# Patent

## Title
Preventing interference between tooth models

## Abstract

Systems and methods are disclosed to prevent interference between two physical tooth models in a physical dental arch model by acquiring the coordinates of a plurality of points on the surfaces of each of the two physical tooth models and digitally representing the surfaces of each of the two physical tooth models by a mesh of points in three dimensions using the acquired coordinates. The meshes representing the surfaces of the two physical tooth models intersect at least at one point to form an overlapping portion. The method also includes calculating the depth of the overlapping portion between the two meshes to quantify the interference of the two physical tooth models.

## Background
CROSS-REFERENCES TO RELATED INVENTIONS
This application is a continuation application of U.S. patent application Ser. No. 11/933,350, filed Oct. 31, 2007, which is a continuation application of U.S. patent application Ser. No. 11/013,154, now U.S. Pat. No. 7,309,230, filed Dec. 14, 2004, the entire content of each of which is herein incorporated by reference.
The present invention is also related to commonly assigned U.S. patent application Ser. No. 11/013,152, now U.S. Pat. No. 7,922,490, titled “Base for physical dental arch model” by Huafeng Wen, filed Dec. 14, 2004, commonly assigned U.S. patent application Ser. No. 11/012,924, titled “Accurately producing a base for physical dental arch model” by Huafeng Wen, filed Dec. 14, 2004, commonly assigned U.S. patent application Ser. No. 11/013,145, titled “Fabricating a base compatible with physical dental tooth models” by Huafeng Wen, filed Dec. 14, 2004, commonly assigned U.S. patent application Ser. No. 11/013,156, titled “Producing non-interfering tooth models on a base” by Huafeng Wen, filed Dec. 14, 2004, commonly assigned U.S. patent application Ser. No. 11/013,160, now U.S. Pat. No. 7,435,084, titled “System and methods for casting physical tooth model” by Huafeng Wen, filed Dec. 14, 2004, commonly assigned U.S. patent application Ser. No. 11/013,159, titled “Producing a base for accurately receiving dental tooth models” by Huafeng Wen, and filed Dec. 14, 2004, commonly assigned U.S. patent application Ser. No. 11/013,157, titled “Producing accurate base for dental arch model” by Huafeng Wen, filed Dec. 14, 2004.
The present invention is also related to U.S. patent application Ser. No. 10/979,823, now U.S. Pat. No. 7,384,266, titled “Method and apparatus for manufacturing and constructing a physical dental arch model” by Huafeng Wen, filed Nov. 2, 2004, now U.S. Pat. No. 7,384,266, issued Jun. 10, 2008, U.S. patent application Ser. No. 10/979,497, titled “Method and apparatus for manufacturing and constructing a dental aligner” by Huafeng Wen, Nov. 2, 2004, U.S. patent application Ser. No. 10/979,504, titled “Producing an adjustable physical dental arch model” by Huafeng Wen, filed Nov. 2, 2004, and U.S. patent application Ser. No. 10/979,824, titled “Producing a base for physical dental arch model” by Huafeng Wen, Nov. 2, 2004. The disclosure of these related applications are incorporated herein by reference.


