Abstract:
The present invention is an impression cap for use with an implant/abutment impressioning system for taking impressions of cement-on-crown abutments to mirror the contour of the soft tissue and bone in a patient&#39;s mouth. The impression cap is configured to uniquely fit over one of an abutment and a dental implant via a novel flange. The flange is located at the bottom of the impression cap forming a bottom rim and is constructed to grasp the collar of an implant in a press, friction fit manner. The flange of the impression cap automatically captures the implant margin by pushing gingival tissue away when the component is seated.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S)  
       [0001]    This application is a continuation-in-part of U.S. patent application No. 10/099,930, filed Mar. 13, 2002, which is hereby incorporated by reference, and claims priority to U.S. provisional patent application No. 60/427,147, filed Nov. 18, 2002. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to an Implant/Abutment Impressioning System with a novel impression cap for an implant fitted in the human body in order to transfer the implant end protruding from the tissue structure to a master cast.  
         BACKGROUND  
         [0003]    The following discussion refers in the first instance to the example of dental implants. For taking an impression of the situation in the patient&#39;s mouth and for transferring the impression obtained to a master cast, on which the tooth replacement is then modeled, a number of elements have hitherto been used. The work steps that have had to be performed, and the elements used in these work steps, are dealt with in detail by SCHROEDER, A.; SUTTER, F.; BUSER, D.; KREKELER, G.: Orale Implamologie [Oral implantology], Georg Thieme Verlag Stuttgart, 2nd edition, 1994, page 202 et seq. On the one hand, the assembling of the elements in the patient&#39;s mouth, particularly in the area of the molars, is problematic because of the resulting overall height of the elements, especially if a screwing instrument has to be used as well. Moreover, the work procedures are demanding for the patient, and they are time-consuming as regards impression-taking and production of the master cast. In addition to this, inaccuracies occur. The difficulties result primarily from the fact that the impression cap does not hold itself on the implant fitted in the mouth or on the manipulation implant to be used subsequently in the production of the master cast. DE 44 15 670 Al discloses an impression cap which, at the open end facing the implant, has resilient flaps which, when applied, engage over the shoulder of the conical superstructure, the latter being fitted into the implant. The impression cap described there cannot therefore be used for taking an impression of the implant end protruding from the gingiva and projecting into the mouth, but instead only for taking an impression of the outer contour of the superstructure while the implant is positioned below the gingiva.  
           [0004]    U.S. Pat. No. 6,068,478 discloses alternatives to the prior impression/implant systems. U.S. Pat. No. 6,068,478 describes an impression system which comprises as its principal component an impression cap for transferring an end, protruding from a human tissue structure, of an implant which is fitted in the human body, including possible superstructures, to a master cast. The outwardly directed implant end has an undercut contour on its outside, and the impression cap has a geometry which complements the undercut contour and engages therein. The undercut contour is formed either by an implant geometry tapering in a trumpet shape towards the implant bed, or by a recess near the implant end. After the impression cap is secured to the implant, it is encased in impression material. The impression cap embedded in the impression compound present in the impression tray is removed from the fitted implant and receives a manipulation implant to make a master cast.  
           [0005]    Two main types of surgical procedures are used in the field to accomplish placement of dental implants in a patient&#39;s mouth. In the first procedure, known as single-stage implantation, the dental implant has a threaded portion and a head. A hole is drilled into the underlying bone structure (i.e., the maxilla or the mandible), and the threaded portion is threaded into the hole. The head portion of the implant extends through the gingiva such that the top surface of the head protrudes slightly. The gingiva is then sutured around the head of the implant. After a sufficient length of time for healing, the patient then returns for creation of a master cast.  
           [0006]    In the second procedure, known as a two-stage implantation, the dental implant again has a threaded portion and a head. In the two-stage procedure, however, the head of the implant extends slightly above the underlying bone structure and under the surface of the gingiva. After placement of the implant and suturing of the gingiva, the patient is given time for healing. The patient then returns and the gingiva is opened above the implant to allow for placement of an abutment. The abutment employed in the two-stage process has a cuff or base and an abutment post protruding upwardly from the cuff. The cuff is sized such that it ends at a level slightly above the gingiva. Typically, the abutment used in the two-stage process is attached to the implant by threading a screw through a longitudinal bore of the abutment and into the implant. After a further time period for healing, the patient returns for creation of a master cast.  
           [0007]    The present invention addresses further constructive alternatives to the prior impression/implant systems. All U.S. patents, patent applications, and other published documents, mentioned anywhere in this application, are incorporated herein by reference in their entirety.  
         BRIEF SUMMARY OF THE INVENTION  
         [0008]    The present invention, in one embodiment, relates to an impression cap for use with an implant/abutment impressioning system for taking impressions of cement-on-crown abutments to mirror the contour of the soft tissue and bone, in a patient&#39;s mouth, as accurately as possible. More particularly, the invention discloses a novel impression cap including a novel retention system for retaining the impression cap to the implant or abutment during the taking of impressions and to the analog during the formation of a stone model. The impression cap is configured to uniquely fit over an implant (in a single-stage implantation) or over an abutment in an abutment/implant assembly (in a two-stage implantation) and grasp the implant or the abutment via a novel flange and internal geometrical design. The flange is located at the bottom of the impression cap forming a bottom rim and is constructed to grasp the collar of an implant or an abutment in a press/friction fit manner. The internal geometry of the impression cap forms surfaces which substantially mirror portions of corresponding external surfaces of the abutment or the abutment/implant assembly. The flange of the impression cap automatically captures the implant or abutment margin by pushing gingival tissue away when the component is seated. This eliminates the need to pack cord, a common but tedious dental procedure.  
           [0009]    The retention system of the present invention is applicable both to a closed impression cap having a substantially closed interior configuration or to an open impression cap in which the cap includes a basket or open structure allowing impression material to form around the implant or the abutment. The preferred embodiment, however, will be described with respect to a closed impression cap.  
           [0010]    According to one embodiment, the present invention is an impression cap for coupling to one of a dental abutment or dental implant in which the abutment or the implant includes a collar with a peripheral retention edge having an outer diameter. The impression cap includes a body having a first end for coupling to the abutment or implant. The body further includes a retention flange at said first end, with the flange having an inner surface engageable with the retention edge of the abutment or implant. To accomplish this retaining engagement, such inner surface has an inside diameter equal to or slightly less than the outer diameter of the retention edge, such that the flange forms a friction fit with the retention edge.  
           [0011]    Another embodiment of the present invention is a reduction-coping method for communicating certain modifications to the size or shape of a dental abutment. The method comprises modifying the abutment or abutment post as desired to create a modified abutment and forming a modified impression cap to match the modified abutment. To form the modified impression cap, a modification cap, in the form of an unmodified impression cap or other structure, is positioned over the modified abutment and reduced to correspond to the modified abutment or the modification cap is positioned over an unmodified abutment and the two are reduced together. The reduced modification cap is then used as a pattern to create a duplicate of the modified abutment, with the duplicate having an external geometry having a size and shape substantially matching that of the modified abutment.  
