Patent Publication Number: US-11654004-B2

Title: Methods, systems and accessories useful for procedures relating to dental implants

Description:
CROSS-REFERENCE 
     This application is a continuation of U.S. patent application Ser. No. 16/922,606, filed Jul. 7, 2020, now U.S. Pat. No. 11,291,533, issued Apr. 5, 2022, which is a continuation of U.S. patent application Ser. No. 15/695,974, filed Sep. 5, 2017, now U.S. Pat. No. 10,722,332, issued Jul. 28, 2020, which is a continuation of U.S. patent application Ser. No. 15/138,034, filed Apr. 25, 2016, now U.S. Pat. No. 9,782,238, issued Oct. 10, 2017, which is a divisional of U.S. patent application Ser. No. 13/960,599, filed Aug. 6, 2013, now U.S. Pat. No. 9,345,562, issued May 24, 2016, which is a divisional of U.S. patent application Ser. No. 12/458,579, filed Jul. 16, 2009, now U.S. Pat. No. 8,509,932, issued Aug. 13, 2013, which claims the benefit of U.S. Provisional Patent Application No. 61/129,770, filed Jul. 17, 2008, the contents of each of which are hereby incorporated by reference in their entirety. 
    
    
     FILED OF THE INVENTION 
     This invention relates to dental implants, in particular to methods, systems and accessories useful in procedures relating to dental implants. 
     BACKGROUND OF THE INVENTION 
     Dental implants are widely used as artificial substitutes for the root portion of missing teeth, and allow a tooth prosthesis to be securely anchored to the jaw via a permanent abutment mounted to the implant. Endosseous implants generally comprise an externally threaded body, often self-taping into the bone tissues, and further comprise an internal chamber that is configured, typically internally threaded, for receiving and securing therein the anchoring stem of a permanent abutment therein. 
     Following implantation of an implant in the intra oral cavity and healing of the surrounding tissues, a physical model of the intra oral cavity is produced for facilitating design and manufacture of the permanent abutment and prosthesis or other restoration that is to be eventually mounted onto the implant. In one procedure, an impression abutment is mounted to the implant so that it projects into the intra oral cavity, and an impression is then obtained of the intraoral cavity using well known techniques and impression materials, for example PVS. The impression abutment may be of the pick-up type, to be embedded with the impression material and retained therein after the impression tray is removed. Alternatively the impression tray is removed without the impression abutment attached thereto, but nevertheless having a recess formed therein complementary to the outer shape of the impression abutment, enabling the transfer-type impression abutment to be mounted therein at a later time. Subsequently an analog, corresponding to the particular implant that is implanted in the patient, is attached to the abutment, which is in situ in the impression material, and plaster is poured into the impression tray including the analog to produce a positive plaster model of the intraoral cavity with the analog embedded. The analog, in particular the internal passage thereof which is substantially identical to the internal passage of the implant that is designed to receive, engage and secure the permanent abutment, is in a position and orientation in the plaster model corresponding to the position and orientation of the implant in the patient&#39;s intra oral cavity. The dental technician can now attach a permanent abutment, or custom design a permanent abutment to fit the implant, build a coping or bridge framework or prosthesis to fit into the intraoral cavity of the patient. 
     By way of general background, the following publications relate to implants: 
     U.S. Pat. No. 6,358,052 discloses a dental implant system and method for effecting a dental restoration using the same. The dental implant system having an implant fixture adapted to be deployed in a bone; an impression coping adapted to be selectively deployed on the implant fixture and in a dental impression; a laboratory analog adapted to be selectively deployed on the impression coping and in a dental cast; a spherical abutment adapted to be selectively deployed on the laboratory analog; and a multiaxis abutment adapted to be adjustably deployed on the spherical abutment; wherein the spherical abutment and the multiaxis abutment are used to generate a cast permanent abutment which may be received by the laboratory analog and the implant fixture. 
     US 2008/032262 discloses a dental implant system comprising an implant member, an abutment member and a transfer key with cooperatively engaging structures for ensuring proper alignment and orientation of an abutment assembled on the implant member and for preparing an accurate dental impression and mold which represents the implantation site and its relationship to adjacent teeth structures. A dental reconstruction method utilizing the dental implant system of the present invention is also disclosed. 
     US 2006/183078 discloses a one-piece, screw-receiving, externally-threaded endosseous dental implant that includes a body portion with external threading and, at its proximal end, an unthreaded, cylindrical portion including a retentive groove for engaging a complementary transfer component or comfort cap; a one- or two-piece screw-receiving implant abutment for attachment to a one or two-piece implant, including a retentive groove for engaging a complementary transfer component or comfort cap; and a fixture mount for insertion in a one-piece implant, that can be sectioned with the distal end used to extend the implant height. 
     SUMMARY OF THE INVENTION 
     The term virtual model is used herein synonymously with “numerical entity”, “3D model”, and other such terms, and relates to a virtual representation in a computer environment of a real object, for example a dentition or at least a part of intraoral cavity, or of a real model thereof, for example. 
     The term “scanning” refer to any procedure directed at obtaining 3D topographic data of a surface, particularly of a dental surface, and thus includes mechanical methods, typically based on 3D probes for example, optical methods, including for example confocal methods, for example as disclosed in WO 00/08415, the contents of which are incorporated herein in their entirety by reference, or indeed any other method. 
     The term “display” refer to any means or method for delivering a presentation, which may include any information, data, images, sounds, etc, and thus the delivery may be in visual and/or audio form. 
     According to a first aspect of the invention, there is provided a method and system for manufacturing a physical dental model. A virtual model is provided representative of at least a portion of the intra-oral cavity including at least one dental implant implanted therein, and the virtual model includes a virtual portion representative of each dental implant. The virtual spatial disposition of each such virtual portion is determined with respect to the virtual model, corresponding to a real spatial disposition of the respective implant with respect to the intra oral cavity. A physical model is then manufactured based on the virtual model, the physical model including a physical analog corresponding to each implant at a respective physical spatial disposition with respect to the physical model corresponding to the respective virtual spatial disposition of the respective virtual portion with respect to the first virtual model as already determined. 
     In some embodiments, a jig is provided configured for maintaining a desired physical spatial disposition between the physical analog and a cavity of the physical dental model at least until the physical analog is affixed in the cavity. 
     According to this aspect of the invention, there is provided a method for manufacturing a physical dental model, comprising 
     (a) providing a first virtual model representative of at least a portion of the intraoral cavity including at least one dental implant implanted therein, said first virtual model comprising a virtual portion representative of the or each said dental implant; 
     (b) determining a virtual spatial disposition of the or each said virtual portion with respect to the first virtual model corresponding to a real spatial disposition of the respective said implant with respect to said portion of the intra oral cavity; and 
     (c) manufacturing a physical model of said portion of the intra-oral cavity based on said first virtual model, said physical model including a physical analog corresponding to the or each said implant at a respective physical spatial disposition with respect to said physical model corresponding to the respective said virtual spatial disposition of said virtual portion with respect to the first virtual model based on said determination in step (b). 
