COMPANION ENGINEERING AND MANUFACTURING PROCESSES (CEMP) TO OPTIMIZE MULTI-LAYERED ZIRCONIA CROWNS

Abstract

A companion engineering and manufacturing process to optimize multi-layered zirconia crowns, and improved substructure are provided.

Claims

1. A method of manufacturing a dental restoration comprising the steps of: providing a structural body for the restoration that includes at least one support structure located along a side wall of the structural body at a location spaced from, but generally near, an occlusal end of the substructure body; veneering the structural body with veneering material having an ideal thermal expansion coefficient that is generally ≦1.0×10.sup.−6/° C. of the structural body material to form a first modifier layer; and veneering the structural body with one or more successive layers of veneering material; firing said veneering layers at an ideal temperature that is preferably slightly less than the recommended high firing temperature; withdrawing the structural body from said firing step through a rapid cool-down protocol.

2. The method as claimed in claim 1 wherein said modifier layer includes a special effect-shading that enhances the aesthetic appearance of the veneer.

3. The method as claimed in claim 1 wherein the structural body comprises a Zirconia material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] A preferred embodiment of the invention, illustrative of the best mode in which the applicant has contemplated applying the principles, is set forth in the following description and is shown in the drawings and is particularly and distinctly pointed out and set forth in the appended claims.

[0047] FIG. 1 is front elevation section view of a dental restoration including a conventional substructure.

[0048] FIG. 2 is a front elevation section view of a dental restoration of an embodiment of the instant invention.

[0049] FIG. 3 is a top plan section view of the dental restoration of FIG. 2

[0050] FIG. 4 is a front elevation section view of a dental restoration substructure of an embodiment of the instant invention.

[0051] FIG. 5a is a proximal section view of a dental restoration of another embodiment of the instant invention showing the areas of greatest compression of veneering porcelain.

[0052] FIG. 5b is an occlusal section view of the dental restoration of FIG. 5a.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0053] As required, a detailed embodiment of the present invention is disclosed herein; however, it is to be understood that the disclosed embodiment is merely exemplary of the principles of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure.

[0054] Referring to FIG. 1, a dental restoration including a conventional substructure is shown. As is shown in FIG. 1, the restoration includes abutment portion 10 over which thin core 20 is fit. Crown 30 is formed about core 20 from a veneer porcelain to the shape of the final restoration. As can be seen in FIG. 1, a considerable amount of bulking out of the veneer porcelain is required to establish the final form of the restoration. The stresses from the mandibular posteriors tend radiate out from tip 35 of the buccal cusps. The conventional reinforcement structures, such as collar 12 located at the base of the substructure, are greatly limited in location due to aesthetic concerns. Because such reinforcement structures are located away from the region of stress, 35, fractures in the porcelain for crown 30 can occur.

[0055] Referring to FIGS. 2 and 3, a dental restoration including an embodiment of the reinforced substructure of the instant invention is shown. As is shown in FIG. 2, the restoration includes abutment portion 10 over which core 20 is fit. Core 20 includes a body with a generally uniform outer surface and including annular protrusion 25 located generally near an occlusal portion of the restoration, and circular/superior protrusion (“Occlusal Beam” or “Coronal Beam”) 45 that generally runs below the cusps and along the marginal ridges. Crown 30 is formed about core 20 from a veneer porcelain to the shape of the final restoration in the manner discussed above. As can be seen in FIG. 2, protrusion 25 is located near the location of the most considerable amount of bulking out of the veneer porcelain that is used to establish the final form of the restoration. As with the conventional restoration shown in FIG. 1, the stresses from the mandibular posteriors tend to radiate out from tip 35 of the buccal cusps; however, protrusion 25 is located in close proximity to (right under in the shown embodiment) this high stress region to provide a contact region and support for the veneering porcelain of crown 30. In addition to providing support, locating the relatively thin reinforcement 25 in the region of the thickest veneering porcelain also allows protrusion 25 to be concealed by the porcelain. In addition, the location of reinforcement protrusion 25 allows core 20 to be relatively thin at the margin (base) resulting in optimal aesthetics for the restoration. The circular protrusion 45 acts to “zone/subdivide” the veneering porcelain to increase the strength of veneering bond by “design.” The “fish mouth” style of the embodiment shown in FIGS. 2 and 3 of this Occlusal Beam also allows the reduction of mass of the core in a non-critical area of Core strength. This affords increased esthetics (i.e. through thicker porcelain). It also improves porcelain veneering by “regularizing” and/or “standardizing” the morphology of similar pieces of different patient cases such that the thermodynamics can be more closely industrially controlled. The purpose of the two rings (Buttress™ 25 and Occlusal 45) is to make the greatest thickness of veneering porcelain, that will take longer to cool/shrink and consequently contribute the highest “compression” to best fixate the porcelain to the walls. The rings act as a physical “tie” for the porcelain to the core/substructure 20. In another way, in the world of ceramic compression, the rings act as a “corrugation” of the surface that affords increased surface area and increased zones of compression, that can be ideally positioned for the desired result of better retaining veneering porcelain and to reduce localized “chipping and spalling.”

