Abstract:
An impression coping is provided for taking an impression of an implant installed in a patient&#39;s mouth. The impression coping comprises a proximal end and a distal end. The proximal end is adapted to be inserted within a coronal opening formed in the implant and has an anti-rotation formation cooperating with a corresponding anti-rotation formation formed in the implant for preventing relative rotation of the coping and implant. The coping further includes resilient fingers for engaging corresponding surfaces formed within the coronal opening of the implant. The distal end of the coping includes an impression portion adapted to be embedded in a dental impression material for taking a dental impression thereof.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority and benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application Ser. No. 60/186,535, filed March 2, 2000. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to dental impression copings of the type used in implant dentistry to take impressions of a dental implant site from which accurate models can be constructed. More particularly, the invention relates to an improved pick-up type impression coping, which utilizes a snap fit attachment coping with anti-rotational properties. 
     2. Description of the Related Art 
     Implant dentistry involves the restoration of edentulous area(s) in a patient&#39;s mouth using artificial components, including typically an implant fixture or root and a prosthetic tooth and/or final abutment which is secured to the implant fixture. According to state of the art techniques, the process for restoring a tooth and its root is carried out generally in three stages. 
     Stage I involves implanting the dental implant fixture into the bone of a patient&#39;s jaw. The oral surgeon first accesses the patient&#39;s jawbone through the patient&#39;s gum tissue and removes any remains of the tooth to be replaced. Next, the specific site in the patient&#39;s jaw where the implant will be anchored is widened by drilling and/or reaming to accommodate the width of the dental implant fixture to be implanted. Then, the dental implant fixture is inserted into the hole in the jawbone, typically by screwing, although other techniques are known for introducing the implant in the jawbone. 
     The implant fixture itself is typically fabricated from pure titanium or a titanium alloy. Such materials are known to produce osseointegration of the fixture with the patient&#39;s jawbone. The dental implant fixture also typically includes a hollow threaded bore through at least a portion of its body and extending out through its proximal end which is exposed through the crestal bone for receiving and supporting the final tooth prosthesis and/or various intermediate components or attachments. 
     After the implant is initially installed in the jawbone a temporary healing cap is secured over the exposed proximal end in order to seal the internal bore. The patient&#39;s gums are then sutured over the implant to allow the implant site to heal and to allow desired osseointegration to occur. Complete osseointegration typically takes anywhere from four to ten months. 
     During stage II, the surgeon re-accesses the implant fixture by making an incision through the patient&#39;s gum tissues. The healing cap is then removed, exposing the proximal end of the implant. A mold or impression is then taken of the patient&#39;s mouth to accurately record the position and orientation of the implant within the mouth. This is used to create a plaster model or analogue of the mouth and/or the implant site and provides the information needed to fabricate the prosthetic replacement tooth and any required intermediate prosthetic components. Stage II is typically completed by attaching to the implant a temporary healing abutment or other transmucosal component to control the healing and growth of the patient&#39;s gum tissue around the implant site. 
     Stage III involves fabrication and placement of a cosmetic tooth prosthesis to the implant fixture. The plaster analogue provides laboratory technicians with a model of the patient&#39;s mouth, including the orientation of the implant fixture relative to the surrounding teeth. Based on this model, the technician constructs a final restoration. The final step in the restorative process is replacing the temporary healing abutment with the final restoration. 
     To achieve optimal results in terms of overall aesthetics and bio-functioning ability of the tooth restoration, it is essential in stage II that the plaster analogue accurately reflect the true position and orientation of the implant in the patient&#39;s mouth and that in stage III such position and orientation is faithfully replicated when securing the final tooth restoration to the implant. To help achieve this accuracy and faithful replication, one or more indexing means are typically provided on the proximal end of the implant and corresponding mating indexing means are formed on the various mating components which are adapted to be fitted to the implant. Such indexing means provide desired orientation of the implant and mating components relative to one another and also prevent undesired rotation. 