     The first virtual model may be generated in any suitable manner—for example by scanning the intraoral cavity in vivo, or scanning a positive or negative physical model of the intraoral cavity that includes representations of the implant(s) and a part of the dentition in the vicinity the implant(s). 
     In at least some embodiments, step (b) comprises providing a second virtual model at least partially representative of the or each respective said physical analog, and incorporating said second virtual model with said first virtual model based on said determination of the respective said virtual spatial disposition, to generate a third virtual model, wherein in step (c), said manufacturing of said physical model is based on said third virtual model. For example, step (b) may comprise manipulating the or each said second virtual model into an aligned spatial disposition with respect to the respective said virtual spatial disposition, and generating said third virtual model based on the first virtual model and including a virtual cavity (i.e. a virtual representation of the cavity) for virtually receiving and accommodating the or each respective second virtual model therein in a manner corresponding to that required for the respective physical analog with respect to said physical model of the intra oral cavity. 
     Step (c) may comprise forming an outer model surface corresponding to dental surfaces of said portion of the intra oral cavity, and forming a recess in said physical model (corresponding to the virtual cavity) for accommodating a respective said analog at the respective said physical spatial disposition, said recess corresponding to the respective said virtual cavity. 
     In at least some embodiments, at least one said virtual cavity is generated having a form generally complementary to that of the respective said physical analog, such that the respective said recess formed in said physical model provides a friction fit with respect to the respective said physical analog to accommodate the respective said physical analog at the respective said physical spatial disposition. 
     In at least some other embodiments, at least one said virtual cavity is generated having a form generally complementary to that of the respective said physical analog including a jacket, such that the respective said recess formed in said physical model provides a significant clearance gap with respect to the respective said physical analog, wherein said respective physical analog comprises said jacket formed of suitable model material, said jacket having an external form substantially complementary to that of the respective said recess, to enable the respective physical analog including the respective jacket to be accommodated in the respective said recess at the respective said physical spatial disposition. The said external form for the respective said jacket may be configured for fixing the spatial disposition thereof in the respective said recess in six degrees of freedom. For example, the jacket may be formed by a casting process applied to the respective said physical analog, or by applying a layer of said model material on the respective physical analog, and CNC machining said layer to provide the respective said external form. 
     In at least some embodiments, at least one said virtual cavity is generated having a form generally complementary to that of the respective said physical analog, such that the respective said recess formed in said physical model provides a significant clearance gap with respect to the respective said physical analog, wherein a suitable filler material is applied to fill the clearance gap, to enable the respective physical analog including the respective jacket to be accommodated in the respective said recess at the respective said physical spatial disposition. For example, the filler material may comprise a suitable cementing material. A suitable jig may be used for maintaining a said physical spatial disposition between the respective physical analog and the respective cavity at least until the physical analog is affixed therein by means of the filler material. In at least some embodiments, the jig may comprise a base, that is mounted in fixed spatial relationship to the physical dental model, for example affixed to a portion of the physical model, at least until the physical analog is affixed therein. In at least some embodiments, said portion of the physical model does not include physical model representations of teeth adjacent to a said implant. 
     In at least some embodiments, step (c) comprises forming an outer model surface corresponding to dental surfaces of said portion of the intra oral cavity from a blank of model material, wherein said blank integrally includes the or each said physical analog in relative spatial dispositions to one another corresponding to the relative spatial dispositions of the or each dental implants with respect to one another in said portion of the intra oral cavity. 
     In at least some embodiments, step (d) comprises computer controlled manufacture of at least a portion of said physical model. For example, step (d) may comprise manufacturing said physical model via a material removal operation applied to a blank of material or a rapid prototyping process. 
     According to this aspect of the invention, there is also provided a dental model, manufactured according to the above method. 
     According to at least some embodiments, a physical model is manufactured with a hole for friction fit with the analog. 
     According to at least some other embodiments, the analog is embedded in a suitable material, which is milled for a close fit with the hole, which may be useful, for example, when the analog is of a shape that does not allow friction fitting. 
     According to at least some other embodiments, the model is manufactured with a relatively large cavity such as to provide a loose fit for the analog, which is cemented in place while held in a jig. 
     According to another embodiment, a plaster blank is cast with the analog embedded in a particular known position. The blank is then machined to ensure that the analogue is in the correct position/orientation with the other parts (e.g., model dental surfaces) of the finished physical model. 
     According to this aspect of the invention, there is also provided a system for manufacturing a physical dental model of an intra-oral cavity, comprising: 
     (A) scanning apparatus and computer system configured for providing a first virtual model representative of at least a portion of the intra-oral cavity including at least one dental implant implanted therein, said first virtual model comprising a virtual portion representative of the or each said dental implant, and for determining a virtual spatial disposition of the or each said virtual portion with respect to the first virtual model corresponding to a real spatial disposition of the respective said implant with respect to the intra oral cavity; 
     (B) a physical analog corresponding to the or each said implant; 
     (C) a manufacturing system for manufacturing a physical model of said portion of the infra-oral cavity based on said first virtual model, said physical model including a physical analog corresponding to the or each said implant at a respective physical spatial disposition with respect to said physical model corresponding to the respective said virtual spatial as determined by said computer system. 
     The manufacturing system is computer controlled. For example, the manufacturing system may be configured for manufacturing said physical model via a material removal operation applied to a blank of material, or via a rapid prototyping technique. 
     According to another aspect of the invention, there is also provided accessories including one or more of a physical tooth model and a jig. 
     In one embodiment, a jig is provided for maintaining a desired spatial disposition between a respective analog and the respective cavity of a physical model of an intra oral cavity at least until the analog is affixed therein, wherein the jig comprises a base configured for being mounted to a portion of the physical model not including portions representative of adjacent teeth with respect to an implant site. 
     According to another aspect of the invention, there is provided a method for modifying a physical dental model, comprising: 
     (A) providing a physical model representative of at least a portion of the intra-oral cavity including at least one dental implant implanted therein, said physical model comprising a model portion representative of the or each said dental implant; 
     (B) providing a first virtual model representative of at least a portion of the intra-oral cavity including at least one dental implant implanted therein, said first virtual model comprising a virtual portion representative of the or each said dental implant; 
     (C) determining a virtual spatial disposition of the or each said virtual portion with respect to the first virtual model corresponding to a real spatial disposition of 
     the respective said implant with respect to said portion of the intra oral cavity; and 
     (D) modifying said physical model of said portion of the intra-oral cavity by including therein a physical analog corresponding to the or each said implant at a respective physical spatial disposition with respect to said physical model corresponding to the respective said virtual spatial disposition of said virtual portion with respect to the first virtual model based on said determination in step (C). 