TECHNICAL FIELD
This application generally relates to the field of dental care, and more particularly to a system and a method for manufacturing and constructing physical tooth models.
BACKGROUND
Orthodontics is the practice of manipulating a patient's teeth to provide better function and appearance. In treatments using fixed appliance, brackets are bonded to a patient's teeth and coupled together with an arched wire. The combination of the brackets and wire provide a force on the teeth causing them to move. Once the teeth have moved to a desired location and are held in a place for a certain period of time, the body adapts bone and tissue to maintain the teeth in the desired location. To further assist in retaining the teeth in the desired location, a patient may be fitted with a retainer.
To achieve tooth movement, orthodontists and dentists typically review patient data such as X-rays and models such as impressions of teeth. They can then determine a desired orthodontic goal for the patient. With the goal in mind, the orthodontists place the brackets and/or bands on the teeth and manually bend (i.e., shape) wire, such that a force is asserted on the teeth to reposition the teeth into the desired positions. As the teeth move towards the desired position, the orthodontist makes continual adjustments based on the progress of the treatment.
U.S. Pat. No. 5,518,397 issued to Andreiko, et. al. provides a method of forming an orthodontic brace. Such a method includes obtaining a model of the teeth of a patient's mouth and a prescription of desired positioning of such teeth. The contour of the teeth of the patient's mouth is determined, from the model. Calculations of the contour and the desired positioning of the patient's teeth are then made to determine the geometry (e.g., grooves or slots) to be provided. Custom brackets including a special geometry are then created for receiving an arch wire to form an orthodontic brace system. Such geometry is intended to provide for the disposition of the arched wire on the bracket in a progressive curvature in a horizontal plane and a substantially linear configuration in a vertical plane. The geometry of the brackets is altered, (e.g., by cutting grooves into the brackets at individual positions and angles and with particular depth) in accordance with such calculations of the bracket geometry. In such a system, the brackets are customized to provide three-dimensional movement of the teeth, once the wire, which has a two dimensional shape (i.e., linear shape in the vertical plane and curvature in the horizontal plane), is applied to the brackets.
Other innovations relating to bracket and bracket placements have also been patented. For example, such patent innovations are disclosed in U.S. Pat. No. 5,618,716 entitled “Orthodontic Bracket and Ligature” a method of ligating arch wires to brackets, U.S. Pat. No. 5,011,405 “Entitled Method for Determining Orthodontic Bracket Placement,” U.S. Pat. No. 5,395,238 entitled “Method of Forming Orthodontic Brace,” and U.S. Pat. No. 5,533,895 entitled “Orthodontic Appliance and Group Standardize Brackets therefore and methods of making, assembling and using appliance to straighten teeth”.
Kuroda et al. (1996) Am. J. Orthodontics 110:365-369 describes a method for laser scanning a plaster dental cast to produce a digital image of the cast. See also U.S. Pat. No. 5,605,459. U.S. Pat. Nos. 5,533,895; 5,474,448; 5,454,717; 5,447,432; 5,431,562; 5,395,238; 5,368,478; and 5,139,419, assigned to Ormco Corporation, describe methods for manipulating digital images of teeth for designing orthodontic appliances.
U.S. Pat. No. 5,011,405 describes a method for digitally imaging a tooth and determining optimum bracket positioning for orthodontic treatment. Laser scanning of a molded tooth to produce a three-dimensional model is described in U.S. Pat. No. 5,338,198. U.S. Pat. No. 5,452,219 describes a method for laser scanning a tooth model and milling a tooth mold. Digital computer manipulation of tooth contours is described in U.S. Pat. Nos. 5,607,305 and 5,587,912. Computerized digital imaging of the arch is described in U.S. Pat. Nos. 5,342,202 and 5,340,309.
Other patents of interest include U.S. Pat. Nos. 5,549,476; 5,382,164; 5,273,429; 4,936,862; 3,860,803; 3,660,900; 5,645,421; 5,055,039; 4,798,534; 4,856,991; 5,035,613; 5,059,118; 5,186,623; and 4,755,139.
U.S. Pat. No. 5,431,562 to Andreiko et al. describes a computerized, appliance-driven approach to orthodontics. In this method, first certain shape information of teeth is acquired. A uniplanar target arcform is calculated from the shape information. The shape of customized bracket slots, the bracket base, and the shape of the orthodontic archwire, are calculated in accordance with a mathematically-derived target archform. The goal of the Andreiko et al. method is to give more predictability, standardization, and certainty to orthodontics by replacing the human element in orthodontic appliance design with a deterministic, mathematical computation of a target arch form and appliance design. Hence the '562 patent teaches away from an interactive, computer-based system in which the orthodontist remains fully involved in patient diagnosis, appliance design, and treatment planning and monitoring.
More recently, removable appliances from companies such as Align Technology, Inc. began offering transparent, removable aligning devices as a new treatment modality in orthodontics. In this system, an impression model of the dentition of the patient is obtained by the orthodontist and shipped to a remote appliance manufacturing center, where it is scanned with a CT scanner. A computer model of the dentition in a target situation is generated at the appliance manufacturing center and made available for viewing to the orthodontist over the Internet. The orthodontist indicates changes they wish to make to individual tooth positions. Later, another virtual model is provided over the Internet and the orthodontist reviews the revised model, and indicates any further changes. After several such iterations, the target situation is agreed upon. A series of removable aligning devices or shells are manufactured and delivered to the orthodontist. The shells, in theory, will move the patient's teeth to the desired or target position.
The practice of orthodontics and other dental treatments including preparation of a denture can benefit from a physical dental arch model that is representative of the dentition and the alveolar ridge of a patient to be orthodontically treated. The physical dental arch model, also referred as a physical dental arch model, is often prepared based on an impression model. The physical dental arch model is generally prepared by cutting and arranging individual teeth on the alveolar ridge of the impression model. With this physical dental arch model so prepared, not only is a final goal for the dental treatment made clear, but also the occlusal condition between the maxillary and the mandibular dentitions can be specifically ascertained.
