Abstract:
A dental implant system includes a dental implant having an external thread for threading into bone and an internal thread for attachment of a prosthesis. The internal thread has a plurality of notches which accept a complimentary shaped insertion tool. The insertion tool is used to transport the dental implant to the surgical field and to insert the dental implant into the bone.

Description:
FIELD OF THE INVENTION 
   The present invention relates generally to the field of surgical and prosthetic tools and equipment and more particularly, to a dental implant which incorporates a dental implant with a notched cavity. 
   BACKGROUND OF THE INVENTION 
   The prior art related to the field of dental implants includes various examples of dental implants and insertion tools. 
   A typical dental implant according to the prior art includes an external thread which is driven into the bone and an internal thread which accepts an insertion tool. In the past, the insertion tool was screwed into the implant, the implant was screwed into the bone, the insertion tool was unscrewed from the implant and discarded. This process is inherently time consuming and, therefore, disadvantageous. 
   Another disadvantage of this type of conventional dental insert is related to the process of unscrewing the dental implant from the insertion tool after the implant has been inserted into the bone. The process of unscrewing the insert is disadvantageous because the process inherently tends to loosen the contact between the insert and the bone. 
   Another example of prior art dental inserts is shown in U.S. Pat. No. 4,960,381 issued to Gerald A. Niznick for a Screw-Type Dental Implant Anchor. The Niznick patent shows a screw-type dental implant anchor which includes an externally threaded body portion which includes an internal structure for engaging an insertion tool. The top portion of the implant anchor is open and in registry with an internally-threaded portion. The top portion of the anchor forms a head portion which includes a hex-shaped cavity in its inner wall surfaces for receiving a hex wrench. The internal hex-shaped configuration is intended to allow the insertion of the anchor in the jawbone of a patient using an Allen-type wrench. 
   One of the significant disadvantages of the Niznick device is related to the arrangement of the hex-shaped cavity which is positioned directly above the internally threaded portion. As shown and described in the Niznick patent, the smaller distance across the hex-shaped cavity is greater than the external diameter of the internal threads. This configuration creates stress concentrations which results in high stress lines along the hex corners. This problem has resulted in numerous implant fractures. 
   Another example of prior art dental inserts is shown in U.S. Pat. No. 6,464,500 to Don D. Popovic for a Dental Implant and Abutment System. The Popovic patent showed a screw-type dental implant anchor which includes an externally threaded body portion which includes an internal structure for engaging an insertion tool. The top portion of the implant anchor includes an internally threaded portion. A hex-shaped cavity is located below the internally threaded portion for the purpose of receiving a hex wrench. As in the Niznick patent previously described, the hex-shaped cavity is intended to facilitate the insertion of the anchor in the jawbone of a patient using an Allen-type wrench. As a result of the location of the hex-shaped cavity below the internally threaded portion, the distance between corners of the hex-shaped cavity is smaller than the internally threaded portion. 
   The hex-shaped cavity is therefore so small that at normal insertion torques, there is the distinct possibility of damage to the insertion tool and damage to the insert. This is especially true in the event that the insert binds prematurely in hard bone. This is caused by the required relationship between the internal threads and the hex-shaped cavity. The largest thread normally used has a diameter of about 1.5 millimeters, mm. The distance between the corners of the hex has to be smaller than 1.5 mm, otherwise the insertion tool would not clear the internal threads. 
   As a result, neither the configuration of the Niznick device with the hex-shaped cavity above the internally threaded portion nor the Popovic configuration with the hex-shaped cavity below the internally threaded portion provides a satisfactory dental implant. 
   Another example of a prior art dental implant is shown in U.S. Design Pat. No. D446,859 issued to Steven M. Hurson for a Multi-Lobed Dental Implant. The Hurson patent shows a screw-type dental implant which includes an externally threaded body portion and an internal cavity for engaging an insertion tool. The Hurson device is generally similar to the Niznick device and the top portion of the implant is open and in registry with an internally threaded portion. The top portion of the implant includes a multi-lobed cavity. In a manner similar to the Niznick device, the multi-lobed cavity extends beyond the external or maximum diameter of the internal threads. As explained in connection with the Niznick device, this configuration creates stress-concentrations where there are discontinuities in the cross-section, such as at the corners of the lobes. As explained previously, these stress concentrations can lead to loss of structural integrity of the implant. These problems are increased when there is an attempt to manufacture the Hurson or the Niznick devices in the relatively narrow configurations which are required for narrow edentulous areas. 
