Abstract:
A system including a method and associated structures creates efficiencies in the manufacture of prosthetic tooth support frameworks. Pre-manufactured teeth with matching internal keys are used in the setup of a patient prototype. Each key includes a shaft, a cervical platform, a retention knob and preferably at least one channel for the expulsion of excess adhesive fluid. The cervical platforms are shaped to provide intimate contact with a base of their respective tooth. The same tooth/key pairs are then used to make a framework pattern from the setup positioning. The pattern can be cast or scanned for direct machining to produce the finished framework.

Description:
RELATED APPLICATION 
       [0001]    This patent application is a continuation of co-pending application Ser. No. 15/191,868 entitled “DENTAL PROSTHESIS AND METHOD OF ITS PRODUCTION UTILIZING STANDARDIZED FRAMEWORK KEYS AND MATCHING PREMANUFACTURED TEETH ” filed Jun. 24, 2016 and a continuation of co-pending patent Ser. No. 14/495,036 filed Sep. 24, 2014, entitled “DENTAL PROSTHESIS AND METHOD OF ITS PRODUCTION UTILIZING STANDARDIZED FRAMEWORK KEYS AND MATCHING PREMANUFACTURED TEETH”, which is a divisional of patent application Ser. No. 13/343,566, now U.S. Pat. No. 8,875,398, entitled “Dental Prosthesis and Method of its Production Utilizing Standardized Framework Keys and Matching Premanufactured Teeth” filed Jan. 4, 2012, priority from which is hereby claimed. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to frameworks for dental implant-supported prostheses produced either by conventional dental laboratory procedures including CAD/CAM or by virtual technology. More specifically, it relates to a framework using a uniquely designed set of prosthetic teeth and internal abutments specific to the individual tooth position. 
       BACKGROUND OF THE INVENTION 
       [0003]    A framework for a dental prosthesis as shown in  FIG. 4  is a unified metal or ceramic base structure consisting of a horizontal beam on which vertical posts, specific to the teeth they support are rigidly connected. This framework can be supported by dental implants placed in the jawbone. Such a framework is securely fixed to the jaw by screwing or cementing it onto the implants. The framework supports the specifically designed replacement teeth which are fused to the posts of the framework with a luting cement. The prosthesis containing this framework is patient-specific and must meet the strict requirements of accuracy to reach an optimal fit at the prosthesis/implant interface to distribute chewing and grinding forces appropriately to the underlying jawbone and avoiding high stresses to the underlying bone which could cause implants to deintegrate from the bone. The fit of the framework to the supporting implants should be 50 microns or less. Because the framework is capable of replacing all the teeth in a dental arch, and because the framework connects the occlusal surfaces of the replacement teeth to the osseointegrated dental implants, the dimensions of the framework are generally larger in comparison to traditional dental prostheses like crowns and tooth-supported bridges. The framework is designed to support not only replacement teeth but also the bone and gum tissue that previously immediately surrounded the missing teeth. 
         [0004]    The traditional or conventional dental laboratory method for creating these frameworks is based on the manual design of a physical model of the framework in wax or resin and the production of the framework by means of lost wax casting or copy milling. These previous methods of framework production can be highly precise however they require very skilled dental laboratory technicians doing time-consuming modeling of the frame, a process that is inefficient and costly. The traditional lost wax process is very lengthy and highly labor intensive, consisting of many manual steps that include the design, manual contour and fabrication of the wax pattern, investing the pattern in a refractory mold, melting and evaporating the wax pattern in a high temperature burn out oven over many hours, melting the metal and casting it into the pattern mold, devesting the solidified metal framework and refining the surface of the framework to permit the next phase to begin. A current alternative to the lost wax casting method of framework construction is the use of CAD/CAM technology to scan the wax or resin pattern frame and robotic ally mill a precise copy of the pattern. Framework production by virtual technology is available but its ability to create tooth support mechanisms is limited. 
         [0005]    Following completion of the metal or ceramic framework, impressions of that framework are made and stone casts are produced to replicate the metal framework. These casts are then cut into sections providing individual stone dies being replicas of the vertical tooth support portion of the framework pattern, upon which individual teeth are manually created from wax relying on the artistic skill of the dental technician. These individual teeth may then be either scanned or copy milled in a tooth colored material. These steps of custom fabrication of the individual prosthetic teeth are eliminated by the present invention thus avoiding time-consuming and highly skilled labor required of the dental technicians and ceramists. Furthermore, later if a tooth needs to be replaced because it has become worn or chipped, the above-described process must be repeated to provide a replacement for that tooth. There is therefore a need in the dental arts for a method of prosthesis production which is less time-consuming and labor-intensive and which requires less skill. Further, there is a need for such a system which can also provide the highest quality result for the patient. 