           [0012]    The present invention, according to another embodiment, is a method of creating a temporary crown to cover an abutment attached to a dental implant in a patient&#39;s mouth. The method comprises providing an impression cap having a first end connectable to one of the dental implant or the abutment and having an internal opening forming an interval cavity sized to receive the abutment. A temporary crown is formed on the impression cap. The impression cap, with formed crown, is then attached to the dental implant or the abutment. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is an implant and an abutment in an exploded view;  
         [0014]    [0014]FIG. 2 is an implant/abutment assembly and an impression cap in an exploded view;  
         [0015]    [0015]FIG. 3 is an implant/abutment assembly and an impression cap mounted thereon;  
         [0016]    [0016]FIG. 4 is an abutment in an impression material tray and an analog in an exploded view;  
         [0017]    [0017]FIG. 5 is an abutment in an impression material tray and an analog in an assembled view;  
         [0018]    [0018]FIG. 6 is a cut-away view showing a partial cross-section of an implant/abutment assembly and an impression cap mounted thereon;  
         [0019]    [0019]FIG. 7 is a detailed cut-away view showing a partial cross-section of a portion of FIG. 6, as indicated;  
         [0020]    [0020]FIG. 7A is an enlarged view, partially in section, showing the retaining engagement between the impression cap and an implant;  
         [0021]    [0021]FIG. 8 is a view of an impression cap;  
         [0022]    [0022]FIG. 8A is a view of an impression cap;  
         [0023]    [0023]FIG. 9 is a view of an impression cap;  
         [0024]    [0024]FIG. 10 is a cut-away view showing a partial cross-section of the impression cap;  
         [0025]    [0025]FIG. 11 is a detailed cut-away view showing a partial cross-section of a portion of FIG. 10, as indicated;  
         [0026]    [0026]FIG. 12 is a detailed cut-away view showing a partial cross-section of a portion of FIG. 10, as indicated;  
         [0027]    [0027]FIG. 13 is a detailed cut-away view showing a partial cross-section along lines  13 - 13  of FIG. 10;  
         [0028]    [0028]FIG. 14 is side view of the impression cap with phantom lines;  
         [0029]    [0029]FIG. 15 is a partial cross-sectional view of the impression cap with phantom lines;  
         [0030]    [0030]FIG. 16 is a top view of the impression cap;  
         [0031]    [0031]FIG. 17 is a bottom view of the impression cap;  
         [0032]    [0032]FIG. 18 is a view of an alternative embodiment of the impression cap;  
         [0033]    [0033]FIG. 19 is a view of the alternative embodiment of the impression cap;  
         [0034]    [0034]FIG. 20 is a cut-away view showing a partial cross-section of the alternative embodiment of the impression cap;  
         [0035]    [0035]FIG. 21 is a detailed cut-away view showing a partial cross-section of a portion of FIG. 20, as indicated;  
         [0036]    [0036]FIG. 22 is a detailed cut-away view showing a partial cross-section of a portion of FIG. 20, as indicated;  
         [0037]    [0037]FIG. 23 is a detailed cut-away view showing a partial cross-section along lines J-J of FIG. 22;  
         [0038]    [0038]FIG. 24 is a detailed cut-away view showing a partial cross-section of a portion of FIG. 20, as indicated;  
         [0039]    [0039]FIG. 24A is an exaggerated cut-away view showing a partial cross-section of an alternative embodiment of the impression cap;  
         [0040]    [0040]FIG. 25 is a top view of the alternative embodiment of the impression cap;  
         [0041]    [0041]FIG. 26 is a bottom view of the alternative embodiment of the impression cap;  
         [0042]    [0042]FIG. 27 is side view of the alternative embodiment of the impression cap shown in FIG. 25;  
         [0043]    [0043]FIG. 28 is a detailed cut-away view showing a partial cross-section along lines H-H of FIG. 27;  
         [0044]    [0044]FIG. 29 is a partial cross-sectional view of the alternative embodiment of the impression cap;  
         [0045]    [0045]FIG. 30 is a detailed cut-away view showing a partial cross-section along lines G-G of FIG. 29;  
         [0046]    [0046]FIG. 31 is a cut-away view showing a partial cross-section of an implant/abutment assembly and an impression cap mounted thereon;  
         [0047]    [0047]FIG. 32 is a detailed cut-away view showing a partial cross-section of a portion of FIG. 31, as indicated;  
         [0048]    [0048]FIG. 33 is an isometric view of a two-stage dental implant and an extension abutment, according to one embodiment of the present invention;  
         [0049]    [0049]FIG. 34 is an isometric view of the extension abutment of FIG. 33 and an impression cap adapted for mounting over the extension abutment;  
         [0050]    [0050]FIGS. 35A and 35B are cross-sectional views (oriented at 90 degrees relative to one another) of the impression cap, taken along the lines  35 A- 35 A and  35 B- 35 B in FIG. 34, respectively;  
         [0051]    [0051]FIG. 36 is a flowchart showing a process for performing reduction coping on an abutment, according to one embodiment of the present invention; and  
         [0052]    FIGS.  37 A- 37 F are diagrams showing a process for performing reduction of an abutment in a stone model and a corresponding reduction to an abutment in a patient&#39;s mouth, according to one embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0053]    The present invention relates to the taking of an impression of an implant  10  fitted in the mouth of a patient, here a dental implant as a full screw. As shown in FIG. 1, the implant  10  has an implant head  12  which includes an outer surface  17  that widens conically upwardly and a plurality of threads  14  for insertion into the patient. The implant head  12 , which will be shown in detail in later figures, includes an implant collar  16  having a retention edge and an angled implant surface or shoulder  18 . An internal threaded bore  20  is also formed in the implant  10 .  
         [0054]    An abutment  22  is screwed into the implant  10  via its threaded part  24  into the internal threaded bore  20  of the implant  10 , as further shown in FIG. 1. The abutment  22  has a base  25  and an abutment post or portion  26 , which is generally conical and has a female abutment flat  28 . The abutment post  26  may have one or more abutment flats  28 . An abutment flat  28  is a flat surface formed by a generally vertically extending recess or groove used to prevent rotation when further pieces are placed over the abutment post  26 .  
         [0055]    The abutment post  26  also has one or more circumferential grooves  30 . The grooves provide additional retention of the crown after cementing. They also may be used to indicate the height of the abutment so that the user may determine the appropriate cap. Typical heights include 4.0 mm and 5.5 mm. The height of the abutment post  26  is such that it extends upwardly to a point generally located between about one half and the full height of the surrounding teeth. Such a height will provide adequate structure to which a crown can be mounted securely and not extend above the surrounding teeth.  
