Abstract:
A dental implant including an implant body having a top surface, and at least one non-annular cutaway portion longitudinally extending downwardly from the top surface along one side of the body and outwardly to the periphery, and a method for making the implant. The implant body preferably includes a body portion and a head portion integrally formed with the body portion, the body portion has a periphery and the head portion has a non-circular periphery, and the periphery of the head portion is smaller than the periphery of the body portion.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to the field of dental implants and, more particularly, to the design of the implant&#39;s head that maximizes long term stability of the hard and soft tissues surrounding the implant, the abutment and the prosthesis connected to it. 
       BACKGROUND OF THE INVENTION 
       [0002]    Dental implants are used to replace teeth that have been lost. An implant is placed in the jaw bone at the site of the missing tooth and a dental prosthetic unit is attached to it. The long term functional and aesthetic success of dental implants, and the prostheses attached to them, is determined by the response of the hard and soft tissues around them. Throughout the history of the art of dental implantology, it has been known that some bone loss and subsequent soft tissue recession always occur and have to be accepted. 
         [0003]    In recent years, it has been shown that bone loss and soft tissue loss can be lessened by improving the tissue environment around the head of the implant and its connection with the prosthetic unit. Several implant designs having reduced connection diameter provided more soft tissue volume above the implant head and around the prosthetic abutment and have shown better hard and soft tissue responses. See, for example, the conventional, prior art implant  1  shown in  FIG. 1  and shown, in use, in  FIG. 2 . Implant  1  includes a body  2  having a root-like apex  3 , typically with screw threads  4  around the outside surface, and an implant head  5  having a top surface  6 . A screw receiving bore  7  is defined in body  2  for receiving the prosthetic unit, typically an abutment having an abutment screw  8  and a crown  9  mounted on the abutment. 
         [0004]    However, bone loss still occurs where there is less bone thickness around the implant head. This effect is most evident, and results in the most disturbing outcome, when it occurs in the thin bone plates buccal to implants placed in the anterior region of the mouth where the tissues are exposed in the smile, as well as between adjacent implants, particularly in the anterior region. Dental professionals go to great lengths to prevent this effect by trying to locate the implant head away from the buccal plate, thus attempting to allow more bone thickness buccal to the implant head. But bone ridge size and implant dimensions may hinder their success. 
         [0005]    Similarly, when adjacent implants are required, it may be difficult to leave sufficient space between the implants to permit the required tissue volume. 
         [0006]    It is an established clinical fact that thicker buccal bone and larger bone volume are associated with reduced bone loss and reduced soft tissue loss. For that reason, smaller diameter implants are sometimes used in the anterior region of the mouth but at the expense of sacrificing mechanical strength of the fixture and of the connection or sacrificing prosthetic flexibility (such as when using one piece implants). 
         [0007]    In addition, it is sometimes of great practical advantage to be able to directly access the abutment-to-implant connection screw through the crown unit. However, in the anterior maxillary regions, where it may be most desired to access from the lingual (palatal) direction, it is, in many cases, not possible due to the anatomy, size and orientation of the bone ridge (as seen in  FIG. 2 ). To compensate for the angular limitations when restoring implants in the anterior maxillary region dentists sometimes resort to cemented crown solutions or use of angle-correcting prosthetic parts for screw retained crowns, which could sacrifice the preferred geometry of the sub-gingival prosthetic unit, the aesthetic outcome and connection strength (as by requiring smaller diameter screws). 
         [0008]    Accordingly, there is a long felt need for a dental implant which results in reduced bone and soft tissue loss and which can be more successfully implanted in more problematic situations. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention solves this problem by providing a modified head portion on the dental implant that allows more bone volume in critical locations around the implant head. At the same time, the mechanical strength of the implant and of the connection is maintained by retaining the remainder of the implant unchanged with reference to conventional implants. In this way, bone resorption and gum recession in critical areas around dental implants can be reduced. 
         [0010]    There is thus provided, in accordance with the present invention, a dental implant including an implant body having a top surface, and at least one non-annular cutaway portion longitudinally extending downwardly from the top surface along one side of the body and outwardly to the periphery. 
         [0011]    According to one embodiment of the invention, the dental implant further includes a screw receiving bore extending downwards from the top surface for coupling an abutment to the implant. The screw receiving bore may be concentric with the longitudinal axis of the implant, it may be non-concentric with the longitudinal axis of the implant, and/or it may be formed at an angle relative to the longitudinal axis of the implant. 
         [0012]    According to another embodiment of the invention, the implant is a one-piece implant and the cut away portion extends along at least part of the intrabony portion and may include the trans-mucosal portion of the implant. 
         [0013]    According to some embodiments, the cutaway portion is tapered. According to others, the cutaway portion ends in a shoulder. According to still others, the cutaway portion extends along the entire length of the body. 
