Abstract:
The invention is an assembly that connects prosthetic teeth to dental models. The assembly forms a two part analog pin that snaps into a sleeve. Also disclosed are kits for installing the assembly, dental models that contain the assembly, and methods for making dental models that contain the assembly. The assembly expedites the connection and separation of prosthetic teeth to and from dental modes and can be employed with dry set dowel pins.

Description:
RELATED APPLICATIONS  
       [0001]    This application claims priority to Provisional Patent Application No. 60/438,304, of the same title, filed Jan. 7, 2003, and designated Attorney Docket No. 12648P. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The invention is an assembly that connects prosthetic teeth to dental models. The assembly forms a two part analog pin that snaps into a sleeve. Also disclosed are kits for installing the assembly, dental models that contain the assembly, and methods for making dental models that contain the assembly. The assembly expedites the connection and separation of prosthetic teeth to and from dental models and can be employed in conjunction with dry set dowel pins.  
         DESCRIPTION OF RELATED ART  
         [0003]    The present invention improves on a technology described in three patents issued to the same inventor, namely, U.S. Pat. Nos. 5,658,147, 5,788,494 and 5,934,906. Priority to the applications leading to these patents is not claimed. However, these patents are incorporated herein by reference.  
           [0004]    It is known in the art to implant replicated teeth that have been removed or are otherwise missing. A replicated tooth designed for implantation is referred to herein as a “prosthetic tooth.” Often, a single prosthetic is made to replicate multiple adjacent missing teeth. Accordingly, it should be understood that the phrase “prosthetic tooth” as used herein also embraces the replication of multiple teeth.  
           [0005]    A prosthetic tooth generally comprises a hollow core, surrounded by a metal abutment which, in turn, is surrounded by a ceramic facing. The ceramic facing is shaped to replicate, as nearly as possible, the missing tooth. The core of the prosthetic tooth is open at both ends. Surrounding one end of the core is an engaging head with a geometric recess.  
           [0006]    It is known in the art to attach a prosthetic tooth to a patient&#39;s jaw using an “implant fixture” that is embedded in the patient&#39;s jaw by osseointegration. Implant fixtures generally comprise an internally and externally threaded hollow tube with an opening at one end. Surrounding the open end of the implant fixture is an engaging head with a raised geometric abutment. The shape of the abutment corresponds, inversely, to the shape of the recess on the engaging head of the prosthetic tooth. To accomplish attachment, the recess on the engaging head of the prosthetic tooth is placed around the abutment on the engaging head of the implant fixture. This provides a non-rotating friction fit. Then, a headed screw is passed through the core of the prosthetic tooth and rotated into the internal threads of the implant fixture until the screw head rests on a ridge inside the core of the prosthetic tooth. This provides a more permanent attachment. Afterwards, the exposed opening in the prosthetic tooth is capped with porcelain, or some other material, so that it is not readily apparent to the naked eye.  
           [0007]    It is known in the art to facilitate the design of a prosthetic tooth with an accurate replica of the patient&#39;s teeth and gums called a “dental model.” The dental model usually includes some form of analog, generally called an “analog pin,” that replicates the initial engaging portions of the implant fixture. “Initial engaging portions” means the raised abutment on the head of the implant fixture and a portion of the internal threading in the implant fixture.  
           [0008]    Dental models containing analog pins are typically created by a multi-step process. First, a coping is fitted onto an implant fixture that is, in turn, affixed to a patient&#39;s jaw by osseointegration. To coping and implant fixture fit together because, like a prosthetic tooth, the coping contains an engaging head with a recess that inversely corresponds to the abutment on the engaging head of the implant fixture. Second, an impression material is placed around a selected region of the mouth, including the coping, and allowed to set. Setting binds the coping to the impression. Third, the set impression, with bound coping, is removed from the patient&#39;s mouth and connected to an impression tray to provide a negative model of the selected portion of the patient&#39;s mouth. Fourth, an analog pin is friction fit to the engaging head on the coping. To accomplish this friction fit, the analog pin has an engaging head that mimics the engaging head of the implant fixture and, accordingly, fits into the recess on the head of the coping. In addition, the analog pin contains an internally threaded hollow that replicates at least a portion of the internal threading in the implant fixture. Fifth, die stone is poured into the dental impression and permitted to set. When the die stone sets, it forms a dental model that has an analog pin affixed therein. Sixth, the dental model is removed from the impression. As a result of the process, the engaging head on the analog pin is exposed on the tooth bearing surface of the dental model at the exact point where attachment of a prosthetic tooth is desired.  