     Such indexing means frequently take the form of a hexagonal boss or recess (“hex”) formed on the proximal portion of the implant exposed through the crestal bone. For externally threaded implants the hex may also be used to engage a driving tool for driving the implant into an internally threaded bore or osteotomy prepared in the patient&#39;s jawbone (mandible or maxilla). When the implant is fully installed in a patient&#39;s jawbone the hex or other indexing means is typically exposed through the crestal bone so that accurate indexing may be provided between the implant and the final prosthesis and/or various intermediate mating prosthetic components. 
     As noted above, during stage II of the dental restorative process a mold or impression is taken of the patient&#39;s mouth to accurately record the position(s) and orientation(s) of the indexing means within the mouth at the implant site(s) and to thereby providing the information needed to fabricate the restorative replacement(s) and/or intermediate prosthetic components. According to the state of the art, this is done using a casting or impression material formed of a soft resin—typically polyvinylsiloxane or polyether—which can be applied over the implant site using a suitable impression tray and allowed to cure in situ. The impression material is sufficiently resilient such that it can be removed from the patient&#39;s mouth after it is cured (or partially cured) while at the same time retaining an accurate impression of the patient&#39;s mouth and particularly the implant site. 
     However, because the indexing means of the implant is typically quite small and may be recessed partially beneath the gums of a patient, a secondary or intermediate impression element is typically used to help transfer accurately the orientation of the indexing means of the implant. This intermediate impression element is commonly called a “coping” or “impression coping.” Examples of impression copings as found in the prior art are shown in U.S. Pat. No. 4,955,811 to Lazzara et al., e.g., FIGS. 5,  6 , and  9 . There are primarily two types of such impression copings used today—so-called “transfer” impression copings and so-called “pick-up” impression copings. Both are conveniently adapted to be screw-retained to the implant. The choice of which technique is to use (open tray vs. closed tray) is based primarily on individual patient characteristics and the clinician&#39;s preference. 
     Conventional transfer impression copings have an impression portion adapted to form a unique or indexed impression in the impression material and a base portion having mating indexing means adapted to mate with the exposed indexing means of the implant. In use, the impression coping is temporarily secured to the exposed proximal end of the implant fixture such that the mating indexing means of the impression coping and implant are interlockingly mated to one another. Typically, a threaded screw or bolt is used to temporarily secure the impression coping to the implant fixture. 
     Once the impression coping(s) is secured to the implant fixture(s), an impression of the coping(s) relative to the surrounding teeth is taken. A U-shaped impression tray filled with an impression material is placed in the patient&#39;s mouth over the implant site. The patient bites down on the tray, squeezing the impression material into the implant site and around the impression coping(s). Within a few minutes, the impression material cures or hardens to a flexible, resilient consistency. The impression tray is then removed from the patient&#39;s mouth to reveal an impression of the implant site and the impression coping(s). The restorative dentist then removes the impression coping(s) by unthreading the screw from the implant. The coping(s) is then removed from the patient&#39;s mouth and is transferred back into the impression material, being careful to preserve the proper orientation of the indexing means. This impression method using transfer impression copings is commonly referred to as the “closed-tray” technique. While the closed-tray technique is simple in its design and execution, it is sometimes prone to inaccuracies where sufficient care is not taken during the step of reinserting the impression coping(s) into the impression material. 
     Conventional pick-up impression copings are similar to transfer copings described above, except that pick-up impression copings typically include an embedment portion adapted to non-removably embed the impression coping securely within the impression material. Typically, the embedded portion comprises a protuberant “lip” or similar embedment projection at their coronal aspect, such that the diameter of the lip is larger than the diameter of the immediately adjacent (more apical) area of the transfer coping. This allows for “grabbing” or retention of the impression material as it is being removed from the patient&#39;s mouth. In this case, once the impression is taken the tray is removed from the patient&#39;s mouth, the impression coping(s) remain in the impression material and are “picked up” and pulled away from the patient&#39;s mouth along with the impression material. To facilitate such pick-up removal of conventional screw-secured impression copings, the tray is provided with one or more apertures or openings through which a tool may be inserted to loosen the screw or bolt securing each coping. Thus, this impression technique is commonly referred to as the “open-tray” technique. The open-tray technique is particularly well suited for multi-site dental restoration procedures, especially when there is a large divergence angle between multiple adjacent implants, or when the dentist wishes to utilize a verification stent to check the accuracy of the working stone model. The opentray technique is generally preferred for accuracy, but do to the need to cut holes or apertures in the tray, it is more complex. As a result, it often takes more time to prepare and execute. 
