EP2550615A2

EP2550615A2 - Improving dental prosthesis robustness

Info

Publication number: EP2550615A2
Application number: EP11710433A
Authority: EP
Inventors: Matts Andersson; Timo Kero
Original assignee: Nobel Biocare Services AG
Current assignee: Nobel Biocare Services AG
Priority date: 2010-03-24
Filing date: 2011-03-22
Publication date: 2013-01-30
Also published as: JP2013521958A; WO2011116934A2; WO2011116934A3

Abstract

Presented herein are methods, systems, devices, and computer-readable media for improving dental prosthesis robustness. Embodiments include systems, methods, and computer readable media for choosing a support point configuration for a prosthesis optionally based on robustness of the support point configuration, where the support points in the support point configuration are located on the inner surface of the prosthesis away from the marginal edge. Additional embodiments include determining at least two candidate support point configurations, wherein each candidate support point configuration may optionally be generated based on a configuration of seed positions. One of the candidate support point configurations may optionally be chosen based on a robustness rating. The chosen configuration of support points may optionally be exported as a surface, a milling path, etc. and may be used in the manufacturing of the prosthesis. Other embodiments include a prosthesis, such as a crown, coping, or bridge, that includes plurality of support points that provide support between a prosthesis and the prepared tooth, and those support points are positioned on the inner surface of the prosthesis away from the marginal edge and / or away from the top area of the inner surface of the prosthesis.

Description

IMPROVING DENTAL PROSTHESIS ROBUSTNESS

BACKGROUND

Field of the Invention

[0001] The embodiments herein are related to dental prosthesis planning and improved dental prostheses. More specifically, embodiments herein are directed to improving the robustness of dental prostheses.

Description of the Related Art

[0002] In the field of dentistry, mass customization of dental crowns and other prostheses is becoming more common. During the process of mass customization, a dentist or other practitioner will design a prosthesis, such as a crown, to fit onto a prepared tooth. A tooth-supported artificial dental prosthesis, such as a coping, crown, or bridge, can cover portions of a tooth surface and is normally fabricated away from the patient's mouth, in a lab, and then assembled in the mouth by the dental practitioner. A tooth preparation or prepared tooth, as used herein, is a tooth that has been reshaped for accepting dental prosthesis. To achieve a strong fitting of a dental prosthetic, it is important for the surface of the tooth preparation to coincide closely with the mating surface of the dental prosthetic. That is, it is important that a prosthesis sit, without much rotation, and without much translation (as compared to the planned placement of the prosthesis) on a prepared tooth. In the currently-used methods of prosthesis design and manufacturing, however, the prosthesis will typically find support only along the finish line of the prepared tooth, because when a prosthesis is designed physically, a die spacer is usually placed on top of the prepared tooth in order to create a uniform gap between the prepared tooth and the physical design. Similarly, when a prosthesis is designed in CAD (computer-aided design), 3D, or other software, a fixed width gap between the prepared tooth and the prosthesis is required or provided for by the software. In either the case of a physical design or CAD design, because there is a gap between the tooth and the prosthesis at all points except along the finish line, the assembled prosthesis will only find support along the finish line. When the prosthesis finds support only along the finish line of the prepared tooth, it may rotate or translate with little constraint. This rotation and translation of the prosthesis contributes to the final variation of placement of the prosthesis and is undesirable.

[0003] Another problem with the prior art is that gap between a prosthesis and a prepared tooth may be irregular. This gap between the prosthesis and the prepared tooth is sometimes called a cement space. If the cement space is irregular, then the prosthesis may not be as strong, and may have a shorter life span. A prosthesis with an irregular cement space may, for example, have a lifespan that is years shorter than a prosthesis with a uniform cement space.

[0004] These problems and others are addressed by the systems, methods, devices, and computer-readable media described herein.

SUMMARY

[0005] Presented herein are methods, systems, devices, and computer-readable media for dental prosthesis manipulation, selection, and planning. This summary in no way limits the invention herein, but instead is provided to summarize a few of the embodiments.

[0006] Embodiments herein include systems and methods for improving dental prosthesis robustness. Some embodiments include methods, systems, and computer-readable media for improving dental prosthesis robustness, and the prostheses thereby made. Embodiments may include determining a support point configuration for a prosthesis based at least in part on robustness of the support point configuration. The prosthesis may include an inner surface, an outer surface, and a marginal edge, the marginal edge being disposed between the inner surface and the outer surface. The support point configuration may include a plurality of discrete points and the plurality of discrete points is disposed on the inner surface of the prosthesis; and data for producing the prosthesis may be generated based, at least in part, on the support point configuration. The prosthesis may be a coping, crown, veneer, bridge, etc.