           [0009]    During the design process, the prosthetic tooth is repeatedly installed on, and subsequently removed from, the dental model. This is necessary to insure that the prosthetic tooth will function and appear naturally in the patient&#39;s mouth. Generally, installation and removal has been accomplished in a manner identical to final installation and removal on an implant fixture. In other words, the engaging heads on the prosthetic tooth and analog pin are contacted and then a headed screw is passed through the hollow core of the prosthetic tooth into the internal threads of the analog pin. Often, a specially designed screw driver is required. Accordingly, attachment, removal and reattachment of the implant has been a laborious and time consuming process.  
           [0010]    The invention described in U.S. Pat. Nos. 5,658,147, 5,788,494 and 5,934,906 greatly simplified this process. As described therein, an assembly comprising an analog pin and a sleeve is utilized. The prosthetic tooth is screwed into the analog pin. The analog pin, in turn, slides through, and snaps into, the sleeve. The sleeve, in turn, is permanently fixed to the dental model. Accordingly, removal of the prosthetic tooth from the dental model no longer requires unscrewing a screw. Instead, the analog pin, and attached prosthetic tooth, quickly snap out of, and back into, the sleeve as a single unit. When the prosthetic tooth is removed from the dental model, the analog pin remains attached and provides a handle to better manipulate the prosthetic tooth during finishing.  
           [0011]    Unfortunately, the assembly described in U.S. Pat. Nos. 5,658,147 and 5,788,494 and 5,934,906, like prior art analog pins, is not well adapted for use with dry set dowel pins. Dry set dowel pins are a device commonly utilized in the dental industry to facilitate the design of tooth restorations, as opposed to tooth replacements. Dowel pins are a means for supporting sectioned dies on a dental model. Each section, or die, consists of one or more replicated teeth connected to a base in the dental model by the dowel pins.  
           [0012]    The conventional process for setting dowel pins is called “dry set” and involves a number of steps. First, die stone is poured in excess into a dental impression previously made from the patient&#39;s mouth. Once the die stone sets, it creates a “die model.” Second, the die model is removed and its underside is trimmed and leveled—using, for instance, a grinding stone. This produces a smooth flat surface on the bottom of the dental model close to the underside of the replicated teeth. Third, holes are drilled into the bottom of the dental model. The holes are positioned immediately below the portions of the die model that replicate teeth in need of restoration. Fourth, dowel pins are fastened into the holes. Dowel pins generally comprise a fastening portion that is relatively short, rough, and thin and a pin portion that is relatively long, smooth, and tapered. The dowel pins fit into a dowel sleeve. The fastening portion is inserted into the dowel pin holes and attached, for example, by an adhesive. Once fastened, the pin portion projects away from the underside of the die model. The pin portion of the dowel pin is then sheathed into the dowel sleeve. Fifth, the base is formed. This is done by pouring base stone into a base former (or reservoir) and inserting the die model, sleeved dowel pins first, into the base former. The base sets underneath the die model and around the dowel sleeves. Sixth, the die model is lifted off the base. Removal can be facilitated by using different types of die stone in the model and base and/or positioning a thin intermediate plastic layer between the die stone and base prior to pouring the base. Upon removal, the dowel pins slide out of the dowel sleeves—which remain fixed to the base. Seventh, and finally, the desired sections, or dies, are cut. Each die in the dental model consists of one or more replicated teeth. Each die in the dental model has dowel pins extending from the underside to permit proper positioning and easy placement and removal from the base.  
