Abstract:
Method according to which an individual implant ( 19 ) is modelled taking into account the individual shape of a tooth ( 2 ) and/or a hole ( 6 ) in a jaw-bone ( 3 ).

Description:
FIELD OF INVENTION 
       [0001]    The present invention refers to a method relating to dental implants. 
       BACKGROUND 
       [0002]    It is known that an implant with a screw shape is screwed into a jaw. To this end a corresponding hole must be drilled into the jaw. Mountings, abutments, or the like, can be provided on such an implant for holding denture parts, such as bridges, caps, crowns, or the like. 
       SUMMARY OF THE INVENTION 
       [0003]    It is the object of the present invention to provide an improved method, devices therefor, and implants improved thereby. 
         [0004]    According to one embodiment of the invention, a method is provided comprising modeling an individual implant taking into account the individual shape of a tooth and/or a hole in a jawbone. 
         [0005]    According to another embodiment, a computer-readable medium is provided with instructions to a computer for executing the above method. 
         [0006]    According to another embodiment, a computer is provided with the above computer-readable medium. 
         [0007]    Preferred embodiments are disclosed in the description and claims. 
         [0008]    In the method an implant is individually modeled, i.e. depending on the individual shape of the tooth or a hole in a jawbone. 
         [0009]    The tooth may be a natural tooth. In such a case the hole is then also a naturally shaped hole (alveole). A hole, however, may also be created artificially, e.g. by drilling. 
         [0010]    After extraction of a tooth or tooth residue a hole remains in the jawbone. In the method either the shape of the tooth or the shape of the hole is taken into account for modeling an individual implant. Here, when the implant is being shaped, the form of the tooth or the hole can be taken into account as accurately as possible so that an implant can be modeled showing a good primary and a good secondary stability. The primary stability follows from the shape of an implant, for instance from the screwed-in thread in prior-art implants, the secondary stability following from the ingrowth of the implant in the bone due to bone growth. 
         [0011]    The individual shape of the implant is of relevance especially in the region inserted into the jawbone. This part is of importance to a good primary stability and a fast and good secondary stability, respectively. For the part of the implant projecting from the jawbone, an individual shape is also advantageous as it is thereby possible to take into account the existing situation made up of neighboring teeth, neighboring denture parts, counter bite, etc., with an adaptation that is as good as possible. Likewise, the shape of the original tooth can also be taken into account. 
         [0012]    For modeling the implant the individual shape of the tooth or the hole in the jawbone can be stored in a data set, said data set being used by a software for modeling the implant. 
         [0013]    This enables a computer-assisted modeling where large data volumes can be processed in a precise way. 
         [0014]    The data set describing the shape of the tooth or the hole in the jawbone can be obtained in different ways. For instance, it is possible to scan an extracted tooth (cleaned). Based on the shape of the tooth, the shape of the hole in a jawbone, into which an implant is to be inserted, is in principle also known since the shape of the tooth and the shape of the corresponding hole in the jawbone are matching, with a small gap, in which holding fibers for the tooth are provided (part of the periodontium), remaining between tooth and bone as a rule. 
         [0015]    The shape of an extracted tooth can be sensed with an optical or mechanical probe. 
         [0016]    Instead of the tooth itself, it is also possible to use a model or casting of the tooth (e.g. a plaster model). 
         [0017]    However, it is also possible to scan a tooth that has not been extracted yet, or a hole in which the tooth is still positioned, e.g. by computer tomography. X-ray tomography, but also for example NMR tomography may here be employed. 
         [0018]    It is also possible to measure the hole created by the extraction of a tooth, or another existing hole, optically, mechanically or by computer tomography (X-ray, NMR). A cast or model of said hole (for instance with a plaster model) can also be scanned. 
         [0019]    For modeling the implant the data set of the tooth or the hole in the jawbone is displayed in the modeling of the implant. For instance, the surface of a tooth or the hole can be shown as in a three-dimensional view on a two-dimensional screen. The view may be transparent or nontransparent. It is also possible to display sections of the tooth or the hole. 
         [0020]    For the software-assisted modeling of the implant it is advantageous when the software automatically generates a proposal for the shape of the implant or at least for a part thereof. For instance, the shape of the root or a part of the root of the tooth or of the hole can here be adopted as the desired shape of the corresponding part of the implant. The adoption of the shape yields an individual implant. When the shape is adopted, it is possible to take into account some clearance, i.e. the implant or the part thereof that is inserted into the jawbone is modeled slightly reduced in size in comparison with the hole in the bone. The play may e.g. be 0.001, 0.005, 0.01, 0.05, 0.1, 0.2 or 0.5 mm. 
