# Patent

## Title
System and method for automated generating of a cutting curve on a surface

## Abstract

A computer-implemented method for the automated adjustment of the position of a cutting tool when cutting dental aligner material includes using a computer for generating digital data that define (a) a first cutting angle in a labial cutting area along a dynamic cutting curve, (b) a second cutting angle in a lingual cutting area along the dynamic cutting curve, and (c) a third cutting angle in a back molar cutting area along the dynamic cutting curve. The cutting tool is automatically moved from the labial cutting area to the back molar cutting area while gradually increasing a cutting tool angle from the first cutting angle to the third cutting angle. The cutting tool is also automatically moved from the lingual cutting area to the back molar cutting area while gradually increasing the cutting tool angle from the second cutting angle to the third cutting angle.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a divisional of application Ser. No. 11/551,395, filed Oct. 20, 2006 now U.S. Pat. No. 7,711,447, the disclosure of which is incorporated herein in its entirety.


TECHNICAL FIELD
The present invention relates, generally, to mass customization of form fitting objects, and in particular to a system and method for automated generating of a cutting curve on a surface, such as for the generation of a cutting curve on a gingival surface to facilitate the cutting of an aligner material used in orthodontic treatment.
BACKGROUND OF THE INVENTION
The use of plastics or other materials to create form fitting objects requires precise development and manufacturing processes. Common form fitting objects typically include medical products like hearing aids, prosthetics or clear aligners for repositioning teeth.
The use of clear, plastic-type aligners for the re-positioning of teeth is becoming increasingly popular. Such aligners are typically produced by forming a plastic material over stereolithography (SLA) molds that represent various stages of treatment of a patient's orthodontic treatment. After forming the aligner material over a mold, the cutting of the aligner material occurs on the gingival surface along the interproximal area, i.e., a region that is proximate the gingival surface between the teeth and gums, to define the plastic aligner from the SLA molds. Conventional methodologies for creating such a cutting curve have various drawbacks.
For example, in many instances, the cutting curve has too many straight lines between the interproximal areas, with such straight line portions unable to provide sufficient resistance force to effectively facilitate teeth movement, and potentially cutting into the gingival surface of the patient and causing great pain. In other interproximal areas, a sharp shaped portion of the aligner material can result in stress risers, potentially causing the aligner material to break during treatment.
Manual trimming of the aligner material is also required in many instances, such as the punctured inner shell. As another example, in some cases the interproximal areas can have the cutting curve passing inside the jaw mold that leads to puncturing of the stereolithography (SLA) mold, requiring the SLA mold to be rebuilt and manually trimmed. Manual trimming is also typically required with such conventional processes in treating pontic cases, often requiring pontic cases to be filtered out from automation trimming line before such manual trimming, as well as in the back molar region to address extraneous material produced.
Still further, conventional techniques for generating cutting curves do not suitably address the potential for collisions of a cutting tool within the cutting machine when cutting the aligner material from the SLA molds.
SUMMARY OF THE INVENTION
In accordance with various aspects of the present invention, a system and method for automated generating of a cutting curve on a surface is provided. In accordance with an exemplary embodiment, a computer-implemented method for automated generating of a cutting curve on the surface to facilitate cutting of a material, e.g., for a form-fitting object, comprises defining initial surface curves along the line around the object, replacing the initially defined surface curves with a modified, dynamic curve, and then outputting a complete dynamic curve to facilitate cutting of the material for the form-fitting object.
In accordance with another exemplary embodiment, a computer-implemented method for automated generating of a cutting curve on a gingival surface to facilitate cutting of an aligner material comprises the defining of initial gingival curves along the line around a tooth (LAT) on a patient's jaw. The initial gingival curves are replaced with a modified, dynamic cutting curve, with the resulting complete dynamic cutting curve then output for conversion into machine executable code to facilitate cutting of the aligner material.
In accordance with other exemplary embodiments, the computer-implemented method for automated generating of a cutting curve on the gingival surface can also be configured to modify the dynamic cutting curve in a back molar region to remove extraneous material and/or to define a cutting curve region around a pontic object between two teeth.
In accordance with another exemplary embodiment of the present invention, to avoid collision of a cutting tool with teeth, attachment, inner shell and a fixture when cutting the aligner material, a computer-implemented method can also be provided to suitably define cutting angles and otherwise adjust the cutting tool along the dynamic cutting curve to provide a method for dynamic adjustment of the cutting tool.



