Abstract:
A one-piece dental implant having a longitudinal axis comprises a head portion at a first end of the implant, a tip portion at a second end of the implant and a body portion between the head portion and the tip portion. The body portion has a first portion proximate the head portion with a plurality of longitudinal grooves substantially parallel to the longitudinal axis and a second portion proximate the tip portion having a substantially circumferential groove, wherein the outer diameter of the first portion is greater than the outer diameter of the second portion. The first and second portions are for being embedded in the jaw bone. The dental implant is preferably dimensioned to conform to the natural shape of the cervical  ⅓  of the root of the tooth being replaced, and to the natural relationship between the cemento-enamel junction of the tooth being replaced and to minimize adverse immunological responses by the jaw bone during healing, thereby improving the aesthetic appearance of the implant and prosthetic tooth attached thereto. A dental implant and prosthetic tooth system is also disclosed, wherein the prosthetic tooth conforms to the shape of the cervical  ⅓  of the crown of the tooth being replaced. A method for implanting a dental implant through use of a reference, is also disclosed.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     Dental implants are inserted into the base of the jaw and have a portion protruding through the mucous gum tissue for providing attachment anchorage for artificial teeth. An artificial tooth may be attached directly to the implant, or to an abutment connected to the implant. Dental implants are becoming increasingly popular alternatives to dentures.  
         [0002]     Dental implants have been used in the hard bone of the lower jaw with great success. The upper jaw bone, however, is very soft and it is common for dental implants in the upper jaw to lack primary stability.  
         [0003]     There are three major types of dental implants: 1) press-fit; 2) self-tapping; and 3) pre-tapping. The press-fit type implants are inserted into holes drilled into the bone without rotation. Press-fit implants do not couple tightly to the soft bone of the upper jaw.  
         [0004]     Self-tapping and pre-tapping type implants have horizontal threads for being screwed into holes drilled into the jaw-bone, for better mechanical coupling to the jaw bone. Self-tapping implants create grooves in the hole as the implant is screwed in. Prior to the insertion of pre-tapped implants, a tool is used to form threads in the hole. While screwing self-tapping and pretapping implants into the bone generally improves the mechanical coupling between the implant and bone, it has been found that in the soft bone of the upper jaw, the rotation of both the self-tapping and pre-tapping implants may destroy the grooves, preventing tight coupling between the implant and the bone.  
         [0005]     After insertion of the implant, a sufficient period of time must be given for the tissue to heal and for the bone to grow sufficiently around (and sometimes through) the implant for the dental implant to become securely engaged in the jaw. This typically requires about three months. An artificial tooth is then attached to the implant, directly or by attachment to an abutment attached to the implant.  
         [0006]     Primary stability, osteointegration and the aesthetic appearance of the implant and prosthetic tooth in the mouth are important considerations in the design of a dental implant. Mechanical solutions to achieving primary stability and osteointegration have generally ignored the natural shapes of the root and crown of the natural tooth being replaced and have not conformed to the natural relationship between the tooth and the jaw bone, resulting in adverse immunological responses by the jaw bone which both weakens primary stability and osteointegration, and sacrifices aesthetics.  
         [0007]      FIG. 1  shows two adjacent natural adult teeth  100 , in the upper jaw. A tooth  100  has a crown and a root. The crown may be divided into a cervical {fraction (1/3)}, a middle {fraction (1/3)} and an incisal {fraction (1/3)}. The root may be divided into a cervical {fraction (1/3)}, a middle {fraction (1/3)} and an apical {fraction (1/3)}. The interface between the cervical {fraction (1/3)} of the tooth and the cervical {fraction (1/3)} of the root is referred to as the cemento-enamel junction. It has been observed that in a natural tooth, the distance d 3  between the cemento-enamel junction  104  and the crest  102  of the jaw bone is typically about 1.8 mm and the distance d 4  between the crest  102  of the jaw bone and the gingival margin  108  is typically about 3 mm.  
         [0008]     Adverse immunological responses may be caused by a variety of stimuli. For example, it has been found that the failure of interface between the dental implant and the prosthetic tooth to conform to the shape and location of the cemento-enamel junction between the crown and root of the tooth being replaced causes an adverse immunological response by the bone to the dental implant, resulting in bone resorbtion. This can weaken the bond between the implant and the bone and leave pockets which can collect plaque. In addition, since a constant distance is naturally maintained between the bone crest and the gingival margin, as the bone resorbs, the gingival margin recesses, presenting an unpleasant aesthetic appearance.  