           [0013]    Analog pins, including those described in the assemblies of U.S. Pat. Nos. 5,658,147 and 5,788,494 and 5,934,906, are not well adapted for use with dry set dowel pins. In contrast to dry set dowel pins, analog pins are positioned prior to casting and remain exposed on the tooth bearing surface of the dental model. Accordingly, when the die model is trimmed and leveled close to the underside of the replicated teeth, as required to dry set dowel pins, the previously positioned analog pins are severed or otherwise destroyed.  
           [0014]    This is not to say that there is no means known in the art that permits the use of dowel pins in conjunction with analog pins. In fact, FIG. 3 in U.S. Pat. Nos. 5,658,147 and 5,788,494 and 5,934,906 show that the present inventor has successfully created such an arrangement. However, in such cases, the dowel pins are set using a process called “wet set.” This process is more complicated, more prone to error, and less familiar to dental practitioners than the aforementioned “dry set” process.  
           [0015]    In the wet set process, dowel pins are inserted into the die stone before the die stone sets, e.g., while the stone is still wet. There is no trimming and/or leveling prior to positioning the dowel pins. Accordingly, extreme care must be taken not to place the dowel pins too deep or to shallow in the die stone, or in the wrong position, or at the wrong angle. Even experienced practitioners make mistakes using the wet set process.  
           [0016]    Accordingly, it would be advantageous to develop an assembly that permits an analog pin to be used in conjunction with dry set dowel pins. This would enhance the ability to design prosthetic teeth and tooth restorations for a single patient on a single dental model. Additionally, it would be desirous to design such an assembly in a manner that utilizes the quick connect features of the assembly described in U.S. Pat. Nos. 5,658,147 and 5,788,494 and 5,934,906.  
         BRIEF SUMMARY OF THE INVENTION  
         [0017]    The invention is directed to an assembly that connects prosthetic teeth to dental models. The assembly forms a two part analog pin that snaps into a sleeve. Also disclosed are kits for installing the assembly, dental models that contain the assembly, and methods for making dental models that contain the assembly. The assembly expedites the connection and separation of prosthetic teeth to and from a dental model and can be employed in conjunction with dry set dowel pins.  
           [0018]    The principle components of the assembly are as follows: (i) an engaging head; (ii) a tail; and (iii) a sleeve. Optionally, but preferably, a pin relief is also employed.  
           [0019]    The engaging head can be divided into upper, middle and lower portions. The upper portion contains a raised abutment and an opening and mimics the engaging head on an implant fixture. The middle portion contains an internally threaded hollow tube that extends to the opening and mimics at least a portion of the internal threads on an implant fixture. The lower portion contains a vertical projection.  
           [0020]    The tail comprises a pin attached to the lower portion of the analog engaging head. When attached, the tail projects away from the analog engaging head. Connection may be accomplished by a variety of means, including friction fit mechanisms, interlocking spiral threads, and/or an adhesive. The engaging head and tail are designed to connect together to form an two part analog pin.  
           [0021]    The sleeve comprises a hollow tubular body, open at both ends, that has a shorter axial length than the two part analog pin. The sleeve fits around the lower portion of the engaging head and most of the tail of the two part analog pin.  
           [0022]    Additionally, and preferably, the assembly contains a pin relief. The pin relief contains a hollow that fits around the lower portion of the tail. The pin relief serves to lock the two part analog pin in place.  
           [0023]    Kits for installing the assembly into a dental model include the aforementioned engaging head, tail, sleeve and pin relief. The kits additionally contain a cavity preserver. The cavity preserver is a soft, hollow, tubular body, generally made of rubber, open at one or both ends. The cavity preserver is longer than the lower portion of the engaging head. The cavity preserver is designed to fit around the lower portion of the engaging head prior to casting a model.  