BRIEF DESCRIPTION OF THE DRAWINGS
The exemplary embodiments of the present invention will be described in connection with the appended drawing figures in which like numerals denote like elements, and wherein:
FIG. 1A illustrates a diagram of an exemplary method for automated generating of a cutting curve on a surface in accordance with an exemplary embodiment of the present invention;
FIG. 1B illustrates a diagram of an exemplary method for automated generating of a cutting curve on a gingival surface in accordance with another exemplary embodiment of the present invention;
FIG. 2A illustrates diagram of an exemplary gingival surface and gingival parametric curves in accordance with an exemplary embodiment of the present invention;
FIG. 2B illustrates a diagram of an Hermite-Spline curve in accordance with an exemplary embodiment of the present invention;
FIG. 2C illustrates a diagram of Hermite basic functions in accordance with an exemplary embodiment of the present invention;
FIG. 2D illustrates a diagram of an exemplary interproximal area between two neighboring teeth, as a sampled points and a gingival parametric curve in accordance with an exemplary embodiment of the present invention;
FIG. 2E illustrates a diagram of an average plane and its normal from the sample points derived from FIG. 2D in accordance with an exemplary embodiment of the present invention;
FIG. 3 illustrates a diagram and graphical representations of an exemplary method of projecting sample points and generation of a cylinder in accordance with an exemplary embodiment of the present invention;
FIG. 4 illustrates a diagram and graphical representation of a dynamic cutting curve region in accordance with an exemplary embodiment of the present invention;
FIGS. 5-7D illustrate a diagrams of a back molar region and lifting of a dynamic cutting curve in accordance with an exemplary embodiment of the present invention;
FIG. 8 illustrates a cutting curve without a pontic object in accordance with an exemplary embodiment of the present invention;
FIG. 9 illustrates a dynamic cutting curve configured with a pontic object in accordance with an exemplary embodiment of the present invention;
FIG. 10 illustrates an exemplary complete dynamic cutting curve in accordance with an exemplary embodiment of the present invention;
FIG. 11 illustrates a diagram for a cutting tool and fixture in which collision can occur in accordance with an exemplary embodiment of the present invention;
FIG. 12 illustrates a diagram for adjusted cutting areas in accordance with an exemplary embodiment of the present invention;
FIG. 13 illustrates diagrams for a cutting tool and attachment with and without adjustment of the cutting angles in accordance with an exemplary embodiment of the present invention;
FIGS. 14 and 15 illustrate diagrams for adjustment of the cutting tool in accordance with exemplary embodiments of the present invention; and
FIG. 16 illustrates a block diagram for control system for facilitating automated generation of the dynamic cutting curve and/or for dynamic adjustment of the cutting tool in accordance with an exemplary embodiment of the present invention.