   An example of the problems associated with prior art implants is described in an article titled “Ridge Augmentation for Immediate Postextractive Implants: Eight Year Retrospective Study” by A. Ashman, DDS, J. Lo Pinto, DDS, and J. Rosenlicht, DMD, in  Practical Periodontics and Aesthetic Dentistry,  Vol. 7, No. 2, March 1995, page 89. The article shows an insert with a hex-shaped cavity cut in the internal thread, in which the internal thread was stripped by the insertion tool during surgical placement. This problem resulted in a need to cut a new thread into the implant. 
   Despite the developments of the prior art, there remains a need for a dental implant which can be installed in a safe and reliable manner. 
   OBJECTS AND SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a dental implant system which includes a dental implant having a notched cavity and a complimentary shaped insertion tool. 
   Another object of the present invention is to provide a dental implant system which includes a threaded cavity which can accept either a threaded fastener or a multilobed insertion tool. 
   Another object of the present invention is to provide a dental implant system which can be manufactured in relatively narrow configurations and which can be placed in very narrow edentulous areas. 
   Another object of the present invention to provide a dental implant which can accept an insertion tool with a friction fit. 
   Another object of the present invention is to provide a dental implant which does not require a screw-type of connection with the insertion tool. 
   Another object of the present invention is to provide a dental implant which can be quickly installed on an insertion tool. 
   Another object of the present invention is to provide a dental implant which demonstrates relatively great resistance to fracture thereby providing a safe and reliable installation. 
   Another object of the present invention is to provide a dental implant which can be quickly and easily removed from an insertion tool after the dental implant is inserted into the bone. 
   Another object of the present invention is to provide a dental implant which does not require being unscrewed from the insertion tool after the dental implant has been inserted into the bone. 
   Yet another object of the present invention is to provide a dental implant which facilitates secure transportation from the dental implant pack to the surgical field. 
   Other objects and advantages of the invention will become evident hereinafter. 
   In accordance with the present invention, there is provided a dental implant system which incorporates a dental implant which includes an external thread for threading into the bone. The implant includes an internally threaded portion which accepts a post for the attachment of a prosthesis. A key feature of the invention is a notched cavity which is cut through the internally threaded portion. The notched cavity preferably has a configuration in the shape of a circular array with six grooves with the external diameter of the grooves approximately equal to the major diameter of the threads and the internal diameter of the grooves approximately equal to the minor diameter of the threads. In addition, the dental insert includes an internally tapered portion. The internally tapered portion and the notched cavity accept an insertion tool of complementary shape. 
   The insertion tool can be inserted into the dental implant and then used to transport the dental implant to the surgical field in a safe and convenient manner. The insertion tool can then be used to insert the dental implant into the bone. After the insertion process has been completed, the insertion tool is simply withdrawn from the implant without a need for unscrewing or other cumbersome techniques. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other important objects and advantages of the invention will be apparent from the following detailed description of the invention taken in connection with the accompanying drawings in which: 
       FIG. 1  is an overall perspective view of a dental implant made according to the present invention; 
       FIG. 2  is another overall perspective view of the dental implant of  FIG. 1 ; 
       FIG. 3  is a side elevation view taken along the line  3 — 3  of  FIG. 1 ; 
       FIG. 4  is an end view along the line  4 — 4  of  FIG. 3 ; 
       FIG. 5  is a cross-sectional view taken along the line  5 — 5  of  FIG. 1 ; 
       FIG. 6  is an end view taken along the line  6 — 6  of  FIG. 3 ; 
       FIG. 7  is an overall perspective view of an abutment for use with the dental implant of  FIG. 1 ; 
       FIG. 8  is a side elevation view of the abutment of  FIG. 7 ; 
       FIG. 9  shows the start of the insertion of the abutment of  FIG. 8  into the dental implant of  FIG. 1 ; 
       FIG. 10  shows the abutment inserted into the dental implant; 
       FIG. 11  shows an overall perspective view of an insertion tool for use with the dental implant of  FIG. 1 ; 
       FIG. 12  is a cross-sectional view showing the insertion tool of  FIG. 11  inserted into the dental implant of  FIG. 1 ; 
       FIG. 13  is a side view partially in section showing an alternative embodiment of the dental implant of  FIG. 1 ; and 
       FIG. 14  is an end view of the dental implant of  FIG. 13 . 
       FIG. 15  is an end view generally similar to  FIG. 6  showing another embodiment of the dental implant of  FIG. 1 ; 
       FIG. 16  is an end view generally similar to  FIG. 6  showing yet another embodiment of the dental implant of  FIG. 1 ; and 
       FIG. 17  is a cross-sectional view of an alternative embodiment of the insertion tool shown in  FIG. 11 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   With reference to the drawings, in which like reference numbers designate like or corresponding parts throughout, there is shown in  FIGS. 1–12  a dental implant system  10  made in accordance with the present invention, which includes a dental implant  12  which has a body portion which has a self-tapping threaded exterior surface  16 . The end  18  of the body portion  14  has a full radius resulting in a convex configuration. The dental implant system  10  also includes an insertion tool  20  which will be described presently. 