         [0021]    In such a method it is further advantageous when the insertability of the implant is checked or taken into account. For instance, there may be tooth root shapes that due to the shape of the corresponding hole in the jaw cannot be inserted without difficulty. This may easily happen particularly with molars or wisdom teeth since several roots may here point into several directions. Such a problem hardly arises with incisors or canines. 
         [0022]    It is also possible that the software makes several proposals for implants, among which one can then be chosen. It is here advantageous when at least two different proposals are made that consist of a different number of implant parts. 
         [0023]    Of advantage is also an embodiment in which a surface roughness or surface structure is provided for an implant. Such roughnesses or structures, e.g. grooves, knobs, or the like, improve stability through a splined growing together with the bone. Such roughnesses can also be accomplished through a specific milling operation because a rapid milling operation yields rougher surfaces than a slow one. Hence, a rapid milling operation may also be of advantage to a rough surface (apart from a faster fabrication). Moreover, a special method step may be taken for creating surface roughness, e.g. sand blasting, salt blasting, or the like, grinding with sandpaper or brushes. 
         [0024]    The result of the modeling operation is preferably a data set indicative of the shape of the implant. 
         [0025]    A part of the implant may also be intended for mounting an abutment or another mounting structure. A given data set can be used for such a part of the implant. Said data set may be stored in a database or a library or in another file. 
         [0026]    Apart from the shape of the hole or the shape of the tooth, a data set may also be taken into account that describes at least a part of the shape of the jawbone next to the hole into which the implant is to be inserted. It can thereby for instance be checked whether stability problems might arise from the jaw due to the insertion of the implant. Such problems can e.g. be checked with a “finite element method”. 
         [0027]    Apart from the implant, it is further possible to model a counterpart that can be mounted on an outwardly oriented part of the implant. An outwardly oriented part is e.g. one that is oriented away from the part that is to be inserted into the jawbone. This may e.g. be the masticatory surface or the part on which an abutment or another mounting is to be installed. However, it may also be that part that is to be covered to replicate a natural tooth. The counterpart is adapted in its shape preferably individually to the implant. It may e.g. have an area that is matched in its shape to the part of the implant, on which the counterpart is to be mounted, such that a planar contact is achieved (even with an uneven or irregularly formed surface of the counterpart or implant, respectively). 
         [0028]    With such a counterpart an implant can for instance easily be inserted into a jawbone as the implant itself can be pressed into the jawbone or into the corresponding hole by applying pressure on the counterpart. It is also possible to hammer in the counterpart without the risk that the implant itself will thereby get damaged. 
         [0029]    Furthermore, a method is of particular advantage wherein a part of the implant which is to substitute a tooth root portion is made integral with such a part of the implant that is used as a cover or is to be connected to an abutment or another mounting. It is thereby possible to implement the function of the implant and an abutment, as known from the prior art, with a single piece, resulting in a particularly high stability. 
         [0030]    Furthermore, the implant can also fully correspond to the shape of the original tooth or fully to the shape of the tooth crown of the original tooth. This means that it is e.g. manufactured in a CAM method such that it can be inserted into the jaw without any further veneer. To this end the implant need also not exactly match the original tooth in the area of the tooth crown, but can also have a different tooth crown shape that assumes the function of a complete tooth. With these implants no space can e.g. be left for veneers. The implant can thus e.g. be formed directly with the masticatory surface. Masticatory surfaces are e.g. in molars or in wisdom teeth the dental surfaces (which are horizontal and lie transverse to the tooth axis) used for grinding, and in canines and incisors the ends that project from a jaw to the furthest extent. 
         [0031]    Implants that already include the masticatory surface and/or at least in the area of the tooth crown fully correspond to the original tooth or to a tooth of equal function are furthermore preferably completely unitary or at least made unitary with at least one, several or all root substitute portions of the implant. This permits a good stability of the implant. 
         [0032]    In a method a modeled implant, as described above or further below, is manufactured in a computer aided manufacturing (CAM) method, such as e.g. milling. 