     The method according to this aspect of the invention may comprise one or more of the elements and features as provided herein regarding the first aspect of the invention, mutatis mutandis. 
     According to another aspect of the invention there is provided an accessory in the form of a jig configured for maintaining a desired physical spatial disposition between a physical analog and a cavity of a physical dental model at least until the physical analog is affixed in said cavity. 
     The cavity is typically larger (wider and/or deeper than the the part of the analog that needs to be embedded in the physical model providing a fellable clearance gap therebetween, and the analog is ultimately secured in the cavity via a suitable filler material, for example. 
     According to at least some embodiments, the jig may comprise a strut having a first end configured for being mounted with respect to the dental model at a first spatial disposition with respect thereto, and a second end configured for enabling the physical analog to mounted to the second end at a second spatial disposition with respect thereto, wherein said first end is at a third spatial disposition with respect to said second end, and wherein said first spatial disposition, said second spatial disposition and said third spatial disposition are chosen to provide said desired physical spatial disposition between the physical analog and the cavity when said strut is mounted with respect to the dental model and the physical analog is mounted to said strut. 
     In at least some embodiments, the jig may comprise a spacer member, wherein said strut comprises an elongate arm comprising said first end and said second end at opposed longitudinal ends of said elongate arm, wherein said first end comprises a strut base portion configured for being mounted to the dental model via said spacer member wherein to provide said first spatial disposition between said first end and the dental model. 
     Said strut base portion may be configured for enabling said spacer member to be mounted to said strut by engagement to the strut base portion. At least one of the strut base portion and said spacer member may comprise a first engagement arrangement to ensure that the spacer member may be mounted to the strut base portion in a spatial disposition with respect thereto that is fixed in six degrees of freedom. For example, the first engagement arrangement may comprise at least two laterally spaced pins projecting from a second spacer end of said spacer member and corresponding complementary wells formed in the strut base portion for receiving each said pin. Other alternative configurations for the first engagement arrangement may of course be provided. 
     The dental model may include a model base portion configured for enabling said spacer member to be mounted to the dental model by engagement to the model base portion. At least one of the model base portion and said spacer member may comprise a second engagement arrangement to ensure that the spacer may be mounted to the model base portion in a spatial disposition with respect thereto that is fixed in six degrees of freedom. For example, said second engagement arrangement may comprise at least two laterally spaced pins projecting from a first spacer end of said spacer member and corresponding complementary wells formed in the model base portion for receiving each said pin. Other alternative configurations for the second engagement arrangement may of course be provided. 
     In at least some embodiments, said spacer comprises a first spacer end and a second spacer end, wherein said first spacer end is configured for being mounted to said first end via said strut base portion in a spatial disposition with respect thereto that is fixed in six degrees of freedom, and wherein said second spacer end is configured for being mounted to the dental model via a model base portion of the dental model in a spatial disposition with respect to the model base portion that is fixed in six degrees of freedom. 
     The geometric form of the jig, in particular the specific spatial dispositions of the various parts thereof to properly mate with the physical dental model, can be based on the method provided according to the first aspect of the invention. 
     For example, the jig may be integrally produced from a suitable blank via a material removal operation or integrally produced via a suitable rapid prototyping operation, based on the geometric form previously determined. 
     According to this aspect of the invention there is also provided a jig particularly useful for dental implant procedures, comprising: 
     an arm having a first arm end and a second arm end spaced from said first arm end, said first arm end having a first engagement arrangement, and said second arm end being configured for releasably holding a physical analog; 
     a spacer element having a first spacer end and a second spacer end spaced from said first spacer end, said first spacer end being configured for engagement to said first arm end via said first engagement arrangement, and said second spacer end being configured for being mounted to a physical dental model representative of at least a portion of the real dentition of a patient, said dental model comprising a cavity 
     wherein in operation to maintain a desired physical spatial disposition between the physical analog and said cavity of the physical dental model, wherein the physical analog is at least partially received within the cavity, at least until the physical analog is affixed in said cavity. 
     As for other embodiments of the jig, said desired physical spatial disposition of the physical analog with respect to the dental model corresponds to a spatial disposition of a dental implant corresponding to the analog with respect to the real dentition that is being represented by the dental model. 
     According to this aspect of the invention there is also provided a kit particularly useful for dental implant procedures, comprising: 
     a physical dental model comprising a model dentition representative of a first real dentition of a patient, and further comprising a cavity configured for accommodating therein via a fellable gap a physical analog in a model spatial disposition with respect to said model dentition corresponding to a real spatial disposition of an implant with respect to said real dentition; 
     a jig configured for holding said physical analog in said model spatial disposition with respect to said cavity at least until the physical analog is affixed in said cavity. 
     In at least some embodiments, the jig may comprise a spacer member and a strut, said strut comprising a strut base portion configured for being mounted to said dental model via said spacer member, and a strut end configured for holding the physical analog thereat. 
     The dental model may comprise a model base portion configured for enabling said spacer member to be mounted to the dental model by engagement to the model base portion. 
     The spacer may comprise a first spacer end and a second spacer end, wherein said first spacer end is configured for being mounted to said strut via said strut base portion in a spatial disposition with respect thereto that is fixed in six degrees of freedom, and wherein said second spacer end is configured for being mounted to the dental model via said model base portion of the dental model in a spatial disposition with respect to the model base portion that is fixed in six degrees of freedom. 
     The model dentition is generally representative of a set of adjacent real teeth of a first dental arch of a patient, and may comprise a set of model teeth corresponding to a set of real teeth of at least a portion of a first dental arch of a patient, and wherein said cavity is located adjacent at least one said model tooth at a position corresponding to a missing tooth in the real dentition. 
     The kit may optionally further comprise an auxiliary dental model representative of a second real dentition of at least a portion of a second dental arch of the patient, wherein the second real dentition is occlusally opposed with respect to the first real dentition. The auxiliary dental model may be configured for being mounted with respect to said dental model in an occlusal relationship corresponding to that between said first real dentition and said second real dentition. This may be accomplished by mounting the two models to the spacer, or to a suitable articulator, for example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to understand the invention and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: 
         FIG.  1    is a schematic illustration of a system according to an embodiment of the invention. 
         FIG.  2    is a schematic illustration of a method according to embodiments of the invention. 
         FIG.  3 ( a )  and  FIG.  3 ( c )  illustrate in side view and top view, respectively, an implant and impression abutment according to an embodiment of the invention;  FIG.  3 ( b )  and  FIG.  3 ( d )  illustrate in side view and top view, respectively, an analog corresponding to the implant of  FIG.  3 ( a )  and  FIG.  3  ( c ) . 