           [0024]    Dental models that contain the assembly contain the two part analog pin formed by attaching the tail to the engaging head. The two part analog pin is snapped into a sleeve that is, in turn, fixed to a cast base. Preferably, the dental models also contain a pin relief. One of the advantages of the invention is that the dental models may also contain one or more sectioned dies connected to a base by one or more dry set dowel pins.  
           [0025]    Dental models that contain the assembly can be produced by a method comprising at least the following steps:  
           [0026]    (i) positioning the engaging head onto a coping in a dental impression;  
           [0027]    (ii) casting and setting a dental impression to form a die model affixed to the engaging head;  
           [0028]    (iii) attaching the tail to the lower portion of the engaging head;  
           [0029]    (iv) placing the sleeve around the lower portion of the engaging head and upper and middle portions of the tail; and  
           [0030]    (v) casting a base to form a dental model.  
           [0031]    The invention is further described in the following illustrative drawings and detailed description. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0032]    [0032]FIG. 1 illustrates a conventional core aligned with a conventional implant fixture.  
         [0033]    [0033]FIG. 2 illustrates a conventional prosthetic tooth.  
         [0034]    [0034]FIG. 3 illustrates a conventional prosthetic tooth aligned with a conventional implant fixture analog.  
         [0035]    [0035]FIG. 4 illustrates the attachment of a conventional prosthetic tooth to a conventional dental model.  
         [0036]    [0036]FIG. 5 illustrates the attachment of a conventional prosthetic tooth to a conventional implant fixture embedded in a patient&#39;s mouth.  
         [0037]    [0037]FIG. 6 illustrates a kit made in accordance with the invention.  
         [0038]    FIGS.  7 (A),  7 (B),  7 (C),  7 (D),  7 (E) and  7 (F) illustrate the interaction between components of the invention.  
         [0039]    FIGS.  8 (A),  8 (B),  8 (C),  8 (D) and  8 (E) illustrate steps for using the invention in conjunction with a die model and dry set dowel pins. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0040]    The invention improves upon the technology described in FIGS.  1 - 5 . The invention also improves upon the technology described in three patents issued to the same inventor, namely, U.S. Pat. Nos. 5,658,147, 5,788,494 and 5,934,906, the disclosures of which are incorporated herein by reference.  
         [0041]    [0041]FIG. 1 illustrates a conventional implant fixture  110  and core  120 . The implant fixture  110  is a hollow tubular device that contains: (1) an engaging head  111  that contains a raised abutment  112  thereon to facilitate engagement with a prosthetic tooth; (2) a threaded exterior  112  to facilitate osseointegration into a patient&#39;s jaw and prevent retrograde movement after installation; and (3) a threaded socket (not shown) that extends axially into the implant fixture  110  to facilitate reception of a screw shaft. The core  120  is a hollow tubular device that contains an engaging head  121  that contains a recess (not shown) that is proportionate to the abutment  112  on the engaging head  111  of the implant fixture  110 . The core  120  has a hollow interior  121 , open at each end  121   a  and  121   b , adapted to receive a headed screw (not shown). The upper portion  122   a  of the interior surface  121  of the core  120  has a relatively large diameter adapted to receive the head of a screw. The lower portion  122   b  of the interior surface  121  of the core  120  has a relatively narrow diameter adapted to receive the shank of a headed screw. The upper  122   a  and lower  122   b  portions of the interior surface  121  of the core  120  cooperate to form a shoulder  123  for seating the head of a screw.  
         [0042]    [0042]FIG. 2 illustrates a conventional prosthesis  210  of the UCLA-type that contains two replicated teeth  220  and  221 . The prosthesis  210  comprises a core  120  (such as the core shown in FIG. 1) and an integrally formed abutment  230 . The abutment  230  is typically formed of metal, usually gold. A ceramic facing  240 , typically porcelain, is formed over the abutment  230  to replicate the dentition.  