         [0033]    It is advantageous when with the same, an equal or a different manufacturing method a counterpart (also see above or further below) is also fabricated. It may here e.g. be advantageous when the material of the implant is a very hard material, such as ceramics or titanium, but the counterpart is made from a softer material, e.g. plastics, or the like. When the implant is e.g. pressed or hammered in, this accomplishes a good pressure distribution on the surface of the implant, thereby reducing the risk of breakage or deformation of the implant during insertion. 
         [0034]    As for ceramics that are dense-sintered after machining (milling), a corresponding data set of the implant can be increased so that after dense-sintering the desired shape (reduced in size in comparison with the prepared (milled) shape) is obtained. 
         [0035]    In general, different materials are suited for the implant, for instance a metal, titanium, titanium with a grade 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33 . . . (the grade information refers e.g. to the ASTM specifications), ceramics, zirconia ceramics, or doped zirconia ceramics. A material that corresponds or is similar to a tooth material, such as hydroxyapatite or also fluorapatite, or mixtures with these materials (also with further materials), is suited for the implant. The implant can further comprise different layers, coatings, or the like, made from different materials. 
         [0036]    A freshly inserted implant is preferably disoccluded. To this end appropriate means, such as caps or bridgings, may also be manufactured in a CAD/CAM method. 
         [0037]    Furthermore, an implant is preferably fixed in its position in which it is to grow in, at least during ingrowth, so that ingrowth can take place as fast and undisturbed as possible. The implants can be moved by the tongue or the counter bite, which slows down or suppresses the ingrowth process. 
         [0038]    For such a fixation an adhesive may be provided e.g. on the root substitute portion of the jaw at least in some regions or also throughout the whole root substitute region. The adhesive can be applied in a corresponding method step, e.g. by immersion into a liquid adhesive. The term adhesive shall also encompass so-called cements, as are used in dental technology. The adhesive can also be decomposed or dissolved in the patient&#39;s body, so that it will disappear during bone growth, thereby providing room for the bone growing process. 
         [0039]    The implant may also be connected with the help of appropriate connecting means to the neighboring teeth. This will also fix the implant in the desired position. Said connecting means can also be made by CAD/CAM. 
         [0040]    The method can be used for implants at dental positions of wisdom teeth, molars, canines or incisors. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0041]    Advantageous embodiments of the invention shall now be explained with reference to the attached figures, of which: 
           [0042]      FIG. 1  shows a tooth in the jawbone; 
           [0043]      FIGS. 2   a  and  2   b  show schematic sectional drawings of implants in the jawbone; 
           [0044]      FIG. 3  is a schematic view showing data on a computer for modeling an implant; 
           [0045]      FIG. 4  is a three-dimensional schematic view of an implant and of a counterpart; 
           [0046]      FIG. 5  is a three-dimensional schematic view of an implant and a counterpart in a further embodiment; 
           [0047]      FIGS. 6   a ,  6   b  and  6   c  show different surface structures of implants; 
           [0048]      FIGS. 7   a ,  7   b  and  7   c  show different means for fixing an implant or for disoccluding an implant. 
       
    
    
     DETAILED DESCRIPTION 
       [0049]      FIG. 1  shows a tooth in a jawbone  3 . The roots  5  of the tooth  2  are positioned in a hole  6  in the jawbone. A gingival layer  4  is located on the jawbone  3 . 
         [0050]    The tooth neck  8  is positioned between the root portion  10  and the tooth crown portion  9 . 
         [0051]    The dental enamel bears the reference numeral  7 . 
         [0052]    The distance between the tooth  2  and the jawbone  3  is very small in reality. Fibers that connect the tooth to the bone are found in this gap. 
         [0053]      FIG. 2   a  gives an example how an implant may be shaped after the tooth  2  of  FIG. 1  has been extracted. The implant  19  comprises two root portions  12 ,  13  having shapes that exactly match those of the roots  5  of  FIG. 1   
         [0054]    In  FIG. 2   a , the implant  19  substantially fills the space of the hole  6  in the jawbone  3 . Since the implant  19  is relatively close to the bone  3 , ingrowth can here take place very rapidly, which results in a secondary stability very rapidly. 