Also, the patient when the physical dental arch model is presented can visually ascertain the possible final result of orthodontic treatment he or she will receive and, therefore, the physical dental arch model is a convenient presentation tool to the patient.
Making a model for a whole or a large portion of an arch is more difficult than making one tooth abutment for implant purposes. Single tooth does not have the concavities and complexities as in the inter-proximal areas of teeth in an arch. Some prior art making the physical dental arch model is carried out manually, involving not only a substantial amount of labor required, but also a substantial amount of time. It is also difficult to machine an accurate arch model because of the various complex shapes and the complex features such as inter-proximal areas, wedges between teeth, among others, in an arch.
Another issue with the assembling of tooth models into a physical dental arch model is that the adjacent tooth models can sometimes interfere with each other during an orthodontic treatment. The interference can occur between the tooth portions of the two neighboring tooth models when they are inserted into a base plate, or between the pins that assist them to be mounted onto a base plate.
SUMMARY OF THE INVENTION
Systems and methods provide a practical, effective and efficient methods and apparatus to manufacture and construct the physical dental arch model.
In one aspect, the present invention relates to a method for preventing interference between two physical tooth models in a physical dental arch model, comprising:
acquiring the coordinates of a plurality of points on the surfaces of each of the two physical tooth models;
digitally representing the surfaces of each of the two physical tooth models by a mesh of points in three dimensions using the acquired coordinates, wherein the meshes representing the surfaces of the two physical tooth models intersect at least at one point to form an overlapping portion; and
calculating the depth of the overlapping portion between the two meshes to quantify the interference of the two physical tooth models.
In another aspect, the present invention relates to a method for preventing interference between two physical tooth models in a physical dental arch model, comprising:
acquiring the coordinates of a plurality of points on the surfaces of each of the two physical tooth models;
digitally representing the surfaces of each of the two physical tooth models by a mesh of points in three dimensions using the acquired coordinates, wherein the meshes representing the surfaces of the two physical tooth models intersect at least at one point to form an overlapping portion;
calculating the depth of the overlapping portion between the two meshes; and
adjusting the positions or the orientations of at least one of the two physical tooth models in accordance with the depth of the overlapping portion between the two physical tooth models to prevent the interference between the physical tooth models. In yet another aspect, the present invention relates to a method for preventing interference between two physical tooth models in a physical dental arch model, comprising:
acquiring the coordinates of a plurality of points on the surfaces of each of the two physical tooth models;
digitally representing the surfaces of each of the two physical tooth models by a mesh of points in three dimensions using the acquired coordinates;
interpolating each of the two meshes to produce one or more surfaces to represent the boundaries of one of the two physical tooth models, wherein the interpolated surfaces intersect at least at one point to form an overlapping portion; and
calculating the depth of the overlapping portion between the two interpolated surfaces to quantify the interference of the two physical tooth models.
Embodiments may include one or more of the following advantages. An advantage of the present invention is that adjacent physical tooth models in a physical dental arch model can be simulated. The interference between the two physical models can be predicted before they are assembled to form a physical arch model. The positions and the orientations of the tooth models can be adjusted to prevent the interference. As a result, the precision and effectiveness of the orthodontic treatments are improved.
Another advantage of the present invention is that the physical tooth models can be used to form different tooth arch models having different teeth configurations. The pin configurations can be modified without changing the tooth models themselves to be modified to prevent interference between adjacent tooth models at different steps of an orthodontic treatment. Moreover, the tooth models can be reused as tooth positions are changed during a treatment process. Much of the cost of making multiple tooth arch models in orthodontic treatment are therefore eliminated. The tooth models can have pins that assist their assembling with a base.
Another advantage of the present invention is that the same base can support different tooth arch models having different teeth configurations. The base can include more than one sets of receiving features that can receive tooth models at different positions. The reusable base further reduces cost in the dental treatment of teeth alignment. Furthermore, the receiving features can be modified to receive tooth models having different pin configurations to avoid interference between the adjacent tooth models in a tooth arch model.
The physical tooth models include features to allow them to be attached, plugged or locked to a base. The physical tooth models can be pre-fabricated having standard registration and attaching features for assembling. The physical tooth models can be automatically assembled onto a base by a robotic arm under computer control.
The physical dental arch model obtained by the disclosed system and methods can be used for various dental applications such as dental crown, dental bridge, aligner fabrication, biometrics, and teeth whitening. The arch model can be assembled from segmented manufacturable components that can be individually manufactured by automated, precise numerical manufacturing techniques.
The physical tooth models in the physical dental arch model can be easily separated, repaired or replaced, and reassembled after the assembly without the replacement of the whole arch model. The manufacturable components can be attached to a base. The assembled physical dental arch model specifically corresponds to the patient's arch. There is no need for complex and costly mechanisms such as micro-actuators for adjusting multiple degrees of freedom for each tooth model. The described methods and system is simple to make and easy to use.
The details of one or more embodiments are set forth in the accompanying drawing and in the description below. Other features, objects, and advantages of the invention will become apparent from the description and drawings, and from the claims.



BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawing, which are incorporated in and form a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention:
FIG. 1 is a flow chart for producing a physical dental arch model in accordance with the present invention.
FIG. 2 illustrates a tooth model and a base respectively comprising complimentary features for assembling the tooth model with the base.
FIG. 3 illustrates fixing a stud to a tooth model comprising a female socket to produce a tooth model having a protruded stud.
FIG. 4 illustrate a tooth model comprising two pins that allow the tooth model to be plugged into two corresponding holes in a base.
FIG. 5 illustrate a tooth model comprising a protruded pin that allows the tooth model to be plugged into a hole in a base.
FIG. 6 illustrates cone shaped studs protruded out of the bottom of a tooth model.
FIG. 7 illustrates exemplified shapes for the studs at the bottom of a tooth model.
FIG. 8A illustrates an example of a base comprising a plurality of female sockets for receiving a plurality of tooth models for forming a physical dental arch model.
FIG. 8B illustrates another example of a base comprising a plurality of female sockets for receiving a plurality of tooth models for forming a physical dental arch model.
FIG. 9 illustrates a tooth model that can be assembled to the base in FIGS. 8A and 8B.
FIG. 10 illustrates an example in which the pins at the bottom portions of two adjacent tooth models interfere with each other.
FIG. 11 illustrates an example in which two adjacent tooth models mounted on a base interfere with each other at the tooth portions of the tooth models.
FIG. 12 illustrates a tooth model having pin configurations that prevent the tooth models from interfering with each other.
FIG. 13(a) is a front view of two tooth models having pin configurations of FIG. 12.
FIG. 13(b) is a perspective bottom view of two tooth models having pin configurations of FIG. 12.
FIG. 14 illustrates a mechanism for fixing tooth models to a base using removable pins.
FIG. 15 illustrates a mechanism for fixing tooth models to a base using spring-loaded pins to prevent interference between tooth models.
FIG. 16 illustrates a triangulated mesh that simulates the surfaces of a patient's tooth.
FIG. 17 illustrates the calculation of the buffer width.
FIG. 18 illustrates the set-up of an orthogonal bounding box for calculating the buffer width.
FIG. 19 shows the grid over a rectangular face of a bounding box for the digital tooth model.
FIG. 20 illustrates the calculation of the interference depth between two tooth models.