       SUMMARY OF THE INVENTION 
       [0006]    In order to meet the needs in the art described above, the present invention has been devised which for the first time provides a rapid and precisely accurate method of prosthesis production that is highly repeatable, requiring limited technical ability by dental technicians. 
         [0007]    This is achieved by a simplified system for the production of the final implant-supported prosthesis by using the identical tooth set that was used at or shortly after the surgical placement of the implants for the provisional temporary prosthesis. By using the identical tooth set of the final prosthesis, the provisional prosthesis becomes the prototype for the position of the teeth in the final prosthesis. This position can be recorded manually with a variety of indices or virtually by scanning the provisional teeth. In an optional more advanced adaptation of the invention, individual tooth data files can be incorporated into software systems to accelerate the process by virtual construction of the framework followed by CNC copy milling. It also provides “off the shelf’ future replacement teeth that will fit the vertical framework supports precisely should tooth wear or fracture occur with patient natural function. 
         [0008]    As further described in greater detail herein, the present invention provides premanufactured prosthetic teeth available in resin, ceramic, or wax, with highly specific and precise matching internal struts (hereinafter “keys”) that are use to support the teeth when affixed to the horizontal beam of the unified framework. Once the tooth arrangement selected from a library of individual teeth has been determined to be positioned appropriately for individual patient function and appearance, this setup position of the teeth is recorded either physically or digitally. Based on the position of the teeth with the vertical keys still occupying each individual tooth (hereafter “keyed teeth”), the keyed teeth pairs are easily and quickly connected to the horizontal beam during its formation with a wax or resin or connected virtually in a computer design system containing the specific files for the tooth matching vertical keys. 
         [0009]    Once the properly positioned keyed teeth have the keys attached to the horizontal beam, the teeth are removed from the keys revealing the completed pattern. This pattern, either wax or resin, can then be invested and cast using traditional dental laboratory methods, or it can be scanned and the file transmitted to a CNC milling machine for the production of the metal or ceramic framework. Whether cast or milled, the present framework is composed of a very rigid and highly precise metal or ceramic that is biocompatible and capable of resisting complex heavy loading forces applied to the specific individual teeth, providing long term functionality required by implant-supported prostheses. 
         [0010]    When the framework is completed, the previous set of keyway teeth can be installed onto the framework and fused to the frame with a luting cement. The prosthesis is then completed with the application of pink gingival resin or composite material. Replacement of teeth on the framework will be precise and accurate due to the high level of fit of the individual teeth to the vertical keys. 
         [0011]    In general terms the invention may be described as a method for producing a prosthetic tooth support framework including a horizontal beam, vertical support struts and implant prosthetic connectors comprising the steps of: 
         [0012]    constructing a working model of at least a portion of a human dental arch; 
         [0013]    arranging pre-manufactured teeth on said model to create a prototype setup representing a finished prosthesis, said teeth each including an axial internal keyway for receiving a key; 
         [0014]    inserting a plurality of keys into a closely fitting keyway of the teeth forming keyed tooth 
         [0015]    pairs, an attachment portion of each key extending from a base of each tooth;
       holding said keyed tooth pairs in a setup location adjacent a dental arch defined by said       
 
         [0017]    model, said model including implant prosthetic connectors; 
         [0018]    affixing said key attachment portions onto a horizontal beam and said implant prosthetic connectors while held in said setup location during the formation of a beam assembly; 
         [0019]    removing the teeth from the beam assembly leaving a framework pattern; and 
         [0020]    constructing a finished prosthetic tooth framework using said beam assembly as a pattern, the pattern keys each matching the configuration and location of the permanent teeth support struts of said finished framework. 
         [0021]    The present invention may comprise a free-standing one-piece key utilized in forming a pattern for a prosthetic framework strut that may be affixed upon one or more implants or implant abutments within a prosthetic tooth, the key comprising a shaft having a coronal aspect at a coronal end of the shaft, a retention knob at an opposite end of the coronal end, the retention knob having a width greater than that of the shaft and the shaft at the coronal end being configured to fit within a socket of a tooth comprising an axial internal keyway, a cervical platform between the retention knob and the coronal end, and comprising a supporting base of the key, the cervical platform further having circumference configured to support a cervical aspect of the tooth. The key may include an elongate channel extending along a surface of the shaft to cervical platform for the expulsion of excess adhesive fluid, wherein said channel may be an axial groove that forms a release opening at a margin between the tooth and the cervical platform, forming a release opening at a margin between the tooth and the cervical platform. The shaft may inwardly tapered from said platform toward the coronal aspect of the key. The retention knob of the key may be a spheroid or other shapes that are greater than diameter or width of the shaft. The shaft may resemble a triangular prism. 
