Abstract:
Disclosed is a dental prosthesis including an implant, a customised abutment, a restoration and an implant screw for securing the customised abutment to the implant, wherein the implant includes a screw bore extending from a first end of the implant for receiving at last a part of the implant screw, the customised abutment includes a through-going bore for receiving at least a part of the implant screw, the screw bore and the through-going bore are coaxially aligned along an implant axis when the implant screw is arranged in the screw and through-going bore, the abutment includes a customised abutment base and a customised abutment top where the customised abutment base and the customised abutment top defines an assembly axis along which they were assembled during manufacturing, where the implant axis is different from the assembly axis.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to a customisable dental abutment for use with a dental implant and a restoration to form a dental prosthesis. In particular the invention relates to a dental prosthesis comprising a two-piece abutment wherein both pieces are customisable. This provides for an abutment which is both durable and allows for a more esthetical restoration than previously known. 
         [0002]    The invention furthermore relates to a method for designing the two-piece abutment and to a method for producing said abutment. 
       BACKGROUND OF THE INVENTION 
       [0003]    Within restorative dentistry high customisability is often desired. This is due to the highly varied anatomy of the set of teeth for each human, which makes it very difficult to provide standard solutions that accommodate everyone. This is also the case for restorative dentistry using implants as will be discussed further herein. 
         [0004]    The use of implants is a very specific branch of dentistry which has evolved rapidly within the last half century. 
         [0005]    An implant is placed in the bone of the jaw where it is secured as the bone grows into very close apposition to the implant. This process is also known as osseointegration. In particular titanium has shown to have very good osseointegration properties and is currently the most preferred material to use for implants. 
         [0006]    When osseointegration is complete and the implant is secure in the bone it may subsequently be used as a base for dental restorations and prosthetics. Typically so-called abutments are placed in the implant. The abutment serves as an interface between the implant and the final anatomical restoration, for example a crown or a bridge. 
         [0007]    However, in some cases there are constraints on where an implant can be placed, this can for example be due to weak bone tissue or other considerations. Thus, depending on the anatomy of the patient the implant is often placed in different positions, for example at different angles. The abutment has to be designed to correct such difference in placement and angulation. There exists standard angulated abutments, however, these are only useable if the implant are placed within a specific angled interval. 
         [0008]    Thus, in order to provide a higher flexibility for placing the implant different customisable abutments have been developed. 
         [0009]    In general these can be categorised into two categories. 
         [0010]    The first category relates to so-called one-piece customisable abutments, which is illustrated in  FIG. 1   a.    
         [0011]      FIG. 1   a  shows a dental prosthesis  101  comprising an implant  102 , a one-piece customised abutment  103  and a restoration  104 , e.g. in the form of a crown. 
         [0012]    The implant  102  is placed in the bone tissue  105  of the jaw in an angled position along an implant axis A-A. In general, when referring to the angled position of the implant herein, it should be understood as being in relation to the general anatomy of the restoration and how the restoration protrudes from the jaw. 
         [0013]    The one-piece customised abutment extends from the implant along an abutment emergence profile  110 . The emergence profile is the shape of the one-piece customised abutment as it relates to the surrounding tissue, typically bone and gingiva, as it extends from the implant towards the exposed gingiva surface  111 . The abutment typically ends sub-gingival, i.e. below the exposed gingiva surface, where it extends into the restoration  104 . From the abutment the restoration extends along a restoration emergence profile  112  to the exposed gingiva surface from where it extends with an anatomic shape designed to be aesthetic and functional. 
         [0014]    Unless explicitly stated otherwise the term “emergence profile” as used herein refers to the emergence profile of the abutment. 
         [0015]    The one-piece customised abutment  103  is held in place by an implant screw  106 , which is placed in a through-going bore  107  of the customised abutment  103  and engages with threads  108  in the implant to hold the screw and thereby the abutment in place. 