[0056] It will be appreciated that the use of the phrase “generally uniform” to describe the outer surface of the body of core 20 of the instant invention refers to the fact that the outer surface of core 20 generally (other than protrusions 25 and 45) does not include any significant variations in contour from those variations typically found in conventional core structures which generally follow the contours of (i.e. are concentric with) the surface of the restorations for which they are substructures. Such contours often include various asymmetrical and irregular shapes that may include both concave and convex patterns in a single structure. Therefore, the generally uniform surface does not require the surface to be smooth or even, or of any standardized or symmetrical shape or form. It will further be appreciated that reference to the outer surface of the body of core 20 as being generally uniform is not intended to require a uniform thickness for core 20, even though the embodiment of core 20 shown in FIGS. 2 and 3 does include a generally uniform thickness.

[0057] As the shape of the outer surface of core 20 will vary significantly, so too will the shape of protrusions 25 and/or 45. Although shown and described in the preferred embodiment as a generally annular, symmetrical shape (as protrusion 25), it will be appreciated that the contact region/support structure (“protrusions”) of the instant invention may take on any number of shapes both symmetrical and asymmetrical, can be a single structure that generally encircles the substructure body (as is shown and described herein with respect to annular protrusion 25 and/or circular protrusion 45), can be multiple structures that generally encircle the substructure body, can be one or more substructures that partially encircle the substructure body, or can be one or more substructures that each protrudes from a single point along the substructure body. Furthermore, the terms “protrusion” and “protruding” are intended to include, but not be limited to, any convex shape that is not a coincident concentric duplicate shape of the preparation; any complex amplification of shape that is not just a convex derivative of the shape of the preparation; any shape having a concave approach from each side approach to an amplified area of protrusion that can not be described in simple harmonics, but only complex wave form; any superseding amplification of form that is not accidental or rendered for strictly artistic purpose; any concentric enlargement that is disproportionately distributed toward the superior (non-apical) portion of the long axis of the preparation; any asymmetrical appendage added to a design by computer generated pre-made shape or file added for specific structural considerations of subsequent materials added to a restoration infrastructure. Furthermore, it will be appreciated that the “protrusions” of the instant invention may be designed as an integral portion of an infrastructure (as is shown and described herein with respect to core 20 and protrusions 25 and 45), or alternatively, the “protrusions” may be one or more separate components that are attached to or otherwise combined with an infrastructure. Examples of “protrusion” shapes of the instant invention in addition to the generally annular protrusion 25 and circular protrusion 45 shown herein include but are not limited to bulges, power-swells, tumors, bumps, blobs, raised protuberances, etc.

[0058] As is shown in FIG. 1, conventional substructures tend to taper upward from the base of the substructure (located generally at the gums), so that the greatest thickness of veneering ceramic will be applied toward the top of the substructure, concealing the substructure at the location in which it would be most visible once finally installed. As is shown in FIG. 2, core 20 of the instant invention also includes this upward tapering shape. Thus, as is already mentioned above, it will be appreciated that the phrase “generally uniform” with respect to the outer surface of core 20 is not intended to limit the shape of the outer surface of core 20, which can be generally cylindrical, conical, generally convex (especially for the majority of the labial and lingual portions) or any other simple or complex shape desired, whether now known or hereafter discovered.

