(12) United States Patent
`Chishti et al.
`
`I 1111111111111111 11111 lllll lllll 111111111111111 1111111111 1111111111 11111111
`US006227850Bl
`US 6,227,850 Bl
`May 8, 2001
`
`(10) Patent No.:
`(45) Date of Patent:
`
`(54) TEETH VIEWING SYSTEM
`
`(75)
`
`Inventors: Muhammad Ziaullah Khan Chishti,
`Sunnyvale; Phillips Alexander Benton,
`Mountain View, both of CA (US)
`
`(73) Assignee: Align Technology, Inc., Santa Clara,
`CA(US)
`
`( *) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by O days.
`
`(21) Appl. No.: 09/313,290
`May 13, 1999
`
`(22) Filed:
`
`(51)
`
`Int. Cl.7
`
`A61C 3/00
`
`(52) U.S. Cl. ............................. 433/24; 433/213; 433/215
`
`(58) Field of Search ............................... 433/24, 213, 215
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`
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`5,273,429
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`5,340,309
`5,342,202
`5,368,478
`5,382,164
`5,395,238
`5,431,562
`5,447,432
`5,452,219
`5,454,717
`
`5/1972 Andrews ................................ 433/24
`1/1975 Levine .............................. 235/151.1
`7/1988 Abbatte et al. .......................... 433/6
`1/1989 Breads ..................................... 433/6
`8/1989 Breads et al. ............................ 433/6
`6/1990 Walker et al.
`......................... 623/23
`4/1991 Lemchen .................................. 433/6
`7/1991 Breads et al. ............................ 433/6
`10/1991 Abbatte et al. ........................ 433/24
`10/1991 Breads et al. ............................ 433/6
`8/1992 Andreiko et al. ...................... 433/24
`2/1993 Breads et al. ............................ 433/6
`12/1993 Rekow ................................. 433/215
`8/1994 Wu et al. ............................. 433/213
`8/1994 Robertson .............................. 433/69
`8/1994 Deshayes ............................. 434/270
`11/1994 Andreiko et al. ...................... 433/24
`1/1995 Stern .................................... 433/223
`3/1995 Andreiko et al. ...................... 433/24
`7/1995 Andreiko et al. ...................... 433/24
`9/1995 Andreiko et al. ...................... 433/24
`9/1995 Dehoff et al. ................... 364/474.05
`10/1995 Andreiko et al. ...................... 433/24
`
`5,474,448
`5,528,735 *
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`5,645,421
`
`12/1995
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`
`Andreiko et al. ...................... 433/24
`Strasnick et al. .................... 395/127
`Andreiko et al. ...................... 433/24
`Stern .................................... 433/223
`Andersson et al. ............. 364/468.04
`Kuroda et al. ....................... 433/214
`Andersson et al. .................. 433/223
`Slootsky .................................. 433/6
`
`OTHER PUBLICATIONS
`
`Biostar Operation & Training Manual, Great Lakes Orth(cid:173)
`odontics, Ltd. 199 Fire Tower Drive, Tonawanda, New York,
`14150---5890, 20 pgs.
`Chiappone, "cconstructingthe gnathologic setup and posi(cid:173)
`tioner," J. Clin. Orthod., 1980, 14:121-133.
`Cottingham,
`"Gnathologic
`clear plastic positioner,"
`Am.J.Orthod. 1969, 55:23-31.
`Cureton, "Correcting malaligned mandibular incisors with
`removable retainers," J.Clin. Orthod. 1996. 30:390-395.
`Elsasser, "Some oobservationson the history and uses of the
`Kesling positioner," Am. J. Orthod. 1950, 36:368-374.
`Kamada et al., "Case reports on tooth positioners with LTV
`vinyl silicone rubber and some case reports," J. Nihon
`University School of Dentistry 1982, 24(1):1-27.
`Kesling, "The philosophy of the tooth positioning appli(cid:173)
`ance," Am. J. Orthod. Oral. Surg. 1945, 31(6):297-304.
`Kesling, "Coordinating the predetermined pattern and tooth
`positioner with conventional treatment," Am. J. Orthod.
`Oral. Surg. 1946, 32:285-293.
`Kleeman et al., "The speed positioner," J. Clin. Orthod.
`1996, 30:673-680.
`
`(List continued on next page.)
`
`Primary Examiner-John J. Wilson
`(74) Attorney, Agent, or Firm-Fish & Richardson P.C.
`
`(57)
`
`ABSTRACT
`
`A computer is used to create a plan for repositioning an
`orthodontic patient's teeth. The computer receives a digital
`data set representing the patient's teeth and uses the data sets
`to generate one or more orthodontic views of the patient's
`teeth.
`
`38 Claims, 6 Drawing Sheets
`
`Provide high resolution
`IDDS
`
`Convert data into quad
`edge data structure
`
`Remove unnecessary
`structurewltheraser
`
`Matching high
`resolution and low
`resolution components
`
`Place component in
`final position
`
`Align EX1024
`Align v. 3Shape
`IPR2022-00144
`
`