         [0009]     Another cause of adverse immunological responses in the jawbone are microgaps between the dental implant, whose top surface is typically positioned at or below the bone crest, and the abutment attached to the implant. Once again, bone resorbtion and gingival margin recession may result.  
         [0010]     Some dental implants, such as the ITI(R) implants from the Straumann Company, Waltham, Mass., position the top surface of the implant above the bone crest. The jaw bone is not, therefore, exposed to microgaps between the implant and an abutment, decreasing adverse immunological responses. However, the flat tops of these implants do not match the shape of the cemento-enamel junction of the natural tooth being replaced. Bone resorbtion and the resulting recession of the gingival margin still occur, particularly interproximally.  
         [0011]     Dental implants are also typically cylindrical. However, teeth are not so regularly shaped. While attempts have been made to conform the abutment and the prosthetic tooth to the natural shape of the cervical {fraction (1/3)} of the root and the cervical {fraction (1/3)} of the crown of the tooth being replaced, the unnatural shape of the dental implant limits how closely the natural shape of the root and crown can be recreated. Voids are therefore present between the dental implant and the bone of the jaw, and between the prosthetic tooth and the gingivus, which can allow for the growth of soft tissue and the collection of plaque. Such soft tissue may interfere with the osteointegration of the implant, resulting in implant failure. Attempts have been made to prevent soft tissue growth by filling the gaps between the implant and the jaw bone by artificial bone or by covering the interface between the gums and the implant with a membrane. Such designs have an increased risk of infection and lack osteointegration. Rotation of the implant, either during rotation of the implant to insert the implant into the jaw bone or after final positioning of the implant, also interferes with attempts to close such gaps.  
       SUMMARY OF THE INVENTION  
       [0012]     In one aspect of the invention, a dental implant has both longitudinal and vertical grooves for improved primary stability and osteointegration. In other aspects of the invention, a dental implant and a dental implant/prosthetic tooth system substantially conforms to the natural relationships and shapes of the tooth being replaced. In particular, a dental implant is shaped and dimensioned to substantially conform to the natural biological relationship between the bone crest and the cemento-enamel junction. The gingival margin is therefore maintained. The preferred dental implant combines these aspects of the invention.  
         [0013]     A one-piece dental implant is disclosed having a longitudinal axis comprising a head portion at a first end of the implant, a tip portion at a second end of the implant and a body portion between the head portion and the tip portion. The body portion has a first portion proximate the head portion with at least one longitudinal groove substantially parallel to the longitudinal axis and a second portion proximate the tip portion having a substantially circumferential groove or threads. Preferably, a plurality of longitudinal grooves are provided. The outer diameter of the first portion is greater than the outer diameter of the second portion. The first and second portions are embedded in the jaw bone. The longitudinal grooves of the implant are received in longitudinal grooves formed in the opening made in the jaw bone for receiving the implant, preventing rotation of the implant during placement and healing. During healing, the jaw bone grows into the circumferential groove, securing the implant in the jaw bone. The circumferential groove may be a spiral thread which circles the body portion a plurality of times, or a plurality of parallel grooves substantially perpendicular to the longitudinal axis.  
         [0014]     In another embodiment of the embodiment of the invention, a dental implant is disclosed having a head portion. The head portion has a top surface with a circumference substantially matching the circumference of the tooth to be replaced, at the cemento-enamel junction of the tooth being replaced.  
         [0015]     In another embodiment of the embodiment of the invention, a dental implant is provided having a buccal side for being aligned with the buccal side of the jaw bone, a lingual side for being aligned with a lingual side of the jaw bone and interproximal sides between the buccal and lingual sides. The height of the top portion of the dental implant is less on the buccal side of the implant and rises toward the interproximal sides of the implant, as does the cemento-enamel junction. The height of the top portion may decrease from the interproximal sides of the implant to the lingual side, as well.  