         [0016]    The restoration  104  in the form of a crown is placed on the abutment. The crown is designed to fit between two neighbouring teeth  109 . Typically the restoration and the abutment are cemented together. 
         [0017]    As can be seen the abutment functions as an interface which can be designed so that the restoration can be designed to resemble a tooth as much as possible without being completely restricted to the angle of the placed implant. 
         [0018]    The one-piece customised abutment  103  shown in  FIG. 1   a  thus allow the dentist to place the implant much more freely than done before. However, since it is a monolithic one-piece abutment it can only be made of one material. 
         [0019]    Typically the one-piece abutment is made of a metal, most commonly the same metal as the implant as this provides a robust and solid base for the restoration  104 . However, since the restoration in many cases is made to resemble a tooth the restoration will typically be semi-transparent. This causes the metal of the abutment to shine through creating a greyish look of the final prosthesis which is not esthetical desirable. 
         [0020]    Attempts have been made to form the one-piece customisable abutment of a material which has better aesthetic characteristics, such as zirconia. However, this has caused an increase in cases where the abutment breaks, in particular around the connection to the implant. 
         [0021]    The other category is the two-piece semi-customisable abutments  203  as shown in  FIG. 1   b , which solves some the problems related to the one-piece customisable abutments. 
         [0022]    The two-piece abutment  203  is formed of an abutment base  220  and an abutment top  221 . The abutment base  220  is provided as a standard unit which fits the specific implant  202 . The abutment top  221  is customised and then attached, e.g. by cementing, to the abutment base. 
         [0023]    The two-piece abutment  203  allows for the use of two materials. Thus, the abutment base  220  can be formed of a metal, e.g. titanium, and the abutment top  221  can be formed of e.g. zirconia. Thus, the abutment provides a base which is suitable for a dental restoration, such as a crown  204 , having a high esthetical quality without risking that the abutment breaks. 
         [0024]    However, the use of a standard abutment base  220  results in limitation to the customisation of the abutment top  221 . For example in the circled critical area  230  the minimal thickness of the abutment top is compromised due to design restrictions applied by the standard shape of the abutment base. 
         [0025]    Moreover, the emergence profile  210  of the abutment, which is defined by the base emergence profile  222  of the abutment base and the top emergence profile  223  of the abutment top, is not fully customisable since the designer is not free to design the base emergence profile  222 . 
         [0026]    Accordingly, there exists a need to provide an abutment which gives the dentist and the dental laboratory a high degree of freedom of design while at the same time providing a dental prosthesis having high aesthetic and durable characteristics. 
       SUMMARY 
       [0027]    In a first aspect the invention relates to a dental prosthesis comprising an implant, a customised abutment, a restoration and an implant screw for securing the customised abutment to the implant, wherein
       the implant comprises a screw bore extending from a first end of the implant for receiving at last a part of the implant screw,   the customised abutment comprises a through-going bore for receiving at least a part of the implant screw,   the screw bore and the through-going bore are coaxially aligned along an implant axis when the implant screw is arranged in the screw bore and the through-going bore,   the customised abutment comprises a customised abutment base and a customised abutment top where the customised abutment base and the customised abutment top extends along an abutment axis, and   where the implant axis is different from the abutment axis.       
 
         [0033]    This provides a dental prosthesis which is both esthetical and durable, as the choice of e.g. material and design can be chosen individually for the abutment base and the abutment top. 
         [0034]    Moreover, the designer also has a high degree of freedom when designing the dental prosthesis since the designer is not limited to a design where the implant axis and the assembly axis are co-axially fixed. 
         [0035]    In one embodiment the abutment axis forms an assembly axis along which the customised abutment top and the customised abutment base were assembled during manufacturing. 
         [0036]    To ensure proper fit and reduce the risk of misalignment the abutment base and the abutment top are in one embodiment provided with respective base and top guiding means for guiding the abutment base and top together along the abutment axis. 
         [0037]    To ensure durability and strength the abutment base is in one embodiment formed of a metal. 