DETAILED DESCRIPTION
The present invention may be described herein in terms of various components and processing steps. It should be appreciated that such components and steps may be realized by any number of hardware and software components configured to perform the specified functions. For example, the present invention may employ various electronic control devices, visual display devices, input terminals and the like, which may carry out a variety of functions under the control of one or more control systems, microprocessors or other control devices. In addition, the present invention may be practiced in any number of orthodontic, dental, medical or other treatment or therapeutic contexts, and/or any protective equipment or athletic applications, and the exemplary embodiments relating to a system and method for automated generating of a cutting curve on the gingival surface, and/or the control of a cutting tool to avoid collision, as described herein are merely a few of the exemplary applications for the invention. For example, the principles, features and methods discussed may be applied to any application or process in which the automated generation of a curve to facilitate the cutting or other separation of materials is conducted, or in which the cutting of such materials during the manufacture of devices and equipment can be suitably utilized, such as in the generation, design and/or manufacture of any form-fitting device. e.g., eye glass frames, contact or glass lens, hearing aids or plugs, artificial knee caps, prosthetic limbs and devices, orthopedic inserts, as well as protective equipment such as knee guards, athletic cups, or elbow, chin, and shin guard and other like athletic/protective devices.
In accordance with various aspects of the present invention, a system and method for automated generating of a cutting curve on a surface is provided. In accordance with an exemplary embodiment, with reference to FIG. 1A, a computer-implemented method 100A for automated generating of a cutting curve on the surface to facilitate cutting of a material, e.g., for a form-fitting object, comprises defining initial surface curves along the line around the object, such as within interproximal areas between two surfaces (102A), replacing the initially defined surface curves with a modified, dynamic curve (104B), and then outputting a complete dynamic curve to facilitate cutting of the material for the form-fitting object (106B). Such a method can be utilized in the field of form-fitting and other like devices to suitably cut plastics and other materials in manufacturing the device.
For example, in the design and manufacture of form-fitting objects such as eye glasses, method 100A can define initial surface curves around the nose-region of the eye glass frames (102A), e.g., along the lines of the eye glass frames around the upper nose surface, and then replace those initial surface curves using the processes disclosed herein to provide a modified, dynamic curve (104A). Such a modified, dynamic curve can then used suitably provided in an appropriate format to facilitate the cutting of the eye glass frames from composite materials, plastics or other suitably materials for eye glass frames. Similarly, when form-fitting an ear piece to be used, for example, as a hearing aid, audio ear piece, or noise reduction plugs, method 100A can define initial surface curves of the inner ear (102A), and then replace those initial surface curves using the processes disclosed herein to provide a modified, dynamic curve (104A). Such a dynamic curve can be provided in an appropriate format to facilitate the cutting of the form fitting ear piece from a desirable material.
In accordance with an exemplary embodiment, with reference to FIG. 1B and the application to a gingival surface, a computer-implemented method 100B for automated generating of a cutting curve on the gingival surface to facilitate cutting of an aligner material comprises defining initial gingival curves along the line around a tooth (LAT) of a patient's jaw, including within interproximal areas between two teeth of a patient (102B), replacing the initially defined gingival curves with a modified, dynamic curve (104B), and then outputting a complete dynamic curve to facilitate aligner cutting (106B).
Defining the initial gingival curves along a line around a tooth (LAT) on a jaw within an interproximal area between two teeth (102B) can be suitably conducted by various conventional processes for providing a gingival curve along the LAT. For example, such generation of gingival curves can comprise any conventional computational orthodontics methodology or process for identification of gingival curves, now known or hereinafter derived. For example, the methodologies and processes for identification of gingival curves can include those disclosed in U.S. Pat. No. 7,040,896, entitled “Systems and Methods for Removing Gingiva From Computer Tooth Models”, and assigned to Align Technology, Inc. (the “'896 patent”) and U.S. Pat. No. 6,514,074, entitled “Digitally Modeling the Deformation of Gingival”, and assigned to Align Technology, Inc. (the “'074 patent”), and the various patents disclosed in the '896 and '074 patents. In the '896 patent, for example, such a process for identification of gingival curves can comprise a computer-implemented method separates a tooth from an adjacent structure, such as a gingiva, by defining a cutting surface, and applying the cutting surface between the tooth and the structure to separate the tooth in a single cut. In the '074 patent, for example, such a process for identification of gingival curves can comprise having a computer obtain a digital model of a patient's dentition, including a dental model representing the patient's teeth at a set of initial positions and a gingival model representing gum tissue surrounding the teeth, wherein the computer then derives from the digital model an expected deformation of the gum tissue as the teeth move from the initial positions to another set of positions.
In such processes, to obtain a digital model used to generate the gingival curves, a digital data set representing a tooth arrangement can be obtained, referred to as the IDDS. Such an IDDS may be obtained in a variety of ways. For example, the patient's teeth may be scanned or imaged using well known technology, such as X-rays, three-dimensional x-rays, computer-aided tomographic images or data sets, magnetic resonance images, etc. Methods for digitizing such conventional images to produce data sets are well known and described in the patent and medical literature. By way of example, one approach is to first obtain a plaster cast of the patient's teeth by well known techniques, such as those described in Graber, Orthodontics: Principle and Practice, Second Edition, Saunders, Philadelphia, 1969, pp. 401-415. After the tooth casting is obtained, it can be digitally scanned using a conventional laser scanner or other range acquisition system to produce the IDDS. The data set produced by the range acquisition system may, of course, be converted to other formats to be compatible with the software which is used for manipulating images within the data set. General techniques for producing plaster casts of teeth and generating digital models using laser scanning techniques are also described, for example, in U.S. Pat. No. 5,605,459.
In accordance with an exemplary embodiment, with reference to FIGS. 2A-2C, the initial gingival curves 250 can be generated by use of the conventional Hermite-Spline process. In general, the Hermite form of the cubic polynomial curve segment is determined by constraints on the endpoints P1 and P4 and tangent vectors at the endpoints R1 and R4. The Hermit curve can be written in the following form:

Q(s)=(2s3−3s2+1)P1+(−2s3+3s2)P4+(s3−2s2+s)R1+(s3−s2)R4;s[0,1]  (1)

Equation (1) can be rewritten as:

Q(s)=F1(s)P1+F2(s)P4+F3(s)R1+F4(s)R4;  (2)

Wherein equation (2) is the geometric form of Hermite-Spline Curve, the vectors P1,P4,R1,R4 are the geometric coefficients, and the F terms are Hermit basis functions. FIG. 2B shows a Hermite-Spline defined by P1,P4,R1,R4, and FIG. 2C shows four Hermite basis functions.