         [0016]     In another embodiment of the invention, a dental implant and prosthetic tooth system is disclosed,.wherein the height of the top portion of the dental implant is less on the buccal side of the implant and rises toward the interproximal sides of the implant. The prosthetic tooth has a portion having a shape substantially matching the shape of the cervical {fraction (1/3)} of the crown of the tooth being replaced. The height of the top portion may decrease from the interproximal sides of the implant to the lingual side.  
         [0017]     In another embodiment of the invention, a dental implant and prosthetic tooth system is disclosed comprising a dental implant having a head portion, a tip portion and a body portion between the head portion and the tip portion. The head portion has a top surface with a circumference substantially matching the circumference of the tooth being replaced, at about the cemento-enamel junction of the tooth being replaced. A prosthetic tooth for being attached to the top surface of the implant has a shape substantially matching the shape of the cervical {fraction (1/3)} of the tooth being replaced.  
         [0018]     In another embodiment of the invention, a method of implanting a dental implant is disclosed wherein a reference provided on the implant is used to properly position the implant in the jaw bone. The reference can be defined by the ends of longitudinal grooves extending into the head of the implant, or by the end of the surface treated portion of the head of the implant, which is positioned at or slightly below the bone crest. Preferably, the head portion of the implant is positioned above the bone crest after implantation. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]      FIG. 1  is a view of two adjacent teeth of the upper jaw;  
         [0020]      FIG. 2  is a side view of the buccal side of a dental implant in accordance with one embodiment of the present invention;  
         [0021]      FIG. 3  is a side view of the proximal side of the dental implant of  FIG. 1 ;  
         [0022]      FIGS. 4   a  and  4   b  are side views of the buccal side and proximal side of an alternative configuration for the dental implant of the present invention.  
         [0023]      FIGS. 5   a - 5   c  are plan views of the top surfaces of the dental implants of showing preferred shapes for supporting a molar, a premolar and an anterior incisor, respectively;  
         [0024]      FIGS. 6   a - 6   f  are a series of saggital cross-sectional views of the upper jaw, illustrating a method of inserting the dental implant of  FIG. 1  into the upper jawbone in accordance with the present invention;  
         [0025]      FIG. 7   a  and  FIG. 7   b  are side views of osteotomes for use in the process of the present invention;  
         [0026]      FIG. 8  is a front view of the upper jaw bone with the dental implant of the present invention positioned therein;  
         [0027]      FIG. 9  is a side view of the proximal side of another implant in accordance with the present invention;  
         [0028]      FIGS. 10   a - 10   c  illustrate various steps in the method of inserting the dental implant in the upper jawbone to replace a tooth to be extracted in accordance with the present invention; and  
         [0029]      FIGS. 11   a  and  11   b  are side views of the buccal and proximal sides, respectively, of a dental implant with a head portion which is longer than in the configuration of  FIGS. 4   a  and  4   b.   
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0030]      FIG. 2  is a side view of the buccal side of a dental implant  10  in accordance with one embodiment of the present invention.  FIG. 3  is a side view of the proximal side of the dental implant  10  of  FIG. 2 . The dental implant  10  is preferably a single piece with a head portion  12 , a body portion  14  and a tip portion  16 , extending along a longitudinal axis “L”.  
         [0031]     The body portion is cylindrical and includes a first section  18  with a plurality of longitudinal grooves  20  substantially parallel to the longitudinal axis L of the implant  10 , proximate the head portion  12 . Preferably, at least some of the longitudinal grooves  20  extend into the head portion  12 . The depth of each groove  20  may be about 1 mm. The outer diameter of the first section is preferably from about 3.75 mm to about 5.00 mm depending on the type of tooth being replaced and the position of the tooth in the mouth.  
         [0032]     The cylindrical body portion  14  includes a second section  22  with a circumferential spiral thread  24 . Preferably, the spiral thread  24  encircles the second section  22  of the body portion  14  a plurality of times. Alteratively, a plurality of parallel circumferential grooves can be provided. Such parallel grooves can be perpendicular to the longitudinal axis L of the implant or they may be at a slight angle from perpendicular. The circumferential thread  24  or grooves may be rough or serrated. The outer diameter of the horizontal thread  24  or grooves of the second section  22  is less than the outer diameter of the vertical grooves  20  of the first section  18 .  
         [0033]     A narrow flat walled section  26  is preferably provided between the first section  18  and the second section  22  to separate the first and second sections, easing manufacture of the implant  10 . The outer diameter of the flat walled section  26  is preferably about the same as the outer diameter of the second section  22 .  