         FIGS.  4 ( a ),  4 ( b ) and  4 ( c )  illustrate virtual models respectively of the intraoral cavity, the analog including impression abutment, and of the physical model to be manufactured. 
         FIG.  5    illustrates in isometric view a physical model corresponding to the virtual model of  FIG.  4 ( c ) , according to a first embodiment of the invention. 
         FIG.  6    illustrates in isometric view a physical model according to a second embodiment of the invention;  FIG.  6 ( a )  illustrates in cross-sectional side view a casting apparatus for casting a jacketed analog for use with the model of  FIG.  6   . 
         FIG.  7    illustrates in isometric view a physical model according to a variation of the second embodiment of the invention;  FIG.  7 ( a )  illustrates in isometric view a virtual model of a jacketed analog corresponding to the model of  FIG.  7   . 
         FIG.  8    illustrates in isometric view a physical model according to a third embodiment of the invention, including a positioning jig for use therewith. 
         FIG.  9    illustrates in side view a variation of the jig of  FIG.  8   . 
         FIG.  10    illustrates in side view another embodiment of the jig. 
         FIG.  11    illustrates in isometric view a physical model according to the third embodiment of the invention, including a spacer member of a positioning jig for use therewith. 
         FIG.  12    illustrates in isometric view the physical model of  FIG.  11   , including a positioning jig for use therewith. 
         FIG.  13    illustrates in isometric view the physical model of  FIGS.  11  and  12   , with the analog fixed in place. 
         FIG.  14    illustrates in isometric view the physical model of  FIG.  13   , including the spacer member of  FIG.  11   , and an auxiliary dental model of an opposed dentition, in occlusal relationship. 
         FIG.  15    illustrates in side view a blank for manufacturing a physical model according to a fourth embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     According to one aspect of the present invention there is provided a system and method for use in dental implant procedures. 
       FIG.  2    illustrates a block diagram of a method  400  for use in dental implant procedures according to an embodiment of the invention, and  FIG.  1    illustrates the main elements of a system  200  for carrying out the method according to an embodiment of the invention. 
     While the present description is directed to a single implant, it is readily appreciated that the invention is applicable, mutatis mutandis, to a plurality of implants that may be implanted in the intra oral cavity of a patient, whether the implants are independent from one another, each being used for a separate prosthesis, or whether at least some of the implants are to be coupled to be used together for a single bridge prosthesis or other multiple tooth prostheses, for example. 
     The system  200  comprises: a first module, including a scanner  250 , and a microprocessor or any other suitable computer system  260 ; a second module comprising a physical analog  230  corresponding to the implant  240  that it is desired to have implanted in the intra oral cavity of a patient, and a manufacturing system  280  for manufacturing a physical model  600  of the intra oral cavity including the analog  230 . 
     The computer system  260  comprises an input interface or module  210  such as a keyboard, mouse, tablet, and so on, an output device or display means or module  220 , typically a screen or monitor but may additionally or alternatively include a printer, or any other display system, a processing unit or module  230  such as for example a CPU, and a memory  235 . 
     The scanner  250  is configured for providing surface data of surfaces, in particular hard dental surfaces, other tissue surfaces of the intra oral cavity of a patient, and of the implant  240 , in situ or before implantation, and is also operatively connected to the computer system  260  and interacts therewith. The computer system  260  is suitably programmed for reconstructing such surfaces from the surface data provided to provide a first virtual model  500  of the intraoral cavity. Such a scanner may comprise, for example, a probe for determining three dimensional structure by confocal focusing of an array of light beams, for example as marketed under the name of iTero or as disclosed in WO 00/08415, the contents of which are incorporated herein in their entirety. Alternatively, the required scanning may be accomplished using any suitable scanning apparatus for example comprising a hand held probe. Optionally, color data of the intraoral cavity may also provided together with the 3D data, and thus the first virtual model  500  comprises spatial and color information of the dental surfaces scanned. Examples of such scanners are disclosed in US 2006-0001739, and which is assigned to the present Assignee. The contents of the aforesaid co-pending application are incorporated herein by reference in their entirety. 
     Referring also to  FIG.  3 ( a )  to  FIG.  3 ( d ) , the physical analog  230  comprises a housing  234  having an inner passage or chamber  231 , for example including a hexagonal entrance and internally threaded portion, that enables mating with a complementary structure in the permanent abutment, enabling the latter&#39;s position with respect to the analog (and thus the physical tooth model) to be dictated in six degrees of freedom. The inner chamber  231  thus corresponds and is nominally identical to the inner chamber  241  of the implant  240 . The external form of housing  234  is configured for being embedded in a physical model  600  of the intraoral cavity. 
     The manufacturing system  280  comprises a computer controlled manufacturing system configured for manufacturing a physical model from a virtual model, with respect to a machine coordinate system C. In this embodiment, the manufacturing process itself is a material removing process such as CNC milling, the physical model  600  incorporating, or being capable of incorporating, the physical analog  230  in the correct spatial orientation and position with respect to the physical model of intraoral cavity corresponding to the spatial orientation and position of the implant  240  in the patient&#39;s intra oral cavity. 
     Referring again to  FIG.  2   , process  400  broadly includes the following steps: 
     Step  410 —implanting at least one implant  240  in an intra oral cavity of a patient. 
     Step  420 —providing a first virtual model  500  representative of at least a portion of the intra-oral cavity of a patient including the or each dental implant, wherein the location and orientation of the implant in relation to the intra oral cavity is determinable with respect to the first virtual model. 
     Step  430 —providing a second virtual model representative of a physical analog of the implant. 
     Step  440 —manipulating said second virtual model into an aligned spatial disposition, i.e. in spatial registry, with respect to said first virtual model corresponding to the relative disposition between the intraoral cavity and the implant, and generating a third virtual model based on the first virtual model having a virtual cavity for receiving and accommodating the second virtual model therein in a manner paralleling that of the physical analog with respect to a physical model of the intra oral cavity. 
     Step  450 —computer controlled manufacture of a physical dental model  600  incorporating the analog  230 , based on the third virtual model. 
     Referring to each step in turn, step  410  comprises implanting at least one implant in an intra oral cavity of a patient, and follows well-established dental procedures in the art, which will not be described in further detail herein. 
     Step  420  comprises acquiring an accurate 3D representation, (herein also referred to interchangeably as “three-dimensional model”, “3D model”, “virtual model” and the like) of the required part of the intraoral cavity of the patient, which forms the focus of the particular implant procedure for a particular patient and regarding which it is desired to obtain the 3D topographical or surface data thereof. The required part may include partial or the full mandibular or maxillary arches, or both arches, and may further include details of the spatial relationship between the two arches in occlusion, and includes the implant in situ in the intra oral cavity. 