     SUMMARY OF THE INVENTION 
     In one embodiment the present invention provides an impression coping for taking an accurate dental impression of an implant installed in a patient&#39;s jawbone. The impression coping has a proximal end and a distal end. The proximal end is configured and adapted to be secured to the implant and includes a protrusion that is sized and dimensioned to engage a recess formed in the implant. The coping also includes an indexing boss and/or recess formed for interlockingly engaging a corresponding mating indexing boss and/or recess formed on the implant. The distal end includes at least one annular recess, slot(s), wings, button, ball, or a criss-cross configuration for retaining the impression coping in the impression material. The coping may be configured and used as either a transfer coping or pick-up coping, as desired. 
     In another embodiment the present invention provides an impression coping for taking an impression of an implant installed in a patient&#39;s mouth. The impression coping comprises a proximal end and a distal end. The proximal end is adapted to be inserted within a coronal opening formed in the implant and has anti-rotation means cooperating with corresponding anti-rotation means formed in the implant for preventing relative rotation of the coping and implant. The coping further includes resilient fingers for engaging corresponding surfaces formed within the coronal opening of the implant. The distal end of the coping includes an impression portion adapted to be embedded in a dental impression material for taking a dental impression thereof. The coping may be configured and used as either a transfer coping or pick-up coping. 
     In yet another embodiment the present invention provides an impression coping for recording the position and orientation of an implant installed in a patient&#39;s jawbone. The impression coping comprises a proximal end and a distal end. The proximal end is configured with one or more resilient prongs adapted to be inserted into a coronal opening formed in the implant and to snappingly engage and secure the coping to the implant. The proximal end also includes an indexing boss or recess formed therein for interlockingly engaging a corresponding mating indexing boss or recess formed on the implant. The distal end includes an impression portion for embedding in an impression material for taking a dental impression. The coping may be configured and used as either a transfer coping or pick-up coping, as desired. 
     In yet another embodiment the present invention provides an impression coping for recording the position and orientation of a dental implant installed in a patient&#39;s mouth. The impression coping includes a first end adapted to be snappingly and anti-rotationally mated to the implant and a second end including one or more blade portions adapted to be embedded in an impression material for taking a dental impression. The coping may be configured and used as either a transfer coping or pick-up coping, as desired. 
     In yet another embodiment the present invention provides an impression coping for recording the position and orientation of a dental implant installed in a patient&#39;s mouth. The impression coping is snappingly and anti-rotationally mated to the implant and comprises at least one blade portion for embedment in an impression material for taking a dental impression thereof. The coping may be configured and used as either a transfer coping or pick-up coping, as desired. 
     In yet another embodiment the present invention provides an impression coping for recording the position and orientation of an implant installed in a patient&#39;s jawbone. The impression coping comprises a proximal end and a distal end. The proximal end is sized and adapted to matingly and anti-rotationally engage the implant. The proximal end also has resilient fingers for snappingly mating with corresponding recesses formed within a coronal opening in the implant. The distal end comprises a generally elongated impression portion including one or more substantially flat blade portions extending radially therefrom. The coping may be configured and used as either a transfer coping or pick-up coping, as desired. 
     In yet another embodiment the present invention provides an impression coping for taking an impression of an implant installed in a patient&#39;s mouth. The impression coping comprises a proximal end and a distal end. The proximal end is sized and adapted to be inserted within a coronal opening formed in the implant. The proximal end further includes anti-rotation means cooperating with corresponding anti-rotation means formed on the implant for preventing relative rotation of the coping and implant when the coping is inserted in the implant. The coping further includes resilient snap means for snappingly engaging corresponding surfaces formed within the coronal opening of the implant. The distal end of the coping includes an impression portion adapted to be embedded in a dental impression material for taking a dental impression thereof. The coping may be configured and used as either a transfer coping or pick-up coping, as desired. 
     For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention have been described herein above. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein. 