[0007] In some embodiments, a dental prosthesis may include a body that includes an inner surface, an outer surface, and a marginal edge, the outer surface being generally disposed on the outward facing portion of the prosthesis, the inner surface being generally designed to fit a prepared tooth, and the marginal edge being disposed between the inner surface and the outer surface. The prosthesis may also include a support point configuration that has a plurality of support points and the plurality of support points are non-uniformly disposed on the inner surface away from the marginal edge.

[0008] In some embodiments, determining the support configuration for the prosthesis may include determining, using the computer system, at least two candidate support point configurations, where the candidate support point configurations each include a plurality of discrete points; determining, using the computer system, a robustness rating for each of the candidate support point configurations; and choosing one of the at least two candidate support point configurations as the support point configuration based at least in part on the at least two robustness ratings. The support points may be located away from the top and / or marginal edge of the prosthesis.

[0009] In some embodiments, determining the candidate support point configuration may include performing the Wang algorithm, a modification thereof or generating a configuration of random seed positions as prospective support point positions and iteratively moving the prospective support point positions to find a configuration of support point positions in which support points at those positions have improved robustness over the robustness of previous iterations' prospective support point configurations. Any other appropriate algorithm may also be used. The number of candidate support point configurations to consider may be predefined or additional candidate support point configurations may be determined until the robustness rating for at least one of the candidate support point configurations is above a predefined threshold. The robustness rating may be calculated based on a root mean square or a worst-case calculation or best-case calculation of variations in location of an inner surface of the prosthesis over multiple simulated assemblies.

[0010] Numerous other embodiments are described throughout herein.

[0011] For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention are described herein. Of course, it is to be understood that not necessarily all such objects or advantages need to be achieved in accordance with any particular embodiment. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught or suggested herein without necessarily achieving other objects or advantages as may be taught or suggested herein.

[0012] All of these embodiments are intended to be within the scope of the invention herein disclosed. These and other embodiments will become readily apparent to those skilled in the art from the following detailed description having reference to the attached figures, the invention not being limited to any particular disclosed embodiment(s).

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is flow diagram that illustrates the lifecycle of a dental prosthesis.

[0014] Figure 2 illustrates a flow diagram for a method for dental data planning. [0015] Figure 3 is a first abstract representation of a prosthesis with a cavity, pictured from below.

[0016] Figure 4 is a second abstract representation of a prosthesis with a cavity, pictured from below.

[0017] Figure 5 is an illustration that depicts three different areas within the inner surface of the cavity of a prosthesis.

[0018] Figure 6 is an illustration that depicts a variety of shapes and sizes of support points.

[0019] Figure 7 illustrates a system for improving dental prosthesis robustness.

DETAILED DESCRIPTION

Dental Prostheses

[0020] As shown in Figure 1, there are numerous steps between the examination of the patient and the production and assembly of a prosthesis. Generally, a dentist will examine the patient and determining what type of prosthesis is needed. This is shown in step 110 of the treatment lifecycle 100 in Figure 1. The doctor may grind down or otherwise prepare the tooth so that it will be able to accept and support a prosthesis, such as a crown, coping, or bridge. Step 110 may include making a gypsum model of the prepared tooth. Step 110 may also include taking an impression either physically or virtually, with a scanner. After the examination and any preparations are completed, a 3D model of the prepared tooth may be obtained. A 3D model of the prepared tooth could be available directly from the scan of the prepared tooth, if the tooth was scanned using a 3D scanner. If instead, a physical impression or model of the tooth was made, then, in step 120 the impression or model of the tooth may be scanned in order to obtain a 3D model. The output of the direct scanning of the prepared tooth or the scanning of the impression or model of the tooth will typically be a 3D model, such as a point cloud or a triangulated mesh surface model. The prosthesis is designed based on the scanned model of the prepared tooth in step 130. The design of the prosthesis can be accomplished by any practitioner using a variety of CAD, 3D modeling, NobelProcera, and / or other types of software. Based on the design of the prosthesis that is made in step 130, the prosthesis is manufactured in step 140. Manufacturing can take a number of different forms. For example, for a coping, the coping in itself may be produced and sent to a dental technician who may then paint a porcelain layer onto the tooth. In some embodiments, when producing an entire crown, the entire crown including the surface may be produced. A glaze or other color layer may later be painted on by a technician, or applied automatically as part of the manufacturing process. After the prosthesis is manufactured in step 140, it is sent to a practitioner to be assembled in the patient's mouth as part of step 150. The term assembly, as used herein, may refer to a practitioner placing a prosthesis over a prepared tooth. Those skilled in the art will recognize that other treatment lifecycles exist and may be used with the embodiments herein.

[0021] In some embodiments, a prosthesis may have an inner surface, an outer surface, and a marginal edge. The said outer surface may be the outward facing portion of the prosthesis. For example, for a crown, the outer surface may be the part of the prosthesis that would be visible once the crown is assembled. The inner surface may be the part of the prosthesis that is design to fit over the prepared tooth. It is on the inner surface that, in some embodiments, support points will be distributed. The marginal edge may be the interface disposed between the inner surface and the outer surface.