         [0014]    In some embodiments, there are two, oppositely disposed, cutaway portions longitudinally extending downwardly from the top surface along opposite sides of said body and outwardly to the periphery. In other embodiments, there are three cutaway portions longitudinally extending downwardly from the top surface, equidistant around the body and outwardly to the periphery. 
         [0015]    Further according to the present invention, there is provided a dental implant including a body portion and a head portion integrally formed with the body portion, the head portion having a top surface; the body portion having a periphery and the head portion having a non-circular periphery; and wherein the periphery of the head portion is smaller than the periphery of the body portion. 
         [0016]    There is further provided, in accordance with the invention, a method of forming a dental implant, the method including forming an implant body having a top surface; and cutting away at least one non-annular portion longitudinally extending downwardly from the top surface along one side of the body and outwardly to the periphery. 
         [0017]    There is further provided, in accordance with the invention, a method of forming a dental implant, the method including providing a substantially cylindrical or conical implant body having a longitudinal axis; and forming a head portion having a top surface on the body. The head portion is formed by cutting away a portion of the periphery of the head portion so that the head portion has a non-circular periphery that is smaller than the periphery of the body. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The present invention will be further understood and appreciated from the following detailed description taken in conjunction with the drawings in which: 
           [0019]      FIG. 1  is a schematic illustration of a prior art dental implant head; 
           [0020]      FIG. 2  is a schematic sectional illustration of the prior art dental implant of 
           [0021]      FIG. 1  in use; 
           [0022]      FIG. 3  is a schematic illustration of a dental implant constructed and operative in accordance with one embodiment of the present invention; 
           [0023]      FIG. 4  is an isometric view of the implant head of the dental implant of  FIG. 3 ; 
           [0024]      FIG. 5   a  is a schematic sectional view of a conventional prior art implant in use; 
           [0025]      FIGS. 5   b,    5   c  and  5   d  are schematic sectional views of implants according to different embodiments of the invention having flattened portions of different lengths; 
           [0026]      FIGS. 6   a,    6   b,    6   c  and  6   d  are isometric views of implants according to different embodiments of the invention having different arrangements of cutaway portions; 
           [0027]      FIGS. 7   a,    7   b,    7   c  and  7   d  are top views of the implants of  FIGS. 6   a,    6   b,    6   c  and  6   d;    
           [0028]      FIGS. 8   a,    8   b  and  8   c  are schematic illustrations of three exemplary embodiments of implants according to the invention, in use; 
           [0029]      FIGS. 9   a  to  9   d  are side sectional illustrations of implants according to different exemplary embodiments of the invention; 
           [0030]      FIGS. 10   a  to  10   e  are side sectional views of implants of varying size and design, all formed according to different embodiments of the present invention; 
           [0031]      FIGS. 11   a  to  11   c  are schematic illustrations of implant heads according to further embodiments of the invention; 
           [0032]      FIG. 12   a  is a schematic of a conventional prior art implant head with prosthetic unit; and 
           [0033]      FIG. 12   b  is a schematic illustration of a dental implant according to a further embodiment of the invention. It will be appreciated that the drawings are only schematic and are not to scale. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0034]    The present invention relates to a dental implant with a modified head portion that allows more bone in critical locations around the implant head without sacrificing the mechanical strength of the implant and of the connection. An object of the present invention is to reduce bone resorption in critical areas around dental implants by employing this modified design of the head of the implant. 
         [0035]    The new design involves providing an implant having a body and an integrally formed head of substantially smaller periphery than the periphery of the body, where the periphery of the head is not annular. The implant includes an implant body having a top surface from which one or more parts of the circumference of the predominantly tubular shape of the implant body are cut away from the top surface down to a desired height. The flattened surface allows more bone thickness adjacent to it, as compared to an implant having a full contour tubular shape, as the cutaway area becomes filled with new bone growth. The gain in bone thickness in critical areas, such as where there is a thin buccal bone plate or a thin mandibular ridge or between adjacent implants, is substantial and results in a lower risk of bone resorption and the consequent aesthetic compromise 
         [0036]    One example of an implant  10  according to the present invention is shown in cross-section in  FIG. 3 , and in an isometric view in  FIG. 4 . Implant  10  includes an implant body  11  and an implant head  12  defining a top portion  13 . Head  12  has a longitudinal, non-annular cutaway portion  14 , extending downwards from top portion  13  and outwards to the periphery of the implant. The result is that the head  12  has a smaller periphery than the body. Implant  10  also includes a screw receiving bore  15  for receiving an abutment screw (not shown) to hold a prosthetic unit  17 . The cutaway portion  14  of the implant head  12  is indicated in broken lines in  FIG. 3 , to show the substantial difference in periphery of the head produced by the cut away portion  14 . The cutaway portion can extend along the length of the implant as far as desired and may be parallel to the longitudinal axis of the implant or tapered at an angle to the longitudinal axis or may end in a shoulder  16 , as in the embodiment Illustrated in  FIG. 3 . Several examples of flattened portions of different lengths are shown in  FIGS. 5   b,    5   c  and  5   d,  shown alongside a conventional prior art implant in  FIG. 5   a.    