     In any case, this first virtual model  500  may be provided by scanning the intraoral cavity in-vivo using any suitable equipment for scanning a patient&#39;s teeth. Such scanning equipment comprises, in this embodiment, the scanner  250  of system  200 , though in other embodiments, any other suitable scanner may be used. Alternatively, the 3D digitized data may be obtained in any other suitable manner, including other suitable intra oral scanning techniques, based on optical methods, direct contact methods or any other means, applied directly to the patient&#39;s dentition. Alternatively, X-ray based, CT based, MM based, or any other type of scanning of the patient&#39;s intra-oral cavity may be used. 
     The 3D virtual model is created such as to include sufficient 3D information regarding the implant  240  so that its position with respect to intra oral cavity may be determined in the first virtual model  500 . For this purpose it may be sufficient to retain the healing abutment engaged with the implant  240  during scanning, if the engagement position of the healing abutment with respect to the implant  240  is unique and determinable from viewing or scanning at least the exposed part of the healing abutment in the intraoral cavity. Otherwise before the scanning operation, and in the present embodiment, the healing abutment is removed and replaced with an impression abutment  246  ( FIG.  3 ( a ) ) that is shaped, and/or comprises suitable markers or other positional indicators  245  ( FIG.  3 ( c ) ) on the exposed part of the impression abutment  246  in the intraoral cavity, that provide information about the position and orientation of the impression abutment  246 , including with respect to the cavity  241  (for example the hexagonal entry configuration in which the permanent abutment is eventually to be seated, in many examples of implants) of the implant  240 . 
     In alternative embodiments, a physical model may be provided of the intraoral cavity, for example via an impression of the intraoral cavity and subsequent casting the impression with plaster, including the implant  240  and the impression abutment  246  (or indeed a suitable healing abutment), and the physical model (or the impression) scanned in any suitable manner to provide the first virtual model  500 . 
     Thus, and referring to  FIG.  4 ( a ) , first virtual model  500  comprises portions  509  corresponding to the real teeth, portions  508  corresponding to the gingival tissues, and a portion  502  corresponding to the exposed part of the impression abutment  246 . 
     In step  430 , and referring to  FIG.  4 ( b ) , a second virtual model  550  is provided, comprising a first virtual portion  554  representative of the physical analog  230  of the implant  240 , and a second virtual portion  551  representative of the impression abutment  246  coupled thereto. 
     In the first embodiment, the analog  230  is of constant cross-sectional shape, or alternatively of a tapering cross-sectional shape, such that it is possible to insert the analog in an axial direction into a cavity having a complementary shape. At the same time the cross-section is such (for example oval, asymmetric, polygonal etc) that inserting the analog into a complementary-shaped cavity fixes the position of the analog in the cavity in six degrees of freedom. 
     In step  440 , the second virtual model  550  is manipulated in the virtual environment of the computer system  260  into an aligned spatial disposition with respect to said first virtual model  500 , in spatial registry therewith, to generate a third virtual model  560 , corresponding to some extent to a virtual combination of said first virtual model and said second virtual model, illustrated in  FIG.  4 ( c ) , in which the second virtual model is essentially “subtracted” from the first virtual model. 
     The first virtual model  500  and the second virtual model  550  are virtually aligned by manipulating the virtual models by means of the computer system  260  such that the portion  502  corresponding to the exposed part of the impression abutment  246  is brought into registry with a corresponding portion  552  of the second virtual model  550 . This may be accomplished in many ways as are known in the art—for example using suitable shape recognition software that compares the shape of one portion at a time of one of the virtual model with different portions of the other virtual model, until a match is found within a particular error threshold. Optionally, the process can be accelerated by user interaction with the computer system  260 , wherein the user can identify the general areas of the two virtual models that are common to one another, whereupon the computer system searches for matching the models within the identified areas. Once a match is found, one or both of the models can be rotated and/or translated so as to bring into registry the aligned parts, and thereby aligning the models. Thus aligned, portion  552  (and portion  502 ) are effectively removed from the first model  500 , and a surface  565  is added to the first model to generate the third model  560 . Surface  565  comprises the remainder of the first virtual portion  551 , i.e. lower portion  553  (corresponding to the part of the outer surface of the impression abutment  246  that is hidden from view), plus the second virtual portion  554 . Optionally, surface  565  may be scaled in a radial or lateral direction away from the longitudinal axis  569  of the second virtual model for facilitating a friction fit between the physical model  600  and analog  230 . 
     Virtual model  560  thus comprises an outer virtual surface  561  representative of the dental tissues that are exposed in the intra-oral cavity, and an inner virtual surface  565  representing a cavity for receiving and retaining therein the second virtual model, or at least the part thereof corresponding to the analog, in the same relative position as the implant in the intra oral cavity. 
     In step  450 , and referring to  FIG.  5   , a physical dental model  600  is manufactured incorporating the analog  230 , based on the third virtual model by the manufacturing system  280 . In this embodiment, a computer controlled material removing manufacturing process, such as for example CNC milling or machining, is used for milling or otherwise machining the physical model  600  from a blank of material, producing an outer model surface  661  corresponding to surface  561  of the third virtual model  560  and representing dental tissues that are exposed in the intra-oral cavity, and producing a cavity  665  having an internal surface corresponding to surface  565 , into which the analog  230  is inserted in a friction fit to assume a position and orientation that is fixed in 6 degrees of freedom with respect to the model  600 , corresponding to the position and orientation of the implant  240  in the intraoral cavity of the patient. 
     Suitable CNC machining paths for producing the external surface  661  and cavity  665  of the model  600  from a blank are generated from the third virtual model  560  in a manner known in the art. 
     A feature of CNC controlled manufacturing process of the model  600  according to this and other embodiments of the invention is that the machining instructions for producing both, the external surface  661  and cavity  665  of the model  600 , are derived from the same virtual model  650  and are thus referenced to the same machine coordinate system C. This enables the same CNC controlled manufacturing system to be used for machining the outer part  661  of the model as well as the cavity  665  of the model, either in parallel or in series, in an accurate and consistent manner, and in one machining operation. Further, there is no need for an intervening scanning operation to determine the 3D shape of the outer surface  661 , and then attempt to align the CNC machining of the cavity thereto, as may be required if the outer surface  661  and cavity  665  are manufactured using different methods or which are not based on the same virtual model. The manufacturing process according to the invention is thus also quick and efficient. 
     The aforesaid computer controlled machining process thus provides a high degree of dimensional accuracy at least in terms of the position and alignment of the cavity  665  with respect to the outer surfaces  661 , and thus of analog  230  with respect to the model  600  when mounted therein, as the machining process for both the cavity  665  and surface  661  are based on the same coordinate system. 