         [0043]    [0043]FIG. 3 illustrates the alignment of a prosthesis  210  (such as the prosthesis shown in FIG. 2) with a conventional analog pin  310 . The analog pin  310  contains an engaging head  311  with a raised abutment  312  that corresponds to the abutment  112  on the engaging head  111  on the implant fixture  110 . The engaging head  311  facilitates engagement of the analog pin  310  with the prosthesis  210 . The analog pin contains ridges  220  to facilitate bonding to dental model casting materials (not shown). A threaded socket (not shown) extends axially into the analog pin  310  to enable reception a screw (not shown).  
         [0044]    [0044]FIG. 4 illustrates a known procedure for mounting a prosthesis  210  (such as that shown in FIG. 2) to a dental model  410  using an analog pin  310  (such as that shown in FIG. 3). The analog pin  310  is physically affixed to the dental model  410  by positioning the analog pin in casting material used to make the dental model  410  prior to setting. The raised abutment  312  on the engaging head  311  of the analog pin  310  is structured to cooperate with the recess on the engaging head  121  of the core  110  of the prosthesis  210 , so that the prosthesis  210  sits on the analog pin  310  in a manner that prevents rotational movement. A headed screw  420  is passed through the core  110  in the prosthesis  210  and rotated into the threaded screw shaft of the analog pin  310  to affix the prosthesis  210  to the analog pin  310 .  
         [0045]    [0045]FIG. 5 illustrates a known procedure for attaching a prosthesis  210  (such as that shown in FIG. 2) to a patient&#39;s jaw  510  using an implant fixture  110  (such as that shown in FIG. 1.) The prosthesis  210  is mounted onto the implant fixture  110  after it has been fixed into the patient&#39;s jaw  510  by the medium of osseointegration. The raised abutment  112  on the engaging head  111  of the implant fixture  100  is structured to interact with the recess on the engaging head  121  of the core  110  of the prosthesis  210  to insure that the prosthesis  210  does not rotate on the implant fixture  110 . A headed screw  520  is passed through the core  110  in the prosthesis  210  and rotated into the threaded screw shaft of the implant fixture  110  to affix the prosthesis  210  to the implant fixture  110 . The exposed end  121   a  of the hollow core  120  of the prosthesis  210  is capped with a plug  530  of porcelain or some other material.  
         [0046]    [0046]FIG. 6 illustrates a kit  600  made in accordance with the present invention. The kit  600  contains an engaging head  610 , a cavity preserver  620 , a tail  630 , a sleeve  640  and a pin relieve  650 .  
         [0047]    The engaging head  610  can be divided into upper  611   a , middle  611   b  and lower  611   c  portions. The upper portion  611   a  contains a geometric abutment  612  that surrounds a central opening  613  and mimics the abutment  112  on the engaging head  111  of an implant fixture  110 . For example, the abutment  612  may be a raised hollow hexagon. The middle portion  611   b  contains an internally threaded hollow tube  614 . Preferably, the outer surface of the tube  614  contains ridges  615 . More preferably, the ridges  615   a  run vertically down the outer surface of the tube  614 . The ridges  615   a  provide an uneven surface which facilitates the adhesion of the engaging head  610  to casting material as it constricts during the setting process. The lower portion  611   c  contains a vertical projection  616 . Preferably, the outer surface of the vertical projection  616  contains ridges  615   b  and/or threads (not shown) that assist attaching the engaging head  110  to the tail  130  by adhesive and/or interlocking threads, respectively.  
         [0048]    The engaging head  610  is relatively short, i.e., no more than 0.5 inches (i.e., 0.25 inches) in length. Thus, the engaging head  610  is smaller than the width of typical die models, even after the die models are trimmed and leveled. Accordingly, the engaging head  610  is not damaged if it is affixed to a die model that is trimmed and leveled to permit the dry setting of dowel pins.  
