Abstract:
Dental implant ( 10 ) for supporting a dental prosthesis on a jaw bone, is equipped with a main body ( 12 ), which comprises a securing portion ( 14 ) intended to be anchored in the bone tissue and, lying opposite it, a head portion ( 16 ). The head portion ( 16 ) protrudes radially beyond the securing portion ( 14 ) with respect to the longitudinal axis of the main body ( 12 ) to form a support face ( 26 ), in such a way that, in the state of insertion in the jaw bone, the pressure of the dental implant ( 10 ) on the jaw bone is reduced, and a sinking movement of the dental implant ( 10 ) into the jaw bone is effectively avoided, even over quite long periods of time.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a dental implant for supporting a dental prosthesis on a jaw bone and to a dental implant system including said dental implant. 
       BACKGROUND 
       [0002]    Removable dental prostheses are usually fixed releasably to the jaw using so-called adhesive creams or mechanically on the residual dentition, which is equipped with special anchor elements for connection to the dental prostheses. Particularly at the rear free-end gaps, or in cases of particularly flat alveolar ridges presenting a small quantity of bone, the use of conventional dental implants is not possible, or is possible only with quite considerable effort. 
         [0003]    The normal masticatory forces can also lead to the dental prosthesis sinking deeper into the jaw bone the longer it continues to be used. This results in the gum beneath the dental prosthesis being compressed, which can lead to extremely unpleasant pain for the person wearing the dental prosthesis. This can be expected to lead to bone degeneration and, consequently, to a lack of support of the posterior teeth and to joint changes. 
       SUMMARY OF THE INVENTION 
       [0004]    In accordance with one or more embodiments of the present invention, a dental implant is provided for supporting a tooth prosthesis on a jaw bone, which dental implant can be of a particularly simple structure, can be inexpensive to manufacture, can be safely fitted in the jaw bone and, over the long term, can avoid a sinking movement of the entire assembly including the dental prosthesis. 
         [0005]    The dental implant system according to one embodiment of the invention comprises a substantially cylindrically symmetrical, one-piece main body, which is divided into a securing portion and a head portion. The securing portion is used for anchoring the dental implant in the bone tissue. The head portion is oriented in the coronal direction, when the dental implant is in the inserted state in the jaw bone, and it supports a dental prosthesis, lying on top of it, against the jaw bone. According to the invention, the head portion protrudes beyond the securing portion radially or at right angles with respect to the longitudinal axis of the main body. This protruding configuration results in the formation of a support face, which extends substantially perpendicular to the longitudinal axis and which ensures that the forces exerted by the tooth prosthesis on the dental implant are distributed over a greater surface area compared to the cross section of the securing portion, and thus ensures that the supported tooth prosthesis does not sink in the direction of the jaw bone. 
         [0006]    By virtue of its simple structure, the dental implant according to one embodiment of the invention can be produced in small dimensions and inexpensively. The dental implant can therefore also be used in free-end gaps and in cases where there are particularly flat alveolar ridges presenting only a small quantity of bone. By virtue of the cylindrically symmetrical main body, known drilling techniques can be employed for installation into the jaw bone. 