         [0034]     The head portion  12  has an outwardly flaring side wall and a top surface  28  including a hex  30  for attachment of an artificial tooth. The edge  30   a  between the top surface  28  and the hex  30  preferably has a chamfer-like finish so that the edge  30   a  is curved. An internal hex may also be provided through the top surface of the implant, as is known in the art. Other attachment mechanisms may be used, as well. The portion of the head portion  12  between the longitudinal grooves and the top surface  28  is preferably polished to provide a smooth surface which inhibits the collection of bacteria.  
         [0035]     The extent of the outward flare of the head portion  12  is sufficient to close the opening formed in the jaw bone for receiving the implant, as described further, below. In addition, the shape of the side wall of the head portion  12  preferably substantially matches the shape of the cervical {fraction (1/3)} of the root of the natural tooth being replaced. The shape of the root of the natural tooth may be determined through a CAT and clinical measurements scan prior to extraction of the tooth, as is known in the art. If the natural tooth is not present, then the shape of the root may be approximated by analysis of adjacent teeth by CAT scan and/or clinical measurements, which is also known in the art.  
         [0036]     The distance “d 1 ” from the terminus of the body portion  14  to the top surface  28  is preferably less at the buccal side of the implant and rises toward the interproximal side of the implant, as shown in  FIG. 2 . More preferably, the surface contour of the top surface substantially matches the shape of the cemento-enamel junction of the tooth being replaced, at least from the mid-buccal portion to the mid-interproximal portion of the implant  10 , as shown in  FIG. 8 .  
         [0037]     Returning to  FIGS. 2 and 3 , as mentioned above, it is preferred that the longitudinal grooves  20  extend into the head portion  12  of the dental implant  10 . During implantation, described further below, it is preferred that the ends of the longitudinal grooves be positioned at or slightly below the bone crest, to help maintain natural bone morphology during healing. The ends of the longitudinal grooves  20  can be up to about 0.5 mm below the bone crest to obtain this advantage. In addition the top of the longitudinal grooves  20  in this embodiment provide a reference position for the practitioner to know when the implant has been sufficiently inserted. In the insertion of prior art implants, it is difficult to precisely position the implant, resulting in penetration of the sinus cavities.  
         [0038]     The distance “d 2 ” between the end of each groove  20  within the head portion  12  and the top surface  28  of the implant  10  is preferably constant. For a typical implant, 1.80 mm, which is the natural distance from the crest  102  of the jawbone to the cemento-enamel junction  104  in an adult tooth, is the preferred distance d 2 . (See  FIGS. 2 and 3 ). The top surface  28  of the implant is then positioned approximately at the location of cemento-enamel junction of the tooth being replaced.  
         [0039]     The shape of the circumference of the top surface  28  of the head portion  12  also preferably substantially matches the circumference of a cross-section the natural tooth at the cemento-enamel junction of the natural tooth.  FIGS. 5   a ,  5   b  and  5   c , are plan views of the top surfaces  28  of three head portions of three dental implants, showing the preferred shapes for supporting a molar, a premolar and an incisor, respectively.  
         [0040]     Returning to  FIGS. 2 and 3 , the tip portion  16  of the implant  10  preferably includes a hole  32  extending therethrough. Preferably, the hole  32  extends completely through the tip portion  16 , but that is not required. The surface of the tip portion  16  is preferably roughened. The tip portion preferably has a slight inward taper from the end of the body portion to the tip  17  of the implant  10 , as shown in  FIGS. 2 and 3 .  
         [0041]     The dental implant  10  is preferably made of titanium in accordance with known manufacturing techniques. Other biocompatible materials used as dental implants may be used, as well.  
         [0042]      FIGS. 4   a  and  4   b  are side views of an alternative configuration of a dental implant  10   a , wherein the longitudinal grooves  20  do not extend into the head portion. Instead, a lower portion of the head portion  12   a , below line X in the implant  10   a , is surface treated by acid etching, sand blasting with large grit and acid etching (“SLA”), titanium plasma sprayed (“TPS”) or blasted with hydroxyapetite (“HA”), as is known in the art, to improve bone integration with the implant  10 . As above, the upper portion of the head  12   b , above line X in  FIGS. 4   a  and  4   b , is preferably polished to provide a smooth surface which inhibits the collection of bacteria. The interface between the upper portion of the head  12   b  and the lower portion  12   a  is preferably positioned at or slightly below the bone crest and provides a reference position for placement of the dental implant  10   a . The distance from line X to the top surface  28  is also preferably a constant 1.80 mm. The remainder of the implant  10   a  is the same as the implant  10  in  FIGS. 2 and 3 .  