         [0049]    The cavity preserver  620  is a soft, hollow, tubular body, with an opening  621  on at least one end. For instance, the cavity preserver  620  may be a piece of rubber tubing. The cavity preserver  620  is generally softer and longer than the lower portion  611   c  of the engaging head  610 . The function of the cavity preserver  620  is to extend away from the lower portion  611   c  of the engaging head  610  and, thereby, preserve a cavity leading to the engaging head  610  during the casting, curing, grinding and trimming of a die model. The cavity preserver  620  should be soft enough that its length is easily ground and trimmed, similar to cast material. Thus, when the underside of the die model is trimmed and leveled to permit the dry setting of dowel pins, the cavity preserver  620  is also trimmed and leveled. When trimming and leveling is complete, the remnants of the cavity preserver  620  are removed and discarded. When the cavity preserver  620  is removed, a hole remains in the die model that permits access to the engaging head  610 .  
         [0050]    The tail  630  is a pin structure designed to connect to the engaging head  630  to form a two part analog pin (not shown) after the initial casting, grinding and trimming of a die model. The tail  630  attaches to the lower portion  611   c  of the engaging head  630  through a cavity in the die model that is created by the cavity preserver  620  and exposed when the cavity preserver  620  is removed. The two part analog pin, when assembled, is similar to those described in U.S. Pat. Nos. 5,658,147 and 5,788,494 and 5,934,906.  
         [0051]    The tail  630  is divided into upper  631   a , middle  631   b  and lower  631   c  portions. When attached to the engaging head  610 , the tail  630  projects away from the engaging head  610 . Attachment can be accomplished by a number of means including friction fit, interlocking thread, and/or an adhesive. Preferably, the tail  630  contains an opening  632  in the upper portion  631   a  that facilitates attachment. The opening  632  fits around the lower portion  611   c  of the engaging head  610  to form a friction fit. Preferably, the fit is made more permanent by deploying an adhesive into the opening  632  before the fit is made. The ability of the adhesive to bind to the internal surface of the opening  632  may be facilitated by the incorporation of threads or ridges on the internal surface.  
         [0052]    The tail  630  contains a slight surface undulation  633  somewhere on its surface. The undulation  633  is designed to interact with sleeve  640  to prevent axial movement of the two part analog pin when it is sheathed in the sleeve  640 .  
         [0053]    The tail  630  contains a flat  634  or equivalent structure somewhere on one side of its surface. The flat  634  cooperates with the sleeve  640  to insure that there is no rotational movement of the two part analog pin when it is sheathed in the sleeve  640 .  
         [0054]    Preferably, the tail  630  contains an indentation  635  on the lower portion  631   c . The indentation  635  is designed to engage a pin relief  650  and, thereby, provide an additional locking mechanism to prevent unintended axial movement of the two part analog pin when it is sheathed in the sleeve  640 .  
         [0055]    The sleeve  640  is hollow tubular body that has an upper opening  641   a  and a lower opening  641   b  (not shown). The sleeve  640  fits around portions of the two part analog pin, e.g., around the lower portion  111   c  of the engaging head  610  and the upper  131   a  and middle  131   b  portions of the tail  630 . Preferably, the two part analog pin is sufficiently longer in axial length than the sleeve  630  to permit lower portion  631   c  of the tail  630  to extend through the bottom opening in the sleeve  640 . This permits axial force to be exerted on the two part analog pin from below to remove the two part analog pin from the sleeve  640 .  
         [0056]    Surrounding the lower opening  641   b  is an annular flange  642 . The annular flange  642  provides an uneven surface sufficient to affix sleeve  640  into a setting casting material.  
         [0057]    The inside surface of sleeve  640  has a slight surface undulation  642  that interacts with the surface undulation  633  on the surface of tail  630 . This provides the snap connection between the two part analog pin and sleeve  640 . Axial force must be applied sufficient to move, or snap, the undulations past one another when installing and removing the two part analog pin.  
         [0058]    The sleeve  640  contains a flat  643  or equivalent structure somewhere on at least its inside surface  644  (not shown), and preferably on its inside  644  and outside  645  surfaces. The flat  643  in the sleeve  640  corresponds to the dimensions of the flat  634  on the tail  630  and interacts with the flat  634  on the tail  630  to insure that the two part analog pin can only be inserted into the sleeve  640  in one direction, namely, the direction dictated when the flats align.  