     The physical model  600  thus prepared can assist the dental technician in the design and/or preparation of the permanent abutment, coping, prosthesis and so on, in a manner known in the art. 
     A system and method according to a second embodiment of the invention comprises all the elements and features of the first embodiment as disclosed herein, mutatis mutandis, with the following differences. In the second embodiment, the analog may not be suitable for, or is unable to be, press-fitted into a cavity in an axial direction. For example the desired analog may be a commercially available analog that may comprise laterally projecting protrusions designed for anchoring the analog in a plaster model when the model is cast using prior art methods with the analog in its properly aligned place by virtue of an impression abutment fixed in the impression material. 
     According to the second embodiment, and referring to  FIG.  6   , the analog  230  is embedded in a jacket  300  to form a composite analog  310 . In this embodiment, the jacket  300  is made from a machinable material, which is milled or otherwise machined in situ on the analog  230  to have an external shape that is readily insertable in a suitable direction, for example an axial direction with respect to the analog  230 , in a complementary cavity  340  formed in the physical model, referred to herein by the reference numeral  601 . The method steps of  FIG.  2    are applicable to the second embodiment, mutatis mutandis, with the main difference that in general at least some of the steps therein relating to the analog  230  and cavity  665 , may be applied, in the second embodiment, to the composite analog  310  and cavity  340  instead, mutatis mutandis. 
     Thus steps  410  and  420  for the second embodiment are substantially the same as for the first embodiment, mutatis mutandis. 
     In step  430 , though, the second virtual model, while representative of the physical analog  230 , is further representative of the jacket  300 , and thus of the composite analog  310 . The shape and relative position of the outer surface  315  of the jacket  300  that is to mate against the internal surface  325  of cavity  340  may be predefined, or may be designed as part of the method of the invention. 
     According to the first option, the shape and relative position of the outer surface  315  of the jacket  300  that is to mate against the internal surface  325  of cavity  340  may be predefined. The jacket  300  is formed on the analog  230 —for example the analog  230  is cast or otherwise embedded in a blank of material, and the jacket  300  is machined until a desired form is provided for outer surface  315 . Alternatively, and referring to  FIG.  6 ( a ) , a cast material  317  may be poured into a precision mold  316  of a predefined internal shape, while analog  230  is being held in a predefined spatial relationship with respect thereto by a jig  318  or the like. In any case, in step  430 , the resulting composite analog  310  is scanned, for example, to accurately determine the surface coordinates thereof, while impression attachment is attached to the analog  230 , thereby providing a first virtual portion representative of the impression abutment, and a second virtual portion, representative of surface  315 . Then, in step  440 , the third virtual model is generated in a manner substantially similar to that of the first embodiment, mutatis mutandis, directed to the first and second virtual portions defined in step  430 , comprising the outer surfaces corresponding to the exposed surface of the intra oral cavity and a virtual cavity which is substantially complementary to the non-exposed part of the first virtual portion and to the second virtual portion obtained in this embodiment. In the manufacturing step  450 , the outer surface and the cavity  340  of the physical model are manufactured in a similar manner to that of the first embodiment, mutatis mutandis, and the composite analog  310  can then be affixed into the cavity  340  in a manner such that the analog  230  is aligned with the model  601  in a manner paralleling the position and orientation of the implant  240  in the intra oral cavity. 
     According to the second option, the shape and relative position of the outer surface  315  of the jacket  300  that is to mate against the internal surface  325  of cavity  340  is designed as part of the method. Thus, in step  430 , the second virtual model representative of the analog  230  is provided in a similar manner to that disclosed herein for the first embodiment mutatis mutandis. This second virtual model is then modified by adding a suitable external virtual surface, outwardly displaced with respect to the virtual surface in a manner that allows for an insertion path to a complementary virtual recess or cavity provided in the third virtual model. For example, the aforesaid external virtual surface may comprise a generally prismatic form, for example corresponding to that of the external surface  315  illustrated in  FIG.  6   . Alternatively, and referring to  FIGS.  7  and  7   ( a ), for example, the external virtual surface, marked at  360 , may correspond to part of the first virtual model and is representative of an exposed part of the outer surface of the buccal and labial gingival tissues close to the position of the implant  240  in the intra oral cavity, and further include virtual side portions  361  and base  362  to enclose the initial virtual model of the analog in a virtual volume. In step  440 , the third virtual model is generated from the first virtual model by effectively removing a virtual surface corresponding to surface  360  of the second virtual model, and adding virtual surfaces complementary to side portions  361  and base  362  to form a virtual recess or cavity configured for enabling the second virtual model to fit therein. In step  450 , the physical model  602  is manufactured in a similar manner to that in the first embodiment, mutatis mutandis, producing a recess or cavity  345  as well as the external surfaces corresponding to parts of the intra oral cavity. Step  450  also comprises manufacturing the composite analog  340 , based on the modified second virtual model generated in step  430 , and this may be done, for example, by casting or otherwise embedding the normally hidden parts of the analog  230  in a blank of material, and the jacket  342  is then CNC machined based the second virtual model, in which the analog is held in a known position with respect to the manufacturing system  280 . 
     A system and method according to a third embodiment of the invention comprises all the elements and features of the first and second embodiments as disclosed herein, mutatis mutandis, with the following differences. In the third embodiment, the analog is not press-fitted in place with respect to the physical model—for example, the analog may not be suitable for, or is unable to be, press-fitted into a cavity in an axial direction. 
     According to the third embodiment, and referring to  FIG.  8   , a physical model  603  of the intra oral cavity is manufactured in a similar manner to that disclosed herein for the first embodiment, mutatis mutandis, with two main differences. The first difference is that the machined cavity  666  is significantly larger than required for accommodating the analog  230  in a tight fit, and the cavity may be of any desired shape so long as the analog may be inserted therein, with a clearance  662 , in the position and orientation with the respect to the model  603  that parallels the position and orientation of the implant  240  in the intra oral cavity. For example, in step  440  it may only be necessary to establish the spatial relationship between the second virtual model and the first virtual model, but thereafter the virtual cavity corresponding to cavity  666  may be created by effectively removing a “slice” of the first virtual model that is bounded by the location of the two adjacent teeth in the model: The second difference is that the third virtual model is created to include a virtual representation of an integral mating platform  670 , which is then integrally manufactured with the physical model  603 . 
     According to another aspect of the invention, a jig is also provided for the third embodiment of the system and method of the invention, for holding the analog  230  within the cavity  666  in the desired position and orientation therein until a filling and fixing material, for example epoxy resin, is placed in the clearance gap  662  and allowed to set, cementing the analog in place, after which the jig can be disengaged from the analog  230  and from the model  603 . 