         [0056]    [0056]FIG. 2 shows the abutment  22  screwed into the implant  10  to form an abutment/implant assembly  31 . An impression cap  32  is then lowered over the abutment post  26 . As will be shown below, the internal geometry of the impression cap  32  is configured to uniformly fit over the post  26 . FIG. 3 illustrates the impression cap  32  lowered onto the abutment  22 .  
         [0057]    In FIG. 3, the impression cap  32  press fits down over the collar  16  of the implant  10  to capture the implant margin and position. Impression material is then placed over and around the installed impression cap  32  to take an impression of the gum around the abutment/implant assembly. The impression material, with the impression cap embedded therein, is then removed from the abutment/implant assembly and the patient. Thus, the impression cap  32  remains is the impression material when it is removed.  
         [0058]    [0058]FIG. 4 shows the removed impression cap  32  in the impression material  34 . A negative  36  of the gum surface is formed in the impression material  34 . An analog  38  is then inserted into the impression cap  32 . The analog  38  has a handle  39 , a head  40  and an abutment post  42 . The head  40  and the abutment post  42  mimic the shape of the head  12  and the abutment post  26  of the implant  10 . This provides a fit which replicates the fit between the impression cap  32  and the abutment/implant assembly  31 .  
         [0059]    [0059]FIG. 5 shows the engagement between the impression cap  32  within the impression material (not shown) and the analog  38 . Stone model material is then poured over and around the analog  38  and onto the surface of the impression material  36 . This material is then allowed to harden to create a stone model. After the material sufficiently hardens, the impression cap  32  and the impression material  36  are removed, leaving the analog  38  and the newly formed stone model. The stone model has an outer surface which mimics the surface of the gum line around the inserted abutment/implant assembly  31 . The analog  38  remains fixed in the stone model and together they replicate the position of the Cement-on-Crown Abutment that is in the patient&#39;s mouth. This apparatus may be used for future construction of dental implants which will fit uniformly in the patient&#39;s mouth.  
         [0060]    Further discussion will address particular components of the Implant/Abutment Impressioning System.  
         [0061]    [0061]FIG. 6 illustrates a cross-sectional view of FIG. 3. The device is positioned to view the abutment flat  28  from the side. In this figure, the abutment  22  is screwed into the implant  10  and the impression cap  32  is positioned on the abutment post  26 . FIGS. 6, 7, and  7 A illustrate the fit between the impression cap  32  and the abutment/implant assembly  31 , as well as the fit between the abutment  22  and the implant  10 .  
         [0062]    [0062]FIGS. 7 and 7A are enlarged views of a portion of FIG. 6. Except for a secondary vent  13 , which will be discussed below, FIG. 7 illustrates the engagement between the press fit or friction fit mechanism of the impression cap  32  and the implant  10 , while FIG. 7A represents the same view, but with the implant and abutment in position prior to engagement. This engagement occurs primarily between the peripheral portions of the implant collar  16  and the engagement end or press fit mechanism of the impression cap  32 . The press fit or friction fit mechanism of the impression cap provides an inwardly directed radial force against the periphery of the collar  16 .  
         [0063]    As shown in FIGS. 7 and 7A, at the engagement end, the press fit mechanism of the impression cap  32  has a circumferential flange  44  to guide the engagement end of the impression cap  32  over the implant collar. The flange  44  has a press or squeeze surface  46  which engages the outer periphery of the collar  16 . Preferably, the surface  46  is cylindrical with its side walls substantially parallel to the axis  9  of the implant  10 . In this preferred structure, the surface  46  preferably has a length dimension, and more particularly a cylindrical length dimension, measured in a direction parallel to the implant axis, of about 0.010 inches to about 0.035 inches and more preferably about 0.020 inches to about 0.025 inches.  
         [0064]    In the preferred embodiment, the outer periphery of the collar  16  includes an outer peripheral retention edge  47 . The edge  47  defines the maximum diameter of implant collar  16 . Preferably, the edge  47  has an outer cylindrical surface portion with a length dimension measured parallel to the implant axis of about 0.004 inches to about 0.010 inches, and no less than about 0.003 inches. The above length dimension of the edge is preferably shorter than the corresponding length dimension of the surface  46 . The connection between the flange  44  and the collar  16  is a pressure frictional fit, wherein the flange  44  squeezes or exerts a force against the outer surface or retention edge  47  of the collar  16 . Although as described above, the retention edge  47  which contacts the flange  44  may be flat and of cylindrical configuration to provide a greater contact surface, the edge  47  may also terminate at a point or be provided with other cross-section configurations, if desired.  
         [0065]    Although the surface  46  is preferably cylindrical as described above, the surface  46  may also slope inwardly, or have a portion that slopes inwardly as it extends downwardly. In such an embodiment, the surface  46  would still include at least a portion, and preferably a generally cylindrical portion, which engages only the retention edge  47 . In this embodiment, no portion of the surface  46  would engage any portion of the sloping outer surface  17  of the head  12 .  
         [0066]    The flange  44  further includes a lead in taper in the form of a tapered surface  48  to guide the flange  44  over the collar  16  so that the surface  46  engages the edge  47 . During assembly of the impression cap  32  onto the implant  10 , the tapered surface  48  contacts the outer surface or edge  47  of the implant collar  16  first. This initial contact helps expand the flange  44  of the impression cap  32  so that the press surface  46  can press fit (or friction fit) against the maximum diameter (the retention edge  47 ) of the implant collar  16 . The lead in tapered surface  48  can be a chamfer, radius, or the like. In one embodiment, this tapered surface  48  tapers downwardly and outwardly from the edge  47  at an angle “A” of about 30 degrees to about 60 degrees and terminates at the lowermost end  51  of the flange  44  and the impression cap. In another embodiment, the angle “A,” formed by the tapered surface  48  is from about 40 degrees to about 50 degrees.  
         [0067]    The impression cap  32  also comprises an angled surface  50  which engages and thus provides a reference stop with the angled shoulder  18  of the implant  10 . This surface  50  to surface  18  contact provides a consistently accurate means of determining that the impression cap  32  is fully seated on the implant/abutment assembly  31 . When the angled surface  50  contacts the implant shoulder surface  18 , it produces a tactile feel, which indicates to the user that the impression cap  32  is fully seated. When the impression cap  32  and implant  10  are fully seated, the angled surfaces ( 50  &amp;  18 ), provide stability by aligning and self-centering the impression cap  32  on the implant  10 .  