With reference to FIG. 2A, a gingival surface 251 comprises a set of gingival parametric curves 256. A gingival surface 251 is defined by gingival curves 250 on all teeth and a base line 252, with base line 252 being obtained from a digital model of the patient's jaw. Thus, with a plurality of gingival curves 250 and base line 252, a Hermite surface patch that represents gingival surface 251 can be generated. While a Hermite-Spline approach to generation of gingival curve 250 and gingival surface 251 is used in the exemplary embodiment, any other process for defining initial gingival curves along a line around a tooth (LAT) on a jaw within an interproximal area between two teeth and/or generation of gingival surfaces can be utilized.
Rather than having gingival curves 250 comprise a sharp point or other narrow region in the interproximal areas 258, as illustrated in FIG. 2D, that can cause weakening of the aligner material during use, the initial gingival curves 250 are replaced with a modified, dynamic cutting curve. In accordance with an exemplary embodiment, with reference to FIG. 2D, a modified curve can be generated to replace the initial gingival curves (104B) by initially obtaining a plurality of sample points, e.g., s1, s2 . . . s9 and s10, from a pair of gingival curve portions 230A and 230B residing on each side of an interproximal area. Sample points s1-s10, are then converted into point lists with associated geometric information, for example, into ADF or other like data formats. In accordance with an exemplary embodiment, five sample points are collected from each of curve portions 230A and 230B; however, fewer or more sample points can also be collected. Sample points s5 and s6 are suitably selected proximate the inner region between two teeth, but sufficiently distanced from where the two teeth meet or come to a point or narrow region within interproximal area 258.
Such a collection of sample points s1-s10 provide a plurality of points in space (not in the same plane) that can be used to generate an average plane and its normal. For example, with reference to FIG. 2E, an average plane (P) passing through ten points in space collected from sampled points s1-s10 can be generated, along with its normal (N). Sample points s1-s10 can then be projected onto plane (P) to generate two new curves, A and B as illustrated in FIG. 3, that are associated with gingival curve portions 230A and 230B.
To minimize weakening of a region of the aligner material within the interproximal area, the modified dynamic curve can be configured with an offset adjustment that comprises a minimum radius requirement in the interproximal area 258 (see FIG. 2D) to prevent breakage of the aligner material during use. As shown in FIG. 3, two parallel curves A′ and B′ can be defined with an offset adjustment 350 between curves A and B and parallel curves A′ and B′. An intersection point 352 between parallel curves A′ and B′ is then generated. In accordance with an exemplary embodiment, offset adjustment 350 comprises approximately 3 mm, but can comprise longer or shorter values in other embodiments so long as an intersection point 352 is generated. In the event that an initial offset adjustment 350 does generate an intersection point 352, offset adjustment 350 can be suitably increased or decreased in increments, e.g., in 0.1 mm increments, until an intersection point 352 is found. Offset adjustment 350 is further configured to take into account that a resulting dynamic cutting curve should have sufficient radius in the interproximal area to facilitate enough resistance force applied to the teeth to cause effective movement, but not too small radius as to facilitate breakage, e.g., a sharp point or other narrow portion of material can create a stress region susceptible to break during use.
Next, a cylinder 354 with an axis at intersection point 352 and direction N, having a radius equal to offset adjustment 350, can be suitably generated. Cylinder 354 can then facilitate the defining of the modified gingival curve. For example, with reference to FIG. 4, tangent points t1 and t2 between cylinder 354 and curve portions 230A and 230B (defined by sample points s1, s2, . . . s10) and intersection points i1, i2 and i3 between cylinder 354 and a plurality of gingival parametric curves 456 can be suitably defined to generate a dynamic cutting curve between teeth 220A and 220B (see FIG. 2D). Gingival parametric curves 456 can be suitably generated in various manners, for example, such as by use of the conventional Hermite surface patch process, or any other process for generating gingival parametric curves. In addition, while two tangent points t1 and t2 and three intersection points i1, i2 and i3 are defined in the exemplary embodiment, additional or fewer points can also be utilized to generate the dynamic cutting curve between two teeth.
Accordingly, rather than have the cutting curve comprise a sharp point or other narrow region, a plurality of intersection points, such as i1, i2 and i3, and tangent points t1 and t2, are used to generate a dynamic cutting curve in the interproximal region. For example, the dynamic cutting curve illustrated in FIG. 4 can be defined as the curve passing through sample points s1-s4, then tangent point t1, intersection points i1-i3, tangent point t2, and then sample points s7-s10.
Such a process for defining a dynamic cutting curve between two teeth can then be suitably applied to the interproximal regions of other teeth within a patient, with the complete dynamic cutting curve then being output for conversion into machine executable code to facilitate cutting of the aligner material (106B) (see FIG. 1B).