[0022] Various embodiments herein may also be used as part of an determination of robustness or sensitivity for an entire assembly process, such as is described in US Patent Application No. 12/678.137, filed March 12, 2010, which claims priority to PCT/EP08/07469, entitled "Method and System for Planning a Medical Procedure and Generating Data Related to Said Medical Procedure," which is incorporated herein by reference in its entirety for all purposes.

Robustness for Dental Prostheses

[0023] Numerous of the embodiments herein provide the ability to improve the robustness for a designed prosthesis. Robustness, as used herein, is a measure of how close to a designed or desired placement a prosthesis will be once assembled. Put another way, robustness is the characteristic of the crown or other prosthesis that allows it to be assembled with minimal variation in position and orientation. Robustness can be estimated by simulating numerous assemblies of the prosthesis and measuring how "far off' the assemblies are relative to the designed or desired placement. In the design, it may be important to minimize the marginal opening and the gap between the prepared tooth and the inner surface of the prosthesis, while still providing sufficient space for cement, and in particular, a uniform cement space. As noted above, a uniform or nearly uniform cement base may be desirable in order to improve the durability of a prosthesis. The robustness is an important aspect of the design because a robust design will also minimize the marginal opening and the gap over many possible assemblies. When a prosthesis is being designed for a prepared tooth for a patient, there will typically be a gap between the prosthesis and the prepared tooth. This gap will typically be filled with cement to affix the prosthesis to the prepared tooth. The space between the prepared tooth and the prosthesis is sometimes called the "cement space." The cement space can be any thickness or width, such as 40-60 micrometers.

[0024] The position of a prosthesis with respect to the prepared tooth will be defined by the assembly of the prosthesis on the prepared tooth. Traditionally, a prosthesis is placed on the prepared tooth and the contact points between the prosthesis and the prepared tooth will be along the finish line at the bottom of the prepared tooth. It is difficult to predict precisely which points along or near the finish line of the prepared tooth will be in contact with the prosthesis. Using the traditional method, the points of contact along the finish line may be approximately coplanar or may all be in a very narrow band near the finish line. In part because the points of contact along the finish line are approximately coplanar when using the traditional method, when the prosthesis is inserted over the prepared tooth, it may be inserted in the way that is, with respect to the desired placement, rotated and / or translated vertically and / or horizontally. Various embodiments herein help correct this problem by determining support points or contact points on the prosthesis in order that a prosthesis may be guided into the proper position over a wider variety of assemblies of the prosthesis onto the tooth.

Improving Robustness

[0025] In order to improve robustness of a prosthesis, support points may be added to the inner surface of the prosthesis. These support points provide points of contact between a prosthesis and the prepared tooth. Support points may be defined over several iterations of an algorithm that will choose a candidate support point configuration for each iteration based on seed values. In some embodiments, the robustness for the candidate support point configurations for all iterations is compared and one of them is chosen for use with the prosthesis. This chosen support point configuration can then be used in the manufacturing of the prosthesis in order to produce a prosthesis that will be more robust during the assembly process. Generally, each candidate support point configuration will include a plurality of support points on the inner surface of a prosthesis. In some embodiments, the plurality of support points will be distributed non-uniformly. Further details on seeding and choosing among the candidate support point configurations are discussed more below with respect to various embodiments.

[0026] Figure 2 illustrates a flow diagram for a method for dental data planning. The method 200 contains numerous steps that can be performed in various orders. Some steps may be performed more than once, groups of steps may be performed more than once, some steps may be omitted, and the steps may be performed in a different order. In some embodiments, the steps are performed as shown in Figure 2.

[0027] In step 210, candidate support point configurations are determined. In some embodiments, step 210 may include determining the positions of the support points in the candidate support point configuration. In some embodiments, step 210 may also include determining the size and / or shape of the support points. In yet other embodiments, the size and / or shape of the support points may be determined as part of another step in method 200 either before or after step 210 or in a step not depicted in method 200. Considerations related to the size and shape of support points are discussed more below.

[0028] The positions of the support points may be determined using any appropriate algorithm. For example, in some embodiments, seed points may be distributed around the inner surface or cavity of a prosthesis that will be fitted onto a prepared tooth. The positions of those seed points of those points may be moved and / or redistributed and the effects on the robustness of the prosthesis may be checked after those movements or redistributions. If the new positions of the support points provide a better robustness rating, then the new positions are adopted. In some embodiments, one support point's position is moved at a time, and the robustness rating is compared after each individual movement. The movement of the points may desist once no more increases in robustness are achieved by moving points. Once movement of the points has stopped, the positions of the support points may become the candidate support point configuration.