         [0038]    In an even further embodiment the abutment base is formed of the same material as the implant, e.g. titanium. 
         [0039]    In order to provide an improved esthetical look of the dental prosthesis the abutment top is in one embodiment formed of a material identical to or which has similar esthetical properties as the restoration. The material can for example be a ceramic, lithium-silicate, composites, glass-ceramics or porcelain material. One preferred example is zirconia. 
         [0040]    In another aspect the invention relates to a customised two-piece abutment comprising a customised abutment base and a customised abutment top, wherein a through-going bore is formed in at least the abutment base for receiving an implant screw, said through-going bore defines an implant axis, and where the abutment base and the abutment top extends along an abutment axis, where the implant axis is different from the abutment axis. 
         [0041]    This provides a two-piece customised abutment which is particular suitable for use in a dental prosthesis which is desired to be both esthetical and durable. 
         [0042]    Moreover, the designer also has a high degree of freedom when designing a dental prosthesis comprising such a two-piece abutment. 
         [0043]    In one embodiment the abutment axis forms an assembly axis along which the customised abutment top and the customised abutment base were assembled during manufacturing. 
         [0044]    As can be understood, the customised abutment described in respect of the current aspect can also comprise the features and embodiments of the customised abutment as described in the previous aspect relating to the dental prosthesis. 
         [0045]    In yet another aspect the invention relates to a method for designing a virtual model of a customised abutment for use in designing a virtual dental prosthetic comprising the customised abutment, an implant and a restoration, the method comprising the steps of,
       obtaining a digital data set representing a dental situation of a patient comprising information on implant type, position and orientation along an implant axis,   designing a customised abutment by designing an implant surface for contact to the implant along the implant axis and a restoration surface for contact to a restoration, where an emergence profile of the abutment is designed which separate the implant surface and the restoration surface,   splitting the customised abutment into a customised abutment base, which is suited to be arranged adjacent to the implant, and a customised abutment top adjacent to the abutment base, where the customised abutment base and the customised abutment top extends along an abutment axis.       
 
         [0049]    This advantageously allows a designer to design a two-piece customised abutment specifically for an individually placed implant. This is partly possible because the abutment base and the abutment top are customised as defined by the designed emergence profile. 
         [0050]    Moreover, a dental prosthesis which is both esthetical and durable may be provided by manufacturing the dental prosthesis having an abutment designed according to the method. 
         [0051]    In one embodiment the abutment axis forms an assembly axis along which the customised abutment top and the customised abutment base are adapted to be assembled during manufacturing. 
         [0052]    Furthermore, in an additional or alternate embodiment, to ensure proper fit and reduce the risk of misalignment the method further comprises designing respective base and top guiding means on the customised abutment base and the customised abutment top for guiding the customised abutment base and customised abutment top together along the abutment axis. 
         [0053]    In one embodiment the method further comprises setting the assembly axis different from the implant axis. 
         [0054]    This advantageously gives the designer a high degree of freedom when designing the abutment since the designer is not limited to a design where the implant axis and the assembly axis are co-axially fixed. 
         [0055]    In one embodiment the abutment is advantageously split across the emergence profile. This ensures that the split between the customised abutment top and customised abutment base is visibly hidden beneath the gingiva when the physical abutment is placed in the implant. 
         [0056]    In one embodiment the method comprises designing an anatomical model of the dental restoration. Based on this the customised abutment is subsequently designed. In this way the abutment is designed partly based on the dental restoration which further ensures a very good fit and final result. 
         [0057]    In another aspect the description discloses a user interface comprising a 3D virtual design environment for virtually displaying a virtual abutment defined by a emergence profile extending between an implant surface and a restoration surface, and at least one virtual tool button for modifying the virtual abutment when activated, wherein the at least one virtual tool splits the customised abutment into a customised abutment base and a customised abutment top along a split indication defined by the user. 
         [0058]    Such a split indication can for example be a virtual plane provided in the design environment which intersects the virtual abutment where the user wants the split to be placed. 