         [0007]    The dental implant system according to one embodiment of the invention comprises, in addition to the dental implant, a dental drill with a drill stop for particularly simple production of an implant-specific recess in the jaw bone, and an anchor element that can be mounted on the dental implant. The anchor element makes it possible to produce a releasable connection between the dental implant and the tooth prosthesis and thus permits, in addition to the supporting function, a securing function. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    Particular embodiments of the dental implant according to the invention and of the dental implant system are described in detail below with reference to the attached drawing, in which: 
           [0009]      FIG. 1  shows a phantom view through a dental implant according to one embodiment of the invention, with a rounded contact face on the head portion, which contact face surrounds an opening of a blind hole equipped with an inner thread; 
           [0010]      FIG. 2  shows a perspective phantom view through the dental implant shown in  FIG. 1 ; 
           [0011]      FIG. 3  shows a phantom view of another embodiment of a dental implant according to the invention, with a contact face in the shape of a segment of a sphere; 
           [0012]      FIG. 4  shows a perspective phantom view through the dental implant shown in  FIG. 3 ; 
           [0013]      FIG. 5  shows a sectional view through a part of a jaw bone, through a dental implant according to one embodiment of the invention and through a dental prosthesis, where a support element engaged in the dental prosthesis, on the alveolar ridge side, rests on the contact face of the dental implant; 
           [0014]      FIG. 6  shows a side view of the support element depicted in cross section in  FIG. 5 ; 
           [0015]      FIG. 7  shows a perspective phantom view through the support element shown in  FIG. 6 ; 
           [0016]      FIG. 8  shows a partial phantom view through a dental implant according to one embodiment of the invention, in which an anchor element with a spherical anchor head is screwed onto the dental implant; 
           [0017]      FIG. 9  shows a section through an ampule for transport and storage of a dental implant according to one embodiment of the invention; and 
           [0018]      FIG. 10  shows a dental drill with two drill sections which have different diameters and lie one behind the other in the direction of advance, and with a drill stop, which dental drill is used to create a recess in the jaw bone for receiving a dental implant according to one embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    The dental implant  10  according to one embodiment of the invention shown in  FIGS. 1-4  comprises a substantially cylindrically symmetrical, screw-like main body  12 , which is divided into a securing portion  14  and a head portion  16 . The securing portion  14  is provided with a self-cutting outer thread  18  and is used for anchoring in the tissue of a jaw bone. The self-cutting property of the outer thread  18  is achieved by cutting edges  20 , which partially delimit a groove  22  in the outer thread  18 . The groove  22  is used to guide tissue material away while the dental implant  10  is being screwed into the jaw bone, and it makes the dental implant  10  easier to screw in. In the securing portion  14 , at the end toward the head portion, the outer thread  18  is adjoined by an undercut  24  which, for production reasons, is not provided with thread turns. 
         [0020]    The head portion  16  is mushroom-shaped, and its cross section protrudes radially beyond the cross section of the securing portion  14  to form a support face  26 . In the particularly preferred design of the dental implant  10  with a cylindrically symmetrical main body  12 , the support face  26  forms a circular ring. The cross section of the head portion  16 , enlarged by the support face  26 , has the effect that forces acting on the dental implant  10  in the direction of its longitudinal axis L apply less pressure to the jaw bone, thus avoiding a sinking movement of the dental implant and of a dental prosthesis supported on the latter, in other words, of the whole assembly. 
         [0021]    In the head portion  16 , the support face  26  is adjoined by a radially outwardly directed head circumference surface  28 , seen in the longitudinal direction away from the securing portion  14 . The head circumference surface  28  is designed as a cylinder jacket. In the embodiments of a dental implant  10  according to the invention shown in  FIG. 1  to  FIG. 4 , it extends at least approximately parallel to the longitudinal axis L of the main body  12 . Alternatively, the head circumference surface  28  can also taper conically or be equipped with edges. 
         [0022]    At the end area, directed away from the securing portion  14 , the head circumference surface  28  is adjoined by a contact face  30 . When the dental implant  10  is in its inserted state in the jaw bone, the contact face  30  forms the coronally oriented limit face of said dental implant  10 . The contact face  30  surrounds an opening  32  of a blind hole  34 , which extends coaxially with respect to the longitudinal center axis L of the main body  12  and reaches into the head portion  16 . As can be seen very clearly in the phantom views of the dental implant  10 , the blind hole  34 , for the purpose of creating a screwed connection, is equipped with an inner thread  40  for engaging a dental screw (not shown), an anchor element  36  (shown in  FIG. 8 ) or a screw-in adapter  38  (shown in  FIG. 9 ). For the case shown in  FIG. 5 , where no anchor element  36  is to be mounted on the dental implant  10 , the blind hole  34  is sealed with a biocompatible filler material after the dental implant  10  has been fitted and the screw-in adapter  38  has been removed. 