[0029] In some embodiments, in step 210, the candidate support point configuration may be determined by the algorithm of Wang et al., Optimizing Fixture Layout in a Point-Set Domain, IEEE Transactions on Robotics and Automation, Vol. 17, No. 3, June 2001. Generally, this algorithm (called the "Wang algorithm" herein) uses seed points at various locations on the surface and optimizes the location of those points in order to minimize the amount of translation and rotation that might occur during assembly. The details of that algorithm are given herein. Using the Wang algorithm, and referring to Figure 3 and Figure 4, each of which is an abstract representation of a prosthesis 300 or 400 with a cavity 310 or 410 that is designed to fit on top of a prepared tooth, the method will first pick set of random points 321 - 326 located about the inside of a cavity 310 of a prosthesis 300. After running the Wang algorithm on the seed points 321 - 326, the candidate support point configuration is determined, as depicted by support points 421 - 426 in Figure 4. In some embodiments, the candidate support point configuration will have a non-uniform distribution.

[0030] The seed points used in the Wang or any other algorithm may be distributed randomly over the entire inner surface of the cavity of the crown or other prosthesis. In some embodiments, the seed points are distributed over less than the full area of the inner surface of the cavity of the prosthesis. Distributing support points over less than the full area of the surface may reduce the range of support point configurations, and therefore eliminate some robust solutions, but may be preferable for a variety of reasons, such as manufacturing limitations or installation considerations. For example, support points near the marginal edge might detract from sealing of the prosthesis and the prepared tooth. Also, having a support point at the top, roof, or cap of the inner surface may cause the prosthesis to rock or sway on the prepared tooth. As another example, the size of the support point may also influence how close a support point may be to the marginal edge of the prosthesis. For example, if the support point protrudes 0.1 mm and the desired thickness of the cement space is 0.1 mm, then it may be important to keep support points at least 0.1 mm away from the marginal edge.

[0031] The strength of the material used to make the prosthesis may also help define where support points may and may not be placed. If the prosthesis is ceramic, for example, then support points might not be placed where the prosthesis is too thin in order not to cause the prosthesis to fracture. This may mean placing support points away from the marginal edge or any other area where the prosthesis is thin. Therefore, in some embodiments, either because the support points are being kept away from the marginal edge or in order to avoid placing support points where prosthesis is too thin, the seed points may be distributed over a band of the inner surface of the cavity of the prosthesis that excludes the base of the prosthesis near the marginal edge and / or the head of the prosthesis furthest from the marginal edge. This is illustrated in Figure 5. Figure 5 is an illustration that depicts three different areas within the inner surface of the cavity of a prosthesis. Surface 510 is a band of the inner cavity of the prosthesis that is near the bottom of the prosthesis near the marginal edge. Surface 520 shows the entire inner surface of the prosthesis. Surface 530 is a band of the inner surface of the prosthesis excluding the band near the marginal edge and the top, roof, cap, or zenith of the inner surface of the prosthesis, this might be called the middle band surface 530. As noted, in some embodiments, the seed support points could be distributed about the entire inner surface 520 of the prosthesis or about a subset of the inner surface of the prosthesis such as a middle band surface 530. Further, in some embodiments, the output of the Wang or any other algorithm, e.g., the candidate support point configuration, may be limited to support points that are also on a subset of the inner surface of the prosthesis, such as the band depicted by surface 530 in Figure 5.

[0032] In some embodiments, the candidate support point configuration may include a non-uniform distribution of support points. A non-uniform support point configuration may take many forms. For example, if there are three support points, the plane containing the three support points may be non-perpendicular to the longitudinal axis of the prosthesis. If there are four or more support points, they may not all be contained within a single plane. In some embodiments, the support points may each be at different heights with respect to the base of the prosthesis. The support points may also be distributed non-uniformly around the circumference of the prosthesis. For example, the angle along the circumference between a pair of support points may be different than the angle along the circumference between any other pair of support points.

[0033] The top of the inner surface of a prosthesis may be defined in a number of ways. For some prostheses, the sides of the inner surface of the prosthesis may be approximately vertical whereas the top may have an approximately horizontal surface. One may be able to define the top by looking at the inner surface of the prosthesis and determine where there exists a "shoulder" between the horizontal portion of the inner surface and the approximately vertical portion of the inner surfaces. The approximately horizontal portion of the inner surface may be defined as the top. The top of the inner surface may also be defined in terms of percentage distance from the uppermost or highest point on the inner surface. For example, the top may be defined as the highest approximately 2%, 5%, 6%, 10%, 30%, or any other appropriate percentage of the inner surface. Similarly, when the support points are distributed away from the marginal edge, the minimum distance from the edge that any support point is positioned may be at least approximately 2%, 5%, 6%, 10%, 30%, or any other appropriate percentage of the inner surface away from the marginal edge. [0034] In some embodiments, the plurality of seed points used to determine the candidate support point configuration may be three or more. For example, six support points may be used in order to control the six degrees of freedom, e.g., rotation and translation, in which the prosthesis, during the mounting process, may vary from the desired mounting placement. In some embodiments, the six degrees of freedom may be the X, Y, and Z directions and pitch, roll, and yaw. In some embodiments, more support points may be added during the iterations in order to improve robustness. For example, even if three seed points were initially set, then one, two, three, or more seed points may be added to improve robustness.