         [0059]    In another embodiment the split indication may for example be provided by a virtual spline drawn by the user on the abutment. The abutment is then split along this spline. 
         [0060]    Standard connection means and/or guiding means may be provided between the customised abutment base and the customised abutment top. Such connections or guiding means may be manually designed or provided from template shapes after the split has been provided. 
       DEFINITIONS 
       [0061]    The term “dental prosthesis” as used herein refers to the complete artificial tooth or dental replacement placed in the patient. Thus, this term covers the implant, the abutment and the restoration. 
         [0062]    The term “dental replacement” as used herein refers to the parts which the lab or the appropriate designer/technician designs. Thus, this term covers the abutment and the restoration. 
         [0063]    As will be understood herein when referring to the different parts of the dental prosthesis in relation to the design method as disclosed, it is not a physical part as such, but a virtual representation of a physical part which is described. However, with respect to the final product this will comprise physical parts which have been provided by manufacturing the specific parts based on the virtual representation established during the design process. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0064]    The above and/or additional objects, features and advantages of the present invention, will be further elucidated by the following illustrative and non-limiting detailed description of embodiments of the present invention, with reference to the appended drawings, wherein: 
           [0065]      FIG. 1   a  shows one type of a dental prosthesis according to prior art, 
           [0066]      FIG. 1   b  shows another type of a dental prosthesis according to prior art, 
           [0067]      FIG. 2  shows a dental prosthesis according to the invention, and 
           [0068]      FIG. 3  shows a work flow of how to design a virtual model of a dental prosthesis. 
       
    
    
       [0069]    In order to facilitate reading the reference numbers of the drawings are numbered in order to show similar parts for different embodiment. Accordingly, the hundreds digit, i.e. the third digit left of the decimal point indicates the embodiment. The units digits and the tens digit, i.e. the first and second digit left of the decimal point indicates the feature. Thus, for similar features the units and tens digits are similar for separate embodiments, but the hundreds digit will be different. 
       DETAILED DESCRIPTION 
       [0070]    In the following description, reference is made to the accompanying figures, which show by way of illustration how the invention may be practiced. 
         [0071]      FIG. 2  shows a dental prosthesis  301 . The dental prosthesis is formed of an implant  302 , a customised abutment  303  and a restoration  304  in the shape of a crown. 
         [0072]    The implant  302  is arranged in the bone tissue  305  of the jaw and extends along an implant axis A-A. It should be noted that the drawings are not exact and illustrative only. The implant shown has a one-to-one length to width relationship. Typically this relationship will be two-to-one, however, any other relationship and dimension could be provided within the scope of the present invention. 
         [0073]    The abutment  303  is formed of an abutment base  320  and an abutment top  321  which are attached to each other. A through going bore  307  extends through the abutment and is adapted for receiving an implant screw  306  which engages with corresponding internal threads  308  arranged in the implant. The abutment and the implant are arranged in such a way that the through going bore  307  and the implant  302  are co-axially arranged along the implant axis A-A. 
         [0074]    The abutment base  320  and the abutment top  321  are attached together, e.g. by cementing, and have been designed such that they are assembled together along an assembly axis B-B. Alternatively, in another embodiment the abutment base and the abutment top may be attached together by a screw connection which extends along the abutment axis B-B. 
         [0075]    As can be seen, the implant axis A-A and the assembly axis B-B differs, i.e. they are not co-axial and as shown in the figure are rotated at an angle. Accordingly the abutment base of the abutment is brought into contact with the implant when inserted along the implant axis A-A, and the abutment top of the abutment is brought into contact with the restoration when the restoration is put on along the assembly/abutment axis B-B. 
         [0076]    By separating these axes from each other a high degree of design freedom is achieved when designing the abutment. This result in that the dentist can provide a treatment where the patient receives a dental prosthesis which is very aesthetic and durable while at the same time allowing the dentist a high degree of freedom when placing the implant. In particular it provides the freedom to design a dental prosthesis  301 , where the abutment  303  has an emergence profile  326  that fits well to the surrounding tissue, e.g. the gingiva  310 . 