     All of these embodiments are intended to be within the scope of the invention herein disclosed. These and other embodiments of the present invention will become readily apparent to those skilled in the art from the following detailed description of the preferred embodiments having reference to the attached figures, the invention not being limited to any particular preferred embodiment(s) disclosed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features of the invention will now be described with reference to the drawings of the preferred embodiments, which are intended to illustrate and not to limit the invention, and in which: 
     FIG. 1 is a side view of a dental implant having certain features and advantages according to the present invention; 
     FIG. 2 is a cross-sectional view of the dental implant of FIG. 1 taken along line A—A; 
     FIG. 3 is a top view of the dental implant of FIG. 1; 
     FIG. 4 is a side perspective view of an impression coping having features and advantages according to the present invention. 
     FIG. 5 is a side view of the impression coping of FIG. 4; 
     FIG. 6 is an opposite side view of the impression coping of FIG. 4; 
     FIG. 7 is a bottom view of the impression coping of FIG. 4; 
     FIG. 8 is a top view of the impression coping of FIG. 4; 
     FIGS. 9A-C are partial cross-sectional time assembly views illustrating the impression coping of FIG. 4 being inserted into the implant; 
     FIGS. 10A and B are detail views of the coping in the snapping chamber of implant assembly; 
     FIG. 11 is a cross-sectional view of an impression tray filled with impression material with an impression coping embedded therein and illustrating the intersection of an implant analog therein; 
     FIG. 12 is a cross-sectional view of an implant analog embedded in dental modeling material forming a positive cast of the implant site; 
     FIGS. 13A-E are perspective, side, opposite side, bottom, and top views, respectively, of another preferred embodiment of an impression coping having features and advantages according to the present invention; 
     FIGS. 14A-E are perspective, side, opposite side, bottom, and top views, respectively, of another preferred embodiment of an impression coping having features and advantages according to the present invention; 
     FIGS. 15A-E are perspective, side, opposite side, bottom, and top views, respectively, of another preferred embodiment of an impression coping having features and advantages according to the present invention; 
     FIGS. 16A-D are side, opposite side, bottom, and top views, respectively, of another preferred embodiment of an impression coping having features and advantages according to the present invention. 
     FIGS. 17A and B are perspective, and top views, respectively, of another embodiment of an impression coping having features and advantages according to the present invention; and 
     FIGS.  18 (A and B) are perspective, and top views, respectively, of another embodiment of an impression coping having features and advantages according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1-3 illustrate a dental implant  10  particularly suited for receiving a snap-in dental impression coping having certain features and advantages according to one embodiment of the present invention. The implant  10  has an outer surface that is preferably divided into three regions: a body portion  12 , a neck region  14 , and a top portion  16 . The body portion  12  preferably includes threads, and represents the portion of the implant  10  that is placed in either the mandible or the maxilla. As shown, the body portion  12  of the implant is substantially cylindrical or slightly tapered; however, the body portion  12  could also assume a conical shape or other known implant shapes, as desired. The threads of the body portion  12  preferably match preformed threads formed along the inner surface of an osteotomy formed in the patient&#39;s jawbone. However, the implant  10  could also be designed so as to be self-tapping. Preferably, the top portion  16  of the implant is substantially cylindrical and has a top surface  18  that is substantially flat. 
     As best seen in FIGS. 2 and 3, the implant  10  includes an inner cavity  20 . The inner cavity  20  includes a screw chamber  22 , a snapping chamber  24 , and an indexing means chamber  26 . Preferably, the diameter of the screw chamber  22  is smaller than the diameter of the snapping chamber  24 . The snapping chamber  24  preferably includes a recess  25  that has an inner diameter that is slightly larger than the indexing chamber  26 . 
     The screw chamber  22  is preferably sized and configured so as to receive a bolt (not shown). The bolt can be used to temporarily or permanently attach a dental component, such as, for example, a temporary healing abutment or a final restoration to the implant  10 . As will be described later, the snapping chamber  24  and the recess  25  are sized and configured to engage a corresponding snapping structure in an impression coping. 