DESCRIPTION OF INVENTION
Major operations in producing a physical dental arch model are illustrated in FIG. 1. The process generally includes the following steps. First individual tooth model is created in step 110. An individual tooth model is a physical model that can be part of a physical tooth arch model, which can be used in various dental applications. Registration features are next added to the individual tooth model to allow them to be attached to each other or a base in step 120. A base is designed for receiving the tooth model in step 130. The tooth model positions in a tooth arch model are next determined in step 140. The digital tooth models are developed in step 150. The interference between the physical tooth models is predicted in step 160. In step 170, the pin configurations affixed to the tooth models are selected to prevent interference between adjacent tooth models when they are mounted on the base. A base is fabricated in step 180. The base includes features for receiving the individual tooth model having the selected pin configurations. The tooth models are finally attached to the base at the predetermined positions using the pre-designed features in step 190.
Details of process in FIG. 1 are now described. Individual tooth model can be obtained in step 110 in a number of different methods. The tooth model can be created by casting. A negative impression is first made from a patient's arch using for example PVS. A positive of the patient's arch is next made by pouring a casting material into the negative impression. After the material is dried, the mold is then taken out with the help of the impression knife. A positive of the arch is thus obtained.
In an alternative approach, the negative impression of the patient's arch is placed in a specially designed container. A casting material is then poured into the container over the impression to create a model. A lid is subsequently placed over the container. The container is opened and the mold can be removed after the specified time.
Examples of casting materials include auto polymerizing acrylic resin, thermoplastic resin, light-polymerized acrylic resins, polymerizing silicone, polyether, plaster, epoxies, or a mixture of materials. The casting material is selected based on the uses of the cast. The material should be easy for cutting to obtain individual tooth model. Additionally, the material needs to be strong enough for the tooth model to take the pressure in pressure form for producing a dental aligner. Details of making a dental aligner are disclosed in commonly assigned and above referenced U.S. patent application titled “Method and apparatus for manufacturing and constructing a dental aligner” by Huafeng Wen, filed Nov. 2, 2004, the content of which is incorporated herein by reference.
Features that can allow tooth models to be attached to a base (step 120) can be added to the casting material in the casting process. Registration points or pins can be added to each tooth before the casting material is dried. Optionally, universal joints can be inserted at the top of the casting chamber using specially designed lids, which would hang the universal joints directly into the casting area for each tooth.
Still in step 110, individual tooth models are next cut from the arch positive. One requirement for cutting is to obtain individual teeth in such a manner that they can be joined again to form a tooth arch. The separation of individual teeth from the mold can be achieved using a number of different cutting methods including laser cutting and mechanical sawing.
Separating the positive mold of the arch into tooth models may result in the loss of the relative 3D coordinates of the individual tooth models in an arch. Several methods are provided in step 120 for finding relative position of the tooth models. In one embodiment, unique registration features are added to each pair of tooth models before the positive arch mold is separated. The separated tooth models can be assembled to form a physical dental arch model by matching tooth models having the same unique registration marks.
The positive arch mold can also be digitized by a three-dimensional scanning using a technique such as laser scanning, optical scanning, destructive scanning, CT scanning and Sound Wave Scanning. A digital dental arch model is therefore obtained. The digital dental arch model is subsequently smoothened and segmented. Each segment can be physically fabricated by CNC based manufacturing to obtain individual tooth models. The digital dental arch model tracks and stores the positions of the individual tooth models. Unique registration marks can be added to the digital tooth models that can be made into a physical feature in CNC base manufacturing.
Examples of CNC based manufacturing include CNC based milling, Stereolithography, Laminated Object Manufacturing, Selective Laser Sintering, Fused Deposition Modeling, Solid Ground Curing, 3D ink jet printing. Details of fabricating tooth models are disclosed in commonly assigned and above referenced U.S. patent application titled “Method and apparatus for manufacturing and constructing a physical dental arch mode” by Huafeng Wen, filed Nov. 2, 2004, the content of which is incorporated herein by reference.
In another embodiment, the separated tooth models are assembled by geometry matching. The intact positive arch impression is first scanned to obtain a 3D digital dental arch model. Individual teeth are then scanned to obtain digital tooth models for individual teeth. The digital tooth models can be matched using rigid body transformations to match a digital dental arch model. Due to complex shape of the arch, inter-proximal areas, root of the teeth and gingival areas may be ignored in the geometry match. High precision is required for matching features such as cusps, points, crevasses, the front and back faces of the teeth. Each tooth is sequentially matched to result in rigid body transformations corresponding to the tooth positions that can reconstruct an arch.
In another embodiment, the separated tooth models are assembled and registered with the assistance of a 3D point picking devices. The coordinates of the tooth models are picked up by 3D point picking devices such as stylus or Microscribe devices before separation. Unique registration marks can be added on each tooth model in an arch before separation. The tooth models and the registration marks can be labeled by unique IDs. The tooth arch can later be assembled by identifying tooth models having the same registration marks as were picked from the Jaw. 3D point picking devices can be used to pick the same points again for each tooth model to confirm the tooth coordinates.
The base is designed in step 130 to receive the tooth models. The base and tooth models include complimentary features to allow them to be assembled together. The tooth model has a protruding structure attached to it. The features at the base and tooth models can also include a registration slot, a notch, a protrusion, a hole, an interlocking mechanism, and a jig. The protruding structure can be obtained during the casting process or be created after casting by using a CNC machine on each tooth. The positions of the receiving features in the base is determined by either the initial positions of the teeth in an arch or the desired teeth positions during a treatment process (step 140).
The digital tooth models are developed in step 150. First, the surfaces of the two physical tooth models are measured. A negative impression of a patient's teeth is obtained. A plurality of points on the surfaces of the negative impression is measured by a position measurement device. The coordinates of the points in three dimensional space are obtained. Details of measuring the surface positions of dental impression's surfaces are disclosed in the above referenced and commonly assigned U.S. patent application, titled “Producing a base for accurately receiving dental tooth models” by Huafeng Wen, and filed November 2004 and the above referenced and commonly assigned U.S. patent application, titled “Producing accurate base for dental arch model” by Huafeng Wen, filed November 2004.
The plurality of points representing the surfaces of the negative impression is then used to construct a mesh to digitally represent the surfaces of the patient's teeth in three dimensions. FIG. 16 illustrates a triangulated mesh 1600 that simulates the surfaces of a patient's tooth. The mesh opening can also include other shapes with four, five or more sides or nodes. The mesh points are interpolated into one or more continuous surfaces to represent the surface of the patient's tooth, which serves as a digital model for the tooth.
