior surface that represents oral structure is a negative representation of the oral structure. 18. A method of preparing a dental model comprising the acts of: making an impression of oral structure; placing a quantity of hardenable mold material in the impression; engaging a textured surface of a holder with the mold material before the mold material has hardened; and allowing the mold material to harden and thereby securely couple the holder to the resulting model. 19. A method of preparing a dental model according to claim 18 wherein the act of engaging a textured surface of a holder with the mold material includes the act of placing undercut regions of the textured surface in contact with the mold material. 20. A method of preparing a dental model according to claim 18 and including the act of coupling an exterior surface of the holder opposite the textured surface to a fixture for supporting the dental model. 21. A method of preparing a dental model according to claim 20 wherein the act of coupling the exterior surface of the holder to a fixture includes the act of releasably coupling the exterior surface of the holder to the fixture. 22. A method of connecting a dental model to a fixture comprising the acts of: making an impression of oral structure; placing a quantity of hardenable mold material in the impression; engaging a textured surface of a holder with the mold material before the mold material has hardened; allowing the mold material to harden while the mold material is in engagement with the textured surface of the holder; and coupling the holder to the fixture. 23. A method of connecting a dental model to a fixture according to claim 22 wherein the act of engaging a textured surface of a holder with the mold material includes the act of placing undercut regions of the textured surface in contact with the mold material. 24. A method of connecting a dental model to a fixture according to claim 22 wherein the act of coupling the holder to the fixture includes the act of releasably coupling the holder to the fixture. 25. A method of connecting a dental model to a fixture according to claim 24 wherein the act of coupling the holder to the fixture includes the act of coupling a hook and loop fastener assembly together. 26. A method of connecting a dental model to a fixture according to claim 22 wherein the act of coupling the holder to the fixture includes the act of coupling a protrusion of the holder to the fixture. 27. A method of connecting a dental model to a fixture according to claim 22 and including the act of collecting a set of electronic data corresponding to at least part of the oral structure from at least a portion of the model after the holder is coupled to the fixture. 28. A method of connecting a dental model to a fixture according to claim 27 and including the act of using the set of electronic data for one or more of the following: as a patient record, for patient education, for insurance verification, for fabrication of a prosthetic, for diagnosis, for treatment planning, for insurance authorization, and to transmit the data to a third party. 29. A method of connecting a dental model to a fixture according to claim 27 and including the act of constructing a dental restoration using the set of electronic data. 30. A method of making a negative dental model comprising the acts of: placing a holder in contact with a quantity of impression material; placing the impression material in an impression tray; placing the impression material in contact with oral structure; and allowing the impression material to at least partially harden in the impression tray while the holder is in contact with the oral structure. 31. A method of making a negative dental model according to claim 30 and including the act of placing the holder in the impression tray before the impression material is placed in the impression tray. 32. A method of making a negative dental model according to claim 30 wherein the holder includes a textured surface. 33. A method of making a negative dental model according to claim 30 and including the act of collecting a set of electronic data corresponding to at least part of the oral structure from the impression material after the impression material has at least partially hardened. 34. A method of making a negative dental model according to claim 33 and including the act of constructing a dental restoration using the data set. 35. A method of making a negative dental model according to claim 33 and including the act of using the set of electronic data for one or more of the following: as a patient record, for patient education, for insurance verification, for fabrication of a prosthetic, for diagnosis, for treatment planning, for insurance authorization, and to transmit the data to a third party. 36. A dental kit comprising: a container; a holder having a textured surface in the container; and a dental prosthetic material in the container. 37. A dental kit according to claim 36 wherein the dental prosthetic material is a mill blank. 38. A dental kit according to claim 36 and additionally including at least one of the following: a dental cement, a dental adhesive, an impression material, an abrasive, a dental tool, shade guide, a dental restorative material, a temporary dental restorative material and an impression tray.

Inventors: KINSKY TIMOTHY R, RUSIN RICHARD P, KINSKY, TIMOTHY, R., RUSIN, RICHARD, P.
Applicants: 3M INNOVATIVE PROPERTIES CO, 3M INNOVATIVE PROPERTIES COMPANY
Application year: 2000
Main classification: A61C13
IPC codes: A61C13