         [0037]    It should be noted that the topology of the cutaway portion of the implant head may be designed in any one of a variety of ways. The smaller periphery portion may be flat or planar, or it can be curved. If desired, the narrow periphery portion can have the same surface topology as the remainder of the head of the implant, for example, with microthreads or rings for improved adhesion to bone and tissue. As stated above, the smaller periphery head portion may extend to include any part of the implant&#39;s length up to its entire length. In addition, more than one longitudinal cutaway portion may be provided, preferably arranged symmetrically around the body. For example,  FIG. 6   a  is an isometric view and  FIG. 7   a  is a top view of an implant  20  having two cut away portions  22 ,  24 , one opposite the other. This type of implant is particularly suitable where the bone ridge is narrow, for example, in the posterior mandible. See, for example,  FIG. 8   b,  showing a cross-section of a posterior mandible  26  with a mandibular nerve canal  27 . An implant  20  having cut away portions  22 ,  24  is implanted therein. As can be seen, the body of the implant remains of conventional size to retain the mechanical strength of the fixture and of the connection in the bone, but the head has a smaller periphery to provide narrow emergence in the buccal/lingual dimension, which permits minimum bone loss around the implant head and enhanced soft tissue response. Thus, an enlarged area  28  of bone buccal to the implant head and an enlarged area  29  of bone lingual to the implant head relative to conventional implants are obtained. 
         [0038]      FIG. 6   b  shows an isometric view and  FIG. 7   b  shows a top view of an implant  30  having three cutouts  32 ,  34 ,  36  equidistant about the longitudinal axis of the implant. This type of implant is particularly suitable for use with adjacent implants, particularly in areas where there is low bond volume buccal to the implant heads and between the implants. This design is particularly advantageous in the anterior part of upper jaw. See, for example,  FIG. 8   a,  showing an occlusal view of an anterior maxillary bone crest  31  wherein two adjacent teeth  33  have been replaced with implants, after healing of the bone. Two implants  30  having cut away portions  32 ,  34 ,  36  are implanted in place of the two removed teeth. As can be seen, an enlarged area  35  of bone buccal to the implant heads and an enlarged area  37  of bone between the implant heads is provided, relative to conventional cylindrical (not cut away) implants. 
         [0039]    According to certain embodiments of the invention, the screw receiving bore for connecting the abutment is not concentric with the longitudinal axis of the implant. This permits the periphery of the implant head to be even smaller than in the symmetrical implant according to the invention described above.  FIG. 6   c  shows an isometric view and  FIG. 7   c  shows a top view of an implant  40  having a single cutout  42 , similar to the implant of  FIG. 4 , but having an eccentrically disposed screw receiving bore  44  substantially aligned with the longitudinal axis of the implant. This design provides an implant having an even larger cutout area than the concentric implant of  FIG. 4 , particularly useful in areas where it is desired to provide extra (maximum) bone volume. 
         [0040]      FIG. 6   d  shows an isometric view and  FIG. 7   d  shows a top view of an implant  50  having a single cutout  52 , similar to the implant of  FIG. 6   c,  having a screw receiving bore  54  non-concentrically disposed relative to the longitudinal axis of the implant. However, in  FIG. 6   d,  the screw receiving bore  54  is not aligned with the longitudinal axis of the implant but rather is formed at an angle thereto, as best seen in  FIG. 7   d.  This design is particularly useful in the anterior region of the upper jaw to ensure extra volume of buccal bone and lingual access to the abutment screw. See, for example,  FIG. 8   c,  where an implant  50  is shown, which has a screw receiving bore  54  having an axis  56  disposed at an angle to the longitudinal axis  58  of implant  50 . It will be appreciated that this particular positioning allows for non symmetry in the location and angulation of the abutment connection and its screw relative to the implant. Thus, the connection and screw hole centers can be positioned more lingually (away from the cutout  52 ) and they can be oriented so as to greatly increase the probability that the abutment screw could be accessed from the lingual aspect  59  of the restoration. 