`

`US 6,227,850 Bl
`Page 2
`
`OIBER PUBLICATIONS
`
`Kuroda et al., "Three---dimensinal dental cast analyzing
`system using laser scanning," Am. J. Orthod. Dentofac.
`Orthop. 1996 110:365-369.
`Nishiyama et al., "A new construction of tooth repositioner
`by LTV vinyl silicone rubber," J. Nihon Univ. School of
`Dentistry 1977. 19(2): 93-102.
`Nippon Dental Review, "New orthodontic device-dynamic
`positioner (D.P.)-1 Approach to the proposal of D.P. and
`transparent silicone rubber," 1980, 452:61-74.
`Nippon Dental Review, "New orthodontic device-dynamic
`positioner (D .P.)-11, Practice application and construction of
`D.P. and transparent silicone rubber," 1980, 454:107-130.
`Nipon Dental Review, "New orthodontic device-dynamic
`positioner (D.P.)-III, Case reports of reversed occlusion,"
`457:146-164.
`Nippon Dental Review, "New orthodontic device-dynamic
`positioner (D.P.)-Case reports of reversed occlusion,"
`1980,458: 112-129.
`Raintree Essix & ARS Materials, Inc., Raintree Essix,
`Technical Magazine Table of contents and Essix Appliances,
`httpz;//www.essix.com/magazine/dafault.html Aug.
`13,
`1997, 7 pgs.
`
`finishing problems with
`Shilliday, "Minimizing
`mini-positioner," Am J. Orthod. 1971, 59:596-599.
`
`the
`
`Warunek et al., "Physical and mechanical properties of
`elastomers in orthodonic positioners," Am. J. Orthod.
`Dentofac. Orthop. 1989, 95:388-400.
`
`Wells, "Application of the positioner appliance in orth(cid:173)
`odonic treatment" Am. J. Orthodont. 1970, 58:351-366.
`
`Lawrence F. Andrews, D.D.S., "The six to normal occlu(cid:173)
`sion," Am. J. Orthod. 9/1972, 269-308.
`
`Lawrence F. Andrews, D.D.S., "Straight Wire, The Concept
`and Appliance," The Six Keys to Optimal Occlusion, 15-24.
`
`Kamada et al., "Construction of Tooth Positioners with LTV
`Vinyl Silicone Rubber and Some Case Reports," J. Nihon
`University School of Dentistry 3/1982, 24(1):1-26.
`
`Schroeder et al., "Algoritms I," The Visualization Toolkit
`chapter 6-9.9, 1996.
`
`Warunek et al., "Clinical Use of Silicone Elastomer Appli(cid:173)
`ances," JCO 10/1989, 694-700.
`
`* cited by examiner
`
`