         [0068]    The flange  44  further includes an exterior angled surface  52  formed near its lower end. This surface  52  extends from the lowermost end  51  upwardly and outwardly where it is joined with the outer surface of the impression cap at the upper end of the flange  44 . In one embodiment, the angle “B” which the surface  52  forms with the implant axis is about 15 degrees to about 30 degrees. In another embodiment, the angle “B,” formed by the surface  52  is from about 20 degrees to about 25 degrees. During installation of the impression cap, the surface  52  pushes or retracts the gingival tissue away from the implant table. This allows the impression cap  32  to automatically capture the implant margin, or collar  16 . This also eliminates the need to pack cord, a common but tedious dental procedure.  
         [0069]    Because the impression cap is retained relative to the implant head and more specifically relative to the retention edge  47  via a press or friction fit, the retaining force between these two elements will be directly proportional to the amount of surface contact between the surface  46  and the edge  47  and the amount of force exerted by the flange  44  radially inwardly against the edge  47 . The amount of force exerted by the flange  44  will in turn be dictated by the extent of interference or dimensional difference between the outer diameter of the edge  47  and the inner diameter of the surface  46 . The amount of this radially inwardly directed force for a given dimensional interference, will also be dictated in part by the flexibility and thus the geometry of the flange  44 .  
         [0070]    In general, the retaining force between the impression cap and the implant for an installed impression cap should preferably be sufficient to retain the cap on the implant, and to prevent its inadvertent displacement or removal, during the application of the impression molding material and creation of the impression mold as described in greater detail below. To achieve this retaining force, the inner diametrical dimension of the surface  46  should preferably be about 0.004 inches to about 0.008 inches less than the outer diametrical dimension of the edge  47 , which is equivalent to an interference dimension of about 0.002 inches to about 0.004 inches. More preferably, this interference dimension should be about 0.0025 inches to about 0.0035 inches. Also, when the impression cap is installed on the implant as shown in FIG. 7, the point at which the edge  47  engages the surface  46  should be below the upper end of the surface  46  and below the point  53  (FIG. 7A) at which the tapered surface  52  joins with the outer surface of the impression cap  32 . Also, in one embodiment, the thickness dimension of the flange  44  measured in a generally radial direction at the midpoint of the surface  46  ranges from about 0.01 inches to about 0.02 inches. In another embodiment, the thickness dimension of the flange  44  measured in a generally radial direction at the midpoint of the surface  46  ranges from about 0.011 inches to about 0.016 inches. It has been found that the geometry of the flange  44  relative to the implant structure and with the above preferred dimensions and angles creates an acceptable retaining force.  
         [0071]    The engagement end of the impression cap  32  also forms a curved relief  54  between the angled surface  50  and the surface  46  of the flange  44 . Because the diametrical dimension of the surface  46  is slightly less than that of the edge  47  as discussed above, installation of the impression cap causes the surface  46  to be forced outwardly relative to the surface  50 , thereby creating a stress at the juncture of such surfaces. This relief  54  removes such stresses formed between the press surface  46  and the angled or stop surface  50 . The curved relief  54  also removes any stress risers that may occur within the material during installation of the impression cap as the lead in taper  48  moves over the implant collar.  
         [0072]    [0072]FIGS. 6 and 7 further shows the fit between the abutment  22  and the implant  10 . The implant  10  has a bored hole  20 , which is partially threaded  56 , partially conical  58  and partially stepped  60 . These portions are mirrored by portions  24 ,  25  and  62  of the abutment  22  for a secure fit. The specific mirroring configurations are not critical as long as there is a snug fit between the implant  10  and the abutment  22 .  
         [0073]    [0073]FIG. 8 is a view of the outside of the impression cap  32 . The outside of the impression cap  32  has contoured retention geometry (CRG). This CRG provides tension and compression resistance when the cap  32  is encased in impression material. The CRG comprises circumferential retention ribs  64  &amp;  66  located at the top  64  and midway down  66  the exterior of the impression cap  32 . Surfaces  68 ,  70 ,  72 , &amp;  74  ( 68  and  72  shown in FIG. 9) provide further tension and compression resistance when the cap  32  is encased in impression material.  
         [0074]    The retention geometry also comprises one or more concave surfaces  76  to provide anti-rotation while encased within the impression material. The embodiment shown in FIG. 8 illustrates the concave surfaces  76  as being formed in the circumferential retention ribs  64 ,  66 .  
         [0075]    Anti-rotation is further provided by one or more flat surfaces  78 , which are formed in retention ribs  64  and  66 . Flat surfaces  78  within the retention geometry are aligned with internal flat  80  (shown in FIG. 9). This allows the flat surfaces  78  to be an indicator of the internal flat&#39;s  80  location. The flat surfaces can better be seen in FIG. 8 a.    
         [0076]    Generally, the impression cap  32  has a tapered body  82 . The tapered body  82  allows surface area  72  on the upper retention rib  64  to be greater than the surface area  70  on the lower retention rib  66 . It also allows the surface area  70  on the top of retention rib  66  to be greater than the surface area  68  on the bottom of retention rib  66 . The increased surface area on the retention ribs  64 ,  66  allows for increased retention of impression cap  32  while encased within the impression material.  
         [0077]    The tapered body  82  allows an increased amount of impression material to reside between the upper and lower retention ribs  64 ,  66  and between the lower retention rib  66  and angled surface  84 . The increased impression material allows for increased retention of the impression cap  32  while encased within the impression material.  
         [0078]    The impression cap  32  further comprises two vertical ribs  86 ,  88 . Suitably these vertical ribs are located 180 degrees apart, relative to a center line through the cap  32  from the top to bottom. Vertical ribs  86  and  88  aid in strengthening the impression cap structure so that the impression cap  32  is not deformed from the compressive force imparted on it during seating of the impression cap  32  on the abutment/implant  31 .  
         [0079]    Vertical ribs  86 ,  88  also provide resistance to rotational movement of the impression cap  32  while encased within the impression material. In this embodiment, the vertical rib  86  has a greater horizontal depth than vertical rib  88  due to the presence of the flat surfaces  78 . Both ribs  86 ,  88 , have increasing horizontal depth from bottom to top for structural stability and for greater contact with the impression material. Vertical rib  88  extends downward from the center of the flat surface  78  and perpendicular to internal flat  80 . This allows the vertical rib  88  to be an indicator of the internal flat&#39;s  80  location.  
         [0080]    The impression cap  32  further comprises a one way vent  90  having a gap  92  for release of air during assembly. During the impressioning process when the impression material covers the cap, the impression material pushes against the vent  90  and seals gap  92 . The seal does not allow impression material to enter the internal cavity  94  and no longer allows air to release.  
         [0081]    [0081]FIG. 9 illustrates a view of the impression cap  32  from a further angle showing a portion of the internal geometry of the inner cavity  96 . The internal geometry of the impression cap  32  matches the geometry of the abutment/implant connection  31 . Internal or abutment flat  80 , which has an inner surface  98 , interrupts the inner surface  53  of the cap. The abutment flat  80  provides anti-rotation and rotational stability.  