     The indexing chamber  26  is best seen in FIGS. 2 and 3. In the illustrated arrangement, the indexing chamber  26  is substantially cylindrical with three lobes  28  that extend from the top surface  18  to the bottom of the indexing portion  26 . The three lobes  28  are substantially half circular in shape and are symmetrically situated around the perimeter of the indexing portion  26 . Preferably, the center of each lobe  28  is 120° apart from each other relative to a center axis  30  of the implant  10 . It should be appreciate however, that the indexing chamber  26  can be formed in a wide variety of other suitable symmetric or non-symmetric shapes that may be used with efficacy, giving due consideration to the goals of providing repeatable indexing and anti-rotation of mating components. For example, the indexing chamber  26  could comprise a hexagonal recess or hexagonal protrusion that is situated on the top surface  18  of the implant. 
     FIGS. 4-8 illustrate one embodiment of an impression coping  32  having features and advantages in accordance with the present invention. Advantageously, due to its snap-in feature the coping  32  may be configured and used as a pick-up type coping that mates with the implant  10  described above, but does not require modification of the impression tray to use. Alternatively, the impression coping  32  may be configured for use as a transfer coping. 
     As best shown in FIGS. 5 and 6, the impression coping  32  can be divided into four regions: an impression area  34 , a cover  36 , an indexing area  38 , and a snapping portion  40 . The illustrated snapping portion  40  consists of a plurality of prongs or tangs  48 . Each prong  41  preferably includes a rounded protrusion  43 . The protrusions  43  are preferably sized and configured to snap into and resiliently engage the snapping chamber  24  of the implant  10 . Accordingly, the protrusions  43  have an outer diameter that is slightly larger than the inner diameter of indexing chamber  26  (see FIGS. 5,  6 ,  9 ). 
     As best shown in FIGS. 4-7, the indexing means  38  has a substantially triangular shape with rounded comers  46 . It should be readily apparent that the indexing means  38  of the impression coping  32  is sized and configured to engage the indexing means  26  of a mating implant  10 . Like the indexing means of the implant  10 , the indexing means  38  may be formed in a wide variety of other shapes that may be used with efficacy, giving due consideration to the goals of providing repeatable indexing and anti-rotation of mating components. For example, the indexing means  38  could comprise a hexagonal boss and/or recess if the implant  10  includes a hexagonal recess and/or boss protrusion, respectively. The cover  36  is substantially circular with a flat surface and preferably has the same outer diameter as the top portion  16  of the implant  10 . Accordingly, when the impression coping  32  is snapped into place the flat surface of the cover  36  will be resting in mating flush contact with the implant  10 . In this manner, precise orientation and placement of the impression coping  32  is provided. 
     In the illustrated embodiment, the impression area  34  comprises three flat blade portions or extensions  42  that extend away from the cover  36 . The length of the blade is preferably between about 7-15 mm and is most preferably about 11 mm. As viewed from the top (see FIG.  8 ), the extensions  42  are arranged so as to form an impression pin or blade  34  having a generally “T” shaped cross-section. However, it should be appreciated that the impression coping  32  could include more or less extensions  42 , which can be arranged differently. For example, the impression coping  32  could include two extensions that form a “V” shape when viewed from the top. Virtually any conceivable geometry that would facilitate indexing may be utilized. The illustrated geometry is preferred however, because this geometry provides for an impression coping  32  which is easier to manufacture. Additionally, because of the limited amount of material available for the blade or pin  34 , a coping  32  which does not have a central bore has more material on the blade or pin to fabricate retentive features such as holes  50 , slots  54 , criss-crosses or mesh  55  configuration, wings (not shown), button  56  or balls  58  and indexing elements such as annular notches  44 . Advantageously, without the center bore the impression coping  32  is smaller and therein more versatile. Thus the coping  32  can be utilized in all areas of the mouth including the lower anterior mandible where interproximal space between abutments is minimal. In addition, the illustrated geometry is preferred because the impression coping  32  is more ergonomic and more efficient for the dentist to place in the mouth. The coping  32  is simply snapped into position instead of the prior art which necessitated placing the coping  32  in the implant  10 , holding the coping  32  in place, grasping a screw driver and screw, and screwing the impression coping  32  into the implant  10 . However, if it is desired to use the impression coping as a temporary abutment the impression coping may contain a center bore, if desired. 