`

`U.S. Patent
`
`May 8, 2001
`
`Sheet 1 of 6
`
`US 6,227,850 Bl
`
`100
`
`~
`
`102
`
`104
`
`106
`
`108
`
`Digitize initial tooth
`arrangement to produce
`initial digital data set
`(IDDS)
`
`Manipulate IDDS to
`produce final digital
`data set (FDDS)
`corresponding to a
`desired final tooth
`arrangement
`
`Generate multiple
`intermediate digital data
`sets (INTDDS's)
`corresponding to
`successive tooth
`arrangements from
`initial to final
`
`Produce incremental
`position adjustment and
`appliances based on
`STDDS's and FDDS
`
`FIG._ 1
`
`Obtain scan data for
`positive model of teeth
`
`Obtain scan data for
`negative model of teeth
`
`Construct two
`geometric models of
`teeth using scan data
`
`Rotate one model to
`match other model
`
`300
`
`302
`
`304
`
`306
`
`308
`
`Perform optimization to
`find best match
`
`Combine matched
`points to form one data
`set
`
`310
`~
`
`FIG._2
`
`Generate camera look
`from point
`
`Generate camera look at
`point
`
`600
`
`602
`
`Generate camera up
`vector
`
`FIG._6
`
`

`

`U.S. Patent
`
`May 8, 2001
`
`Sheet 2 of 6
`
`US 6,227,850 Bl
`
`Receive 3D image data
`
`Isolate tooth casting to
`be modeled
`
`Apply marching cubes
`algorithm
`
`Perform smoothing
`operation
`
`Apply decimation
`algorithm
`
`Calculate error
`
`400
`
`401
`
`402
`
`404
`
`406
`
`408
`
`Store previous mesh as
`tooth model
`
`412
`
`FIG._3
`
`500
`
`502
`
`506
`
`508
`
`510
`
`512
`
`514
`
`516
`
`Provide high resolution
`IDDS
`
`Create lower resolution
`IDDS
`
`Convert data into quad
`edge data structure
`
`Remove unnecessary
`structure with eraser
`tool
`
`Divide data sets into
`independently moveable
`components with saw
`tool
`
`Identify separate
`components
`
`Matching high
`resolution and low
`resolution components
`
`Place component in
`final position
`
`FIG._4
`
`

`

`U.S. Patent
`U.S. Patent
`
`May8,2001
`May 8, 2001
`
`Sheet 3 of 6
`Sheet 3 of 6
`
`US 6,227,850 Bl
`US 6,227,850 B1
`
` [QR] mee [Bigg TE Be
`
`ets
`, .. ,-- 2018
`
`A
`/
`
`\
`i
`'
`'I
`'"-20"12 "-_ 2008
`I
`20T8
`\.2016
`
`
`FIG. 3
`
`

`

`U.S. Patent
`
`May 8, 2001
`
`Sheet 4 of 6
`
`US 6,227,850 Bl
`
`RIGHT BUCCAL
`FIG«_7
`
`LEFTBUCCAL
`FIG._8
`
`RIGHT BUCCAL OVERJET
`FJGM_ 11
`
`LEFT BUCCAL OVERJET
`FIGz_ 10
`
`FJG._ 12
`
`ANTERIOR OVERJET
`
`TOP
`
`BOTTOtv1
`
`

`

`U.S. Patent
`
`May 8, 2001
`
`Sheet 5 of 6
`
`US 6,227,850 Bl
`
`RIGHT LINGUAL
`
`LEFT U t\JG UAL
`
`ANTERIOR
`
`MAXILLARY OCCLUSAL
`FIG~.-16
`
`t¥1ANDIBULAR OCCLUSAL
`
`

`

`U.S. Patent
`
`May 8, 2001
`
`Sheet 6 of 6
`
`US 6,227,850 Bl
`
`FIG._ 18
`
`2100
`
`j
`
`FIG._ 19
`
`2102b
`
`r-------------------------------------
`Storage Subsystem
`500
`
`- - - - - - - - _ ) 5 0 8 , - . - - - - - - - - - - ,
`Memory Subsystem
`
`506
`
`5~
`
`~
`
`51L__r::7
`
`~
`
`File Storage
`Subsystem
`
`514
`
`Bus Subsystem
`
`Modems and
`Network
`Interface
`
`User Interface
`Input & Output
`Devices
`
`518
`
`Processor(s)
`
`502
`
`Scanner
`
`520
`
`Casts
`
`516
`
`Network
`Interface
`
`Fabrication
`Machine
`
`522
`
`Dental Appliances
`
`FIG._20
`
`524
`
`