         [0055]    As shown in  FIG. 2 , there may be cases where an implant  19  cannot be inserted into the hole  6  without difficulty. In the upper portion of the hole  6 , there is a constriction (see reference numeral b), the extension of which is smaller than the broadest extension (see reference numeral a) of the implant  19 . In such a case it may be expedient to make an implant from two parts, so that two parts  12  and  13  can be inserted independently of each other. To this end a separation shown in broken line is provided in the implant  19  in the upper right part. To interconnect the two implant parts, the root part  12  may comprise a thread  14  into which a screw  17  can be screwed, and the head of which in a space  16  can press the part  13  against the root part  12 . Instead of screw and thread, other mechanical connecting means (e.g. an attachment) or also adhesive or cement is suited for connecting the parts  12  and  13 . 
         [0056]    In the upper end of part  13 , a thread  18  is provided for tightly screwing e.g. an abutment. The head of the screw  17  is here countersunk to such an extent that it is not objectionable there. 
         [0057]    In the same way as two parts  12 ,  13  are assembled in  FIG. 2   a  to form an implant  19 , it is also possible to provide even more parts. These parts need also not be interconnected by means of screws  17 , but can be connected with the help of other connecting means, e.g. an attachment, cement, adhesive, or the like. 
         [0058]    Furthermore, as can be seen in  FIG. 2   a , a part of the implant (environment of thread  18 ), which is connected to an abutment or a mounting, is connected to a part that represents root substitute (lower region of part  13 ). 
         [0059]      FIG. 2   b  shows an alternative implant  19 ′, in which flat portions  20   a ,  20   b  are provided on the outer sides and flat portions  20   c ,  20   d  on the inner sides for ensuring insertability, the implant  19 ′, however, being then made of one part. The flat portions  20   a ,  20   b ,  20   c ,  20   d  are configured such that the implant  19 ′ can be pushed through the minimal opening of the hole  6  (see reference numeral b) in  FIG. 2   a ) and can be pushed over the bone part between the two root substitute parts  12 ′,  13 ′. Although this results in a larger gap between the implant  19 ′ and the bone  3 , so that the absence of corresponding implant material leads to a lower primary and secondary stability, on the other hand the implant  19 ′ can be made of one part, which enhances the stability of the implant itself. In this variant the implant also comprises portions—in the part that will be inserted into the jawbone—that match the shape of the hole (see e.g. lower ends  12 ′ and 13′), yielding a good primary and rapid secondary stability. 
         [0060]      FIG. 3  shows a computer  25  displaying a data set  21  which describes the surface of a tooth  2 . In the portion of the tooth neck an optional partition plane  22  is plotted that is to divide the data set  21  into an upper and a lower part. Plane  22  can also be displayed. The position of the plane  22  can be set by hand or can be suggested by the software automatically. The plane  22  separates that part of the data set  21  that is to be adopted as unchanged as possible from the part that is to be changed. The lower part  21  shall be adopted as unchanged as possible for the shape of the implant, so that the implant can be inserted into the hole  6  as accurately fitting as possible. In this portion, however, changes can also be made in the shape, e.g. flat portions, to accomplish e.g. insertability. 
         [0061]    The upper part  21   b  (i.e. the portion corresponding to the part of a tooth crown) should be adapted to create possibilities of fastening for abutments or to create space for veneers so as to replicate the appearance of a natural tooth as much as possible. 
         [0062]    Such veneers can e.g. be made from porcelain. 
         [0063]      FIG. 3  schematically shows how a part  23  above the plane  22  is modeled cylindrically with an elliptical cross-section in which a thread  24  is provided into which e.g. an abutment can be tightly screwed. 
         [0064]    The plane  22  may also be curved. It just serves as an optional modeling aid. 
         [0065]      FIG. 4  shows a three-dimensional view of an implant  30  in which a specific geometrical shape  31  is schematically shown at the upper end. For instance, a ring-shaped rim is provided on the outer periphery of the implant. A counterpart  32  is formed at a side in such a way that it can be brought into contact with the upper side of the implant  30  over an area as large as possible. The counterpart  32  may e.g. be made from plastics. The implant can be driven into the jaw by strokes or by pressure applied to the counterpart  32 . 
         [0066]      FIG. 5  gives an example of an implant  40  in which an upper part  41  is provided that is intended for veneering, and a lower part  42  configured as a root substitute portion. The two parts are made unitary. 