         [0082]    The impression cap  32  further comprises a channel  100  which forms the secondary vent  13  when the cap  32  is coupled with the abutment/implant assembly  31 . While assembling the impression cap  32  to the abutment/implant  31 , air compresses within the internal cavity  96  of the impression cap. The compressed air pushes against the impression cap  32  and causes the impression cap  32  to lift off the abutment/implant  31 . Air pressure relief (release) is beneficial to alleviating the internal air pressure.  
         [0083]    The secondary vent  13  is a relief passage from the internal cavity  96  to the outside. The secondary vent  13  is a relief passage in the reference stop surface  50 . This allows the majority of the trapped air to escape during assembly of the impression cap  32  to the abutment/implant configuration  31 .  
         [0084]    Although only one channel  100  is shown, it should be understood that the invention contemplates a plurality of channels arranged around the angled surface  50 . For example, an embodiment may have a channel  100  as shown in FIG. 9 and a second channel situated 180 degrees around the angled surface and aligned with rib  86 .  
         [0085]    [0085]FIG. 9 also illustrates the bottom rim  102  showing the surfaces which form the flange  44  of the cap  32 . The curved relief  54  follows the angle surface  50  from the inside of the cap  32  toward the outside. The pressing surface is shown at  46 , followed by the lead in taper  48 . Angled surface  52  represents the outer part of the flange  44 . The flange  44  may have an extra surface  51  between angled surface  52  and surface  48  to provide a blunt end to the flange  44 . Surface  51  may be substantially perpendicular to pressing surface  46  or rounded.  
         [0086]    [0086]FIG. 10 shows a cross-sectional view of the cap  32 , wherein the internal flat  80  faces to the left. This figure provides a view of the geometry of the internal cavity  96 . The positioning of the one way vent  90  and the secondary vent  13  are also shown.  
         [0087]    Certain portions, which are indicated in FIG. 10, are blown up and can be seen in FIGS.  11 - 13 . FIG. 11 illustrates the one way vent  90  at the top of the cap  32  in a cross-sectional view. The vent  90  comprises a cover  91  attached to the top of the cap  32  via an attachment piece  89  and a gap  92  to release the air, as described above. It is the cover  91  which is pushed down by the impression material to seal the gap  92 . A recess  93  may also be formed to keep the top surface of the cover  91  at, or below, surface  74 .  
         [0088]    [0088]FIG. 12 shows a cross-sectional view of the flange  44  portion of the cap  32 . The portions numerically indicated are described above. FIG. 13 shows a cross-sectional view along the line  13 - 13  shown in FIG. 10. Similarly, the portions numerically indicated are described above. In this figure, a cross-section of the cap material  32  is shown FIGS.  14 - 17  show the cap  32  from different angles. The portions numerically indicated are described above. FIG. 14 is a view of the cap  32 , wherein the vertical rib  86  is centered in the front. The inner rear surfaces are shown in phantom. FIG. 15 is a view of the cap  32 , wherein the vertical rib  88  is centered in the front. The figure is a partial cross-sectional view and the remaining inner rear surfaces are shown in phantom. FIG. 16 is a top view of the cap  32  and FIG. 17 is a bottom view of the cap  32 .  
         [0089]    FIGS.  18 - 19  show a further embodiment, identified as  110 , of the impression cap. Cap  110  is similar to cap  32 , but it has certain differences which may be added individually. As such, similar features are labeled similarly. Starting at the top of the cap  110 , as shown in FIG. 18, the circumferential retention rib  64  has a flat indicator surface  78 , but is free of recesses, as shown in FIG. 8 at  76 , However, this embodiment does have recesses  76  in circumferential retention rib  66 .  
         [0090]    A further embodiment of the top vent  112  is also shown. This vent  112  will be shown and described in more detail in reference to later figures.  
         [0091]    Also shown in FIG. 18 is a further alternative in the construction of vertical rib  86 . In this embodiment, the bottom end  114  of rib  86  is flared. This extra mass in the bottom  114  of rib  86  aids in preventing cracking during the manufacturing of the cap. In this embodiment, the extra mass is positioned adjacent a second secondary vent, which is formed by a second channel  116 . Second channel  116  is formed similarly to channel  100  and is used similarly for venting. The extra mass provided by bottom end  114  replaces the mass lost in forming channel  116 . Although bottom end  114  is shown in a flared configuration, the present invention contemplates other configurations to increase the mass of rib  86  at the bottom, adjacent to the second channel  116 .  
         [0092]    [0092]FIG. 19 illustrates a view of the impression cap  110  from a further angle showing a portion of the internal geometry of the inner cavity  118 . As with cap  32 , the internal geometry of the impression cap  110  matches the geometry of the abutment/implant connection  31 . In this figure, channel  116 , which forms a second secondary vent  120  when the cap  110  is coupled with the abutment/implant assembly  31 , can be seen. Secondary vents  13  and  120  are formed and work similarly.  
         [0093]    [0093]FIG. 20 shows a cross-sectional view of the cap  110 , wherein the internal flat  80  faces to the left. This figure provides a view of the geometry of the internal cavity  96 . The positioning of the one way vent  112  and the secondary vents  13 ,  120 , are also shown.  
         [0094]    Certain portions, which are indicated in FIG. 20, are blown up and can be seen in FIGS. 21, 22 and  24 . FIG. 21 is a blow-up of the encircled portion in FIG. 20 labeled “FIG. 21,” and illustrates an alternative embodiment of the one way vent  112  at the top of the cap  110  in a cross-sectional view. The vent  112  comprises a cover  119 , having fast and second attachment pieces  121 ,  123 , which attach the cover  119  to the top  125  of the cap  110 . On either side of the cover  119 , there is a vent opening  127  and a vent opening  129  (shown in FIG. 18), to release air when the cap is placed over the abutment. As with vent  90 , the air passages close when impression material is pressed over the cap. As with cap  32 , a recess  93  may also be formed to keep the top surface of the cover  119  at, or below, surface  74 .  
         [0095]    [0095]FIG. 22 shows a cross-sectional view of the flange  44  portion of the cap  110 , indicated as “FIG. 22” in FIG. 20. The cross-section is through second vent  120 . The portions numerically indicated are described above.  
         [0096]    [0096]FIG. 23 shows a cross-sectional view of the flange  44  portion of the cap  110 , indicated as J-J in FIG. 22.  110  indicates the cap material. The portions numerically indicated are described above.  
         [0097]    [0097]FIG. 24 shows a cross-sectional view of a portion of the cap  110 , indicated as “FIG. 24” in FIG. 20. The cross-section is through abutment flat  80 , perpendicular to the abutment surface  98 . The portions numerically indicated are described above.  