`

`US 6,227,850 Bl
`
`1
`TEETH VIEWING SYSTEM
`
`This application is related to U.S. patent applications Ser.
`No. 09/169,036, entitled "System and Method for Position(cid:173)
`ing Teeth", and Ser. No. 09/169,034, entitled "Defining
`Tooth-Moving Appliances Computationally", both filed on
`Oct. 8, 1998, the full disclosures of which are incorporated
`herein by reference.
`
`BACKGROUND
`
`Field of the Invention
`The invention relates generally to the field of orthodontics
`and, more particularly, to computer-automated development
`of an orthodontic treatment plan and appliance.
`Orthodontics is the branch of dentistry that deals with the
`straightening of crooked teeth. Although there are many
`types of appliances that can be used by an orthodontist to
`straighten the teeth, the most common appliance is braces.
`Braces include a variety of appliances such as brackets, 20
`archwires, ligatures, and O-rings, and attaching braces to a
`patient's teeth is a tedious and time consuming enterprise
`requiring many meetings with the treating orthodontist.
`Consequently, conventional orthodontic treatment limits an
`orthodontist's patient capacity and makes orthodontic treat- 25
`ment quite expensive.
`Before fastening braces to a patient's teeth, at least one
`appointment is typically scheduled with the orthodontist,
`dentist, and/or X-ray laboratory so that X-rays and photo(cid:173)
`graphs of the patient's teeth and jaw structure can be taken. 30
`Also during this preliminary meeting, or possibly at a later
`meeting, an alginate mold of the patient's teeth is typically
`made. This mold provides a model of the patient's teeth that
`the orthodontist uses in conjunction with the X-rays and
`photographs to formulate a treatment strategy. The orth- 35
`odontist then typically schedules one or more appointments
`during which braces will be attached to the patient's teeth.
`The formulation of the treatment strategy is typically a
`trial-and-error process where the orthodontist arrives at the
`treatment strategy using a mental model based on the
`orthodontist's experience and skill. Because an exact model
`is not available, the formulation of the treatment strategy is
`an art which is highly dependent on the estimates and
`judgments of the treating orthodontist. Moreover, once the
`treatment strategy has been generated, it is difficult to
`explain the expected result to the patient in words.
`
`2
`teeth can be animated to provide a visual display of the
`movement of the teeth along the treatment paths. A level(cid:173)
`of-detail compression can be applied to the selected data set
`to render the graphical representation of the teeth. A human
`5 user can modify the graphical representation of the teeth,
`which causes modifications to the selected data set in
`response to the instruction from the user. A graphical inter(cid:173)
`face with components representing the control buttons on a
`video cassette recorder can be provided for a human user can
`10 manipulate to control the animation. A portion of the data in
`the selected data set can be used to render the graphical
`representation of the teeth. The human user can select a tooth
`in the graphical representation and read information about
`the tooth. The information can relate to the motion that the
`15 tooth will experience while moving along the treatment
`path. The graphical representation can render the teeth at a
`selected one of multiple viewing orthodontic-specific view(cid:173)
`ing angles. An input signal from a 3D gyroscopic input
`device controlled by a human user can be used to alter the
`orientation of the teeth in the graphical representation.