     Each blade portion or extension  42  preferably includes a shallow annular recess  44  along preferably the lower portion of the extensions  42 . The recess  44  is sized and configured to engage the surrounding impression material, as will be described in more detail below. It should be appreciated that the extensions  42  can include more than one recess  44 , if desired. When the impression coping is used in a transfer technique the recesses  44  serve as an insertion index and retention system creating a positive fit and/or tactile feedback when the coping is reinserted into the impression material. 
     Referring to FIGS. 9A-C, to attach the impression coping  32  to the implant  10  during stage II, the surgeon simply places the impression coping over the implant  10  and pushes the snapping portion  40  of the coping  32  into the implant  10 , as will be described in more detail below. As mentioned above, the protrusion  43  of the coping  32  preferably, has at least a slightly larger diameter than the inner diameter of the indexing chamber  26 . Accordingly, the snapping portion  40  of the coping  32  is compressed as it passes through the indexing chamber  26  (see FIG.  9 A and B). Once the prongs  48  reach the snapping chamber  22 , they partially expand forming a snap fit between the coping  32  and the implant  10  (see FIG.  9 C). Additionally and advantageously, as the cover is mated against the top surface of the implant, the prongs  48  resiliently engage the slanted inner surface  62  of the snapping chamber  22  (see FIG.  10 B). Thus, the pressure exerted against the partially compressed prongs  48  by the slanted inner surface  62  of the snapping chamber  22  creates a reaction downward pulling force. This downward pulling force on the coping  32  causes the mating surface of the cover  36  and the top of the implant  10  to form a seal (see FIG.  9 C). Advantageously, this prevents leakage of saliva and bacterial contaminants into the implant and thus prevents infection. This is particularly important if the coping is to be used as a temporary healing abutment. 
     Clinically and advantageously, the dentist can be assured of the proper placement or seating of the impression coping  32  because as the impression coping  32  is pulled or urged down into the implant  10  the dentist can “feel” the snap fit and hear the audible “click” as the prongs  48  snap into the snapping chamber  22  of the implant. Additionally, the dentist may visually confirm that the impression coping  32  is properly placed or seated by viewing the mated surfaces of the cover  36  and the top of the implant  10  using a dental mirror (see FIG.  9 C). If desired, the proper placement or engagement of the coping  32  may be confirmed by attempting to remove the coping  32 . A properly seated coping will have perceivable resistance to removal forces as the prongs  48  become compressed as they are pulled back into the indexing chamber  26  (see FIG.  9 B). 
     Once the impression coping  32  is attached to the implant  10  a “U” shape impression tray  51  is loaded with an impression material and is placed over the coping, causing the coping to be embedded into the impression material (see FIG.  11 ). The recesses  44  aid in embedding the impression the coping  32  securely within the impression material and/or function as an insertion indexing system if the coping is removed from the impression material and reinserted. Advantageously, an auxiliary embodiment of the impression coping includes holes  50  (see FIGS.  13 A-C), which also aid in embedding the coping  32  securely within the impression material. Another auxiliary embodiment of the impression coping includes slots  54  (see FIGS. 14A-C and  15 A-C), which aid in embedding the coping  32  securely within the impression material. Another auxiliary embodiment of the impression coping includes a criss-cross or mesh like structure  55  (see FIGS.  16 A-C), which aids in embedding the coping  32  securely within the impression material. After the impression material sets up or hardens, the impression tray is removed from the patient&#39;s mouth. In a pick up type impression the coping and implant are configured so that the snapping force created by the snapping portion  40  of the coping  32  and the implant  10  is overcome by the retention force between the impression material and the coping  32 . To help ensure that the coping  32  disengages from the implant  10 , the protrusions  43  are preferably rounded. Alternatively and/or in addition, the protrusions  43  may comprise a lubricious material such as Teflon or may be coated with or otherwise treated with a diamond-like carbon coating (e.g. amorphous diamond), or a titanium anodic coating. 