[0059] In a preferred method of the instant invention, annual protrusion 25 and circular protrusion 45 are incorporated into the CAD-CAM design stage for core 20. In one embodiment core 20 is milled from a ceramic material. Suitable materials for core 20 include, but are not limited to, Lava™ two-stage zirconium dioxide system offered by 3M ESPE, and the Precident™ one-stage Bio-HIP Y-TZP (High Heat and Isostatic Pressure formed yttrium stabilized tetragonal zirconium polymorph) offered by DCS of Switzerland. The Lava™ System utilizes a zirconia dioxide block that is CNC milled in a greenware state then secondarily heat sintered. The Precident System mills directly from the harder presintered Bio-HIP Y-TZP block.

[0060] Core 20, which includes protrusions 25 and 45, may be designed primarily manually using conventional CAD-CAM design software in which the user first designs core 20 without protrusions 25 and 45 in the manner in which core 20 of prior art substructures is design. The user then places pre-made shapes down over an image of core 20 on the screen, increases or decreases the existing shape, distorts the shape in one/multiple vanishing points, increases the volume of the shape from a point or angle, or free hand-paints an area to add protrusions 25 and 45. In a preferred embodiment however, the core 20 of the instant invention is designed primarily automatically by a CAD-CAM application that includes pull down annular shapes for protrusions 25 and 45 that are placed on/around the concentric image being made over the die for core 20 which is chosen from a library of tools/shapes in the software palate. Protrusions 25 and/or 45 may be enlarged (or reduced) in x, y, and z axis as necessary to bulk-up (or down) the core being designed. In such an automated CAD-CAM application, the CAD-CAM software recognizes (or identifies) the outer contour shape (i.e. the surface) of core 20 and conforms the inner surface of the pull-down annular shapes for protrusion 25 and 45 to the outer surface of core 20, such that the inner surface of protrusions 25 and 45 and the outer surface of core 20 are aligned. If desired, the outer surface of protrusions 25 and 45 can also follow the shape of the outer contour of core 20 by spacing each point of the outer surface of protrusion 25 an equal distance away from a corresponding point on the outer surface of core 20.

[0061] In another preferred embodiment of the instant invention core 20 of the instant invention is designed primarily automatically by a CAD-CAM application with the operator of the software pulling the structure from a point, line, cluster of points, etc., to distort a portion of the shape of the main body of the substructure without distorting the overall shape of the main body. Conventional modeling software primarily takes a shape and puts it in a “box” giving the operator the ability to pull at the corners to increase or decrease the volume of the shape or distort it. At all times, the operator is pulling the entire side of the 3D structure, not just the point. This is limiting as the software only allows symmetrical “pulls”, and has a geocentric pivot point for the shape within the box. In this embodiment of the instant invention, the modeling software utilizes a geocentric pivot point that may be displaced anywhere within the volume and/or along any line or curved line of the CAD-CAM image of core 20 so that the beam structures of the instant invention (i.e. protrusions 25 and 45) may be “pulled” from the main body of the substructure (i.e. core 20) without otherwise distorting the shape of the image of the body from which it is pulled.

[0062] In yet another preferred embodiment, the beam structures of the instant invention are pre-designed into the main body of the substructure. In one such embodiment, a basic shape for the main body of the substructure is selected from a library of shapes available in the software application based upon the desired shape for the final restoration, with the reinforcement structure already built into the shape of the main body. Thus, the beam structures' shapes is selected simultaneously with the main body shape. The operator then pushes, pulls, takes away or otherwise erases portions of the pre-designed shape of the main body and the beam structures in the software to meet the needs for the specific restoration. Alternative embodiments of shapes that can be used as preliminary or starting shapes in this particular embodiment of the instant invention include “door-knob” shapes (as shown in U.S. Pat. No. 7,967,606) that can be selected from a library in the design software; and a “coke-bottle,” shape (as shown in U.S. Pat. No. 7,967,606). Once selected, the sides of the preliminary core shape that is selected may be morphed, distorted or otherwise modified by pulling, pushing, taking away, erasing, etc., from the contact points. In a preferred embodiment, the sides are morphed by pulling from the contact points in pre-planned arcs of differing diameters, and controlled by looking down from the top of the shape (i.e. along the y-axis) and/or form the side of the shape to determine where (i.e. how many degrees around the outer surface of the shape) the selected morphing will occur. Examples of morphing include but are not limited to dragging the sides of the original shape apically or occlusally along the y-axis to make a symmetrical or asymmetrical (such as a French curve) arch, dragging the sides along the x-axis outwardly from the body of the shape, and also along the z-axis. It will be appreciated that the blocks of material from which the substructure (such as core 20) is milled may be pre-manufactured in the pre-determined shapes discussed above to minimize the amount of waste material during the milling of the final substructure, once the substructure has been designed in accordance with the instant invention.