         [0077]    Moreover, the high degree of designer freedom also facilitates the design of the anatomy of the dental restoration, such as the crown  304 , so that it fits well to the abutment  303 , between neighbouring teeth  309  and have good functionality, e.g. chewing properties and aesthetics. 
         [0078]    In order to ensure that the abutment base  320  and the abutment top  321  are aligned correctly during assembly guiding means are provided. In the present embodiment the guiding means are provided in the form of a tapering protrusion  331  on the top facing surface of the abutment base and a tapering recess  333  on the base facing surface of the abutment top. The tapering protrusion  331  and the tapering recess  333  are formed so as to match each other. The tapering walls of the protrusion and recess facilitate the guiding function. 
         [0079]    The shape of the tapering protrusion  331  and the tapering recess  333 , when seen along the abutment axis B-B, may be formed to ensure proper orientation of the abutment base and abutment top in respect to each other. The shape can thus be irregular, an oval, an asymmetric triangle or any other shape which only matches when aligned in specific desired positions. A notch and groove configuration may also be provided so that the part may only fit together in one unique relative rotational position. 
         [0080]    Similar means may be provided between the abutment top and restoration in order to ensure correct fit and orientation. Moreover, the restoration may be attached to the abutment top by cementing or by a separate screw fixation. 
         [0081]    The abutment top maybe provided with different designs. The conical shape shown in  FIG. 3  is well known and reliable. However, other designs may also be provided, for example it may have an anatomical surface. An anatomical surface corresponds to the surface of the restoration, although it is offset from the restoration surface. This is for example advantageous in that the designed restoration is provided with an uniform material thickness. 
         [0082]    A workflow  450  showing one embodiment of how to design a dental prosthesis having a two-piece customisable abutment as disclosed herein is shown in  FIG. 3 . The design is preferably performed in a virtual design environment, such as a CAD (Computer Aided Design) program. It should be understood that when referring to different parts in the workflow it is not the physical parts itself that is provided, but virtual models of the respective parts thereof. 
         [0083]    In the first step  451 , a 3D model of the dental situation is obtained. The 3D model is typically obtained either by scanning a gypsum mould of the dental situation, scanning a dental impression of the dental situation or directly scanning in the oral cavity by using an intra-oral scanner. 
         [0084]    The 3D model also includes information on the position of the implant from which an implant axis A-A can be derived. Such information can for example be provided by using so-called scan-abutments during scanning. Briefly discussed the scan-abutment is placed in the implant or the model of the implant in e.g. a gypsum model. When the scan is performed the scan-abutment can then be used to derive the position and angle of the implant. In general this is a well-known method for the person skilled in the art on how to include such information in the scan. 
         [0085]    The 3D model can furthermore include information relating to neighbouring teeth  409 , gingiva  410 , bone tissue  405  and/or additional information on the implant  402 , e.g. type and/or size. 
         [0086]    In the second step  452  the anatomy of the dental replacement  440  is designed. When designing the anatomy both esthetical and functional characteristics are taken into consideration. In addition the emergence profile  422  of the dental replacement is designed. The emergence profile  422  is the design of the dental replacement at the implant and how its contour follows the gingiva  410  and other surrounding tissue such as the bone tissue  405 . The emergence profile  422  of the dental replacement extends from the implant  402  to the expose surface  427  of the gingiva, i.e. the surface of the gingiva which will be free when the dental prosthesis have been finalised, manufactured and placed in the patient. 
         [0087]    A well designed emergence profile provides a final dental prosthesis that has a good fit, i.e. not too wide which can result in friction and pain for the patient as the dental prosthesis will press on the surrounding tissue, but not too narrow so that gaps and openings occurs between the dental prosthesis and the surrounding anatomy. 