The above process for defining the dynamic cutting curve is particularly suitable in the regions between two teeth, for example, in the labial sides of a jaw of the patient. In the back molar region of a patient, where the dynamic cutting curve is originally defined as the LAT of a back molar, extraneous aligner material can sometimes result. For example, with reference to FIG. 5, extraneous aligner material can be left within a region 564 that can result in pain or discomfort to a patient if the aligner material is left in its original unmodified configuration, and thus has to be manually removed or cut under conventional processes. However, with reference again to FIG. 1B, in accordance with another exemplary embodiment, computer-implemented method 100 can also be configured to further modify the dynamic curves in the back molar areas (108B), such as illustrated in FIG. 6, prior to being output for conversion into machine executable code to facilitate cutting of the aligner material (106B) by lifting the dynamic curve within the region proximate the back molars.
For example, the dynamic cutting curve can be lifted by an adjustment based on at least one of two input parameters, including an adjustment of a molar height parameter (AdjustMolarHeight or AMH) and/or an adjustment of a molar length parameter (AdjustMolarLength or AML), as illustrated in FIG. 7A. In adjusting based on the molar height parameter AMH, the dynamic curve is raised up to just above the crown surface of the molar, with an adjustment between approximately 1.0 mm and 3 mm being used, e.g., the dynamic curve being lifted an average of approximately 1.5 mm. In addition, the molar length parameter AML can also be adjusted, wherein parameter AML controls the area where the curve is adjusted gradually, i.e., along the length of the curve for example, and wherein parameter AML can vary from a unit length (AML=1) to shorter length/areas thereof.
For example, with reference to FIG. 7B, in the case where the dynamic cutting curve can be adjusted from point A to B, the parameter AML=1, this means the curve from A to B is lifted gradually with the largest height/lift value (AMH=1.5 mm) at the point B (lifting the curve from B up to B′). In another example, with reference to FIG. 7C and with AML=0.5, the dynamic cutting curve portion from A to C is lifted gradually, and the dynamic cutting curve portion from C′ to B′ parallels that of the curve portion from C to B (comprise an AMH=1.5 mm). Further, with reference to FIG. 7D and with AML=0.2, the dynamic cutting curve portion from A to C is lifted rapidly (to an AMH=1.5 mm), with the dynamic cutting curve portion from C′ to B′ thereafter parallel to that of the curve from C to B. Various other values of parameter AML can also be selected to generate additional “lifted” dynamic cutting curves. The selection of parameters AML and AMH is determined by selecting suitably smooth curves that will allow the aligner material to be configured along the teeth to provide sufficient force for teeth movement and yet avoid the discomfort in the back molar region. Thus, in the above examples, the adjusted/lifted cutting curve in FIG. 7D may not be selected in many instances, instead having the adjusted curves similar to those illustrated in FIGS. 7B and 7C utilized.
As a result of the adjustment of the dynamic cutting curve through the use of lifting parameters AMH and AML, the dynamic cutting curve can be suitably lifted proximate the back molar area, such as illustrated in FIG. 6. Such an adjustment can allow the aligner material to be configured along the teeth to provide sufficient force for teeth movement and yet avoid the discomfort in the back molar region.
In accordance with another exemplary embodiment, method 100B can also comprise the automated generation of dynamic cutting curves within a pontic region of a patient as illustrated in FIG. 9. Pontic objects 972 are placed in locations where two neighboring teeth have a large gap, such as when a tooth has previously been removed. A pontic object comprises a virtual tooth configured to fill in the gap, typically within the labial side of the aligner. Methodologies for generating pontic objects are known in the art, but such conventional methodologies do not take into account the use of pontic objects when generating the cutting curves and thus require manual trimming of pontic cases. However, in accordance with this exemplary embodiment that includes a pontic object, the dynamic cutting curve can be suitably configured as if the pontic object comprised a real tooth, utilizing the techniques disclosed herein to facilitate a suitable cutting curve.
To generate a dynamic cutting curve configured to address such large gaps, with continued reference to FIG. 9, a pontic object 972 is first generated by any conventional methods for generating such pontic objects. Next, a gingival curve 974 is generated around pontic object 972 on the gingival surface. Pontic object 972 and neighboring teeth 976A and 976B define two virtual interproximal areas A and B. Similar to the generation of curve portions 230A and 230B of FIG. 2, curve portions 978A, 978B and 978C can be suitably generated. For example, the collection of sample points s1, s2, . . . sn along the gingival curves of pontic object 972 and teeth 976A and 976B, the generation of average planes (P) and normals (N), and the generation of parallel lines and an intersection point to provide a cylinder like that illustrated in cylinder 354 in FIG. 3 and FIG. 4, can be conducted to define a plurality of tangent points t1, t2, . . . tn and intersection points i1, i2, i3 . . . in within interproximal regions A and B of FIG. 9. As a result, a further modified dynamic cutting curve configured to address pontic objects can be defined.
