Abstract:
An abutment is provided with a screw access hole and a slot in its sidewall adapted to allow a driver to access a screw in the screw access hole at an angle relative to a longitudinal axis of the screw. The abutment may include a screw seat and may be connected to an implant via a screw in the screw seat. A prosthesis, which may include a driver access channel that has a diameter less than the outer diameter of the drive portion of the screw, may be placed over the abutment. Methods of making a dental prosthesis and methods of attaching and removing the dental prosthesis from the implant are also disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 62/235,079, filed Sep. 30, 2015, the entire content of which is incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates generally to screw-retained abutments, and more particularly to screw-retained abutments with an off-axis feature, as well as methods of making and using the same. 
       BACKGROUND 
       [0003]    Edentulism, the condition of being toothless to some extent, may be treated by the implantation of a dental assembly. These assemblies require certain components to rest comfortably and securely in the patient&#39;s oral cavity. The implant fixture, also known as the dental implant or simply the implant, is the part of the dental assembly that becomes fused with the patient&#39;s jaw bone. The implant is available in both cylinder and screw-type varieties and is typically made from titanium or a titanium alloy. Implant abutments are screwed onto the implant and are positioned at and above the patient&#39;s gum line. Finally, a dental prosthesis is placed over the abutment and is designed to look and function like a natural tooth. 
         [0004]    Alternatively, the prosthesis may be formed over the abutment outside of the patient&#39;s mouth, and the combined prosthesis and abutment may then be affixed to the implant with a fixation screw. To install the abutment and prosthesis onto the implant and to access the fixation screw during repair and maintenance of the dental assembly, the prosthesis must contain a screw access channel. In known dental assemblies, this screw access channel can often reside at the labial side of the tooth or on the biting surface, which is not desired as a matter of strength and aesthetics. Additionally, in known dental assemblies, this screw access channel must be of large enough diameter to allow the screw to traverse the channel. However, as the diameter of the channel increases, the strength of the prosthesis becomes more compromised. Also, a fixation screw that may pass through the screw access channel of the prosthesis increases the risk that the screw may become dislodged and lead to swallowing the prosthesis and/or the fixation screw. 
         [0005]    Solutions to the problem of labial access to the fixation screw have been proposed. In one such dental assembly, the screw access channel resides on the lingual side of the prosthesis and is angled relative to the longitudinal axis of the implant. However, the screw access channel still requires a large enough diameter to allow the fixation screw to pass through the prosthesis. Additionally, this dental assembly contains a ceramic abutment affixed to a titanium implant, increasing the likelihood of crack propagation in the ceramic abutment during tightening of the fixation screw, which seats against the ceramic abutment. 
         [0006]    Therefore, there is a need for a dental assembly that addresses the present challenges and characteristics discussed above in regard to the screw access channel placement and the interface between the abutment and dental implant. 
       SUMMARY OF INVENTION 
       [0007]    To these ends, an abutment is provided with a screw access hole and a slot in its sidewall adapted to allow a driver to access a screw in the screw access hole at an angle relative to a longitudinal axis of the screw. The abutment may include a screw seat and may be connected to an implant via a screw in the screw seat. 
         [0008]    In another aspect of the invention, a dental assembly may include the abutment and a screw within the screw access hole of the abutment. Additionally, the dental assembly may include an implant adapted for connection to the abutment via the screw. A prosthesis, which may include a driver access channel that has a diameter less than the outer diameter of the drive portion of the screw, may be placed over the abutment. 
         [0009]    In another embodiment, a process for making a dental assembly includes designing the dental assembly to include a screw access hole and the slot in the sidewall of an abutment of the dental assembly and manufacturing the dental assembly. 
         [0010]    In another embodiment, a method of attaching a prosthesis to a dental implant is provided. The method includes assembling a fixation screw through a screw access hole of an abutment and then fabricating the prosthesis, which includes a driver access channel, over the abutment. The abutment may be aligned with the dental implant and a driver may be passed through the driver access channel and rotated to drive the fixation screw. 
         [0011]    In another embodiment, a method of detaching a prosthesis from a dental implant is provided. The method includes inserting a driver into a driver access channel of the prosthesis, which is affixed to an abutment, and rotating the driver to disengage a fixation screw from the dental implant. The abutment and prosthesis are then removed from the dental implant. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below serve to explain various aspects of the invention. 
           [0013]      FIG. 1  is a diagrammatic view of a prosthesis affixed to an abutment with a fixation screw inserted therein. 
           [0014]      FIG. 2  is a detailed view of an abutment. 
           [0015]      FIG. 3  is a diagrammatic cross-sectional view of a dental assembly with a driver engaged. 
           [0016]      FIG. 4  is a diagrammatic view of a driver. 
           [0017]      FIG. 5  is a diagrammatic view of a driver access channel analog. 
           [0018]      FIG. 6A  is a diagrammatic view of an abutment and fixation screw assembly with a coping affixed. 