The interference between two physical tooth models representing the patient's teeth can be predicted using the digital models of the two patient's teeth, in step 160. First buffer widths are calculated for each digital tooth model. As shown in FIG. 17, a coordinate system 1700 comprising x, y, and z axes is established for a digital tooth model 1710. Along the z direction, as shown in FIG. 17, a plurality of lines 1720 parallel to the z-axis are specified, typically at constant intervals. The lines 1720 intersect with the surfaces of the digital tooth model 1710. The distance between the intersection points, of the segment width, of each line 1720 is called buffer width. The buffer widths are calculated along each of the x, y, and z directions.
An orthogonal bounding box 1800 can be set up as shown in FIG. 18 to assist the calculation of the buffer widths. The bounding box defines maximum range for the digital tooth model along each direction in the coordinate system 1810. The bounding box 1800 includes three pairs of rectangle faces in three directions. To calculate the buffer width along the z direction, a grid of fixed intervals is set up over the rectangular x-y face 1820 of the bounding box 1800.
The intervals of the grid 1900 along x and y direction, shown in FIG. 19, are defined in accordance with the precision requirement. The grid nodes define start and end points for the lines 1720. The grid nodes are indexed. The segment width (i.e. the buffer width) is calculated for each pair of indexed grid nodes at the two opposite rectangular faces o the bounding box 1800. The buffer widths can be rescaled and stored for example in 8 bit or 16 bit values.
The interference between two physical tooth models to be fabricated based on the digital tooth models can be predicted using the corresponding digital tooth models. As shown in FIG. 20, the two digital tooth models 2010 and 2020 overlap in the overlapping portion 2030. The buffer widths of each of the digital tooth models 2010 and 2020 are translated into a common coordinate system. For each of the line 1720, intersection points for each of the digital tooth models 2010 and 2020 are determined or retrieved. The interference depth or the depth of overlapping portion 2030 can be calculated along the line in the z direction. The calculation of the interference depth is repeated for each pair of the x-y grid nodes similar to the procedure described above for each digital tooth model. The maximum interference depth can be determined among all the interference depths between the two digital tooth models.
The simulation of the interference between digital tooth models serves as prediction of the interference between the physical tooth models after they are fabricated and assembled to form a physical dental base mode. The knowledge of the interference between the physical tooth models can be used to prevent such interference to occur. One way to prevent such interference is by adjusting features affixed to the physical tooth models. Another method to prevent the interference is the adjust teeth positions in a dental arch model. Both methods are valuable to an orthodontic treatment.
The tooth models can be affixed with one or more pins at their bottom portions for the tooth models to be inserted into the base. The two adjacent tooth models can interfere with each other when they are inserted into a base. The pin configurations are selected in step 170 to prevent interference between adjacent tooth models.
Two adjacent tooth models 1010 and 1020 are shown in FIG. 10. The tooth models 1010, 1020 are respectively affixed with pins 1015 and pins 1025. The orthodontic treatment require the two adjacent tooth models 1010 and 1020 to be tilted away from each other in a tooth arch model. As a result, the pins 1015 and the pins 1025 interfere with or collide into each other. In another example, as shown in FIG. 11, two adjacent tooth models 1110 and 1120 are required to tilt toward each other by the orthodontic treatment. The tooth models 1110 and 1120 are affixed with pins having equal pin lengths. The tooth models 1110 and 1120 can collide into each other when they are inserted into a base 1130 because the insertion angles required by the long insertion pins.
In accordance with the present invention, the interference between adjacent tooth models mounted on an arch can be resolved by properly designing and selecting configurations of the pins affixed to the bottom portion of the tooth models. FIG. 12 illustrates a tooth model 1200 having two pins 1210 and 1220 affixed to the bottom portion. To prevent interference of the tooth model 1200 with its neighboring tooth models, the pins 1210 and 1220 are designed to have different lengths.
FIGS. 13(a) and 13(b) show detailed perspective views how two tooth models having the pin configurations shown in FIG. 12 can avoid interfering with each other. FIG. 13(a) shows the front perspective view of two tooth models 1310 and 1320 each of which is respectively affixed pins 1315 and 1325. The pins 1315 and pins 1325 are configured to have different lengths so that the pins do not run into each other when they are inserted into a base (not shown in FIG. 13(a) for clarity). The avoidance of interference between the tooth models 1310 and 1320 is also illustrated in a perspective bottom view in FIG. 13(b).
The pin configurations for tooth models can be selected by different methods. In one embodiment, a digital dental arch model that represents the physical tooth model is first produced or received. The digital dental arch model defines the positions and orientations of the two adjacent physical tooth models in the physical dental arch model according to the requirement of the orthodontic treatment. The positions of the physical tooth models including the pins are simulated to examine the interference between two adjacent physical tooth models mounted on the base. The pin configurations are adjusted to avoid any interference that might occur in the simulation. The pin configurations can include pins lengths, pin positions at the underside of the tooth models, and the number of pins for each tooth model.
The tooth models affixed with pins having the selected pin configurations can fabricated by Computer Numerical Control (CNC) based manufacturing in response to the digital dental arch model. At different steps of an orthodontic treatment, the tooth portions of the tooth models can remain the same while the pins affixed to the tooth portion being adjusted depending on the relative orientation of positions between adjacent tooth models. Furthermore, the base can include different socket configurations adapted to receive compatible pin configurations selected for different steps of the orthodontic treatment. The physical tooth models and their pin configurations can be labeled by a predetermined sequence to define the positions of the physical tooth models on the base for each step of the orthodontic treatment.
An advantage of the present invention is that the different pin configurations allow longer pins affixed to the tooth models, which results in more stable physical tooth arch model. Another advantage is that the tooth portion of the tooth models can be reused for different steps of an orthodontic treatment. Modular sockets can be prepared on the underside of the tooth models. Pins of different lengths can be plugged into the sockets to prevent interference between adjacent tooth models.
Before casting the arch from the impression, the base plate is taken through a CNC process to create the female structures for each individual tooth (step 180). Then the base is placed over the casting container in which the impression is already present and the container is filled with epoxy. The epoxy gets filled up in the female structures and the resulting mold has the male studs present with each tooth model that can be separated afterwards. FIG. 2 shows a tooth model 210 with male stud 220 after mold separation. The base 230 comprises a female feature 240 that can receive the male stud 220 when the tooth model 210 is assembled to the base 230.
Alternatively, as shown in FIG. 3, a tooth model 310 includes a female socket 315 that can be drilled by CNC based machining after casting and separation. A male stud 320 that fits the female socket 315 can be attached to the tooth model 310 by for example, screwing, glue application, etc. The resulted tooth model 330 includes male stud 310 that allows it to be attached to the base.