         [0098]    An additional individual feature may also be seen in this figure. In this embodiment, instead of the surface  98  of the abutment flat  80  being parallel with, or slightly angling away from, the center line  126 , as shown in the other embodiments, a portion of the surface  98  angles toward the center line  126  forming a bulge  128 . An exaggerated view of bulge  128  may be seen in FIG. 24 a . The bulge  128  may be positioned at other places along the surface  98 . In the embodiment shown, the bulge  128  is positioned on the lower part of the flat  80 . Eventually, the surface  98  angles back away  130  from the center line  126 . This bulge  128  or extension inward provides an alternative or additional press fit mechanism that provides an increase in rotational and vertical stability. The feature  128  also accounts for manufacturing tolerance by compressing the bulge  128  against the flat  80 . It removes the necessity of having an exact fit between the internal geometry of the impression cap and the outer geometry of the abutment and the circumferential flange  44  and the collar  16  of the implant  10 .  
         [0099]    [0099]FIGS. 25 and 26 are views of the cap  110  from the top and bottom, respectively. The portions numerically indicated are described above.  
         [0100]    [0100]FIG. 27 is a side view of cap  110  with rib  86  in the front. FIG. 28 is a cross-sectional view of a portion of FIG. 27, indicated as H-H. The portions numerically indicated are described above.  
         [0101]    [0101]FIG. 29 is a view of the cap  110 , wherein the vertical rib  88  is centered in the front. The lower portion of the cap  110  is cut away to reveal the channel  116 . FIG. 30 is a cross-sectional view of a portion of FIG. 29, indicated as G-G. Rib  88  is shown as being wider than rib  86  so as to support the internal flat  80  geometry. It is also seen as shallower than rib  86  due to the indicator flat surface  78 . The portions numerically indicated are described above.  
         [0102]    Similar to FIGS.  6 - 7 , FIG. 31 illustrates a cross-sectional view of an embodiment of an impression cap  110  position on an abutment  200 , which is in turn inserted in an implant  202 . The device is positioned to view the abutment flat  28  from the side such that the cross section is through the first  13  and second  120  secondary vents. This particular embodiment incorporates the bulge  128  feature and uses cap  110 , which may accommodate a situation where the internal geometry of the cap  110  is not an exact fit with the external geometry of the abutment, as shown.  
         [0103]    In these figures, the impression cap  110  is positioned on an abutment post  26  of an abutment  200 , which is screwed into an implant  202  to illustrate the fit between the impression cap  110  and the abutment/implant assembly  204 , as well as the fit between the abutment  200  and the implant  202 . This particular embodiment illustrates a slightly different abutment/implant assembly  204 . This particular embodiment utilizes a conical mating system for a secure and stable fit between the abutment  200  and the implant  202 . This mating system differs from the system shown in FIGS.  6 - 7  in one respect in that it does not include the stepped feature  60 ,  62 . The mating system shown in FIG. 31 utilizes a conical male portion  206  of the abutment  200  which fits into a conical female portion  208  of the implant  202 .  
         [0104]    [0104]FIG. 32 is a blown-up view of a portion of FIG. 31, as indicated by the encircled portion labeled “FIG. 32,” in FIG. 31. The cross-section portion is through the second secondary vent  120 . The figure also illustrates the engagement between the press fit mechanism of the impression cap  110  and the implant  202 . This engagement occurs primarily between the peripheral portions of the collar  16  of the implant  202  and the engagement end or press fit mechanism of the impression cap  110 . As mentioned above, the press fit or friction fit of the impression cap is produced by the press fit mechanism of the cap. The mechanism provides an inwardly directed radial force against the periphery of the collar.  
         [0105]    As shown in FIG. 32, at the engagement end, the press fit mechanism of the impression cap  110  has a circumferential flange  44  to guide the engagement end of the impression cap  110  over the collar  16  of the implant  202 . The flange  44  has a press or squeeze surface  46  which is substantially parallel with the axis  9  of the implant  202  and press fits to the maximum diameter of implant collar  16 . The connection between the flange  44  and the collar  16  is a pressure frictional fit, wherein the flange  44  squeezes the outer surface of the collar  16 . The outer surface of the collar  16  which contacts the flange  44  may be flat to provide a greater contact surface.  
         [0106]    The flange  44  further includes a lead in taper  48  to guide the flange  44  over the collar  16 . During assembly of impression cap  110  onto implant  202 , taper  48  contacts the outer surface of the implant collar  16  first. The taper  48  helps expand the impression cap  110  so that pressing surface  46  can press fit (or friction fit) to the maximum diameter of implant collar  16 . The lead in taper  48  can be a chamfer, radius, or the like.  
         [0107]    The flange  44  may have an extra surface  51  between angled surface  52  and surface  48  to provide a blunt end to the flange  44 . Surface  51  may be substantially perpendicular to pressing surface  46  or rounded.  
         [0108]    The impression cap  110  also comprises an angled surface  50  which provides a reference stop with the shoulder  18  of the implant  202 , as described above. Surface  50  is only partially shown in these figures because the cross-section is through the secondary vents.  
         [0109]    The flange  44  further includes angled surface  52  formed by its exterior. This surface  52  retracts the gingival tissue away from the implant table. This allows the impression cap  110  to automatically capture the implant margin, or collar  16 . This also eliminates the need to pack cord, a common but tedious dental procedure.  
         [0110]    As with the above described embodiment, the engagement end of the impression cap  110  also forms a curved relief  54  between angled surface  50  and the body of the flange  44 . This relief  54  removes the acute angle formed between the pressing surface  46  and the angled or stop surface  50 . The curved relief  54  removes any stress risers that may occur within the material during assembly as the lead in taper  48  moves over the implant collar.  
         [0111]    [0111]FIGS. 31 and 32 further show the fit between the abutment  200  and the implant  202 . The implant  202  has a bored hole  20 , which is partially threaded  56  and partially conical  208 . These portions receive threaded portion  24  and conical portion  206  of the abutment  200  for a secure fit.  
         [0112]    [0112]FIGS. 33, 34,  35 A, and  35 B show various views of a two-stage dental implant  220  and an extension abutment  222 . As shown, the implant  220  includes a threaded portion  224  and a head  226 . In the embodiment shown, the head  226  includes a hex support  228 . The implant  220  further includes an internally threaded longitudinal bore  229  extending through the hex support  228  and into the implant  220 . The extension abutment  222  includes a base or cuff  230  and an abutment post  232 , together defining a shoulder  227 . A collar  234  extends around a periphery of a top portion of the cuff  230  to define a retention edge. In addition to the structure shown in FIG. 33, the cuff  230  and the collar  234  may include an outer surface that widens conically upwardly similar to or identical to the surface  17  (FIG. 7A) and the collar  16  (FIG. 1) of the dental implant head  12 .  