         [0041]    The connection itself (the interface between implant and abutment) could be tilted and in line with the tilted screw or, alternatively, the connection could be kept parallel to the longitudinal axis of the implant with just the screw hole and screw access tilted toward the lingual.  FIGS. 9   a,    9   b,    9   c  and  9   d  provide side sectional illustrations of the various angular possibilities.  FIG. 9   a  shows an implant  60  with a cutaway  62  and a screw receiving bore  64  concentrically located and aligned with respect to the longitudinal axis of the implant.  FIG. 9   b  shows an implant  65  with a cutaway  66  and a screw receiving bore  68  concentrically located but tilted at an angle with respect to the longitudinal axis of the implant.  FIG. 9   c  shows an implant  70  with a cutaway  72  and a screw receiving bore  74  eccentrically located but aligned with respect to the longitudinal axis of the implant. Thus, the cut away portion  72  is enlarged in width, relative to the implant of  FIG. 9   a.  And  FIG. 9   d  shows an implant  75  with a cutaway  76  and a screw receiving bore  78  eccentrically located and tilted at an angle with respect to the longitudinal axis of the implant. Thus, the cut away portion  76  can be enlarged in width, relative to the implant of  FIG. 9   b.  It will be appreciated that any of these screw-receiving bore options can be used with any of the designs of implants described above and below and with any of the types of implants desired. 
         [0042]    Thus, it will be appreciated that the particular design of the implant can be selected according to the location in the patient&#39;s mouth and the state of the patient&#39;s jaw. 
         [0043]    It will be appreciated that the modified head design disclosed in the present invention can be applied to all implant designs, regardless of body shape, thread type, length, diameter, connection, surface treatment and material used, or whether it is a bone level, tissue level or one-piece implant. See, for example,  FIGS. 10   a - 10   e,  each illustrating a different type or design of implant implementing the cutaway portion of the present invention.  FIG. 10   a  and  FIG. 10   b  illustrate bone level implants.  10   c  illustrates a tissue level implant.  FIG. 10   d  illustrates a bone level implant with an external connection and  FIG. 10   e  illustrates a one-piece implant, having a prosthetic integrally formed with the implant body. 
         [0044]    An implant with a single flattened or cut away area will have a single most proper (optimal) orientation (i.e., with the cut away area oriented adjacent the thin bone portion of the jaw). This type of implant, with a single cut away portion has a single proper orientation within a full 360 degree of rotational insertion and is better suited for smaller step, tighter thread implants or non-threaded implants. However, this characteristic may be a detriment in the case of threaded implants with a large thread step. While that may not be a problem in the anterior region where sub-bone-level positioning is often carried out, when this is an issue, the heads of the implants could be made with two or three cutouts, as illustrated above, so as to provide two-way or three-way symmetry. In this way, the implant can be rotated until any one of several cutout portions is disposed facing the problematic area of the jaw, so that additional bone growth will be possible in that area. These embodiments of the invention allow for smaller depth variability. A two cutout implant head allows two proper positions within every full rotation and a three cutout implant head allows three proper positions within every full rotation. 
         [0045]    Similarly, proper, advantageous use of an implant incorporating the new design with the non concentric implant head (with just one cutout portion) requires a particular positioning of the implant head so that the cutout is always directed toward the area with reduced bone volume. Many times that would be towards the buccal. It will be appreciated that this particular positioning allows for non symmetry in the location and angulation of the abutment connection and its screw relative to the implant, as described above. 
         [0046]    It should be noted that since the non concentric implant and the screw access are directionally confined, it is no longer necessary to adhere to rotational symmetry in the connection. Instead, the connection and the top surface of the implant could be made to suit the particular needs of such implant-abutment pair better than the conventional types of implant-abutment connections. Three exemplary instances of such a connection, having different features for receiving complementary features on the abutment, are depicted in  FIGS. 11   a,    11   b  and  11   c.  In  FIG. 11   a,  the head defines a protrusion, in  FIG. 11   b,  the head defines a flattened portion with notches, and in  FIG. 11   c,  the head defines a rectangular connection. 
         [0047]    A further advantage of the implants of the present invention is illustrated schematically in  FIGS. 12   a,  showing a prior art implant  80  with a prosthetic unit  82 , and an implant  84 , illustrated in  FIG. 12   b,  according to one embodiment of the present invention. Implant  84  has a single cutaway  86  as described above. Prior art implant  80  is a tissue level implant where bone and tissue loss may occur. When it does, the metal implant  80  becomes visible. That may be very disturbing, particularly if located in the anterior portion of the mouth. The implant  84  of the present invention permits the prosthetic crown  88  to be extended along part or all of the length of the cut away portion  86 . This portion is disposed to be visible in the mouth, so that even if there is some bone or tissue loss, the metal implant  84  will not be visible. 
         [0048]    It will be appreciated that the above descriptions are intended only to serve as examples and that many other embodiments are possible and encompassed within the spirit and the scope of the present invention. The implants described herein and illustrated in the figures are examples only. Implants embodying other variations of the structures described here are within the scope of the present invention. 
         [0049]    While the invention has been described with respect to a limited number of embodiments, it will be appreciated that many variations, modifications and other applications of the invention may be made. It will further be appreciated that the invention is not limited to what has been described hereinabove merely by way of example. Rather, the invention is limited solely by the claims which follow.