Male protrusion features over the tooth model can exist in a number of arrangements. FIG. 4 shows a tooth model 410 having two pins 415 sticking out and a base 420 having registration slots 425 adapted to receive the two pins 415 to allow the tooth model 410 to be attached to the base 420. FIG. 5 shows a tooth model 510 having one pins 515 protruding out and a base 520 having a hole 525 adapted to receive the pin 515 to allow the tooth model 510 to be attached to the base 520. In general, the tooth model can include two or more pins wherein the base will have complementary number of holes at the corresponding locations for each tooth model. The tooth model 610 can also include cone shaped studs 620 as shown in FIG. 6. The studs can also take a combination of configurations described above.
As shown FIG. 7, the studs protruding our of the tooth model 710 can take different shapes 720 such as oval, rectangle, square, triangle, circle, semi-circle, each of which correspond to slots on the base having identical shapes that can be drilled using the CNC based machining. The asymmetrically shaped studs can help to define a unique orientation for the tooth model on the base.
FIG. 8A shows a base 800 having a plurality of sockets 810 and 820 for receiving the studs of a plurality of tooth models. The positions of the sockets 810,820 are determined by either her initial teeth positions in a patient's arch or the teeth positions during the orthodontic treatment process. The base 800 can be in the form of a plate as shown in FIG. 8, comprising a plurality of pairs of sockets 810,820. Each pair of sockets 810,820 is adapted to receive two pins associated with a physical tooth model. Each pair of sockets includes a socket 810 on the inside of the tooth arch model and a socket 820 on the outside of the tooth arch model.
Another of a base 850 is shown in FIG. 8B. A plurality of pairs of female sockets 860, 870 are provided in the base 850. Each pair of the sockets 860, 870 is formed in a surface 880 and is adapted to receive a physical tooth model 890. The bottom portion of the physical tooth model 890 includes a surface 895. The surface 895 comes to contact with the surface 880 when the physical tooth model 890 is inserted into the base 850, which assures the stability of the physical tooth model 890 over the base 850.
A tooth model 900 compatible with the base 800 is shown in FIG. 9. The tooth model 900 includes two pins 910 connected to its bottom portion. The two pins 910 can be plugged into a pair of sockets 810 and 820 on the base 800. Thus each pair of sockets 810 and 820 uniquely defines the positions of a tooth model. The orientation of the tooth model is also uniquely defined if the two pins are labeled as inside and outside, or the sockets and the pins are made asymmetric inside and outside. In general, each tooth model may include correspond to one or a plurality of studs that are to be plugged into the corresponding number of sockets. The male studs and the sockets may also take different shapes as described above.
In another embodiment, the disclosed methods and system can include teeth duplicate with removable or retractable pins, as shown in FIGS. 14 and 15. A tooth model 1450 is placed on a flat surface 1460 in a recess created in the base 1440. The base 1440 include through holes 1425 and 1435. The tooth model 1450 includes at the bottom portion drilled holes 1420 and 1430 that are in registration and alignment with the through holes 1425 and 1435. Pins 1410 can then be inserted along directions 1412, 1413 into the through holes 1425 and 1435 in the base and then holes 1420 and 1430 in the base to affix the tooth models 1450 into the base 1440.
In another embodiment, the tooth model 1510 includes holes 1520. Pins 1540 and 1550 can be inserted into the holes 1520 in spring load mechanisms 1530, 1540. The pins 1540 are retractable with compressed springs to avoid interference during insertion or after the installation of the tooth model over the base. After the tooth models are properly mounted and fixed, the pins 1540 can extend to their normal positions to maximize position and angle control. The overall pin lengths can be cut to the correct lengths to be compatible with the spring load mechanisms to prevent interference between tooth models.
The described methods are also applicable to prevent tooth model interference in precision mount of tooth models in casting chambers. In such cases, the shape and the height of the tooth models can be modified to avoid interference of teeth during insertion or at the corresponding treatment positions.
A tooth arch model is obtained after the tooth models are assembled to the base 800 (step 190). The base 800 can comprise a plurality of configurations in the female sockets 810. Each of the configurations is adapted to receive the same physical tooth models to form a different arrangement of at least a portion of a tooth arch model.
The base 800 can be fabricated by a system that includes a computer device adapted to store digital tooth models representing the physical tooth models. As described above, the digital tooth model can be obtained by various scanning techniques. A computer processor can then generate a digital base model compatible with the digital tooth models. An apparatus fabricates the base using CNC based manufacturing in accordance with the digital base model. The base fabricated is adapted to receive the physical tooth models.
The physical tooth models can be labeled by a predetermined sequence that defines the positions of the physical tooth models on the base 800. The labels can include a barcode, a printed symbol, hand-written symbol, a Radio Frequency Identification (RFID). The female sockets 810 can also be labeled by the parallel sequence for the physical tooth models.
In one embodiment, tooth models can be separated and repaired after the base. The tooth models can be removed, repaired or replaced, and re-assembled without the replacement of the whole arch model.
Common materials for the tooth models include polymers, urethane, epoxy, plastics, plaster, stone, clay, acrylic, metals, wood, paper, ceramics, and porcelain. The base can comprise a material such as polymers, urethane, epoxy, plastics, plaster, stone, clay, acrylic, metals, wood, paper, ceramics, porcelain, glass, and concrete.
The arch model can be used in different dental applications such as dental crown, dental bridge, aligner fabrication, biometrics, and teeth whitening. For aligner fabrication, for example, each stage of the teeth treatment may correspond a unique physical dental arch model. Aligners can be fabricated using different physical dental arch models one at a time as the teeth movement progresses during the treatment. At each stage of the treatment, the desirable teeth positions for the next stage are calculated. A physical dental arch model having modified teeth positions is fabricated using the process described above. A new aligner is made using the new physical dental arch model.
In accordance with the present invention, each base is specific to an arch configuration. There is no need for complex and costly mechanisms such as micro-actuators for adjusting multiple degrees of freedom for each tooth model. The described methods and system is simple to make and easy to use.
The described methods and system are also economic. Different stages of the arch model can share the same tooth models. The positions for the tooth models at each stage of the orthodontic treatment can be modeled using orthodontic treatment software. Each stage of the arch model may use a separate base. Or alternatively, one base can be used in a plurality of stages of the arch models. The base may include a plurality of sets of receptive positions for the tooth models. Each set corresponds to one treatment stage. The tooth models can be reused through the treatment process. Much of the cost of making multiple tooth arch models in orthodontic treatment are therefore eliminated.
Although specific embodiments of the present invention have been illustrated in the accompanying drawings and described in the foregoing detailed description, it will be understood that the invention is not limited to the particular embodiments described herein, but is capable of numerous rearrangements, modifications, and substitutions without departing from the scope of the invention. The following claims are intended to encompass all such modifications.