         [0022]    The present invention may further comprise a vertical strut component to be disposed between a prosthetic framework model and a socket of a prosthetic tooth socket, the strut comprising an elongate shaft having a coronal aspect at a first end of the shaft, a retentive element at a second end of the shaft, the retention element having a width greater than that of the shaft so that it may be mechanically fitted within a prosthetic frame work model, and the coronal aspect being configured to fit within a socket of a tooth comprising an axial internal keyway, a cervical platform between the first and second end having a width greater than the shaft and being configured to support a cervical aspect of the prosthetic tooth, an elongate channel extending along a surface of the shaft to cervical platform for the expulsion of excess adhesive fluid, wherein said channel is an axial groove that forms a release opening at a margin between the tooth and the cervical platform. The shaft may comprise a second elongate channel on an opposite side of the shaft, so that a cross-section of the shaft having an elongate channel and a second elongate channel generally resembles the letter 
         [0023]    This prosthesis construction has many advantages over traditional dental laboratory methods for framework production. These advantages include but are not limited to the following: 1) significant reduction in the time for the labor intense design, 2) fabrication of the framework pattern is simplified by the use of the keys due to the use of standardized key way teeth, 3) technician skill required is reduced due to the simplified pattern fabrication, and 4) maintenance of the implant-supported prosthesis is easier because the replacement teeth are cataloged and the replacement teeth can still be modified or customized to meet specific patient requirements. 
         [0024]    Accordingly, it is the main object of the present invention to provide a procedure and method for the production of a high-strength biocompatible dental implant-supported framework with individually specific vertical keys to support sets of individual prosthetic teeth in a timesaving and labor-saving system. 
         [0025]    It is a further objective to produce these frameworks manually with traditional dental laboratory (lost wax), copy milled or constructed virtually so that the resultant framework will have a precision fit to the implants of less than 50 microns. 
         [0026]    It is another object of the present invention is to offer a diversified system that consists of prosthetic teeth in various shapes, sizes and colors that can be used with a manually built framework pattern. 
         [0027]    Another object of the present invention is to provide an implant-supported prosthesis that permits the cementation of selected prefabricated teeth onto a framework, thereby eliminating the custom fabrication of individual teeth by dental technicians. 
         [0028]    Yet another object of the present invention is to provide a method of easy tooth replacement in the future for patients who have worn or chipped a tooth or a portion of the prosthesis through natural function or accidental trauma. 
         [0029]    In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. 
         [0030]    As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods, and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]      FIG. 1 a    is a diagram showing the process of utilizing the invention. 
           [0032]      FIG. 1 b    is a diagram showing the process of utilizing the invention. 
           [0033]      FIG. 2  is a top rear isometric view of a patient model. 
           [0034]      FIG. 3  is a left side elevation view of a prototype setup built on the model. 
           [0035]      FIG. 4  is a top front isometric view of a typical dental prosthetic framework. 
           [0036]      FIG. 5  is a front isometric view showing a full set of keys and keyway teeth. 
           [0037]      FIGS. 6 a  and 6 b    are elevation views showing the assembly of a keyed tooth pair. 
           [0038]      FIGS. 7 a , 7 b  and 7 c    are isometric views showing detail of the keys. 
           [0039]      FIG. 8  is a rear view showing a matrix impression taken from the model and setup. 
           [0040]      FIG. 9  is a rear view showing keyed teeth held in the matrix. 
           [0041]      FIG. 10 a    is a left side top rear isometric view showing the keyed teeth molded into the horizontal beam supported by the matrix. 
           [0042]      FIG. 10 b    is a top rear isometric view of the horizontal beam, keyway teeth and keys on the module with the matrix removed. 
           [0043]      FIGS. 11 a , 11 b , 11 c  and 11 d    are isometric views showing the use of key protector caps in completing the horizontal beam portion of the framework pattern. 
           [0044]      FIG. 12 a    depicts a completed framework pattern. 
           [0045]      FIG. 12 b    shows the final casting resulting from the pattern of  FIG. 12   a.    
           [0046]      FIG. 13  is an isometric assembly view of the teeth being assembled to the completed framework. 