         [0043]      FIGS. 6   a - 6   h  are a series of saggital cross-sectional views of the upperjaw  50  of a patient, illustrating a method of inserting the dental implant  10  into the upper jawbone, in accordance with the present invention. The gums  52 , an outer layer of cortical bone  54   a , an inner layer of the cortical bone  54   b , a portion of trabecular bone  56  and a sinus cavity  58  are shown.  
         [0044]     An implant drill with a round tip is used to penetrate the outer layer of cortical bone  54   a , as shown in  FIG. 6   a . A 2 mm twist drill  60  is then used to penetrate through the trabecular bone  56 , to the inner layer of cortical bone  54   b , as shown in  FIG. 6   b , forming an opening. A 3 mm twist drill  66  is then used to widen the opening created by the 2 mm twist drill  64 , as shown in  FIG. 6   c.    
         [0045]     A profiling instrument, or osteotome  68 , is then used to shape the opening, as shown in  FIG. 6   d . Two osteotomes  68   a ,  68   b  are shown in  FIGS. 7   a  and  7   b , as well. The osteotome  68   a  is for the implantation of dental implants for supporting molar type prosthetic teeth. The osteotome  68   b  is for the implantation of dental implants for supporting anterior and pre-molar type prosthetic teeth. The osteotomes  68   a  and  68   b  include a body portion with longitudinal grooves  70  substantially matching the longitudinal grooves  20  of the dental implant  10  to be inserted into the opening. The outer diameter and the depth of the longitudinal grooves  70  of the osteotome  68   a ,  68   b  are slightly smaller than that of the longitudinal grooves  20  of the dental implant  10 , so that the implant will fit tightly in the opening, improving primary stability. The depth of the grooves  70  is preferably about 1 mm. The portion  71  of the osteotome  68  between the grooves  70  and the tip of the osteotome is preferably smooth. The outer diameter of the portion  71  is also preferably slightly smaller than the outer diameter of the second section  22  and the tip portion  16  of the dental implant  10 . The longitudinal grooves  70  of the osteotomes  68   a ,  68   b  can have an outer diameter of from about 3.15 mm to about 6.0 mm, for example, depending on the tooth being replaced.  
         [0046]      FIG. 6   e  is a side view of the opening  72  shaped by the osteotome  68 . The osteotome  68  a traumatically forms a plurality of grooves  74  in the trabecular bone  56  and outer layer cortical bone  54   a , substantially in the direction of the longitudinal axis of the opening  72 .  FIG. 6   f  is a cross-sectional view of the opening  72  along line f-f of  FIG. 4   e , showing the longitudinal grooves  74 .  
         [0047]     A dental implant  10  is preferably chosen having a length such that when inserted, the apical tip  76  of the dental implant  10  contacts the inner surface of the inner cortical bone  54   b  and the ends of the longitudinal grooves  20  in the head portion  12  are at the level of the crest  102  of the cortical bone  54   a , or slightly below the crest  102 , as shown in  FIG. 8   g . In  FIG. 9 , which is a front view of upper jaw, a natural -tooth  100  is shown adjacent to the extracted tooth, the cemento-enamel junction  104  of the natural tooth  100 , the gingivus  106  and the gingival margin  108  are also indicated.  
         [0048]     To insert the dental implant  10 , the implant  10  is oriented such that the buccal side of the implant faces the buccal side of the jaw and the lingual side of the implant  10  faces the-lingual side of the jaw. During insertion of the dental implant  10 , the longitudinal grooves  20  of the dental implant  10  are aligned with the longitudinal grooves  70  formed in the wall of the opening  72 , preventing rotation of the implant  10  after placement in the opening  72 . Since the outer diameter of the horizontal thread  24  or grooves of the dental implant  10  is less than the outer diameter of the longitudinal grooves  74  formed in the opening  72 , the horizontal threads  24  of the dental implant  10  pass through the opening  72  unimpeded. The implant  10  is inserted into the opening  72  until the ends of the longitudinal grooves  20  in the head portion are aligned with or slightly below the bone crest  102 . The ends of the grooves  20  are preferably not more than 0.5 mm below the bone crest.  