The dynamic cutting curve can be suitably generated for each of other the teeth and interproximal areas between those teeth, with or without adjustments for back molar regions and/or pontic objects, for both the labial and lingual side of a patients teeth. As a result of generating dynamic cutting curve portions within the various interproximal areas between teeth of a patient, a complete or whole dynamic cutting curve 1080 can be suitably generated, such as that illustrated in FIG. 10.
After generation of the complete dynamic cutting curve 1080 for each of other the teeth and interproximal areas between those teeth, dynamic cutting curve 1080 can then be output for conversion into machine executable code to facilitate cutting of the aligner (106B). For example, in an exemplary embodiment, dynamic cutting curve 1080 can be converted into a GCode or other standard machine executable code used in CNC cutting machines, such as that disclosed in U.S. Pat. No. 7,040,896, entitled “Systems and Methods for Removing Gingiva From Computer Tooth Models” or other like methodologies.
As discussed, conventional methods for generating cutting curves do not suitably address the potential for collisions of a cutting tool within the cutting machine when cutting the aligner material from the SLA molds. For example, with reference to FIG. 11, a cutting tool 1102 can potentially collide with the mold and aligner material during the cutting process, particularly if the cutting angle is not suitably controlled. For example, a cutting angle 1104 cannot be too small or cutting tool 1102 can potentially collide with a fixture 1106A during cutting, but also cannot be too large so as to potentially collide with an upper exterior side 1106B. However, in accordance with another aspect of the present invention, a method for dynamic adjustment of the cutting tool along the dynamic cutting curve can be provided. In accordance with an exemplary embodiment, with reference to FIG. 12, a plurality of cutting areas around the dynamic cutting curve are provided, including a labial cutting area 1202, a lingual cutting area 1204, back molar cutting areas 1206A and 1206B, as well as four transition zones 1208 located between areas 1202 and 1206A, areas 1206A and 1204, areas 1204 and 1206B, and areas 1206B and 1202. Within such areas 1202, 1204, 1206A and 1206B and zones 1208, the method for dynamic adjustment of the cutting tool is configured to suitably adjust cutting angle 1104 to avoid collisions.
For example, in accordance with an exemplary embodiment, cutting angle 1104 is adjusted to approximately 15 degrees within labial area 1202, to approximately 35 degrees within lingual areas 1204, and approximately 40 degrees within back molar areas 1206A and 1206B. By approximate adjustment, within about +/−1.5 degrees is suitable, although a greater range can also be realized, e.g., +/−5 degrees or more. Transition areas 1208 are suitably to facilitate a gradual transition from one cutting area to another cutting area, increasing and/or decreasing cutting angle 1104. For example, as cutting tool 1102 proceeds in a clockwise fashion from an approximate cutting angle of 15 degrees within labial cutting area 1202 to an approximate cutting angle of 40 degrees for back molar cutting area 1206A, a transition zone 1208 in between will gradually increase cutting angle 1104 from approximately 15 degrees to approximately 40 degrees.
To define where areas 1202, 1204, 1206A and 1206B and zones 1208 start and end, with continued reference to FIG. 12, additional parameters such as an angle begin 1210 and an angle end 1212 can be provided. Angle begin 1210, angle end 1212 and transition zones 1208 can comprise float values that are configured to control cutting angle boundaries. Thus, for example as illustrated in FIG. 12, with a reference line drawn from point A to point B that is tangent with the cutting curve in back molar regions, a parallel line can be generated, with that parallel line being spaced a distance equal to the float value of angle begin parameter 1210 and angle end parameter 1212. Thus, for example, for float values of approximately 3 mm for angle begin parameter 1210 and angle end parameter 1212, the locations where the parallel line intersect the length along the cutting curve can suitably define where the cutting areas for back molar regions 1206A and 1206B start and end. Transition zones 1208 are defined by floating values that comprise an additional distance from that parallel line. Thus, for a floating value of approximately 1 mm for transition zones 1208 (that would provide a distance of approximately 4 mm from the tangent line from A to B), the beginning and end of such transition zones can be established, as well as labial and lingual cutting areas 1202 and 1204.
The floating values for angle begin parameter 1210, angle end parameter 1212 and transition zones 1208 can comprise various values. For example, parameters 1210 and 1212 can comprise the same values, or different values, depending on the desired length of back molar cutting areas 1206A and 1206B, as well as when the desired position to start and end such cutting areas. In addition, transition zones 1208 can also comprise the same value, or can comprise different values, again depending on the desired length of labial and lingual cutting areas 1202 and 1204. For example, such starting and ending positions and length can suitably depend upon the diameter and/or settings of the cutting tool.