         [0059]    The pin relief  650  serves to further lock the two part analog pin into the sleeve  640 . The pin relief  650  has a larger diameter than both the lower portion  631   c  of the tail  630  and the sleeve  640 . The pin relief  650  attaches to the lower portion  631   c  of the tail  630  in a removable manner to prevent undesired axial movement of the two part analog pin within the sleeve  640 . Removable attachment may be accomplished by a number of means including a snap fit and interlocking threads. Preferably, however, attachment is accomplished by hooking the indentation  635  on the lower portion  631   c  of the tail  630  into an opening  651  on the surface of the pin relief  650 .  
         [0060]    FIGS.  7 (A),  7 (B),  7 (C),  7 (D),  7 (E), and  7 (F) illustrate the interaction of various components in invention. Each interaction is shown in order it generally occurs when the invention is employed.  
         [0061]    [0061]FIG. 7(A) shows an engaging head  610  connected to a cavity preserver  620 . The opening  621  (not visible) in the cavity preserver  620  is sufficiently wide and sufficiently deep to contain the lower portion  611   c  (not visible) of the engaging head  610 , but insufficiently wide and/or insufficiently deep to contain the upper  611   a  and middle  611   b  portions of the engaging head  610 . The cavity preserver  620  is longer than the lower portion  611   c  of the engaging head  610 .  
         [0062]    [0062]FIG. 7(B) shows an adhesive  710  being poured into an opening  632  in upper portion  631   a  of the tail  630  to facilitate attachment of engaging head  610  to tail  630 . FIG. 7(B) also shows an engaging head  610  aligned to attach to the opening  632  in the upper portion  631   a  of the tail  630 . At this point, the cavity preserver  620  has been removed from the engaging head  610 .  
         [0063]    [0063]FIG. 7(C) shows an engaging head  610  adhered to a tail  630 . This two part structure forms analog pin  720 .  
         [0064]    [0064]FIG. 7(D) shows the two part analog pin  720  partially inserted into sleeve  640 . FIG. 7(E) shows the two part analog pin  720  fully inserted into sleeve  640 . A portion  730  of the two part analog pin  720  protrudes from the lower opening in the sleeve  640 .  
         [0065]    FIG. ( 7 F) shows the two part analog pin  720  fully inserted into sleeve  640 . The portion  730  that protrudes from the lower opening in the sleeve  640  rests in pin relief  650 .  
         [0066]    FIGS.  8 (A),  8 (B),  8 (C),  8 (D) and  8 (E) illustrate the various steps for using the invention in conjunction with a die model and dry set dowel pins. Each step is shown in the order it would generally occur when the invention is employed.  
         [0067]    In FIG. 8(A), the engaging head  610  is connected to cavity preserver  620  and die stone is then cast and set to generate a die model  810 . The upper surface  811   a  of the die model  810  contains one or more replicated teeth,  820   a  and  820   b , and engaging head  610 . Cavity preserver  620 , at this point, is buried in the die model  810 .  
         [0068]    In FIG. 8(B), the lower surface  811   b  of die model  810  is trimmed and leveled in preparation for the dry setting of dowel pins. This step damages a portion of cavity preserver  620 . Engaging head  610  is not damaged in this process.  
         [0069]    In FIG. 8(C), cavity preserver  620  is removed using tweezers  830 . Removal of cavity preserver  620  leaves a cavity  840  in the lower surface  811   b  of die model  810  that exposes the lower portion  611   c  of engaging head  610 .  
         [0070]    In FIG. 8(D), two holes  850   a  and  850   b  are drilled into the lower surface  811   b  of die model  810 . A dowel pin,  860   a  and  860   b , is then aligned with each hole. Dowel pins  860   a  and  860   b  are to be affixed into holes  850   a  and  850   b , respectively, by any number of means, including an adhesive. To create binding sites for an adhesive, each dowel pin usually contains a patterned upper portion  861   a  and  861   b.    