     The jig  700 , according to a first embodiment, comprises a base  710 , and a substantially rigid, inverted U-shaped strut  720 , having one arm  722  rigidly attached to the base  710  and a second arm  724  having a free end  725  onto which an analog  230  may be mounted at the abutment receiving end thereof in a known and unique spatial relationship with respect thereto. There is thus a unique and fixed spatial relationship between the end  725  and the base  710 . The shape of the jig is only illustrative, and any suitable arrangement may be used that has a fixed geometrical relationship between the model-engaging base and the analog engaging end. Furthermore, the mating platform  670  is remote from parts of the model representing dental surfaces, and thus facilitates the cementing procedure for the user as there is a minimum or zero obfuscation of the cavity  666  and analog  230  by the jig. 
     Referring also to  FIG.  9   , the jig  700  is mounted to the model  602  by engaging the mutually abutting surfaces of base  710  and the mating platform  670  in a unique mating position, and is thus engaged in a fixed position therein until removed. In this embodiment, the geometry of the jig  700  is predefined—for example the jig  700  may be a previously manufactured off the shelf item—and the position and orientation of the mating platform  670  with respect to the cavity  666  is designed such that when the jig  700  is properly engaged with the model  603 , with the base  710  firmly seated in position on the mating platform  670 , the end  725  automatically brings the analog  230  attached thereto into its correct position with respect to the cavity  666 , and thus the model  603 . Thus the model  603  may be manufactured having an extended base portion  605 , if necessary, such as to provide the required position and orientation to the base  710  via the mating platform  670 . 
     The corresponding position and orientation of the mating platform  670  can be calculated in step  440  in a relatively straightforward manner. Having already designed the virtual equivalent of the cavity  666  in step  440 , the required position and orientation of the second virtual model representing the analog  230  is also known. The relative spatial position between the end  725  and the base  710  of the jig  700  is also known, and thus by effectively fixing the end  725  to be in an engagement position, in a virtual sense, with the virtual model of the analog  230 , the corresponding position of the base  710  with respect to the third virtual model is automatically fixed. Accordingly, the shape and position of the virtual equivalent of the mating platform  670 , in particular the abutting surface  671  thereof, is readily defined in the third virtual model, being essentially complementary to the abutting surface  761  of the base  710 , which thus enables the physical model  603  to be manufactured integrally with the mating platform  670  in place. 
     It is to be noted that rather than a single jig  700 , there may optionally be provided a family of predefined jigs, each having the same general properties of jig  700 , but each having a different fixed geometrical relationship between the respective end  725  and base  710  thereof. Thus, in step  440 , the computer system  260  may determine automatically, or via interaction with the user, which of the particular jigs provides an optimum design for the model  603  for use therewith. 
     Additionally or alternatively, one or more such jigs may be made from several rigidly connectable modular components, and the user (or computer system  260 ) may choose between the available components to build an optimum jig, on the basis of which the platform  670  is designed and manufactured. 
     In a variation of the third embodiment, and referring to  FIG.  10   , a second embodiment of the jig, designated with the reference numeral  700 ′, comprises all the elements and features of the first embodiment of the jig as disclosed herein, mutatis mutandis, with the following differences. In the second jig embodiment, the jig  700 ′ may be specially designed and manufactured for use with a particular model  603 . In such a case, the jig  700 ′ may have the same general properties and characteristics of jig  700 , but the particular geometrical relationship between the end  725 ′ and base  710 ′ thereof is optimized in any desired manner, with the constraint that the base  710  is to be mounted at a fixed position and orientation on the model  603  to a standard mating platform  670 ′. 
     Referring to  FIGS.  11  to  13   , a third embodiment of the jig, designated with the reference numeral  900 , comprises all the elements and features of the first and second embodiments of the jig as disclosed herein, mutatis mutandis, with the following differences. In the third jig embodiment, the jig  900  comprises a substantially rigid strut  920 , comprising a spacer member  910  and an arm  922  rigidly attachable to the spacer member  910  at one end  921  of the arm  922 . At another end  925  of arm  922  a mounting arrangement  923  is provided, onto which an analog  230  may be mounted at the abutment receiving end thereof in a known and unique spatial relationship with respect thereto. There is thus a unique and fixed spatial relationship between the end  925  and mounting arrangement  923 , and the spacer member  910 . 
     Spacer member  910  comprises two longitudinally opposed free ends  911 ,  912  thereof, and is reversibly attached to end  921  of arm  922  to form L-shaped strut  920  by an engagement arrangement, including a pair of laterally-spaced pins  915  projecting from end  911  and complementary sockets or apertures  916  formed in the end  921  to receive and retain the pins  915 . The mating faces between the ends  921  and  911  and the pins  915  and apertures  916  effectively fix the relative spatial disposition between the arm  922  and the spacer member  910  in six degrees of freedom. In alternative variations of this embodiment, any other suitable engagement or mounting arrangement may be used to ensure that the arm  922  and spacer member  910  are connected to one another in spatially fixed manner with respect to one another, which is reversible and repeatable. 
     At the same time, the tooth model,  602 ′ comprises a base portion  660 ′ onto which jig  900  may be mounted via the spacer member  910 , wherein end  912  is reversibly attached base portion  660 ′ by another engagement arrangement, including a pair of laterally-spaced pins  917  projecting from end  912  and complementary sockets or apertures  918  formed in base portion  660 ′ to receive and retain the pins  917 . The mating faces between the end  912  and base portion  660 ′ and the pins  917  and apertures  918  effectively fix the relative spatial disposition between base portion  660 ′ and the spacer member  910  in six degrees of freedom. In alternative variations of this embodiment, any other suitable engagement or mounting arrangement may be used to ensure that the base portion  660 ′ and spacer member  910  are connected to one another in spatially fixed manner with respect to one another, which is reversible and repeatable. 
     In this embodiment, the geometry of the spacer member  910  is predefined—for example the spacer member  910  may be a previously manufactured off the shelf item and the position and orientation of the base portion  660 ′ with respect to the cavity  666 ′, and the geometry of the arm  922  and relative position between the ends  921 ,  922  thereof, are designed such that when the jig  900  is properly engaged with the model  602 ′, with the spacer member  910  firmly seated in position on the base portion  660 ′, and the arm  922  firmly engaged to the spacer member  910 , the end  925  automatically brings the analog  230  attached thereto into its correct position with respect to the cavity  666 ′, and thus the model  602 ′. 
     For example, the model  602 ′ may be manufactured having base portion  660 ′ in a particular standard form and position with respect to the model dentition  601 ′ (i.e., the parts of the model that have external surfaces representative of the external surfaces of the real teeth), and the form and dimensions of the spacer member  910  can also be standard or chosen from a set of standard sizes/forms. 