   The following dimensions are by way of example only and are not to be considered as limitations on the present invention. The overall length of the dental implant  12  is generally between 5 mm and 20 mm. The outside diameter of the dental implant  12  is generally between 3 mm and 7 mm. The threaded exterior surface  16  is used to anchor the dental implant  12  into the patient&#39;s bone. The dental implant  12  includes an internally threaded portion  21 . The function of the internal thread  22  is to facilitate attachment of a cover screw and prosthetic components or an abutment  24 . The internal thread  22  typically has a major diameter which ranges between 1.3 mm and 2.0 mm. 
   The upper portion  26  of the body portion  14  is unthreaded and is outwardly flared. The radius of curvature of the surface  28  of the outwardly flared portion  26  as shown by the radius “R” in  FIG. 3 . has a preferred radius in the order of approximately 0.5 inches. The end  30  of the body portion  14  has an inwardly tapered cavity  32  which leads from the end  30  of the body portion  14  to an internally threaded portion  22  which extends inwardly from a plane  34  at the base  36  of the tapered cavity  32 . 
   The end  30  of the body portion  14  has a chamfered portion  38  which has a preferred angle in the order of 45 degrees. 
   A notched or grooved cavity  40  which is a key feature of the present invention, extends inwardly from the plane  34  at the base  36  of the tapered cavity  32 . As is best shown in  FIGS. 3–6 , the grooved cavity  40  extends past the end  42  of the internally threaded portion  22 . The grooved cavity  40  as shown in  FIG. 6  has six grooves  44 ,  46 ,  48 ,  50 ,  52 ,  54  with the depth of the grooves extending to a point approximately equal to the major diameter of the threaded portion  22  and with the minor diameter of the groove array approximately equal to the minor diameter of the threaded portion  22 . Wall portions  56 ,  58 ,  60 ,  62 ,  64 ,  66  defining the grooves are generally curved. 
   The curved wall portions  56 ,  58 ,  60 ,  62 ,  64 ,  66  form an important advantage of the present invention  10 . Prior art cavities used for transmitting torque have generally utilized a hexagonal shape. In a hexagon, the distances between the opposing flat portions of a hexagon are nearly equal to the distances between the opposing corner portions of the hexagon. There is thus a relatively small ratio between the dimensions between the corners of the hexagon and the flat portions of the hexagon. 
   The relatively small ratio between the dimensions between the corners of a hexagon and the flat portions of a hexagon results in a tendency to strip or fail especially when a hexagonal cavity is formed in the relatively small sizes required for dental inserts. 
   In the grooved or notched cavity  40 , according to the present invention, which is formed by the concave curved wall portions  56 ,  58 ,  60 ,  62 ,  64 ,  66 , there is a relatively large ratio between the larger dimension as measured between the corners of the grooves typically indicted by the numerals  67 ,  69  and the relatively smaller dimension as measured between the closest points of the curved wall portions typically indicated by the numerals  68 ,  70 . The reference numerals  68 ,  70  thus indicate the narrowest portion of the grooved cavity  40 . This relatively large ratio enables the cavity  40  to be cut into the threads  22  without the danger of weakening the threads. 
   As indicated above in  FIG. 6 , the grooves or notches  44 ,  46 ,  48 ,  50 ,  52 ,  54  are formed to a depth which approximates the major diameter of the internal thread  22  as indicated by the broken lines  72 . 
   As shown in  FIGS. 3–6 , the end  74  of the grooved cavity  40  extends past the inner end  42  of the internally threaded portion  22 . Alternatively, the end  74  of the grooved cavity  40  may end at the inner end  42  of the threaded portion  22 . In another alternative embodiment, the end  74  of the grooved cavity  40  may end at an intermediate portion of the threaded portion  22  as denoted by the reference numeral  78  in  FIG. 5 . 
   As is shown in  FIGS. 3–6 , the internally notched or grooved cavity  40  is cut through the internally threaded portion  22  and can easily accept the grooved portion  80  of the installation tool  20  which is shown in  FIGS. 11 and 12 . The grooved portion  80  of the installation tool  20  compliments the grooved cavity  40  of the dental implant  10 . The insertion tool  20  is typically made of instrument grade stainless steel. 
   After the dental implant  12  has been inserted into the patient&#39;s bone using the installation tool  20 , the installation tool  20  is withdrawn. A screw type of abutment  24  which is shown in  FIGS. 7 and 8  is installed into the dental implant  12  as is shown in  FIGS. 9 and 10 . The threaded portion  82  of the abutment  24  engages the internal thread  22 . As is best shown in  FIG. 10 , the tapered cavity  32  of the dental implant  10  compliments the tapered portion  84  of the abutment  82  resulting in a secure fit. The outwardly flared portion  26  of the dental implant  12  and the chamfered portion  38  cooperate with the abutment  82  to provide an efficient transfer of the dental forces with a minimum size and weight structure. 
   One of the key advantages of the dental implant  12  of the present invention is related to the relatively great strength of the dental implant  12  as compared with prior art devices. Torque testing of the dental implant  12  of the present invention and the hex cavity device shown in the Popovic patent U.S. Pat. No. 6,464,500 is summarized in Table 1. 
   