         [0049]      FIGS. 6   g  and  8  show the dental implant within the opening  72 . The longitudinal grooves  74  of the opening  72  provide primary stability for the implant  10  and properly align the head of the implant in the mid-buccal portion of the osteotomy. Positioning the ends of the longitudinal grooves  20  at or near the bone crest  102  locates the top surface  28  of the implant  10  at or near the cemento-enamel junction  104   a  of the tooth being replaced. The contour of the the top surface  28  of the head portion  12  from the mid-buccal to mid-interproximal portions of the implant, generally follows the shape of the cemento-enamel junction  104 ,  104   a , the bone crest  102  and the gingival margin  108 . The shape of the side wall of the head portion  14  also substantially matches the shape of the outer surface of the cervical {fraction (1/3)} of the root of the natural tooth being replaced. These conditions contribute to minimizing adverse immunological responses.  
         [0050]     After implantation, bone grows into the recesses of the horizontal thread  24  or grooves, as well as the longitudinal grooves  20 , securing the dental implant  10  in position in the jaw bone. The longitudinal grooves  20  continue to prevent rotation of the implant  10  while the horizontal grooves  24  prevent the dental implant from being pulled out. As the bone grows into the opening  32  in the tip portion  16 , it is further secured against pull-out. The surface treatments also contribute to osteointegration.  
         [0051]     After sufficient time for the implant to become integrated with the bone, a prosthetic tooth  120  is attached to the implant, as shown in  FIG. 6   h . Since the head portion  12  matches the shape of the natural tooth and the top surface  28  of the head portion  12  extends above the bone crest  102 , an abutment is not be required. However, an abutment may be used if desired. Use of an abutment does not provoke an adverse immunological response in the bone since the top surface of the implant  10  is above the bone crest  102 .  
         [0052]     Preferably, the shape of the portion  120   a  of the prosthetic tooth  120  corresponding to the cervical {fraction (1/3)} of the crown of the tooth being replaced substantially matches the shape of the cervical {fraction (1/3)} of that tooth, minimizing pockets between the prosthetic tooth and the gingivus. The remainder of the prosthetic tooth can also now more closely match the shape of the natural tooth being replaced. The shape of the cervical {fraction (1/3)} of the tooth being replaced may be determined by taking an impression of the natural tooth, as is known in the art. If there is no natural tooth, then the optimum shape of the prosthetic tooth may be approximated by analysis of adjacent teeth and the height and width of the patient&#39;s face, as is known in the art. Since the shape of the head portion  12  of the dental implant  10  of the invention more closely matches the shape of the cervical {fraction (1/3)} of the root of the tooth being replaced, the prosthetic tooth  120  can more closely match the shape of the cervical {fraction (1/3)} of the tooth being replaced. The transition between the dental implant and the prosthetic tooth is more smooth than with dental implants of the prior art, also decreasing the presence of pockets between the prosthetic tooth and the gingivus.  
         [0053]     The outwardly flaring head portion  12  of the dental implant  10  closes the orifice of the opening  72  in the jawbone, preventing soft tissue penetration and improving bone regeneration. Gaps below the bone line, where soft tissue cannot enter, will be filled with bone as the bone grows around the implant  10 . Voids do not develop which can collect food or plaque, or provide space for the growth of soft tissue. In addition, since the cross-sectional shape of the head portion  12  of the implant  10  generally matches the corresponding cervical {fraction (1/3)} of the root and cervical {fraction (1/3)} of the crown of the natural tooth being replaced, gaps which could develop at the bone line into which soft tissue can grow are minimized.  
         [0054]     As discussed above, the distance d 3  from the crest  102  of the jawbone to the cemento-enamel junction  104  in an natural adult tooth is typically about 1.80 mm and the distance d 4  from the crest  102  to the gingival margin in an adult tooth is typically about 3 mm. The implant system including the dental implant  10  and the prosthetic tooth preferably approximates these natural conditions, minimizing adverse immunological responses by the bone to the implant.  