     The corresponding position and orientation of the base portion  660 ′ can be calculated in step  440  in a relatively straightforward manner. Having already designed the virtual equivalent of the cavity  666 ′ in step  440 , the required position and orientation of the second virtual model representing the analog  230  is also known. The relative spatial position between the end  925  (and mounting arrangement  923 ) and the spacer member  910  of the jig  900  is also known, and thus by effectively fixing the end  925  to be in an engagement position, in a virtual sense, with the virtual model of the analog  230 , the corresponding position of the end  912  of the spacer member  910  with respect to the third virtual model is automatically fixed. Accordingly, the shape and position of the virtual equivalent of the arm  922 , in particular the end  925  and end  921  thereof, may be readily defined in the third virtual model, being essentially such as to position the virtual model of the analog in the desired spatial disposition with respect to the corresponding position of the end  912  of the spacer member  910 . 
     A suitable machining or other material removal operation may be used for manufacturing the arm  922  from a blank, or alternatively the arm  922  may be formed via a rapid prototyping process. Mounting arrangement  923  may be integrally formed with the arm  922 , or alternatively may be formed separately and fixed in place at end  925  is the required spatial disposition with respect thereto. 
     Once the analog  230  is held in place with respect to the cavity  666 ′ via jig  900 , it is cemented in place using any suitable cement, adhesive and/or filler, after which the jig may be removed. Thereafter (as with other embodiments of the physical dental model), the dental model may be used for designing and fitting a prosthesis to the analog  230 , which facilitates the ultimate engagement of the prosthesis with the respective implant in the intra-oral cavity of the patient. To further aid in this process, it may be desired to mount the model  602 ′ in an articulator, and thus, the base portion  660 ′ and the engagement arrangement thereof, in particular the apertures  918 , may be designed in the first place also to be compatible with the mounting arrangement of an articulator, which for example may have mounting pins similar to pins  917 . A physical model of the patient&#39;s opposed dentition in occlusal relationship with the teeth that are represented by model  602 ′ can also be mounted to the articulator, and thus the user can study the occlusal relationship between the two dental models and the effect of the prosthesis. 
     It is to be noted that the jig according to the present invention may be used with any suitable cavity, which can be of any suitable shape and is larger than the part of the physical analog that it is desired to embed therein, such as to provide a clearance gap between this part of the analog and the cavity. Thus, the term “cavity” refers to any well, bore, slot or any other receiving volume created in the physical model in which the analog may be accommodated and cemented in place by means of suitable filler material applied to the clearance gap. 
     Alternatively, and as illustrated in  FIG.  14   , a physical model  980  of the patient&#39;s dentition of the opposed dental arch in occlusal relationship with the teeth  601 ′ can be mounted to the spacer member  910  once the arm  922  is removed, and thus the user can study the occlusal relationship between the two dental models and how this is affected by the prosthesis that is mounted to the implant (not shown). For this purpose, the form and size of the spacer member  910 , as well as the size and form of the engaging base portion  982  of the dental model  980  are such that when the dental models  982 ,  602 ′ are mounted to one another via the spacer member  910 , the corresponding teeth models  981 ,  601 ′ are in occlusal relationship. 
     A system and method according to a fourth embodiment of the invention comprises all the elements and features of the first through third embodiments as disclosed herein, mutatis mutandis, with the following differences. In the fourth embodiment, the analog is not assembled into the manufactured physical model, but rather the physical model is integrally manufactured with the analog. 
     According to the fourth embodiment, steps  410  to  440  can be substantially identical to the same steps as disclosed for the first embodiment, mutatis mutandis. 
     However, and referring to  FIG.  15   , the manufacturing step  450  comprises embedding the analog  230  in a blank  800  of material in a position and orientation that enables the physical model  606  to be machined from the blank  800  such that at the end of the machining or material removal process, the analog  230  will effectively end up in the desired position vis-à-vis the finished model  606 . Thus the starting point of the blank  800  may be such that the analog is effectively fully submerged in the blank  800 , in a known position and orientation with respect to a reference plane P of the blank. For example, the analog  230  may be held in a particular, known, position and orientation with respect to a plate  820  via a rigid, though optionally removable jig  840 . Plate  820  defines plane P at the upper surface  821  thereof. The blank  800  can be formed by casting a suitable machinable material over plate  820  (contained by a suitable surrounding wall, not shown) up to a level above the analog  230  sufficient to ensure that the heights of all parts of the eventual model  606  are below this level. For this purpose, step  440  may further comprise the step of constructing a virtual blank surrounding the third virtual model, and comprising a reference plane corresponding to plane P in the corresponding position with respect to the relative position of the second virtual model re the third virtual model, to that of the relative position and orientation between the analog  230  and plate  820 , as provided by the jig  840 . This facilitates design and manufacture of the blank  800 . 
     Once the blank  800  is ready, it can be positioned in the manufacturing system  280 , calibrated to identify the position and orientation of the analog  230  and plane P with respect to its coordinate system C. For this purpose, plate  820  may optionally be configured for being mountable with respect to the manufacturing system  280  in a predetermined and unique manner relative to the coordinate system C thereof, for example, and thus when mounted for machining in the manufacturing system  280  the position and orientation of the analog  230  with respect to the plate  820 , and thus the manufacturing system&#39;s coordinate system is automatically fixed, thereby automatically aligning the blank in the manufacturing system  280 , which can then mill or otherwise machine the blank  800  to produce the model  606  therefrom. 
     It is to be noted that the computer system  260  in which the virtual models are created and manipulated according to any of the embodiments of the invention does not necessarily need to be located in the same geographical location as the scanner  250  and patient. Thus, while the scanning of the patient is usually done at a dental clinic by the dentist or other dental practitioner, the dental clinic may instead or additionally be linked to one or more dental labs, and possibly also to a dental service center via a communication means or network such as for example the Internet or other suitable communications medium such as an intranet, local access network, public switched telephone network, cable network, satellite communication system, and the like. Additionally or alternatively, the communication means may include postal or courier services, the data being communicated via a transportable medium such as an optical disc, magnetic disc and so on. In any case, once the third virtual model is created, the physical dental model, and other dental procedures not carried out on the actual patient, may be carried out by the dental lab which receives the required data generated by the method  400  via the communications means. The dental service center may be used for manufacturing dental hardware that requires a very high degree of precision, for example inner surfaces of prostheses that are required to match external surfaces of copings, and possibly also the copings themselves. 
     In the method claims that follow, alphanumeric characters and Roman numerals used to designate claim steps are provided for convenience only and do not imply any particular order of performing the steps. 
     Finally, it should be noted that the word “comprising” as used throughout the appended claims is to be interpreted to mean “including but not limited to”. 
     While there has been shown and disclosed example embodiments in accordance with the invention, it will be appreciated that many changes may be made therein without departing from the spirit of the invention.