         [0023]    As in the embodiment of the dental implant  10  according to the invention shown in  FIG. 1  and  FIG. 2 , the contact face  30  can rise in a circular cone shape from the head circumference portion  28  to the opening  32 , or, as in the embodiment shown in  FIG. 3  and  FIG. 4 , it can form a surface in the shape of a segment of a sphere. 
         [0024]    The total length of the dental implant  10  is between 4 mm and 10 mm, preferably 6 mm, the length of the securing portion, measured along the longitudinal axis of the main body  12 , is 3 mm to 5 mm, preferably 3.5 mm, and the length of the head portion  16 , also measured along the longitudinal axis, is between 2 mm and 4 mm, preferably 2.5 mm. The diameter of the head portion  16  is between 3 and 6 mm, preferably 4 mm. The inner thread chosen for the blind hole  34  is preferably M  1 . 8 . The self-cutting outer thread in the securing portion  14  is preferably equipped with a core diameter of 2.2 mm, an external diameter of 3 mm, a flank angle of approximately 60°, and a pitch of approximately 0.7 mm. 
         [0025]    Materials that can be used to produce the dental implant  10  are preferably titanium and titanium alloys, zirconia or other biocompatible materials, preferably metal alloys. 
         [0026]    In  FIG. 5 , the dental implant  10  of the embodiment shown in  FIGS. 1 and 2  is shown in the state when inserted into the jaw bone  42 . The securing portion  14  is received completely in the jaw bone  42 , while the head portion  16  situated radially outside is substantially surrounded by the gum  44  located above the jaw bone  42 . 
         [0027]    Approximately at the level of the limit face between the jaw bone  42  and the gum  44 , a contour line  46  is visible, to which the head portion  16  is embedded in the bone tissue. Measured in the longitudinal direction, the depth of the embedding is approximately 0.2 mm to 0.8 mm, preferably 0.5 mm. 
         [0028]    The part of the surface of the dental implant  10  surrounded by the tissue of the jaw bone  42  below the contour line  46  is specifically functionalized by being roughened (e.g. by etching), by other forms of surface treatment (e.g. by sandblasting) and/or by a coating (e.g. plasma spray process), in order to obtain a more intensive interaction of the bone tissue with the functionalized surface and thus improve the anchoring of the dental implant  10  in the jaw bone  42  (osseointegration). The strongest biochemical bond is achieved at a surface roughness of approximately 1.5 μm (mean roughness value R a ) (G. Hansson, J. Biochem. 2000, 33: 1297-1303); an optimal surface structure is obtained at a mean roughness value R a  of approximately 1 μm and an average peak-to-valley height R z  of 11 μm (A. Wennerberg, thesis, University of Gothenburg, 1996). The figures for the mean roughness values and the average peak-to-valley height correspond to the definition according to DIN 4768. Alternatively, a smaller or larger part of the surface of the dental implant  10  can of course be equipped with a functionalized or roughened surface. 
         [0029]    According to the sectional view shown in  FIG. 5 , the dental implant  10  is preferably screwed to such a depth into the jaw bone  42  that the contact face  30  protrudes above the outer surface of the gum  44 . A support element  48  functioning as patrix lies directly on the contact face  30  acting as matrix. 
         [0030]    The support element  48  is provided, at the dental implant side, with a bearing face  50  which has a negative shape corresponding to the contact face  30 . By virtue of the convex design of the contact face  30  and the correspondingly concave design of the bearing face  50 , this matrix/patrix construction not only has a purely supporting function, but also to some extent a centering function. 
         [0031]    To avoid penetration of liquids, bacteria and food residues in the detachable embodiment shown in  FIG. 5 , where the dental prosthesis  54  rests on the dental implant  10  by way of the support element  48 , the blind hole  34  is, as has already been mentioned, sealed with a suitable filler compound in the head portion  16  of the dental implant  10 . 