     
       
             
           
             
             
             
           
         
             
               TABLE 1 
             
           
           
             
                 
             
             
               COMPARATIVE RESISTENCE TO TORQUE 
             
           
        
         
             
                 
               APPLIED TORQUE 
                 
             
             
               UNIT 
               (Newton Centimeters) 
               RESULTS 
             
             
                 
             
             
               Prior art 
               100 
               Fracture of 
             
             
               Hex-cavity device 
                 
               the insertion 
             
             
               Popovic Patent 
                 
               tool 
             
             
               U.S. Pat. 6,464,500 
             
             
               Dental Implant 
               150–200 
               No fracture or 
             
             
               according to the 
                 
               weakening 
             
             
               present invention 
             
             
                 
             
           
        
       
     
   
   Typical insertion torque is usually 50–130 Ncm. However, this torque can reach higher values if the implant binds prematurely in hard bone. 
   The significantly increased resistance to torque experienced during the installation into the bone of a patent by the dental implant  12  according to the present invention results in a significant increase in the safety and reliability of the installation process. 
   The dental implant  12  may be made of any implantable metal or ceramic material including commercially pure titanium. 
   A preferred material for the dental implant  12  according to the present invention has been found to be 6AL-4V-EL1 titantium. 
     FIGS. 13–14  show an alternate embodiment  100  of the present invention which incorporates an external hex surface  102  at the upper end  104  of the implant. The body  106  of the implant  100  includes an outside surface  108  with a thread pattern  110  for anchoring the implant  100  into bone and an internal thread  112  which is similar to the internal thread  22  previously described. In the embodiment  100  shown in  FIGS. 13–14 , the tapered portion  32  previously described has been eliminated and the grooved cavity  114 , which is similar to the grooved cavity  40  previously described, extends to the top surface  116  of the implant  100 . The end  118  of the implant  100  is flat. 
   In the alternative embodiment of the invention  200  shown in  FIG. 15 , the ends  202 ,  204 ,  206 ,  208  of the grooves  210 ,  212 ,  214 ,  216  extend beyond the major diameter of the internal thread  224  which is shown in broken lines  218 . Alternatively, the grooves  210 ,  212 ,  214 ,  216  may extend to points  230 ,  232  indicated in  FIG. 15  which define a diameter which is smaller than the major diameter  218  of the internal thread  224 . As described previously, the grooves  210 ,  212 ,  214 ,  216  are, in part, defined by curved portions  226 ,  228 ,  230 ,  232 . 
   The alternative embodiment of the invention  200  shown in  FIG. 15  has four (4) grooves  210 ,  212 ,  214 ,  216  or notches, while the alternative embodiment  300  shown in  FIG. 16  has eight (8) grooves  302 ,  304 ,  306 ,  308 ,  310 ,  312 ,  314 ,  316  or notches. The number of grooves or notches may have a preferred range between two (2) and eight (8). 
   The construction of the grooves  302 ,  304 ,  306 ,  308 ,  310   312 ,  314 ,  316  is generally similar to the construction of the grooves previously described in connection with  FIGS. 6 and 15 . With the exception of the grooved cavities  234 ,  318 , the overall construction of the embodiments  200  and  300  shown in  FIGS. 15 and 16  is generally similar to the construction of the insert  12  shown in  FIGS. 1–6 . The ends  202 ,  204 ,  206 ,  208  of each of the grooves  210 ,  212 ,  214 ,  216  in  FIG. 15  are shown as convexly curved. This construction is typical of each of the grooves in the embodiments  12 ,  100 ,  288 ,  300  shown in  FIGS. 1–6 ,  13 , and  16 . 
   In the insertion tool  20  shown in  FIGS. 11 and 12 , the grooves  90  are generally parallel to a central axis. In the alternative embodiment of the insertion tool  400  shown in  FIG. 17 , the walls  404 ,  402 , which define the grooves  406 ,  408 , each include a tapered portion  410  which facilitates a friction fit with the dental inserts  12 ,  100 ,  200 ,  300 . The tapered portion  410  is defined in part by an angular portion designated by the angle “A” in  FIG. 7 . 
   The foregoing specific embodiments of the present invention as set forth in the specification herein are for illustrative purposes only. Various deviations and modifications may be made within the spirit and scope of the invention without departing from the main theme thereof.