[0063] In still another preferred embodiment, the substructure (including the beam structures of the instant invention) is designed by first obtaining the desired shape for the restoration and then subtracting away or deconstructing from that shape to leave the desired substructure shape. In such an embodiment, the part of the final shape of the restoration that is subtracted is determined to maximize the aesthetic appearance of the final restoration by concealing the substructure. In one such embodiment, the software constructs a “mesh framework of point clusters” that are external to (or in addition to) the point clusters established by the scan of the original piece that is being restored (or scan of a model of the piece to establish the desired external appearance of the restoration). These point clusters are used to construct an image of a “concentric” substructure (concentric to the original piece) for the restoration. The operator then embellishes or diminishes certain key areas, after rendering of the substructure image, to design the final substructure shape. Once the basic, overall shape has been rendered, the computer then knows in 3d, through the point clusters, where the operator is working, allowing the operator to easily take away portions of the image to result in a final image for the substructure.

[0064] Although shown and described in connection with a crown implant, it will be appreciated that the reinforcement structure of the instant invention can be used in connection with any dental restorations, including crowns and/or bridges, and including implant and/or restorations supported by teeth. Further, it will be appreciated that the materials used to manufacture the substructure (as well as the veneer) of the instant invention are not limited to those described herein. Although the inventive substructure is particular well suited for use with substructures manufactured of zirconium and other comparable ceramics, the inventive support structure may be utilized in connection with substructures manufactured from any other suitable material without departing from the spirit and scope of this instant invention.

[0065] It will also be appreciated that although the preferred method of the instant invention utilizes CAD-CAM design software, other methods of design (such as free-hand design, hologram or virtual reality modeling) now known or hereafter developed can be utilized without departing from the spirit and scope of the instant invention. Further, it will be appreciated that the inventive reinforcement may be used in connection any manufacturing process for crowns or bridges now known or hereafter discovered, including but not limited to simultaneous milling of a core and implant abutment, milling the core and abutment as a single piece, or milling of crowns and bridges from blocks or rods, etc. In addition, it will be appreciated that the infrastructures of the instant invention may be manufactured in methods other than the milling discussed herein. Alternative methods include but are not limited to press, lay-up, green ware production and subsequent milling or hand finishing.

[0066] Referring to FIG. 4, a front elevation section view of a dental restoration substructure of an embodiment of the instant invention similar to those discussed above and with respect to FIGS. 2 and 3 is shown.

[0067] FIG. 5a shows a proximal section view of a dental restoration of another embodiment of the instant invention showing the areas of greatest compression of veneering porcelain. FIG. 5b is an occlusal section view of the dental restoration of FIG. 5a.

[0068] In the foregoing description, certain terms have been used for brevity, clearness and understanding; but no unnecessary limitations are to be implied therefrom beyond the requirements of the prior art, because such terms are used for descriptive purposes and are intended to be broadly construed. Moreover, the description and illustration of the inventions is by way of example, and the scope of the inventions is not limited to the exact details shown or described.

[0069] Although the foregoing detailed description of the present invention has been described by reference to an exemplary embodiment, and the best mode contemplated for carrying out the present invention has been shown and described, it will be understood that certain changes, modification or variations may be made in embodying the above invention, and in the construction thereof, other than those specifically set forth herein, may be achieved by those skilled in the art without departing from the spirit and scope of the invention, and that such changes, modification or variations are to be considered as being within the overall scope of the present invention. Therefore, it is contemplated to cover the present invention and any and all changes, modifications, variations, or equivalents that fall with in the true spirit and scope of the underlying principles disclosed and claimed herein. Consequently, the scope of the present invention is intended to be limited only by the attached claims, all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

[0070] Having now described the features, discoveries and principles of the invention, the manner in which the invention is constructed and used, the characteristics of the construction, and advantageous, new and useful results obtained; the new and useful structures, devices, elements, arrangements, parts and combinations, are set forth in the appended claims.

[0071] It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.