`In a second aspect, a computer program, residing on a
`tangible storage medium for use in displaying an orthodontic
`view of a patient's teeth, includes executable instructions
`operable to cause a computer to: capture three-dimensional
`(3D) data associated with the patient's teeth; determine a
`viewpoint for the patient's teeth; apply a positional trans-
`formation to the 3D data based on the viewpoint; and render
`the orthodontic view of the patient's teeth based on the
`positional transformation.
`Advantages of the invention include one or more of the
`following. Visualization is used to communicate treatment
`information in a computer-automated orthodontic treatment
`plan and appliance. The invention generates a realistic
`model of the patient's teeth without requiring a user to
`possess in-depth knowledge of parameters associated with a
`patient dental data capture system. Additionally, expertise in
`3D software and knowledge of computer architecture is no
`longer needed to process and translate the captured medical
`data into a realistic computer model rendering and anima-
`40 tion.
`The invention thus allows teeth plan treatment to be
`generated in a simple and efficient manner. It also improves
`the way a treating clinician performs case presentations by
`allowing the clinician to express his or her treatment plans
`45 more clearly and gives a prospective patients an opportunity
`to visualize the facial changes associated with the proposed
`treatment. The invention allows multi disciplinary work
`teams to deal easily and efficiently with the treatment plan.
`Another major benefit is the ability to visualize and interact
`50 with models and processes without the attendant danger,
`impracticality, or significantly greater expense that would be
`encountered in the same environment if it were physical.
`Thus, money and time are saved while the quality of the
`treatment plan is enhanced.
`
`SUMMARY
`
`A computer is used to create a plan for repositioning an
`orthodontic patient's teeth. The computer receives a digital
`data set representing the patient's teeth and uses the data set
`to generate one or more orthodontic views of the patient's
`teeth. The system captures three-dimensional (3D) data
`associated with the patient's teeth; determines a viewpoint
`for the patient's teeth; applies a positional transformation to
`the 3D data based on the viewpoint; and rendering the
`orthodontic view of the patient's teeth based on the posi(cid:173)
`tional transformation.
`Implementations of the invention may include one or 60
`more of the following. The system can generate a right
`buccal overjet view, an anterior overject view, a left buccal
`overjet view, a left distal molar view, a left lingual view, a
`lingual incisor view, a right lingual view and a right distal
`molar view of the patient's teeth. A 3D graphical represen- 65
`tation of the teeth at the positions corresponding to a selected
`data set can be rendered. The graphical representation of the
`
`55
`
`DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a flow chart of a process for producing a system
`of incremental position adjustment appliances.
`FIG. 2 is a flow chart of a process for forming one 3D
`image data set of teeth from two sets of image data.
`FIG. 3 is a flow chart of a process for forming a 3D
`surface mesh from 3D image data.
`FIG. 4 is a block diagram setting forth the steps for
`manipulating an initial digital data set representing an initial
`tooth arrangement to produce a final digital data set corre(cid:173)
`sponding to a desired final tooth arrangement.
`
`