         [0055]     It is noted that the actual cemento-enamel junction drops slightly from the midpoint of the interproximal surface of the tooth toward the lingual side of the tooth. That portion of the junction is preferably not matched by the dental implant  10 , to ease manufacturability and clinical application. Since the top surface of the head portion  12  of the implant  10  is above the bone crest  102  and the majority of the top surface of the head portion  12  (from the mid-buccal to mid-interproximal portion) matches the shape of the cemento-enamel junction there should not be significant bone resorbtion and resulting recession of the gingival margin. Even if there is some bone resorbtion and gingivus recession, however, it is at the rear of the tooth, which cannot be seen.  
         [0056]     If desired, however, the lingual portion of the top surface of the implant could also follow the lingual portion of the cemento-enamel junction of the tooth being replaced.  FIG. 9  is a plan view of the proximal side of such an implant  10   b , wherein the height d 1  of the head portion  12  of the implant, from the body portion  14  to the top surface  28 , increases from the buccal portion B of the implant  10   a , to the interproximal portion I, and the decreases from the interproximal portion I to the longitudinal portion of the implant, as does the cemento-enamel junction of a natural tooth. The height d 1  of the buccal portion is substantially the same as the height d 1  of the lingual portion. The distance d 2  from the ends of the longitudinal grooves  20  in the head portion  14  to the top surface  28  is also preferably maintained constant, at about 1.80 mm. The remainder of the implant  10   b  is the same as implant  10  in  FIGS. 2 and 3 .  
         [0057]      FIGS. 10   a - 10   c  illustrate various steps in the method of inserting the dental implant  10  of the present invention to replace a tooth  100  to be extracted.  FIG. 10   a  shows a tooth  100  to be extracted by an a traumatic technique which minimizes damage to the bone, as is known in the art. Before extraction, the mesial-distal (MD) and buccal-lingual (BL) dimensions of the tooth are measured. A properly sized implant is then selected.  FIG. 10   b  shows the opening  82  left by the extracted tooth. A 3 mm twist drill  64  is then used to widen the hole left by the tooth  100 , as shown in  FIG. 10   c . The osteotome  68   a ,  68   b  is then used and the dental implant  10  is inserted, as described above with respect to  FIGS. 6   d - 6   g.    
         [0058]      FIGS. 11   a  and  11   b  show another configuration of a dental implant  10   b  in accordance with the present invention, wherein the head portion  12 ′ is surface treated as described above with respect to the dental implant  10   a  shown in  FIGS. 4   a , and  4   b . The head portion  12 ′ has a greater length, as measured from the terminus of the body portion  14 ′ to the top surface  28 ′ of the head portion  12 ′, than in the dental implant  10   a  of  FIGS. 4   a  and  4   b . The body portion  14 ′ and in particular the longitudinal grooves  20 ′, are correspondingly shorter. As in the configuration of  FIGS. 4   a  and  4   b , the upper portion  12   b ′ is polished and the interface X′ between the upper portion  12   b ′ and the lower portion  12   a ′ serves as a reference line for positioning of the implant with respect to the bone crest. In this configuration, the distance d 1 ′ from the terminus of the body portion  14 ′ to the top surface  28 ′ of the head portion  12 ′ is less at the mid-buccal portion of the implant  10   b , rises toward the mid-interproximal proximal portion of the implant and then decreases toward the mid-lingual portion of the implant. As above, it is not necessary for that distance to decrease from the mid-interproximal to the mid-lingual portion of the implant.  
         [0059]     It is noted that due to natural asymmetries between the right and left sides of certain types of natural teeth, it may be impractical with current manufacturing and implantation methods to exactly match the cemento-enamel junction, even at the buccal portion of a tooth. It is not necessary for the implant of the present invention to match the right-left asymmetries of cemento-enamel junction of a natural tooth, to achieve the advantages of the present invention. However, if the implant is custom designed for a particular tooth and such asymmetry is matched, even better results may be obtained.  
         [0060]     While the dental implants and prosthetic teeth of the present invention have been discussed with respect to implantation in the upper jaw, such implants and prosthetic teeth may be used in the lower jaw, as well.  
         [0061]     While preferred embodiments for practicing the present invention have been described above, it is understood that modifications may be made from these preferred embodiments without departing from the scope of the present invention, which is defined by the following claims.