Accordingly, with reference to FIG. 13, an example of an uncontrolled cutting angle B within the labial cutting area that is substantially greater than a controlled cutting angle B′, for example having a cutting angle of approximately 15 degrees, can result in collision between the cutting tool and the aligner material, whereas the controlled cutting angle B′ avoids collision.
In accordance with another exemplary embodiment, the method for dynamic adjustment of the cutting tool can also be configured to automatically adjust cutting tool 1102 a specified distance away from the initial cutting tool line, such as moving cutting tool 1102 low as illustrated in FIG. 14 to avoid collision with the teeth or attachment device, and/or away from an inner shell 1510 along the cutting tool axis to avoid collision with inner shell 1510 as illustrated in FIG. 15.
To avoid collision with the teeth or attachment device by moving the cutting tool low, a determination is made as to whether collision with the teeth or attachment device will occur, followed by adjustment of cutting tool 1102 in very small increments from an old tool line to a new tool line, such as increments of approximately 0.01 mm. Such adjustment is continued until the collision with the teeth or attachment device is eliminated or a maximum value of adjustment, e.g., 0.2 mm, is reached. In addition, the determination of collision with the teeth or attachment device and the incremental adjustment process is continuously repeated while moving cutting tool 1102 along the cutting curve. Thus, for example, while cutting tool 1102 may be adjusted approximately 0.04 mm at one point along the cutting curve, at another point along the cutting curve an adjustment of 0.08 mm of the position of cutting tool 1102 may be needed to avoid collision. Further, although adjacent points along the cutting curve may require very different amounts of adjustment, in accordance with an exemplary embodiment, these required amount of adjustments may be suitably modified even further to provide a smooth transition of cutting tool 1102 without collision with the teeth or attachment device as it moves along the cutting curve.
To avoid collision with inner shell 1510 at a position A, a determination is made as to whether collision with inner shell 1510 will occur, followed by automatically adjusting cutting tool 1102 away from inner shell 1510 in very small increments, e.g., in increments of approximately 0.01 mm, until collision with the inner shell is eliminated at a new position A′. Similar to the process above, the determination of collision with inner shell 1510 and the incremental adjustment process away from inner shell 1510 is continuously repeated while cutting tool 1102 is moved or transitioned along the cutting curve. Thus, for example, while cutting tool 1102 may be adjusted way from inner shell 1510 by approximately 0.04 mm at one point along the cutting curve, at another point along the cutting curve an adjustment away from inner shell 1510 of approximately 0.08 mm may be needed to avoid collision. Further, although adjacent points along the cutting curve may require very different amounts of adjustment away from inner shell 1510, in accordance with an exemplary embodiment, these required amounts of adjustment may be suitably modified even further to provide a smooth transition of cutting tool 1102 as it moves along the cutting curve without collision with inner shell 1510.
Such automated generation of the dynamic cutting curve and/or for dynamic adjustment of the cutting tool can be conducted with one or more computer-based systems through the use of one or more algorithms. For example, with reference to FIG. 16, an exemplary computerized system 1600 for facilitating automated generation of the dynamic cutting curve and/or for dynamic adjustment of the cutting tool can comprise one or more computer-based systems or modules, microprocessors, memory systems and/or input/output devices for processing data and information, comprising one or more software algorithms configured for computing and/or performing other functions set forth herein. For example, exemplary computerized system 1600 can comprise memory or storage subsystems 1606-1614, processors 1602, network interfaces 1616, input/output devices 1618 and/or other components 1620-1624 as disclosed in U.S. Pat. No. 7,040,896, entitled “Systems and Methods for Removing Gingiva From Computer Tooth Models”, and assigned to Align Technology, Inc., or any other computerized system components used for computational orthodontics.
The present invention has been described above with reference to various exemplary embodiments. However, those skilled in the art will recognize that changes and modifications may be made to the exemplary embodiments without departing from the scope of the present invention. For example, the various operational steps, as well as the components for carrying out the operational steps, may be implemented in alternate ways depending upon the particular application or in consideration of any number of cost functions associated with the operation of the system, e.g., various of the component and methodologies and/or steps may be deleted, modified, or combined with other components, methodologies and/or steps, depending on the whether the application is for orthodontic, dental, medical or other treatment or therapeutic contexts. Moreover, it is understood that various of the methods and steps disclosed herein, such as generating of IDDS, identifying or gingival curves or other processes can also comprise any other conventional techniques, or any later developed techniques, for facilitating such methods and steps. These and other functions, methods, changes or modifications are intended to be included within the scope of the present invention, as set forth in the following claims.