`

`US 6,227,850 Bl
`
`3
`FIG. 5 is a screen shot of a GUI display used to render 3D
`images of an orthodontic patient's teeth.
`FIG. 6 is a flow chart of a process for rendering 3D images
`of an orthodontic patient's teeth.
`FIGS. 7-17 show exemplary 3D images of an orthodontic
`patient's teeth.
`FIGS. 18-19 illustrate a technique for improving the
`downloading and rendering speed of an orthodontic image
`data file.
`FIG. 20 is a simplified block diagram of a data processing
`system.
`
`DETAILED DESCRIPTION
`
`5
`
`30
`
`4
`destructive scanner or a contact-type scanner, to produce the
`IDDS. The data set produced by the scanner may be pre(cid:173)
`sented in any of a variety of digital formats to ensure
`compatibility with the software used to manipulate images
`represented by the data, as described in more detail below.
`General techniques for producing plaster casts of teeth and
`generating digital models using laser scanning techniques
`are described, for example, in U.S. Pat. No. 5,605,459, the
`full disclosure of which is incorporated in this application by
`10 reference.
`Suitable scanners include a variety of range acquisition
`systems, generally categorized by whether the acquisition
`process requires contact with the three dimensional object
`being scanned. Some contact-type scanners use probes hav-
`15 ing multiple degrees of translational and/or rotational free(cid:173)
`dom. A computer-readable (i.e., digital) representation of the
`sample object is generated by recording the physical dis(cid:173)
`placement of the probe as it is drawn across the sample
`surface.
`Conventional non-contact-type scanners include
`reflective-type and transmissive-type systems. A wide vari(cid:173)
`ety of reflective systems are in use today, some of which
`utilize non-optical incident energy sources such as micro(cid:173)
`wave radar or sonar. Others utilize optical energy. Non-
`25 contact-type systems that use reflected optical energy usu(cid:173)
`ally include special instrumentation that carry out certain
`measuring techniques (e.g., imaging radar, triangulation and
`interferometry).
`One type of non-contact scanner is an optical, reflective
`scanner, such as a laser scanner. Non-contact scanners such
`as this are inherently nondestructive (i.e., do not damage the
`sample object), generally are characterized by a relatively
`high capture resolution, and are capable of scanning a
`sample in a relatively short period of time. One such scanner
`is the Cyberware Model 15 scanner manufactured by
`Cyberware, Inc., Monterey, Calif.
`Both non-contact-type and contact-type scanners also can
`include color cameras which, when synchronized with the
`scanning capabilities, provide means for capturing, in digital
`format, color representations of the sample objects. The
`importance of this ability to capture not just the shape of the
`sample object but also its color is discussed below.
`Other scanners, such as the CSS-1000 model destructive
`scanner produced by Capture Geometry Inside (CGI),
`Minneapolis, Minn., can provide more detailed and precise
`information about a patient's teeth than a typical range
`acquisition scanner can provide. In particular, a destructive
`scanner can image areas that are hidden or shielded from a
`50 range acquisition scanner and therefore may not be subject
`to adequate imaging. The CSS-1000 scanner gathers image
`data for an object by repeatedly milling thin slices from the
`object and optically scanning the sequence of milled sur(cid:173)
`faces to create a sequence of 2D image slices, so none of the
`55 object's surfaces are hidden from the scanner. Image pro(cid:173)
`cessing software combines the data from individual slices to
`form a data set representing the object, which later is
`converted into a digital representation of the surfaces of the
`object, as described below.
`The destructive scanner may be used in conjunction with
`a laser scanner to create a digital model of a patient's teeth.
`For example, a laser scanner may be used first to build a
`low-resolution image of a patient's upper and lower arches
`coupled with the patient's wax bite, as described below. The
`destructive scanner then may be used to form high(cid:173)
`resolution images of the individual arches. The data obtained
`by the laser scanner indicates the relation between the
`
`FIG. 1 shows a process 100 for producing the incremental
`position adjustment appliances for subsequent use by a
`patient to reposition the patient's teeth. As a first step, an
`initial digital data set (IDDS) representing an initial tooth
`arrangement is obtained (step 102). The IDDS is then
`manipulated using a computer having a suitable graphical 20
`user interface (GUI) and software appropriate for viewing
`and modifying the images. More specific aspects of this
`process will be described in detail below.
`Individual tooth and other components may be segmented
`or isolated in the model to permit their individual reposi(cid:173)
`tioning or removal from the digital model. After segmenting
`or isolating the components, the user will often reposition
`the tooth in the model by following a prescription or other
`written specification provided by the treating professional.
`Alternatively, the user may reposition one or more teeth