         [0113]    The extension abutment  222  includes an upper bore  235  and a lower bore  236  extending longitudinally through its center and a retaining shoulder  237  between the bores  234  and  235 . In the embodiment shown, the engagement end of the cuff  234  includes a hex-shaped recess  221  adapted to mate with the hex support  228  of the head  226 . The mating of the hex-shaped recess  221  and the hex support  228  prevents rotational motion of the extension abutment  222  with respect to the implant  220 . When the abutment  222  is installed onto the implant  220 , an implant/abutment screw (not shown) engages the shoulder  237  and is threadly received by the threaded bore  229 .  
         [0114]    [0114]FIG. 34 is an isometric view of the extension abutment  222  and an impression cap  240 . The impression cap  240  shown in FIG. 34 may have a structure similar or identical to the structure of the impression cap  32  or the impression cap  110 . Like the impression cap  32  of FIG. 2 and the impression cap  110  of FIG. 18 described above, the impression cap  240  has a hollow interior geometry having portions that generally mate with corresponding surfaces of the abutment  232 . Also, like the impression cap  32 , the impression cap  240  includes a contoured retention geometry to stabilize the impression cap  240  within the impression material. The impression cap  240  also has a retaining flange  242  adapted to guide the impression cap  240  over the collar  234  of the abutment  222  and to retain the cap  240  relative to the abutment  222  when so installed.  
         [0115]    Like the cap retaining structure of the impression cap  32 , shown in FIGS. 7 and 7A, the flange  242  is sized and configured to form a friction or interference fit with the outer surface of the collar  234  and more specifically, a retaining edge or edge portion of the collar  234 . This interference fit should be sufficient to retain the impression cap  32  on the abutment  222  and to prevent inadvertent displacement or removal during the application of the impression molding material and creation of the impression mold. Thus, the inner diameter of the flange  242  must be equal to or less than the outer diameter of the collar  234 . To achieve this retaining force, the inner diametrical dimension of the flange  242  is, in one embodiment, about 0.004 inches to about 0.008 inches less than the outer diametrical dimension of the edge portion of the collar  234 , which is equivalent to an interference dimension, between the flange  242  and the collar  234 , of about 0.002 inches to about 0.004 inches. In another embodiment, this interference dimension is about 0.0025 inches to about 0.0035 inches. In general, the geometrical and dimensional relationships between the impression cap  32  and implant  10  of FIG. 1 is the same as that between the impression cap  240  and the abutment  222  of FIG. 34. Thus, the flange  242  comprises a structure substantially the same as the flange  44  of FIGS. 7 and 7A including the surfaces  46 ,  48 ,  51 , and  52 . The impression cap  240  further includes an inner angled surface or inner shoulder  225  adapted to mate with the outer shoulder  227  of the extension abutment  222 .  
         [0116]    When the implant  220  is placed in the underlying bone structure, the threaded portion  224  extends into the bone and the head  226  seats against the outer surface of the bone. The extension abutment  222  is then secured to the implant  220  using an abutment screw or bolt (not shown) extending through the extension abutment bores  235  and  236  and into the implant  220 . In one embodiment, a hex-shaped recess  221  (shown in FIGS. 35A and 35B) in the extension abutment  222  is mated with the hex support  228  to prevent rotation of the extension abutment  222  with respect to the hex support  228 . The extension abutment  222  has a cuff  230  having a length that extends slightly above the level of the gingiva. Extension abutments  222  of various lengths can be provided to allow the dentist or surgeon to select the extension abutment  222  having the appropriate length for the patient&#39;s mouth.  
         [0117]    To install the impression cap  240 , the cap  240  is aligned with, and pressed onto, the extension abutment  222 . FIGS. 35A and 35B show cross-sectional views of the impression cap  240  fully seated on the extension abutment  222 . During installation of the impression cap  240  on the extension abutment  222 , the flange  242  contacts and extends over the cuff  230  to form a friction or interference fit and the angled surface  225  of the cap seats against the angled surface or outer shoulder  227  of the abutment  222 . The impression cap  240  is coupled to the collar  234  of the extension abutment  222  by the friction between the outer surface or retention edge of the collar  234  and the inner surface of the flange  242 . As discussed above, the diameters and geometry of the collar  234  and the flange  242  determine the tightness of the interference fit.  
         [0118]    As shown, the collar  234  comprises a generally cylindrical configuration defining the outermost diametrical dimension of the abutment  222  and, unlike the retention surface  47  of FIG. 7A, is longer in a direction parallel to the axis  9 , than the inner surface of the flange  242 . The length of the collar  234  could, however, be shorter, similar to the collar  16  and edge  47  of FIG. 7A. As further shown in FIG. 35B, the impression cap  240 , includes a one-way vent  246  having an air gap  248 , which allows air to escape from the internal cavity of the impression cap  240  during engagement with the abutment  222 . As shown in FIG. 35A, the impression cap  240  also includes a secondary vent  250  located on a lower portion of the impression cap  240  and the retaining flange  242 . The secondary vent  250  also acts to allow air to escape from the internal cavity of the impression cap  240  during engagement with the abutment  222 .  
         [0119]    The impression cap embodiments are made from any material compatible with dental usage and the impressing process. Suitably the material is an elastic or moldable material, including, but not limited to, thermoplastic materials, such as polypropylene, polyethylene, acetal (i.e., Delrin or Celcon), HDPE, PEEK, PEAK, or Thermoset. An elastic material is advantageous to provide sufficient squeezing force between the impression cap and the implant collar  16 . The press/friction fit combined with the squeezing force provided by the elastic material provides sufficient retention of the impression cap to the implant.  
         [0120]    On occasion, the dentist or orthodontic surgeon placing the abutment  22  (in a single-stage system) or the extension abutment  222  (in a two-stage implant system) determines that the height or shape (or both) of the abutment post  26  or the abutment post  232  requires modification. For example, the dentist may decide that the abutment post  26  extends too high within the mouth of the patient with respect to surrounding teeth. Or, for example, the dentist may decide that one side of the abutment post  26  extends too close to the outer surface of the prospective crown. In this situation, the dentist may modify the shape of the abutment post  26  by removing (through grinding or the like) one or more portions. If the dentist modifies the size or shape of the abutment post  26 , information relating to the modification must be communicated to the lab, which creates the model of the patients teeth.  