         [0032]    The disk-like support element  48  shown in the sectional view in  FIG. 5 , with a substantially cylindrical cross section, is either pressed into a corresponding prosthesis seat  52  of the prosthesis  54  and optionally bonded with adhesive, or it has been cast integrally with the prosthesis  54  at the time of production. In the latter case in particular, hollow spaces  56  between the outer surface of the gum  44  and the bearing face  50  protruding beyond the contact face  30  can be filled with biocompatible filler material. 
         [0033]    In the same way as for the dental implant  10  itself, the materials preferably used for the support element  48  are titanium and titanium alloys, zirconia or other biocompatible materials, preferably metal alloys. 
         [0034]    The support element  48  has an external diameter of between 4 mm and 5.5 mm, preferably of 5.5 mm. The height of the support element  48  is between 2 mm and 4 mm, preferably 2.5 mm. 
         [0035]      FIGS. 6 and 7  show the details of the support element  48 . In addition to the concavely curved bearing face  50 , two radially outwardly directed retention grooves  58  are visible. These retention grooves  58  serve for better anchoring of the support element  48  in the dental prosthesis  54 . 
         [0036]    In addition to the supporting function described above, the dental implant  10  can also perform a securing function by connecting it to an anchor element  36  having the shape of a spherical head, for example as shown in  FIG. 8 . In this case, the support element  48  (not shown) in the dental prosthesis  54  is designed, for example, with an elastically deformable or resilient bearing face  50  in the shape of a hollow sphere, such that a releasable connection, for example a click connection, is produced between the dental prosthesis  54  and the dental implant  10  connected fixedly to the anchor element  36 . 
         [0037]    In the anchor element  36  as shown in  FIG. 8 , the anchor head  62 , here of spherical design, is adjoined, in the direction toward the implant, by a tapered anchor neck  64 , and the latter in turn is adjoined by a substantially hexagonal anchor attachment  66 . This anchor attachment  66  serves in particular for interaction with a screwing tool, for example a wrench, when screwing the anchor element  36  into the blind hole  34  provided for it in the head portion  16  of the dental implant  10 . 
         [0038]    Before the transition of the anchor attachment  66  into an anchor root  68  provided with a corresponding outer thread, the anchor element  36  widens to form an annular anchor disk  70 . In the view shown in  FIG. 8 , the anchor disk  70  sits in a corresponding inner and centrally positioned recess of a washer  72 , which serves to secure the anchor element  36  on the dental implant  10  against inadvertent loosening of the anchor element  36 . In the embodiment shown, the washer  72  is secured on the anchor disk  70  of the anchor element  36  via a flange. 
         [0039]    Alternatively, it is of course also possible to form the washer  72  directly on the anchor element  36 , that is to say in one piece, or to form the washer  72  and the anchor element  36  as two individual elements. The washer  72 , like the anchor element  36 , is preferably made of a biocompatible metal alloy or of other suitable biocompatible materials (e.g. ceramic). In addition to having a through-hole, it also has a rounded configuration  74  on the outside, at the end directed toward the anchor head. The underside of the washer  72 , directed toward the dental implant, is provided with a negative form of the contact face  30  of the dental implant  10 . 
         [0040]    After the dental implant  10  has been produced, and before it is fitted into the corresponding bore in the jaw bone  42 , the dental implant  10 , together with its screw-in adapter  38 , is stored and transported in a preferably sterile state in an ampule  76  shown in  FIG. 9 . The ampule  76  comprises a substantially cylindrical ampule body  78 , which is closed off at one end and can be sealed with an ampule cap  80  at the other end. For this purpose, the ampule body  78 , and the ampule cap  80  also, are provided with mutually adapted screw threads. The first time the ampule cap  80  is unscrewed from the ampule body  78 , a fastening ring  82  that connects the two elements to one another with a form fit is irreversibly separated from the ampule cap  80 . 