`based on a visual appearance or based on rules and algo(cid:173)
`rithms programmed into the computer. Once the user is
`satisfied, the final teeth arrangement is incorporated into a
`final digital data set (FDDS) (step 104). The FDDS is used
`to generate appliances that move the teeth in a specified
`sequence. First, the centers of each tooth model may be
`aligned using a number of methods. One method is a
`standard arch. Then, the teeth models are rotated until their
`roots are in the proper vertical position. Next, the teeth
`models are rotated around their vertical axis into the proper
`orientation. The teeth models are then observed from the
`side, and translated vertically into their proper vertical
`position. Finally, the two arches are placed together, and the
`teeth models moved slightly to ensure that the upper and
`lower arches properly mesh together. The meshing of the
`upper and lower arches together is visualized using a colli(cid:173)
`sion detection process to highlight the contacting points of
`the teeth.
`Based on both the IDDS and the FDDS, a plurality of
`intermediate digital data sets (INTDDSs) are defined to
`correspond to incrementally adjusted appliances (step 106).
`Finally, a set of incremental position adjustment appliances
`are produced based on the INTDDs and the FDDS (step
`108).
`In step 102, the patient's teeth may be scanned or imaged
`using well known technology, such as X-rays, three(cid:173)
`dimensional X-rays, computer-aided tomographic images or
`data sets, and magnetic resonance images. Methods for
`digitizing such conventional images to produce useful data 60
`sets are well known and described in the patent and medical
`literature. Usually, however, a plaster cast of the patient's
`teeth is obtained by well known techniques, such as those
`described in Graber, Orthodontics: Principle and Practice,
`Second Edition, Saunders, Philadelphia, 1969, pp. 401-415. 65
`After the tooth casting is obtained, the casting is digitally
`scanned by a scanner, such as a non-contact type laser or
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`patient's upper and lower teeth, which later can be used to
`relate to each other the images generated by the destructive
`scanner and the digital models derived from them.
`The destructive scanner can be used to form the initial
`digital data set (IDDS) of the patient's teeth by milling and
`scanning a physical model, such as a plaster casting, of the
`teeth. To ensure a consistent orientation of the casting
`throughout the destructive scanning process, a scanning
`system operator pots the casting in potting material, such as
`Encase-It epoxy from CGI, and cures the material in a
`pressure vacuum (PV) chamber to form a mold. Placing the
`potting material into the PV chamber ensures that the
`material sets relatively quickly with virtually no trapped air
`bubbles. The color of the potting material is selected to
`contrast sharply with the color of the casting material to
`ensure the clarity of the scanned image. The operator then
`mounts the mold to a mounting plate and places the molding
`plate in the destructive scanning system.
`A slicing mechanism ("cutter") in the destructive scan(cid:173)
`ning system mills a thin slice (typically between 0.001" and
`0.006" thick) from the mold, and a positioning arm places
`the milled surface near an optical scanner. The optical
`scanner, which may be an off-the-shelf device such as a
`flatbed scanner or a digital camera, scans the surface to
`create a 2D image data set representing the surface. The
`positioning arm then repositions the mold below the cutter,
`which again mills a thin slice from mold. The resulting
`output of the destructive scanning system is a 3D image data
`set, which later is converted into a digital model of surfaces,
`as described in detail below. A destructive scanning system
`and the corresponding destructive scanning and data pro(cid:173)
`cessing are described in U.S. Pat. No. 5,621,648.
`A patient's wax bite can be used to acquire the relative
`positions of the upper and lower teeth in centric occlusion.
`For a laser scan, this can be accomplished by first placing the
`lower cast in front of the scanner, with the teeth facing
`upwards, then placing the wax bite on top of the lower cast,
`and finally placing the upper cast on top of the lower cast,
`with the teeth facing downwards, resting on the wax bite. A
`cylindrical scan is then acquired for the lower and upper
`casts in their relative positions. The scanned data provides a
`digital model of medium resolution representing an object
`which is the combination of the patient's arches positioned
`in the same relative configuration as in the mouth.
`The digital model acts as a template guiding the place(cid:173)
`ment of the two individual digital models (one per arch).
`More precisely, using software, for example the CyberWare
`alignment software, each digital arch is in turn aligned to the
`pair scan. The individual models are then positioned relative
`to each other corresponding to the arches in the patient's
`mouth.
`The waxbite can also be scanned separately to provide a
`second set of data about the teeth in the upper and lower
`arches. In particular, the plaster cast provides a "positive"
`image of the patient's teeth, from which one set of data is