         [0088]    In the third step  453  the dental replacement is split into a restoration  404 , in this case a crown, and an abutment  403 . The split is preferably placed so that the surface split line  423  is below the upper surface of the gingiva. This divides the emergence profile  422  of the dental replacement into a restoration emergence profile  428  and an abutment emergence profile  426  and hides the surface split line visibly when the dental prosthesis has been placed in the patient. 
         [0089]    This creates a virtual model of the abutment  403  which is defined by an implant surface  424  facing the implant and a restoration surface  425  facing the restoration, which are separated by the emergence profile  426  of the abutment. 
         [0090]    In the fourth step  454  a screw bore  407  is provided in the abutment. The screw bore is arranged co-axially with the implant axis and is designed to fit an implant screw (not shown) that is able to engage with the specific implant  402  so that the abutment  403  is held in place. 
         [0091]    Finally, in the fifth step  455 , the abutment is split across the emergence profile  426  into an abutment base  420  having a base emergence profile  430  and an abutment top  421  having a top emergence profile. By allowing the designer to freely apply this split, i.e. so that the assembly direction of the resulting abutment base and abutment top can be provided along an assembly axis B-B different from the implant axis A-A it is possible to place the abutting surfaces of the abutment base and abutment top as desired. This is advantageous in providing the optimal design, both in respect to aesthetic but also durability of the dental prosthesis, since the designer can place the split based on specific design requirements, e.g. material thickness, visibility etc. 
         [0092]    Materials for the respective parts can now be chosen. In some embodiments materials are chosen before designing the specific parts, or during the design steps. This allows the design software and designer to take material relevant aspects into consideration when designing. This could for example be minimum/maximum thicknesses for which material failure is avoided, e.g. in respect to breakage, curing etc. Other issues, such as manufacturing limitations may also be taken into consideration. 
         [0093]    It should of course be understood that the invention is not limited only to the steps and sequence of steps as discussed in the workflow  450  described above. For example, the abutment could be designed before the anatomy of the dental replacement is designed. Or the step of designing the crown could be left out and designed manually after the customised abutment has been placed in the implant. 
         [0094]    The final design may now be sent to manufacturing using manufacturing methods well known to the person skilled in the art such as milling, stereo-lithography or 3D-printing. 
         [0095]    Although some embodiments have been described and shown in detail, the invention is not restricted to them, but may also be embodied in other ways within the scope of the subject matter defined in the following claims. In particular, it is to be understood that other embodiments may be utilised and structural and functional modifications may be made without departing from the scope of the present invention. 
         [0096]    In device claims enumerating several means, several of these means can be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims or described in different embodiments does not indicate that a combination of these measures cannot be used to advantage. 
       REFERENCE NUMBERS 
       [0000]    
       
           101 . dental prosthesis 
           102 . implant 
           103 . one-piece customised abutment 
           104 . restoration 
           105 . bone tissue 
           106 . implant screw 
           107 . through-going bore 
           108 . threads 
           109 . neighbouring tooth 
           202 . implant 
           203 . two-piece semi customisable abutments 
           204 . restoration 
           220 . abutment base 
           221 . abutment top 
           230 . critical area 
           301 . dental prosthesis 
           303 . customised abutment 
           304 . restoration 
           305 . bone tissue 
           306 . implant screw 
           307 . through going bore 
           308 . threads 
           309 . neighbouring tooth 
           310 . gingiva 
           320 . abutment base 
           321 . abutment top 
           326 . abutment emergence profile 
           331 . tapering protrusion 
           333 . tapering recess 
           402 . implant 
           403 . abutment 
           404 . restoration 
           405 . bone tissue 
           407 . screw bore 
           409 . neighbouring tooth 
           410 . gingiva 
           420 . abutment base 
           421 . abutment top 
           422 . emergence profile 
           423 . surface split line 
           424 . implant surface 
           425 . restoration surface 
           426 . abutment emergence profile 
           440 . dental replacement 
           450 . workflow 
           451 . first step 
           452 . second step 
           453 . third step 
           454 . fourth step 
           455 . fifth step