## Claims

1. A computer-implemented method for dynamic adjustment of the position of a cutting tool when cutting dental aligner material, said computer-implemented method comprising:
using a computer for generating digital data that define (a) a first cutting angle in a labial cutting area along a dynamic cutting curve, (b) a second cutting angle in a lingual cutting area along the dynamic cutting curve, and (c) a third cutting angle in a back molar cutting area along the dynamic cutting curve;
automatically moving a cutting tool from the labial cutting area to the back molar cutting area while gradually increasing a cutting tool angle from the first cutting angle to the third cutting angle; and
automatically moving the cutting tool from the lingual cutting area to the back molar cutting area while gradually increasing the cutting tool angle from the second cutting angle to the third cutting angle.

2. The computer-implemented method according claim 1, wherein said method is further configured to define transition zones between said labial cutting area and said back molar cutting area, and between said lingual cutting area and said back molar cutting area.

3. The computer-implemented method according claim 1, wherein said method is further configured to automatically adjust the cutting tool to a new position away from an initial cutting tool line or away from an inner shell along a cutting tool axis.

4. A computer-implemented method for avoiding collision of a cutting tool with teeth, an attachment, an inner shell or a fixture when cutting dental aligner material, the method comprising:
using a computer for generating digital data that define a first cutting angle in a labial cutting area along a cutting curve;
using a computer for generating digital data that define a second cutting angle in a lingual cutting area along the cutting curve;
using a computer for generating digital data that define a third cutting angle in a back molar cutting area along the cutting curve;
automatically adjusting a cutting tool position in incremental values away from an initial cutting tool line until a collision with the teeth, an inner shell, fixture, or an attachment device is avoided or a maximum adjustment value is reached; and
continuously repeating automatically adjusting the cutting tool in incremental values away from an initial cutting tool line while moving the cutting tool along the cutting curve.

5. The computer-implemented method according to claim 4, wherein said computer-implemented method is further configured for generating digital data that automatically define transition zones between said labial cutting area and said back molar cutting area, and between said lingual cutting area and said back molar cutting area.

6. The computer-implemented method according to claim 5, further comprising moving a cutting tool along a transition zone from one cutting area to another cutting area, wherein the cutting tool has an angle that gradually increases as the cutting tool moves along a transition zone.

7. A computer-implemented method for dynamic adjustment of the position of a cutting tool when cutting of an aligner material, said computer-implemented method comprising:
using a computer for generating digital data that define a labial cutting area, a lingual cutting area, and a back molar cutting area along a dynamic cutting curve;
using a computer for generating digital data that define a first transition zone between the labial cutting area and the back molar cutting area, the first transition zone being configured to facilitate a gradual transition from the labial cutting area to the back molar cutting area;
using a computer for generating digital data that define a second transition zone between the lingual cutting area and said back molar cutting area, the second transition zone being configured to facilitate a gradual transition from the lingual cutting area to the back molar cutting area;
using a computer for generating digital data that define a first cutting angle in the labial cutting area, a second cutting angle in the lingual cutting area, and a third cutting angle in the back molar cutting area, each along the dynamic cutting curve;
automatically moving a cutting tool along the first transition zone from the labial cutting area to the back molar cutting area while gradually increasing an angle of the cutting tool from the labial cutting angle to the back molar cutting angle; and
automatically moving the cutting tool along the second transition zone from the lingual cutting area to the back molar cutting area while gradually increasing the angle of the cutting tool from the lingual cutting angle to the back molar cutting angle.

8. The computer-implemented method according to claim 7, wherein said method is further configured to automatically adjust the cutting tool to a new position away from an initial cutting tool line or away from an inner shell along a cutting tool axis.

9. The computer-implemented method according to claim 7, wherein said method further comprises automatically adjusting the cutting tool in incremental values away from an initial cutting tool line until a collision with teeth or an attachment device is avoided or a maximum adjustment value is reached.

10. The computer-implemented method according claim 9, comprising continuously repeating automatically adjusting the cutting tool in incremental values away from an initial cutting tool line while moving the cutting tool along the dynamic cutting curve.

11. The computer-implemented method according to claim 9, wherein said automatically adjusting the cutting tool away comprises incrementally adjusting the cutting tool in incremental values away from an inner shell until a collision with an inner shell is avoided.

12. The computer-implemented method according to claim 7, wherein the first cutting angle is adjusted to approximately 15 degrees within the labial cutting area, the second cutting angle is adjusted to approximately 35 degrees within the lingual cutting area, and the third cutting angle is adjusted to approximately 40 degrees within the back molar cutting area.

13. The computer-implemented method according to claim 7, wherein the transition zones facilitate a gradual transition from one cutting area to another cutting area by changing an appropriate one of the cutting angles.

14. The computer-implemented method according claim 7, wherein an angle of the cutting tool is adjusted from approximately 15 degrees to approximately 40 degrees.

15. The computer-implemented method according claim 7, wherein each of the lingual cutting area, the labial cutting area and the back molar cutting area starts and ends with an angle begin and an angle end, each of the angle begins and angle ends comprising values that are configured to control cutting angle boundaries.