         [0067]    An example of an implant that fully corresponds to the shape of the original tooth, and thus also in the area of the tooth crown corresponds to the original tooth, is shown by the illustration in  FIG. 1 , on the assumption that the implant has the outer shape of the tooth  2 . Such an implant can e.g. be completely formed from titanium or ceramics (preferably in one part). In the area of the tooth crown it may be formed in a different way, but in such a fashion that the implant assumes the full function of a tooth at the corresponding tooth position. The implant will then also include, for instance, a masticatory surface. 
         [0068]    In this case the counterpart  43  has the shape of the surface  44 , so that it can be mounted in planar contact with this surface  44 . This counterpart  43  thus serves to hammer the implant  40  into a jaw. 
         [0069]      FIG. 6  shows various surface configurations of the implant  19 . In  FIG. 6   a , the surface is substantially smooth.  FIGS. 6   b ,  6   c  show different surface roughnesses or flutes. When the space  6  shown in  FIGS. 6   a  to  6   c  is overgrown with bone material  3 , the flutes (see  FIGS. 6   b  and  6   c ) provide for a particularly good grip of the implant  19  in the bone  3 . 
         [0070]      FIG. 7  shows means with which an implant can be fixed in its position. Here the implant bears reference numeral  51 ; reference numerals  50  or  52  stand for natural teeth. The implant  51  is held with coupling means  53 ,  54  on the teeth  50 ,  52 . The coupling means  53 ,  54  are detachably connected to the implant and the teeth, e.g. glued on. They are only used temporarily for instance for about four to six weeks until ingrowth of the implant  51 . The shape of the coupling means is given by the surface of the implant  51  and the teeth  50 ,  52 . 
         [0071]      FIG. 7   a  shows the tooth  50  with a mounting  55  provided thereon, which prevents the opposing jaw from getting into contact with the implant  51  during chewing. This prevents the exertion of pressure on the implant  51  by the counter bite. 
         [0072]      FIG. 7   b  shows a bridging  56  of the implant  51  as a means for disoccluding the implant. The bridging  56  is supported on the neighbors  50 ,  52  and bridges the position of the implant. This protects the implant  51  even in a better way against the pressure exerted by the opposing jaw. The bridging  56  can be adhesively fixed with cement or adhesive temporarily (for some weeks) onto the neighbors  50 ,  52 . 
         [0073]      FIG. 7   c  shows a variant of a means for fixing the implant  51  in its desired position. The teeth  50 ,  52  are viewed from above along the tooth axis. A fixation  57  is fastened to the outside or inside of the teeth  50 ,  52  (temporarily, possibly with adhesive or cement) and the implant  51  is fastened to said fixation (temporarily, possibly with adhesive or cement). Owing to this fixation the implant  51  can readily grow in in its position. In addition to the fixation  57 , a cap  55  or a bridging  56  may be provided as a means for disoccluding the implant. 
         [0074]    The cap  56 , the coupling means  53 ,  54 , the bridging  56  or the fixation  57  (i.e. in general means for fixing the implant in its position or for disoccluding the same) have each portions that get into contact with the teeth or the implant to be fastened on or to said teeth or implant. To this end it is advantageous when the means are manufactured by way of CAD/CAM to adapt the portions as exactly as possible to the shape of the teeth or the implant. The shape of the implant is known from modeling. The shape of the neighbors (teeth or other implants or denture means) can be determined on the basis of corresponding scan data (see above explanations regarding scanning the tooth or hole, which are here applicable by analogy). 
         [0075]    A special embodiment may e.g. be configured in the following way: A tooth to be extracted is scanned by X-ray computer tomography and a data set generated therefrom, which describes the shape of the tooth or the hole, is loaded into a computer with which the implant is modeled. The computer analyzes the data and suggests a plane  22  that is positioned at the tooth neck. The shape underneath the plane  22  is adopted in unchanged form for the shape of the implant. As for the part above plane  22 , the software searches in a database for a suitable and predefined set of shape data which defines a part of the implant that can be veneered. The predetermined set of shape data is adapted in size and shape automatically or by hand and/or is positioned and connected to the set of part data underneath the plane  22  so as to obtain an individual data set which describes e.g. an implant as in  FIG. 5 . 
         [0076]    Such a data set can be sent to a manufacturing center for denture parts and can there be manufactured in a CAM method. Subsequently, it may be veneered in addition and/or further processed in another way. 
         [0077]    In a method a tooth is extracted from a patient and a fabricated implant as described in this application is inserted directly thereafter, i.e., e.g. within a period of not more than one hour, one day or five days.