[0035] Typically, regardless of the number of seats points that are used initially, at least three discrete support points will be used in the candidate configuration of support points in order to maintain robustness. It is also possible that, one or more of the support points may be co-located with another support point, thereby effectively reducing by one the count of the support points. When this happens fewer than six support points may be used on the inner surface of the prosthesis. In various embodiments, any number of support points may be used. In some embodiments, notwithstanding that two or more of support points may be collocated, there will not be fewer than three discrete support points on the inner surface of a prosthesis in any candidate configuration of support points if all directions of freedom are to be controiied.

[0036] Other algorithms to determine a candidate support point configuration may be used in step 210. Such other algorithms are known to those of skill in the art.

[0037] After the candidate support points are determined in step 210, a robustness rating is determined for that configuration of support points in step 220. In some embodiments, the robustness rating may be determined based on the modeled inner surface of the prosthesis. For example, the inner surface of the prosthesis may be modeled using a triangulated mesh. The triangles in the mesh will share nodes, with each triangle being defined by three nodes. Determining the robustness rating for the candidate support points may include simulating an assembly or mounting process of the prosthesis onto the prepared tooth and determining an error measure of the variation between the nominal or designed placement of the prosthesis and the simulated or estimated placement of the prosthesis. Such a measure may be the root mean square of the perturbed or varied location of the nodes on a triangulated mesh that represents the inner surface of the prosthesis as compared to the nominal, planned, or desired positions of those nodes, said mesh not being pictured in Figure 3 and Figure 4. The root mean square or other measure may be determined over a number of simulations of the mounting or assembly process. For example, 10,000 simulations of the assembly or mounting process, or any number of simulations, may be used in the calculation of the robustness measure. Other measures may also be used. For example, measures calculated based on the standard deviation of the worst-case or best-case scenarios may be used. For example, if one were to want to decrease the impact of potential worst-case scenario, then one might choose as the robustness measure variations seen at some number of standard deviations of the worst-case scenario. By choosing the candidate support point configurations with the most desirable worst-case scenario measure, the worst-case scenario for assembly or mounting of the prosthesis should likely be minimized or mitigated.

[0038] After the robustness rating for those candidate support point configuration is determined in step 220, then in step 230 in determination is made as to whether more candidate support point configurations should be determined. In some embodiments, a predefined number of candidate support point configurations are generated (e.g., 5 or 10). In some embodiments, new candidate support point configurations are generated until a configuration meets a threshold robustness rating or until new candidate support point configurations do exceed a certain threshold relative to previous ratings.

[0039] If no more candidate support point configurations are to be determined, then step 240 is performed. If, however, more candidate support point configurations are to be determined, then steps 210 and 220 are again performed in order to determine another configuration of support points. Specifically, a new configuration of random seed points is used to determine a new candidate support point configuration in step 210. Then the robustness calculation is performed for the newly determined, candidate support point configuration in step 220.

[0040] In step 240, a configuration of support points is chosen from among all of the candidate support point configurations. Choosing among the candidate support points may include, in some embodiments, choosing the one with the "best" robustness rating. If, for example, the root mean square of the positions of the nodes on the inner surface of the cavity of the prosthesis as determined in step 220 is used in choosing which candidate support point configuration should be used, then the choice will be based on which of the candidate support point configurations has the lowest root mean square. Since, in some embodiments, the candidate support point configurations may be non-uniform, the chosen support point configuration may also be non-uniform.

[0041] After the support point configuration is chosen in step 240, then in step 250, data for the dental prosthesis is made based at least in part on the chosen support point configuration. In some embodiments, generating the data for the dental prosthesis may include exporting an STL or SDL model or a surface model for the triangulated mesh representing the prosthesis, including the inner cavity with the chosen configuration of support points. Generation of the surface model may be done in cases where the support points are defined during a software dental design process. The placement of the chosen configuration of support points may alternatively be included in a separate data file from the prosthesis surface. In some embodiments, the data may be generated during a CAM (computer-aided manufacturing) preparation step of the prosthesis. The generated data may include a milling path for milling the inner surface and the chosen support point configuration. Those skilled in the art will recognize that there are numerous ways in which data may be exported and used in subsequent CAD modeling, CAM modeling, or manufacturing. All of those various ways in which the model can be exported and subsequently used are considered within the scope and spirit of embodiments herein.