           [0047]      FIG. 14  is an exploded view from the anterior side of inventive key used in the framework system, 
           [0048]      FIG. 15  shows an embodiment of the keyway system from  14 , with an isolated view of the key being mounted with a prosthetic tooth, 
           [0049]      FIGS. 16-18  illustrates an embodiment of invention depicting side, top and perspective views of an inventive key. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0050]    A step-by-step process showing the methodology and use of the novel structures comprising the invention is depicted in  FIG. 1 . Referring now to  FIG. 2 , the process begins as in current practice with the patient first receiving osseointegrated implants. From an impression of the implants including connectors, a working cast or model  10  is produced. As depicted in  FIG. 3 , a setup using keyway teeth  17  built on the completed working model  10  can be kept in the mouth of the patient for possible adjustments. This completes a prototype of the finished prosthesis. This is similar to current practice but with the use of novel keys and keyway teeth to form the setup, which keys and keyway teeth then are used to construct the vertical struts of the framework in the next steps of the invention. These further steps comprise designing a tooth-supporting framework which includes vertical keys positioned to hold their respective keyway teeth prescribed by the setup. 
         [0051]    Referring now to  FIG. 4 , one goal of the invention is to produce a framework of this type. The basic elements of the inventive framework are the keys  11 , a supporting horizontal beam  13  and implant connectors, in this example, cylinders  15  on the opposite side of the beam. The horizontal beam  13  is an intermediate connecting structure in the framework pattern or final frame, either metal or ceramic, parallel to the bite plane that unites the vertical keys supporting the teeth on one side and the implant prosthetic cylinders that connect underlying dental implants on the other side. The construction of the implant side of the horizontal beam follows current practice and therefore need not be discussed in detail. As further described herein, the main features of the invention are the keyway teeth and keys and the method by which they are employed to create the teeth-supporting abutments of a finished framework. 
         [0052]    Referring now to  FIG. 5 , the keyway teeth  17  of the invention are full anatomic prosthetic teeth made of a variety of materials such as acrylic resin, composite, ceramic or wax. They are specifically designed for implant-supported prosthesis and are catalogued in a similar way that denture teeth are used in current fixed and removable prosthetics. Keyway teeth are so named because they have specific vertical keyways or sockets  18  inside the teeth which intimately receive specially designed pattern keys  19  as further described below and as shown in  FIGS. 6 a  and 6 b    and  FIGS. 7 a , 7 b    and  7   c.    
         [0053]    The keyway teeth are preferably coated with an opaque layer for color control and are cataloged in various shapes and sizes available in numerous shades (colors) just as any traditional denture tooth line. Each different tooth geometry is provided in the above materials. 
         [0054]    The position of the prosthetic screw access channel may dictate the selection of the material used for a given keyway tooth position. By way of example, if the prosthetic screw access channel is directly through the occlusal table of the molar, it may be advantageous to use the wax version of that keyway tooth. The wax keyway tooth can be modified with a hole to provide direct access to the prosthetic retention screw. After modification, the wax version of the keyway tooth can be invested and finalized with a pressed ceramic. In another example, if the prosthetic screw access channel impinges on the cervical margin of the keyway tooth, it may be advantageous to use the green state tooth with appropriate marginal adaptation to accommodate the screwdriver access to the retention screw. Following adaptation would be the crystallization of the green state to a solid ceramic keyway tooth. The keyway teeth also have a cervical groove  50  to aid in retention as a mechanical interlock with the gingival veneering material once the tooth is luted to the framework in a final step in the process shown in  FIG. 13 . 
         [0055]    As shown in  FIGS. 6 a  and 6 b    and with further detail in  FIGS. 7 a , 7 b  and 7 c   , the pattern keys  19  are vertical struts of various configurations that each fit precisely within the socket of a designated keyway tooth  17 . The pattern keys are one of the most important aspects of the present invention. They comprise the following structural features: a retention knob  21  at a base end, a cervical platform  23  adjacent the retentive knob and an elongate tapered shaft  25  extending axially from the platform terminating at an opposite end  27  forming the coronal aspect of the key. The shaft is tapered from the cervical platform to the coronal aspect for optimal cement retention of the keyway tooth. As shown in  FIG. 7 c   , the shaft preferably includes at least one cement release channel  33  which are formed by one or more axial grooves which lie along opposing surfaces of the shaft. Two channels are depicted in this embodiment ( 31 ,  33 ). This embodiment depicts an “H” cross section configuration of the shaft, however it should be understood that various shapes may be employed so long as there are no sharp edges along the surface of the key. The cement release channels run from the coronal aspect of the key to the edge of the cervical platform. The purpose of the channel(s) is to relieve hydraulic back pressure and permit the expulsion of flowable cement or other luting agents when the keyway tooth is fastened to the final unifying framework. The cervical platform  23  is the supporting base of the key that supports the cervical aspect of each keyway tooth. Incorporated into the lingual aspect of the platform is a portion of the cement release channel  33 . The platforms shown are concave but may be any shape so long as it provides an intimately mating surface with the base of the tooth. The retentive knob provides a structural linkage to the horizontal beam by molding into the beam material as it is being formed. The keys are anti-rotational inside the keyway teeth so that only one position of fit exists. The keys are preferably made of a moldable and adjustable material that is chemically compatible with traditional resins and composites when they are connected to adjacent keys and the implant prosthetic cylinders to build the horizontal beam. The junction of all geometric planes of the keys should be round, avoiding any sharp angles. 