         [0071]    In addition, the upper portion  631   a  of tail  630  is aligned with the lower portion  611   c  of engaging head  610  in die model  810 , which is now exposed by cavity  840 . In turn, sleeve  640  is aligned with tail  630  so that the flat  643  on the sleeve  640  is aligned with the flat  634  on the tail  630 . The upper portion  631   a  of tail  630  is to be affixed to the lower portion  611   c  of engaging head  610  by, for example, an adhesive, to create the two part analog pin. The two part analog pin will then be sheathed in sleeve  640 .  
         [0072]    In FIG. 8(E), a complete dental model  888  is shown. Dowel pins,  816   a  and  816   b , have been attached to die model  810  and sheathed in dowel sleeves  817   a  and  817   b . In addition, engaging head  610  and tail  630  have been connected to form a two part analog pin  720 . The two part analog pin  720 , in turn, has been sheathed in the analog pin sleeve  640 . Subsequently, a base  870  has been cast around the exposed portions of analog pin sleeve  640  and dowel sleeves  860   a  and  860   b . The base sets and, in so doing, contracts, to permanently bind the sleeves  640 ,  860   a  and  860   b  into the base  870 . The annular flange  642  on the analog pin sleeve  640  and surface irregularities on the dowel pin sleeves assist in binding the devices to the base  870   b.    
         [0073]    There is a horizontal dividing line  870   a  between die model  810  and base  870  defined by different casting materials and/or a thin plastic divider positioned prior to casting the base  870 . Similarly, there are vertical dividing lines  871   a  and  871   b  that represent cuts made in the die model to permit dies  880   a  and  880   b  to be separated from the remainder of die model  810 . When this happens, the dowel pins  816   a  or  816   b  associated with each die  880   a  or  880   b  separates from its respective dowel sleeve  817   a  or  817   b.    
         [0074]    A portion of the tail  630  on the analog pin  720  extends outside the analog pin sleeve  640 . The analog pin  720  can be removed simply by applying upward axial force to the tail  630 . Accordingly, a prosthetic tooth  210  attached to the analog pin  720  can be easily snapped out of, and snapped into, the sleeve  640  and, thereby, the dental model  888 .  
         [0075]    As is apparent from FIG. 8(E), the invention permits an analog pin  720  to be set and utilized in conjunction with the setting and utilization of dry set dowel pins  816   a  or  816   b . In addition, the invention preservers the quick snap connection capabilities of the assembly described in U.S. Pat. Nos. 5,658,147, 5,788,494 and 5,934,906.  
         [0076]    A method for making a dental model comprising the invention entails the following steps. First, one positions the engaging head onto a coping in a dental impression. Second, one casts and sets a dental impression to form a die model affixed to the engaging head. Third, one attaches the tail to the lower portion of the engaging head, wherein said tail is comprises a pin divided into upper, middle and lower portions, and wherein said pin projects away from the engaging head. Fourth, on places a sleeve around the lower portion of the engaging head and upper and middle portions of the tail. Fifth, one casts a base to form the remainder of the dental model  
         [0077]    Preferably, a method for making a dental model comprising the invention entails the following steps. First, one positions the engaging head onto a coping in a dental impression. Second, one places the cavity preserver onto the lower end of the engaging head. Third, one casts and sets a die model that affixes the engaging head. Fourth, one trims and/or levels the underside of the die model and attaches dowel pins. Fifth, one removes the cavity preserver or any remnants of the same. Sixth, one attaches the tail to the lower portion of the engaging head. Seventh, one places the sleeve around the lower portion of the engaging head and upper and middle portions of the tail. Eighth, one attaches a pin relief to the lower portion of the tail. Ninth, one casts the base to form the remainder of the dental model. Tenth, and finally, the die model is cut to form sectioned dies.  
         [0078]    It should be understood that a number embodiments of the invention are possible. In addition, a number of equivalents may exist which remain consistent with the heart of the invention. Accordingly, the scope of the invention for which protection is sought is defined by the following claims and any equivalents thereof.