[0042] Embodiments herein may include any type of prosthesis, including those that include more than one inner surface area. For example, in the case of a bridge, there may be multiple prepared teeth over which the bridge is mounted. The prosthesis may include an inner surface for each prepared tooth. If a bridge fits over three prepared teeth, for example, there may be three inner surfaces on the bridge and support points may be determined for each prepared tooth using embodiments herein. Additionally, the prosthesis does not have to include an enclosed cap as shown in the embodiments illustrated in the figures. In some embodiments, a prosthesis, such as a veneer or laminate may not include a cavity, but may instead have an inner surface that is designed to mate with the tooth, but forms only a partial covering of the tooth. Embodiments herein include determining the configuration of support points over the veneer, laminate or any other prosthesis.

Support Points

[0043] In addition to determining the positions of the candidate support points, and the chosen support point configuration determined in method 200, a determination may also be made as to the size and / or shape of the support points. This is discussed above with respect to step 210. As noted above, determining the size and / or shape of the support points may be done as part of step 210, or it may be part of another step performed before or after step 210. In some embodiments, the support points may be defined at least in part based on those manufacturing tolerances, such as milling precision or any other appropriate factor. Manufacturing tolerances may be different in different manufacturing sites. Therefore, knowing the manufacturing site may help define the size and / or shape of the support points.

[0044] Another factor that may influence the size and / or shape of the support points may be the desired thickness of the cement space between the prosthesis and the prepared tooth. For example, if a cement space of a particular width is desired, then the support points may be designed to protrude from the inner surface of the prosthesis by that particular width in order to maintain that particular width of cement space between the prepared tooth and the prosthesis. As discussed above, having a uniform width for the cement space may improve the strength and durability of the prosthesis.

[0045] One option for the shape of the support points is a cap, such as a spherical or spheroidal cap. A support point may extend out of the inner surface of the prosthesis as a hemisphere or a spherical cap smaller than hemisphere. Consider the examples in Figure 6, which shows various support points 610 - 640 on the surface 600. Some embodiments will use a single type (e.g., same size and shape) of support point, whereas other embodiments will use multiple types of support points. Support points may be designed in order to more evenly distribute force and friction between the inner surface of a prosthesis, such as a crown, and a prepared tooth. In some embodiments, support points that have a shape that approximate spherical caps, such as support points 610 - 630, will be used. Generally, when a spherical cap support point is used, only half of the sphere, at most, will extend out of the surface 600. Support point 610 extends out of surface 600 as an approximate hemisphere. Support point 620 extends as a spherical cap out of surface 600 less than hemispherically. Support point 630 is a larger sphere than 610 or 620, and extends out of surface 600 is a less than hemispherical spherical cap. Support point 640 is not spherical, but instead is a different kind of spheroid. Support point 640 is just one of many examples of different kinds of support points that may be used with various embodiments herein.

[0046] As further discussion of the shape of the support points, as noted above, the support points may have the shape of spherical caps. The radius of the sphere, the cap of which makes the support point, may be 0.05mm to 2mm, or any other appropriate size. In some embodiments, the larger the radius of the sphere, the less of that sphere that will be used to make the support point. The radius of a support point may be defined based on manufacturing capabilities and / or design considerations. For example, if the prosthesis is milled, the size of the milling tool may put constraints on the size of the support points.

[0047] As noted above, the method 200 may include different steps and the steps included may be performed in a different order. For example, in some embodiments, step 220, the determination of the robustness rating for each candidate support point configuration, may be performed once all of the candidate support point configurations have been determined by iterating over steps 210 and 230. Further, step 220 may be performed as part of the determination of the chosen support point configuration made in step 240.

[0048] As an additional step, not pictured in Figure 2, the corresponding to step 140 in Figure 1, a prosthesis may be generated based at least on the data generated in step 250. In some embodiments, the prosthesis may be milled. In other embodiments, the prosthesis may be created based on a mold created based on the data generated in step 250 in Figure 2. Other appropriate methods and techniques for creating a prosthesis based on the data will be recognized by persons of ordinary skill in the art. Further, as noted in the discussion of Figure 1, the prosthesis generated based on the data from step 250 may be implanted into the patient, such as depicted in step 150 of Figure 1. The manufactured prosthesis, such as a crown, bridge, or coping, may have an inner surfaces which defines a cavity within the prosthesis. As noted above, this inner surface may have a middle band. In some embodiments, the manufactured prosthesis may have one or more of its support points along the middle band. As noted above, having support points along the middle band may improve the robustness of a prosthesis.