## Claims

1. A system for mounting at least two physical tooth models on a physical dental arch model, the system comprising a non-transitory computer readable medium having instructions that when executed cause the system to:
acquire coordinates of a plurality of points on the surfaces of each of the two physical tooth models, the physical dental arch model being one of the group consisting of an upper dental arch model and a lower dental arch model;
digitally represent the surfaces of each of the two physical tooth models as a mesh of points in three dimensions using the acquired coordinates;
predict an interference of the two physical tooth models caused by a first configuration of at least one of: (1) one or more registration features of at least one of the two physical tooth models, or (2) one or more mounting features of the physical dental arch model, the predicted interference based on a determination that the meshes representing the surfaces of the two physical tooth models intersect at least at one point to form an overlapping portion;
calculate the depth of the overlapping portion between the two meshes to quantify the predicted interference of the two physical tooth models; and
use the quantified interference to modify the first configuration to a second different configuration such that when the two physical tooth models are mounted to the physical dental arch model, the one or more registration features interface with the one or more mounting features to constrain each of the two physical tooth models to a respective predetermined position and orientation on the physical dental arch model so as to prevent the predicted interference between the physical tooth models.

2. The system of claim 1, wherein the acquisition of the coordinates of the plurality of points on the surfaces of each of the two physical tooth models includes measuring the positions of points on the surfaces of an impression representing a patient's teeth.

3. The system of claim 1, wherein the surfaces of each of the two physical tooth models are digitally represented by a triangular mesh in three dimensions.

4. The system of claim 1, wherein at least one of the meshes comprises at least one mesh opening having three, four or five nodes.

5. The system of claim 1, wherein the instructions, when executed, cause the system to adjust at least one of mounted position or mounted orientation of at least one of the two physical tooth models in accordance with the depth of the overlapping portion between the two physical tooth models to prevent the predicted interference between the mounted physical tooth models.

6. The system of claim 1, wherein the instructions, when executed, cause the system to configure the one or more registration features so as to be affixed to at least one underside of the two physical tooth models in accordance with the depth of the overlapping portion between the two physical tooth models to prevent the predicted interference between the two physical tooth models when they are mounted to the physical dental arch model.

7. The system of claim 6, wherein the one or more registration features comprise one or more of a pin, a registration slot, a socket, a notch, a protrusion, a hole, an interlocking mechanism, a jig, and a pluggable or an attachable feature.

8. The system of claim 6, wherein the instructions, when executed, cause the system to output data for fabricating the physical tooth models having the one or more registration features.

9. The system of claim 1, wherein the instructions, when executed, cause the system to select the positions and orientations of the one or more physical dental arch mounting features to prevent the predicted interference between the two physical tooth models when they are mounted to the physical dental arch model.

10. The system of claim 9, wherein the physical dental arch mounting features comprise one or more of a pin, a registration slot, a socket, a notch, a protrusion, a hole, an interlocking mechanism, a jig, and a pluggable or attachable feature.

11. The system of claim 9, wherein the instructions, when executed, cause the system to output data for fabricating the physical dental arch model having the physical dental arch mounting features having the selected positions and orientations.

12. The system of claim 1, wherein the mesh is interpolated to produce one or more surfaces to represent the boundaries of one of the two physical tooth models.

13. A system for preventing interference between two physical tooth models in a physical dental arch model, the system comprising a non-transitory computer readable medium having instructions that when executed cause the system to:
acquire the coordinates of a plurality of points on the surfaces of each of the two physical tooth models, the physical dental arch model being one of the group consisting of an upper dental arch model and a lower dental arch model;
digitally represent the surfaces of each of the two physical tooth models by a mesh of points in three dimensions using the acquired coordinates;
predict an interference of the two physical tooth models caused by at least one of: (1) one or more registration features of at least one of the two physical tooth models, or (2) one or more mounting features of the physical dental arch model, the predicted interference based on a determination that the meshes representing the surfaces of the two physical tooth models intersect at least at one point to form an overlapping portion;
calculate the depth of the overlapping portion between the two meshes; and
adjust at least one of a predetermined mounting position and a predetermined mounting orientation of at least one of the two physical tooth models in accordance with the depth of the overlapping portion between the two physical tooth models to prevent the predicted interference between the physical tooth models when mounted to the physical dental arch model.

14. The system of claim 13, wherein the instructions, when executed, cause the system to configure a first feature of the one or more registration features so as to be affixed to at least one underside of the two physical tooth models in accordance with the depth of the overlapping portion between the two physical tooth models to prevent the predicted interference between the two physical tooth models when they are mounted to a base with the assistance of the first feature.

15. The system of claim 14, wherein the first feature comprises one or more of a pin, a registration slot, a socket, a notch, a protrusion, a hole, an interlocking mechanism, a jig, and a pluggable or an attachable feature.

16. The system of claim 14, wherein the instructions, when executed, cause the system to output data for fabricating the physical tooth models having the first feature.

17. A system for preventing interference between two physical tooth models in a physical dental arch model, the system comprising a non-transitory computer readable medium having instructions that when executed cause the system to:
acquire the coordinates of a plurality of points on the surfaces of each of the two physical tooth models, the physical dental arch model being one of the group consisting of an upper dental arch model and a lower dental arch model;
digitally represent the surfaces of each of the two physical tooth models by a mesh of points in three dimensions using the acquired coordinates;
interpolate each of the two meshes to produce one or more surfaces to represent the boundaries of one of the two physical tooth models;
predict an interference of the two physical tooth models caused by a first configuration of at least one of: (1) one or more registration features of at least one of the two physical tooth models, or (2) one or more mounting features of the physical dental arch model, the predicted interference based on a determination that the interpolated surfaces intersect at least at one point to form an overlapping portion;
calculate the depth of the overlapping portion between the two interpolated surfaces to quantify the predicted interference of the two physical tooth models; and
use the quantified interference to modify the first configuration to a second different configuration so as to prevent the predicted interference between the physical tooth models when mounted to the physical dental arch model in respective predetermined positions and predetermined orientations.

18. The system of claim 17, wherein the instructions, when executed, cause the system to adjust at least one of the predetermined positions or the predetermined orientations of at least one of the two physical tooth models in accordance with the quantified interference between the two physical tooth models to prevent the predicted interference between the physical tooth models.

19. The system of claim 18, wherein the instructions, when executed, cause the system to configure a first feature of the one or more registration features so as to be affixed to at least one underside of the two physical tooth models in accordance with the quantified interference between the two physical tooth models to prevent the predicted interference between the two physical tooth models when they are mounted to a base with the assistance of the first feature.