         [0056]    One of the main advantages of the present invention is that it can utilize more commonplace dental laboratory skills and equipment or alternatively can be utilized with technologically advanced optical scanning. This makes the invention available to the greatest number of users. This more commonplace practice will now be discussed. 
         [0057]    Once the tooth setup position has been determined, that position is recorded manually with laboratory indices or virtually in computer programming to dictate the position of the individual teeth and keys as depicted in the layout shown in  FIG. 3 . An impression is then taken of the setup to create a facial matrix  41  positioned on the model  10  as shown in  FIG. 8 . 
         [0058]    The matrix has pockets  43  that can hold each of their respective teeth in its proper position while leaving the bottom portions of the teeth exposed as shown in  FIG. 9 . During this step in the process, the keys  19  remain in the sockets of their respective teeth  17 . The retentive knob attachment portion of the keys extends from the base of each tooth and with the platform portion of the key in intimate contact with the base of the tooth. The matrix-supported keyed teeth are then held in juxtaposition with the implant connectors of the patient modeling. 
         [0059]    Referring now to  FIG. 10 a   , the retentive knobs of the keys are then joined to the implant prosthetic cylinders and to one another during the formation of the intermediate horizontal beam and supported in the setup location by the matrix  41  on the model. After the resin is set, the matrix is removed as shown in  FIG. 10 b   . Half of the teeth in this illustration are removed to reveal the pattern keys. 
         [0060]    Referring now to  FIG. 11 , the process continues with more modifiable resin material added to complete the horizontal beam portion of the framework using protective caps  35  as shown in  FIGS. 11 a , 11 b , 11 c  and 11 d   . The protective caps  35  are installed on the keys  11  prior to the addition of the additional material  37  used to reinforce and contour the horizontal beam. The purpose of the protective caps is to prevent contamination of the keys by excess resin which could distort the pattern and prevent complete seating of the tooth on the final framework. 
         [0061]    The horizontal beam assembly  13  is then removed from the model and the teeth removed from the keys. The remaining structure is refined providing the pattern depicted in  FIG. 12 a    for constructing the final framework shown in  FIG. 12 b    which can be constructed from the pattern using a variety of methods, such as: 
         [0062]    a) Traditional lost wax technique where the framework pattern is invested, burned out and metal is cast into the mold, or 
         [0063]    b) Copy milling using scanning technology where the framework pattern is scanned and data files are developed and transmitted to robotic milling machines for the milling of the final framework from a variety of solid materials (metal or ceramic by example). 
         [0064]    As an option, the above-described procedure following the finished setup can be replaced by more advanced technology which permits the virtual construction of the framework from an optical scanning of the finished setup. In concert with the use of computer software which includes the three-dimensional characteristics of virtual keys that correspond to the individual scanned teeth in the setup, the location and orientation of the keys is then combined with a framework pattern that creates a file which is then copy milled by a CNC milling machine to create the final framework. 
         [0065]    When prosthetic retention screws have their access channel coming through any portion of the keyway tooth, that tooth (either in wax or green state) will be manually or virtually modified to permit screwdriver access to the head of the screw. Acrylic, wax and green state keyway teeth may be modified or customized to accommodate the opposing occlusion, or individual cosmetic patient requirements. 
         [0066]    With the final framework  52  completed, the selected teeth are cemented to the metal or ceramic framework as shown in  FIG. 13  and the gingival veneering material is then applied to complete the prosthesis construction. A cervical groove  50  in the keyway tooth will be covered with the gingival veneering material, providing additional stability and retention of the tooth to the final framework. 
         [0067]    Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention. For example, this invention can be applied to totally or partially edentulous patients being restored with osseointegrated dental implants.