         [0041]    A removable ampule insert  84  is located in the interior of the ampule body  78 . The screw-in adapter  38  is fitted in this ampule insert  84 , again in a removable manner. The screw-in adapter  38  is equipped with a screw extension (not visible in  FIG. 9 ) whose outer thread interacts with the inner thread of the blind hole  34  of the dental implant  10  in such a way that a releasable screwed connection is produced between the screw-in adapter  38  and the dental implant  10 . The screw-in adapter  38  also has two hexagonal engagement portions  86  which, in cooperation with a known dental tool, allow the dental implant  10  to be screwed into the jaw bone  42 . 
         [0042]    Before the dental implant  10  can be screwed into the jaw bone  42 , the gum  44  is first removed from the site in question, and a suitable recess is drilled in the jaw bone  42  using the dental drill  88  shown in  FIG. 10 . Along its longitudinal axis L, the dental drill  88  has a drill head  90  at the drilling end area. The drill head  90  is subdivided by three different cross-sectional areas into three portions: a first drill portion, which tapers to a point in the manner of a spiral drill at the end area and is equipped there with first cutting edges  94  and helical first drill grooves  96  for leading drill debris away, a second drill portion  98  whose cross section is greater than that of the first drill portion  92  and which is equipped with second cutting edges  100  and with second drill grooves  102  which are configured more or less in a continuation of the first drill grooves  96 , and a drill stop  104  whose cross section is in turn greater than that of the second drill portion  98  and is provided, in a continuation of the second drill grooves  102 , with third drill grooves  106 , and which, in contrast to the second drill portion  98 , has no cutting edges  100 , but instead has radially extending abutment faces  107 . 
         [0043]    The first drill portion  92  is used to drill out a recess in the jaw bone  42  with approximately the core diameter of the self-cutting outer thread  18  of the dental implant  10 . As the drilling operation continues, the second drill portion  98  adjoining the first drill portion  92  in the longitudinal direction leads to the formation of the previously described enlarged recess in the gum, which permits partial embedding of the head portion  16  as far as the contour line  46  shown in  FIG. 5 . With its abutment faces  107 , the drill stop  104  acts as a limit stop, such that, upon completion of the drilling operation, the recess in the jaw bone  42  has exactly the required depth for receiving the dental implant  10 , and undesired further deepening of the drilled hole in the jaw bone  42  is avoided. 
         [0044]    The drill head  90  of the dental drill  88  is adjoined by a cylindrical drill shaft  108  which, at the end directed away from the drill head  90 , terminates in a tool-coupling element  110 . The tool-coupling element  110  is designed to be received by a standardized chuck of a drive element. On the tool-coupling element  110 , a recess in the shape of a cylinder segment is formed in the circular cylindrical drill shaft  108  in order to create a substantially plane coupling surface  112 . Upon interaction with a corresponding mating surface of the receiving chuck, the coupling surface  112  serves to transmit a torque to the dental drill  88 . The tool-coupling element  110  is also provided with a coupling groove  114 , which extends in the circumferential direction and which serves to axially fix the dental drill  88  in the chuck. 
         [0045]    Embodiments of the above-described dental implant  10  according to the invention, a dental drill  88  adapted to the specific weight of the dental implant  10 , and an anchor element  36  likewise constructed for the specific dental implant  10 , are generally produced and marketed together as a dental implant system. This ensures that the dental implant  10  is inserted with an exact fit into a recess formed in the jaw bone  42  by means of the associated dental drill  88 , and that the anchor element  36  can be easily mounted on the dental implant  10 . In addition to the comparatively inexpensive production of the relatively simply constructed dental implant  10 , the production and marketing of the corresponding dental implant system simplifies and standardizes the installation of the dental implant  10  and makes it more reliable and more cost-effective.