     Advantageously, the coping  32  remains in the impression material and is pulled away from the patient&#39;s mouth along with the impression material (see FIG.  11 ). The impression containing the coping  32  is then delivered to a dental technician for fabrication of the prosthetic tooth. The dental technician attaches an implant analog  52  to the exposed snap portion  40  of the embedded impression coping  32 . The model is completed by pouring dental stone or any modeling material in the impression and around the implant analog  52 . When the modeling material is set, the model is separated from the impression with the implant analog interlocked in the modeling material  53  (see FIG.  12 ). The analog  52  is properly positioned in the modeling material  53  to allow the dental technician to accurately create a prosthetic tooth in proper alignment and with proper occlusal length. 
     FIGS. 13-16 illustrate several alternative preferred embodiments of the impression coping  32 . These embodiments are essentially the same as the previously described embodiment, other than for the specific differences noted below. As with the first embodiment described above, in each case the impression coping  32  is designed to snap into a mating implant  10 . The main difference is that the impression area  34  does not include annular recess  44  (see FIG.  13 ). Instead, the impression area  34  includes one or more holes  50  that are designed to engage the impression material. These holes  50  ensure that the impression coping  32  remains embedded in the impression material when the tray is removed from the patient&#39;s mouth. Another auxiliary embodiment has slots  54  that are designed to engage the impression material. These slots  54  ensure that the impression coping  32  remains embedded in the impression material when the tray is removed from the patient&#39;s mouth (see FIGS.  14  and  15 ). 
     Another auxiliary embodiment has a criss-cross or mesh  55  like configuration that is designed to engage the impression material (see FIG. 16 FIGS.  16 A-D). This criss-cross or mesh  55  configuration that is designed to engage the impression material. This criss-cross or mesh  55  configuration ensures that the impression coping  32  remains embedded in the impression material when the tray is removed from the patient&#39;s mouth. Another auxiliary embodiment has a D-shaped shaft  60  with an embodiment portion comprising a button or a ball  56  at the distal end to engage the impression material (see FIGS.  17 A and B). Another auxiliary embodiment has a round shaft  61  with an embodiment portion comprising a button or ball  58  at the distal end to engage the impression material (see FIGS.  18 A and B). The preferred embodiment of the button  56  or ball  58  has a flat side to provide for indexing and anti-rotational properties. Those skilled in the art will appreciate that there are a wide variety of other conceivable geometry&#39;s of the impression coping that would facilitate retention by interlocking the impression coping in the impression material that may be utilized. 
     Preferably for pick-up use, the coping  32  remains in the impression material when the tray is removed from the patient&#39;s mouth. Preferably, the withdrawal forces necessary to allow separation of the impression coping  32  and the implant  10  are greater than about 1 lb. to 2 lbs. Accordingly, the unsnapping force between the implant  10  and the coping  32  is desirably less than the retention force between the coping  32  and the impression material. The snapping force is determined primarily by the outer diameter of the protrusions  43 , the inner diameters of the recess  25 , the inner diameter of the indexing chamber  26 , and friction between contacting mated surfaces. To reduce friction, the surface of the protrusions  43  may be coated or otherwise treated with Teflon, diamond-like carbon coating (e.g. amorphous diamond), titanium anodic coating, or any other lubricious coating capable of making the surfaces slide easier. See, for example, U.S. Pat. No. 5,833,463 incorporated herein by reference. To decrease the snapping force, the inner diameter of the protrusions  43  can also be decreased while maintaining the inner diameters of the recess  25  and the indexing chamber  26 . The snapping force may also be decreased or controlled by increasing the diameter of the indexing chamber  26  while maintaining the size of the protrusions  43  and the recess  25 . Correspondingly, the retention force can be increased by adding additional recesses  25  or holes  50 , slots  54 , button  56 , ball  58 , a crisscrossing or mesh configuration  55 , or other embedment retention features to the impression area  34 , which improves the interlocking of the impression material with the impression coping. 
     Although this invention has been disclosed in the context of certain preferred embodiments and examples, it will be understood by those skilled in the art that the present invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof. Thus, it is intended that the scope of the present invention herein disclosed should not be limited by the particular disclosed embodiments described above, but should be determined only by a fair reading of the claims that follow.