`derived, and the waxbite provides a "negative" image of the
`teeth, from which a second, redundant set of data is derived.
`The two sets of data can then be matched to form a single
`data set describing the patient's teeth with increased accu- 60
`racy and precision. The impression from which the plaster
`cast was made also can be used instead of or in addition to
`the waxbite.
`FIG. 2 is a flow chart of a process for deriving a single set
`of data from a positive data set and a negative data set. First,
`scan data representing positive and negative physical tooth
`models is obtained (steps 300, 302). If the scan data was
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`acquired through a destructive scanning process, two digital
`3D geometric models are constructed from the data, as
`described below (step 304). Scan data acquired from an
`optical or range acquisition scanner system typically suffices
`5 as a geometric model. One of the geometric models is
`positioned to match roughly with the other model in the
`digital model space (step 306), and an optimization process
`is performed to determine the best match between the
`models (step 308). The optimization process attempts to
`10 match one point in each model to one point in the other
`model. Each pair of matched points then is combined into a
`single point to form a single set of data (step 310). The
`combining of matched points can be carried out in a variety
`of ways, for example, by averaging the coordinates of the
`15 points in each pair.
`While a laser scanning system typically must perform
`three scans to image a patient's full set of teeth adequately
`( one high resolution scan for each of the upper and lower
`casts and a medium resolution waxbite scan), the destructive
`20 scanning system described above can image a patient's full
`set of teeth adequately with only a single waxbite scan.
`Scanning both casts with the wax bite in place ensures that
`all important surfaces of the upper and lower teeth are
`captured during a destructive scan. Scanning both casts in
`25 this manner also provides a high resolution image data set
`that preserves the relation between the patient's upper and
`lower teeth. Like the potting material described above, the
`wax bite should have a color that contrasts sharply with the
`color of the casting material to ensure the clarity of the
`30 scanned image. The wax bite may be the same color as the
`potting material if no contrast is desired between the waxbite
`and the potting material. Alternatively, the color of the wax
`bite may contrast sharply with the tooth casts and the potting
`material if an image of the wax bite is needed.
`In addition to the 3D image data gathered by laser
`scanning or destructive scanning the exposed surfaces of the
`teeth, a user may wish to gather data about hidden features,
`such as the roots of the patient's teeth and the patient's jaw
`bones. This information is used to build a more complete
`40 model of the patient's dentition and to show with more
`accuracy and precision how the teeth will respond to treat(cid:173)
`ment. For example, information about the roots allows
`modeling of all tooth surfaces, instead of just the crowns,
`which in turn allows simulation of the relationships between
`45 the crowns and the roots as they move during treatment.
`Information about the patient's jaws and gums also enables
`a more accurate model of tooth movement during treatment.
`For example, an x-ray of the patient's jaw bones can assist
`in identifying ankylose teeth, and an MRI can provide
`50 information about the density of the patient's gum tissue.
`Moreover, information about the relationship between the
`patient's teeth and other cranial features allows accurate
`alignment of the teeth with respect to the rest of the head at
`each of the treatment steps. Data about these hidden features
`55 may be gathered from many sources, including 2D and 3D
`x-ray systems, CT scanners, and magnetic resonance imag(cid:173)
`ing (MRI) systems. Using this data to introduce visually
`hidden features to the tooth model is described in more detail
`below.
`Developing an orthodontic treatment plan for a patient
`involves manipulating the IDDS at a computer or worksta(cid:173)
`tion having a suitable graphical user interface (GUI) and
`software appropriate for viewing and modifying the images.
`Specific aspects of the software will be described in detail
`65 hereinafter. However, dental appliances having incremen(cid:173)
`tally differing geometries can be produced by non-computer(cid:173)
`aided techniques. For example, plaster casts obtained as
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`described above may be cut using knives, saws, or other
`cutting tools in order to permit repositioning of individual
`teeth within the casting. The disconnected teeth may then be
`held in place by soft wax or other malleable material, and a
`plurality of intermediate tooth arrangements can then be
`prepared using such a modified plaster casting of the
`patient's teeth. The different arrangements can be used to
`prepare sets of multiple appliances, generally as described
`below, using pressure and vacuum molding techniques.
`The process of creating a 3D surface model of the teeth is
`discussed next. Many ty