           [0019]      FIG. 6B  is a diagrammatic view of an abutment, fixation screw, and coping assembly affixed to an implant analog. 
           [0020]      FIG. 6C  is a diagrammatic view of an abutment, fixation screw, coping, and implant analog assembly with a driver access channel analog included therewith. 
           [0021]      FIG. 6D  is a diagrammatic cross-sectional view of an abutment, fixation screw, and coping assembly. 
           [0022]      FIG. 7  is a diagrammatic view of a computer model of an implant, abutment, and prosthesis blank. 
           [0023]      FIG. 8A  is a diagrammatic cross-sectional view of a dental assembly. 
           [0024]      FIG. 8B  is a diagrammatic cross-sectional view of a dental assembly implanted in a patient&#39;s jaw. 
           [0025]      FIG. 8C  is a diagrammatic cross-sectional view of a dental assembly with a driver engaged. 
           [0026]      FIG. 8D  is a diagrammatic cross-sectional view of a dental assembly with a driver engaged. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    Although the invention will be described next in connection with certain embodiments, the invention is not limited to practice in any one specific type of dental assembly. The description of the embodiments of the invention is intended to cover all alternatives, modifications, and equivalent arrangements as may be included within the spirit and scope of the invention as defined by the appended claims. In particular, those skilled in the art will recognize that the components of the embodiments of the invention described herein could be arranged in multiple different ways. 
         [0028]    With reference now to the FIGS., a dental assembly  10  is shown with an implant  12 , an abutment  14 , and a prosthesis  16 . In  FIG. 1 , prosthesis  16  is shown with driver access channel  18  at an angle θ off the longitudinal access of fixation screw  20  and implant  12 , as best shown in  FIGS. 3 and 8B . A detailed view of the abutment  14  is shown in  FIG. 2 . In the embodiment shown, the abutment may include an optional anti-rotation feature  22  at the apical region  24  of abutment  14  that interfaces with engaging features of the implant at its coronal end (not shown) to position the abutment  14  radially. Similarly, coronal region  26  of abutment  14  may include an optional anti-rotation feature  22  that interfaces with engaging features (not shown) of the prosthesis  16 . Also, in the embodiment shown, the coronal region  26  of the abutment  14  may include grooves to improve securing, e.g. cementing, of the prosthesis  16  to the abutment  14 . 
         [0029]    Slot  28  in the sidewall  29  of abutment  14  allows a driver to access the fixation screw  20  at an angle. Such angular access allows for the placement of the driver access channel  18  on the lingual side of the prosthesis. 
         [0030]    Abutment  14  also includes cavity  30  with a height  32  corresponding to the height  34  of the screw  20 . In this way, the screw  20  may move upwardly when being disengaged from the implant  12  while the prosthesis  16  remains attached to the abutment  14 . Therefore, the screw  20  need not ever be completely removed through the prosthesis  16 , and the risk of inadvertent swallowing of the screw  20  during removal of the prosthesis  16  is decreased. Stated differently, the screw  20  may disengage the implant  12 , but may also be contained within the cavity  30  of abutment  14 . 
         [0031]    Referring still to  FIG. 2 , the abutment  14  may be dual colored. The abutment  14  has an apical portion  24  configured to be positioned within a gingival region of a patient&#39;s mouth, and a coronal portion  26  configured to support the prosthesis  16 . The apical portion  24  may be a first color, generally gingival-colored, and the coronal portion  26  may a second color different from the first color, generally tooth-colored. Such a dual-colored abutment allows for a more aesthetically pleasing installation. However, such dual coloring is optional. 
         [0032]    Although the embodiments discussed herein are drawn toward single-unit dental assemblies, it is also possible to adapt the present invention to multi-unit bridge dental assemblies. In such an embodiment, the anti-rotational features  22  of the abutment  14  are not engaged by the implant  12 . However, the cavity  30  of the coronal portion  26  of the abutment  14  is configured similarly to the cavity  30  of the single-unit dental assemblies. 
         [0033]    As shown in  FIGS. 3 and 4 , a conventional ball-point hex driver  36  may be used to drive fixation screw  20  through the abutment  14  and into the implant  12 . The driver  36  passes through driver access channel  18 , which may be sized such that driver  36  fits therethrough but screw  20  does not. Through the use of a ball-point hex driver  36 , the user may change the angle θ of the driver  36  as driver  36  is rotated to insert or remove the screw  20 . Alternatively, the user may hold the angle θ steady throughout the insertion and removal procedure. However, in applications where it is desirable to make the screw  20  removable, the radius  37  of driver access channel  18  may be widened to allow the screw  20  to pass fully therethrough. 
         [0034]    The dental assembly may be made through two main steps. First, conventional or digital processes may be used to design the dental assembly, which will be unique to each patient and application. Then, the dental assembly may be manufactured either via conventional manufacturing techniques modified to include the driver access channel  18  or through computer-aided manufacturing techniques. 