Example System

[0049] Figure 7 illustrates an embodiment of a system 700 for improving dental prosthesis robustness. The system 700 may include one or more computers 710 coupled to one or more displays 720, and one or more input devices 730. Various embodiments will run just on a system 700 that includes only one or more computers 710, without interaction with an operator 740. In some embodiments, when there is interaction with an operator 740, who may be a dentist, dental technician, or other person, the operator 740 may plan the data for dental prosthesis using system 700 by manipulating the one or more input devices 730, which may be a keyboard and / or a mouse. In some embodiments, while working on the dental design, the operator 740 may view images on a display 720. The display 720 may include one or more display regions or portions of the display, each of which displays a different aspect of the dental design. The display 720 may also have an area that would allow the operator 740 to input patient(s) data, which the operator could input using input devices 730, such as a keyboard and mouse.

[0050] In various embodiments, the computer 710 may include one or more processors, one or more memories, and / or one or more communication mechanisms. In some embodiments, more than one computer 710 may be used to execute the modules, methods, and processes discussed herein. Additionally, the modules and processes herein may each run on one or multiple processors, on one or more computers; or the modules herein may run on dedicated hardware. The input devices 730 may include one or more keyboards (one-handed or two-handed), mice, touch screens, voice commands and associated hardware, gesture recognition, or any other means of providing communication between the operator 740 and the computer 710. The communication among the various components of system 700 may be accomplished via any appropriate coupling, including USB, VGA cables, coaxial cables, FireWire, serial cables, parallel cables, SCSI cables, IDE cables, SATA cables, wireless based on 802.11 or Bluetooth, or any other wired or wireless connection(s). One or more of the components in system 700 may also be combined into a single unit. In some embodiments, all of the electronic components of system 700 are included in a single physical unit.

[0051] The display 720 may be a 2D or 3D display and may be based on any technology, such as LCD, CRT, plasma, projection, et cetera.

[0052] The processes, computer readable medium, and systems described herein may be performed on or may relate to various types of hardware, such as computer systems. In computer systems may include a bus or other communication mechanism for communicating information, and a processor coupled with the bus for processing information. A computer system may have a main memory, such as a random access memory or other dynamic storage device, coupled to the bus. The main memory may be used to store instructions and temporary variables. The computer system may also include a read-only memory or other static storage device coupled to the bus for storing static information and instructions. The computer system may also be coupled to a display, such as a CRT or LCD monitor. Input devices may also be coupled to the computer system. These input devices may include a mouse, a trackball, or cursor direction keys. Computer systems described herein may include the computer 710, display 720, and / or input device 730. Each computer system may be implemented using one or more physical computers or computer systems or portions thereof. The instructions executed by the computer system may also be read in from a computer-readable medium. The computer-readable medium may be a CD, DVD, optical or magnetic disk, laserdisc, carrier wave, or any other medium that is readable by the computer system. In some embodiments, hardwired circuitry may be used in place of or in combination with software instructions executed by the processor.

[0053] As will be apparent, the features and attributes of the specific embodiments disclosed above may be combined in different ways to form additional embodiments, all of which fall within the scope of the present disclosure.

[0054] Conditional language used herein, such as, among others, "can," "could," "might," "may," "e.g.," and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and / or states. Thus, such conditional language is not generally intended to imply that features, elements and / or states are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and / or states are included or are to be performed in any particular embodiment.

[0055] Any process descriptions, elements, or blocks in the flow diagrams described herein and / or depicted in the attached figures should be understood as potentially representing modules, segments, or portions of code which include one or more executable instructions for implementing specific logical functions or steps in the process. Alternate implementations are included within the scope of the embodiments described herein in which elements or functions may be deleted, executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those skilled in the art.

[0056] All of the methods and processes described above may be embodied in, and fully automated via, software code modules executed by one or more general purpose computers or processors, such as those computer systems described above. The code modules may be stored in any type of computer-readable medium or other computer storage device. Some or all of the methods may alternatively be embodied in specialized computer hardware.

[0057] It should be emphasized that many variations and modifications may be made to the above-described embodiments, the elements of which are to be understood as being among other acceptable examples. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims.

Claims

1. A computer-implemented method for improving dental prosthesis robustness, comprising:

determining, using a computer system, a support point configuration for a prosthesis based at least in part on robustness of said support point configuration,

wherein said prosthesis comprises an inner surface, an outer surface, and a marginal edge, said marginal edge being disposed between the inner surface and the outer surface; wherein the support point configuration comprises a plurality of discrete points and the plurality of discrete points is disposed on the inner surface of the prosthesis; and wherein data for producing the prosthesis is generated based, at least in part, on said support point configuration.

2. The method of claim 1 , wherein determining said support configuration for the prosthesis comprises:

determining, using the computer system, at least two candidate support point configurations, wherein the candidate support point configurations each comprise a plurality of discrete points;

determining, using the computer system, a robustness rating for each of said candidate support point configurations; and

choosing one of the at least two candidate support point configurations as said support point configuration based at least in part on the at least two robustness ratings.