         [0121]    [0121]FIG. 36 is a flowchart showing a process for communicating this reduction of the size or shape of the abutment post  26 . As shown in FIG. 36, in one embodiment, after reducing the size of the abutment post  26  (step  260 ), the dentist installs a modification cap, in the form of a first impression cap or other structure, over the abutment post  26  and onto the implant  10  (or an extension abutment  222 ), as described above, such that a friction or interference fit is created between the modification cap and the implant  10  (step  262 ). Although in one embodiment of the process the modification cap is an impression cap similar to those used in the impression process, the modification cap may include other structures as long as the interior size and configuration, and the retaining means, of the other structure is the same as or substantially the same as the impression cap being used in the impression process. The dentist then removes portions of this installed modification cap, such that it matches all newly-formed surfaces resulting from the reduction of the abutment post  26  (step  264 ). For example, if the height of the abutment post  26  was reduced, then the top of the modification cap is removed down to the new reduced height of the abutment post  26 .  
         [0122]    After the modification cap is modified to match the reduction in size of the abutment post  26 , the modified or reduced modification cap is removed and replaced by an impression cap as described above and shown by reference characters  32 ,  110 , or  240 . The dentist then creates a negative  36  (shown in FIG. 4) from impression material  34  according to an impression process, as described above (step  266 ). The negative  36  and the modified or reduced modification cap are then sent to a lab for creation of a stone model of the patient&#39;s teeth, using the steps set forth above (step  268 ). After the lab creates the stone model, the modified or reduced modification cap is placed onto the abutment post of the analog on the stone model, and the abutment post is reduced to match the modified or reduced modification cap. When this is done, the modified abutment post of the analog in the stone model replicates the modified abutment post present in the patient&#39;s mouth (step  270 ).  
         [0123]    Accordingly, an aspect of the present invention is a method of reducing an abutment post and communicating that reduction information to a lab, which includes the steps of providing an abutment and a corresponding modification cap having an interior substantially matching an exterior portion of such abutment. The abutment is then installed and reduced or modified where necessary. Following such reduction or modification, the modification cap is installed onto the implant/abutment or abutment. Such installed modification cap is then modified so that it matches the previously reduced or modified abutment. If desired, the abutment and the modification cap can be modified or reduced at the same time. This modified modification cap is then removed and an impression cap is installed onto the implant/abutment or onto the abutment. An impression is then taken. After curing, the impression material, with the second impression cap embedded therein, is removed from the patient&#39;s mouth and transferred to the lab along with the modified modification cap. After the stone model is created in accordance with conventional procedures, the lab technician installs the modified modification cap into the abutment of the analog and reduces such abutment post to match the modified modification cap. The lab then creates the crown or replacement tooth to match the modified abutment post of the analog and delivers the crown or replacement tooth to the dentist. Thus, the crown or replacement tooth that is delivered to the dentist for installation exactly matches the reduced or modified abutment post in the patient&#39;s mouth.  
         [0124]    In some circumstances, the lab, after having created the stone model replicating the situation in the patient&#39;s mouth, may decide that the abutment requires further modification. For example, the lab may determine that a replacement tooth or crown cannot be properly attached without reducing the height of the abutment. In this situation, the reduction coping technique shown in FIG. 36 can be used in reverse. In other words, the lab can reduce the size of the analog abutment post as needed and then install a modification cap and reduce it to match the reduced abutment. The lab can then send this modified modification cap back to the dentist, along with the replacement tooth or crown. The dentist then reduces the size of the abutment in the patient&#39;s mouth, using the modified modification cap as a pattern or template. The size of the abutment may be reduced using a carbide or diamond bur and copious irrigation.  
         [0125]    FIGS.  37 A-F illustrate one embodiment of this reduction coping technique. FIG. 37A shows a stone model  270  including an abutment  272 . As shown, the abutment  272  extends upwardly in the replica of the patient&#39;s mouth, beyond the adjacent tooth  274 , and thus it requires reduction. As shown in FIG. 37B, the lab technician places a modification cap  278 , in the form of an impression cap, over the abutment  272  in the stone model  270  and seats the modification cap  278  such that it fully engages the abutment  272  and is securely retained by the friction fit, as discussed above. Next, as shown in FIG. 37C, the lab technician removes the top of the modification cap  278  and then reduces the size of both the modification cap  278  and the abutment  272 , until the abutment  272  reaches the desired size and shape. This results in the creation of a modified modification cap  282  surrounding a modified abutment  284 . Next, the technician removes the modified modification cap  282  (shown in FIG. 37D) and fabricates a replacement tooth or crown to fit over the modified abutment  284 .  
         [0126]    Once fabrication of the crown is completed, the lab technician sends both the crown and the modified modification cap  282  to the dentist. As shown in FIG. 37E, the dentist then places the modified modification cap  282  over the abutment  288  located in the patient&#39;s mouth  290 , such that is fully engages the abutment  288 . Full engagement with the abutment  288  is important to insure that an appropriate modification can be made to the abutment  288 . The dentist then reduces the size of the abutment  288 , using any known technique, to create a modified abutment  292  matching the modified modification cap  282  and thus the modified abutment  284  in the stone model. The dentist then removes the modified modification cap  282 , as shown in FIG. 37F. The replacement tooth or crown is then connected to the modified abutment  292 .  
         [0127]    The impression cap, in accordance with the present invention, may also be used as a temporary cap for attaching a temporary crown. In this embodiment, the temporary crown is attached to or built up around the impression cap, which in turn is fit onto the dental implant  10  or the extension abutment  222 . Preferably the impression cap has a white, opaque color to promote the natural look of the temporary crown. In this embodiment, the impression cap has a height such that it terminates short of the height of the surrounding teeth. This allows the temporary crown to be attached or built around the impression cap, without negatively affecting the patient&#39;s bite. After the crown has been formed, the impression cap, with the formed temporary crown, is attached to the implant  10  or extension abutment  222  using a temporary adhesive or the like.  
         [0128]    It should be understood that individual features of the above embodiments may stand alone as improvement or may be combined with each other in multiple configurations where physically possible. The proportional representation illustrated by the figures also represents structural disclosure of various embodiments.  
         [0129]    The invention also contemplates sterilizing the impression cap via gamma sterilization. For this, a material must be chosen which is gamma sterilizable. Suitably a gamma sterilizable plastic, or more suitably a gamma sterilizable polypropylene, may be used.  
         [0130]    The above described impression caps may be made by conventional means such as injection molding. Through injection molding, the caps may be a one piece structure. The invention also contemplates color-coding the separate pieces to denote abutment length and table collar diameter. The impression cap color corresponds to the appropriate color coded abutment and abutment analog. This may be done to aid the physician in matching the appropriate pieces. This is helpful considering the small sized of the pieces. The colors may be imparted into the material being molded into the cap.  
         [0131]    If not described in detail above, the proportions and relative construction of the embodiments may be interpreted from the figures. Any inconsistencies between the figures and the description should be seen as alternative embodiments. Variations in the relative construction which do not change the inventive concepts presented herein are contemplated as possible embodiments of the invention.  
         [0132]    Although the present invention has been described with reference to preferred embodiments, persons skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.