         [0035]    Turning now to  FIGS. 5-6D , the prosthesis  16  may be formed by a modification to conventional methods. First, the dental professional makes an impression of the patient&#39;s oral cavity using conventional transfer techniques. Then, a stone model of the patient&#39;s jaw bone is created, including an implant analog  38  replicating the exact implant  12  orientation and height. Then the dental professional assembles abutment  14  onto implant analog  38  with screw  20 , ensuring that slot  28  in the sidewall  29  of abutment  14  is oriented at the desired position. A coping  40  is placed onto abutment  14 , again ensuring alignment of coping slot  42  in the sidewall  43  with abutment slot  28 . An access-channel plug  44  may be placed into slots  28 ,  42  at the desired off-axis angle  8 . The access-channel plug  44  will represent the driver access channel  18  within the completed prosthesis  16 . Acrylic wax may then be placed around the coping  40  and access channel plug  44 , and the plastic coping  40  may be modified as needed to create the desired prosthetic shape. Standard laboratory processes may be used to fabricate the prosthesis from the wax inverse negative thus formed. As a result, the formed prosthesis will contain a driver access channel  18  of the same diameter as the shaft  46  of access-channel plug  44 , and screw  20  will be contained within abutment  14  in such a manner that it may not pass through the driver access channel  18  and is contained within the cavity  30  of abutment  14 . Driver access channel  18  may thus have a generally elliptical shape with a long axis  45  and a short axis  47 , as best shown in  FIG. 1 . The long axis  45  is configured to allow the driver  36  to move along the driver access channel  18  to contact the screw continuously during rotation of the driver  36 . 
         [0036]    Alternatively, prosthesis  16  may be formed using a digital workflow procedure. First, the dental professional conducts an intra-oral or impression scan using digital impression techniques. The data thus generated are imported into software that determines implant or abutment height as well as the required orientation of the engaging features. This or other software may then be used to determine the correct linear, axial, and rotational location of the dental assembly components, including the desired location and orientation of the side feature  28  of abutment  14 . Software also designs the prosthesis with an appropriate off-axis drive access channel. Finally, the prosthesis is fabricated following computer-aided manufacturing procedures. 
         [0037]    An exemplary computer-aided manufacturing process using a 3SHAPE® CAD/CAM system is provided for further illustration. First, data obtained from either an intra-oral or impression scan of the patient&#39;s oral cavity are imported into the CAD system. Then, a computer model of the implant  12  and abutment  14 , the abutment  14  having a slot  28  in its sidewall  29 , is combined with a computer model of a prosthesis blank  49  in silico. The prosthesis blank  49  includes a scan adapter flat  51  that is aligned with the slot  28  in the sidewall  29  of the abutment  14 . See  FIG. 7 . The implant  12 , abutment  14 , and prosthesis blank  49  are placed within a visual depiction of the patient&#39;s oral cavity in the appropriate location, with the scan adapter flat  51  aligned in the desired direction of the off-axis driver access channel  18 . The angle of this off-axis driver access channel  18  may be modified, as desired, in silico. The design software can then be used to transform the prosthesis blank  49  into an appropriate prosthesis  16  that includes the off-axis driver access channel  18 . 
         [0038]    Once the design of the dental assembly  10  is complete, the actual prosthesis  16  may be formed from a milling process using the data obtained from the CAD software. The milled prosthesis  16  may then be attached to an abutment  14  and implant  12  using cement, for example. It may be beneficial to insert an access channel plug  44  into the off-axis driver access channel  18  during the attachment of the prosthesis  16  to the abutment  14  to protect the screw  20  from the cement. Indeed, the access channel plug  44  may be used to align the prosthesis  16  by inserting the access channel plug  44  into the head  50  of the screw  20  and then passing the prosthesis  16  over the access channel plug  44  and onto the abutment  14 . Once the prosthesis  16  is formed and attached to the abutment  14  and implant  12 , the resulting dental assembly  10  may then be placed inside the patient&#39;s oral cavity. 
         [0039]    Turning now to  FIGS. 8A-8D , dental assembly  10  may be assembled as follows. Implant  12  may be installed in the patient&#39;s jaw  48  using conventional procedures. Pre-assembled abutment  14  and prosthesis  16 , which contains fixation screw  20 , may be aligned with implant  12 . Driver  36  may be used to drive fixation screw  20  through abutment  14  and into implant  12 . Conveniently, head  50  of screw  20  may rest in screw seat  52  of abutment  14 . Screw seat  52  may be formed from titanium or some other similarly strong metal, thus reducing the risk of deformation or cracking during the screw tightening procedure. Removal of the prosthesis may then be accomplished by the reverse of the installation procedure detailed above. 
         [0040]    While the present invention has been illustrated by the description of one or more embodiments thereof, and while the embodiments have been described in considerable detail, they are not intended to restrict or in any way limit the scope of the appended claims to such detail. The various features shown and described herein may be used alone or in any combination. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and method and illustrative examples shown and described. Accordingly, departures may be from such details without departing from the scope of the general inventive concept.