3. The method of claim 2, wherein determining said candidate support point configuration comprises generating a configuration of random seed positions as prospective support point positions and iteratively moving the prospective support point positions to find a configuration of support point positions in which support points at those positions have improved robustness over the robustness of previous iterations' prospective support point configurations.

4. The method of claim 2, wherein determining the candidate support point configuration comprises performing the Wang algorithm.

5. The method of any of the preceding claims, wherein generating data for production comprises generating the shape of the support points to approximate caps protruding from an inner surface of the prosthesis.

6. The method of any of the preceding claims, wherein generating data for production comprises determining the size and shape of the support points based at least in part on manufacturing tolerances.

7. The method of any of the preceding claims, wherein generating data for production comprises selecting the prosthesis from a group consisting of a coping, crown, or bridge.

8. The method of any of claims 2-4, wherein determining said support configuration for the prosthesis comprises determining more than two candidate support point configurations, wherein the number of candidate support point configurations determined is predefined.

9. The method of any of claims 2-4 or 8, wherein determining said support configuration for the prosthesis comprises determining more than two candidate support point configurations, and wherein additional candidate support point configurations are determined until the robustness rating for at least one of the candidate support point configurations is above a predefined threshold.

10. The method of any of claims 2-4 or 8-9, wherein determining said support configuration for the prosthesis comprises calculating the robustness rating, at least in part, based on the root mean square of the movements of an inner surface of the prosthesis over multiple simulated assemblies as compared to a nominal position of the inner surface of the prosthesis.

1 1. The method of any of claims 2-4 or 8-9, wherein determining said support configuration for the prosthesis comprises calculating the robustness rating, at least in part, based on a worst-case calculation or best-case calculation of variations in location of an inner surface of the prosthesis over multiple simulated assemblies.

12. The method of any of the preceding claims, wherein generating data for production comprises generating data for the plurality of discrete support points that comprises three or more discrete support points.

13. The method of any of the preceding claims, wherein generating data for production comprises generating data for at least one support point in said support point configuration such that the at least one support point is located away from the top of an inner surface of the prosthesis.

14. The method of any of the preceding claims, wherein generating data for production comprises generating data that comprises a surface model for the inner surface and said support point configuration.

15. The method of any of the preceding claims, wherein generating data for production comprises generating data for a milling path for milling the inner surface and said support point configuration.

16. A dental prosthesis comprising:

a body comprising an inner surface, an outer surface, and a marginal edge, said outer surface being generally disposed on the outward facing portion of the prosthesis, said inner surface being generally designed to fit a prepared tooth, and said marginal edge being disposed between the inner surface and the outer surface,

wherein the prosthesis also comprises a support point configuration, said support point configuration comprising a plurality of support points and the plurality of support points are non-uniformly disposed on the inner surface away from the marginal edge.

17. The dental prosthesis of claim 16, wherein the plurality of support points approximate the shape of spherical caps protruding from the inner surface of the prosthesis.

18. The dental prosthesis of any of claims 16-17, wherein the size and shape of the plurality of support points are determined based at least in part on manufacturing tolerances.

19. The dental prosthesis of any of claims 16-18, wherein the prosthesis is selected from a group consisting of a coping, crown, or bridge.

20. The dental prosthesis of any of claims 16-19, wherein the plurality of support points comprises three or more discrete support points.

21. The dental prosthesis of any of claims 16-20, wherein the inner surface of the prosthesis further comprises a top portion and wherein at least one of the plurality of support points is disposed away from the top portion of the inner surface.

22. The dental prosthesis of any of claims 16-21 , wherein said support point configuration is determined based on robustness of said support point configuration.

23. The dental prosthesis of any of claims 16-22, wherein said support configuration for the prosthesis is determined based on at least in part on: determining at least two candidate support point configurations, wherein the at least two candidate support point configurations each comprise a plurality of discrete points; determining a robustness rating for each of the at least two candidate support point configurations; and

choosing said support point configuration from among the at least two candidate support point configurations based at least in part on the at least two robustness ratings.

24. A system for improving dental prosthesis robustness, comprising:

one or more computers, each including one or more processors and memory, said computers being configured to:

determine a support point configuration for a prosthesis based at least in part on robustness of said support point configuration,

wherein said prosthesis comprises an inner surface, an outer surface, and a marginal edge, said marginal edge being disposed between the inner surface and the outer surface;

wherein the support point configuration comprises a plurality of discrete points and the plurality of discrete points is disposed on the inner surface of the prosthesis; and

wherein data for producing the prosthesis is generated based, at least in part, on said support point configuration.

25. A computer-readable medium for improving dental prosthesis robustness, said computer-readable medium containing instructions, said instructions operable to execute on a computer system, said instructions when executing on the computer system performing a method comprising:

determining a support point configuration for a prosthesis based at least in part on robustness of said support point configuration,