Patent Publication Number: US-2010112527-A1

Title: Method for fabricating an implanted dental restoration

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Provisional Patent Applications No. 61/110,594 and 61/110,596 both filed Nov. 2, 2008, the entire disclosures of which are hereby incorporated by reference and relied upon. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method for constructing a dental restoration which is retained within the mouth of a patient through the use of implanted devices. 
     2. Related Art 
     The techniques and hardware used for implant dentistry continue to develop steadily. In general, the process of providing dentition based upon implants begins with a visit by a patient to a dentist or oral surgeon, who places one or more implants within the desired structure, such as a mandible. Once the implants have become integrated with the patient&#39;s bony matrix, the patient visits his or her dentist, wherein the process of constructing the restoration device begins. 
     Typically, a problem faced by dentists in executing an implant-based restoration arises from the fact that it is very difficult to assure that the central axes of each of the implants processed by the oral surgeon are in fact parallel to one another. This is important because implants have threaded cavities into which denture attaching abutments are placed, and if the lack of parallelism between abutments is extreme, it may be difficult, if not impossible, to insert a denture without considerable angular adjustments to the fastenings which are affixed to the screwed-in abutments. This lack of angularity requires dentists to cement angular adjusting devices to the abutments, while working inside the patient&#39;s mouth. This is undesirable because achieving the desired parallel orientation may be very time consuming, and also requires the handling of exceedingly small parts within the confines of the mouth. 
     Although it has been recognized for some time that it would be desirable to provide a way of processing the fabrication of a restorative device outside the patient&#39;s mouth, this has not generally been possible because the screw-mounted nature of the abutments used in such restorations allow, by their very nature, the abutments to turn to whatever rotational position in 360° they are placed. Although each abutment is limited to a single position in which it is thread locked against the insert into which the abutment is mounted, it has not been possible to precisely position implant analogs in a dental model which is poured up, typically of plaster in a laboratory, so as to allow the abutments and any hardware attached to them to be precisely oriented at the angle required to allow the denture to be fitted to the patient. 
     It would be desirable to provide a method by which hardware for mounting a denture, and specifically abutments for mounting a denture or other restoration device within a patient&#39;s mouth, may be precisely angularly oriented, while allowing accurate replication of the orientation within the patient&#39;s mouth in the laboratory, thereby permitting almost the entire fabrication process to occur in the more favorable laboratory environment, rather than to be more or less evenly divided between the first steps taken within the patient&#39;s mouth and steps taken in the laboratory. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the present invention, a method for fabricating an implant-based dental restoration includes threadedly fixing an abutment analog into a dental implant contained in a patient&#39;s mouth, and taking an impression of the patient&#39;s mouth, including the abutment analog. The finished impression is then removed from the patient&#39;s mouth and the abutment analog is also removed from the patient&#39;s mouth. An implant analog is threadedly fixed to the abutment analog and the abutment analog is placed into a space defined by the abutment analog in the finished impression. 
     As used herein, the term “abutment analog” means an abutment base combined with an impression coping. This device is said to be an abutment “analog” because it substitutes, or is a surrogate, for the abutment actually used to attach a dental restoration device, such as a denture or bridge, to the patient&#39;s dental implants. Also, the term “implant analog” means a device which closely resembles an implant within a patient&#39;s mandible, for example, but is used within a model of the patient&#39;s oral structure to allow the dental lab to precisely construct the dental restoration device in the laboratory. The implant analog, when attached to the abutment analog, allows a model of the patient&#39;s lower jaw to be poured in plaster, for example, including the implant analog which simulates an implant device carried in the patient&#39;s mandible or other bony structure. 
     According to another aspect of the present invention, a method further includes tightening an abutment analog to a dental implant with a torque wrench, and tightening an implant analog to an abutment analog with a torque wrench. The use of a torque wrench to tighten the abutment analog to the dental implant and to tighten the implant analog to the abutment analog assures that the rotational or angular orientation of the implant analog matches the angular orientation of an implant actually carried within the patient&#39;s mouth. 
     According to another aspect of the present invention, the present method further includes fabricating a model of the patient&#39;s dental configuration from an impression, including the implant analog, and fabricating a dental restoration device using the fabricated model including the implant analog. Finally, the fabricated restorative dentition is affixed to the patient using at least one, or usually more, dental implants. These are the implants which participated in the impression-making part of the process. 
     According to another aspect of the present invention, a method for fabricating an implant-based dental restoration includes attaching an abutment analog to a dental implant contained in a patient&#39;s mouth, with the abutment analog being angularly indexed to the patient, and taking an impression of the patient&#39;s mouth, including the abutment analog. Then, the impression is removed from the patient&#39;s mouth and the abutment analog is also removed from the patient&#39;s mouth. The abutment analog is placed into a space defined by the abutment analog in the impression, with the implant analog first being attached to the abutment analog in an indexed angular position which is the same as the indexed position used for attaching the abutment analog to the implant. 
     According to another aspect of the present invention, a method for fabricating an implant-based dental restoration includes affixing an abutment analog including an abutment base and an impression coping which is attached and indexed to the abutment base, to a dental implant contained in a patient&#39;s mouth, with the abutment analog being angularly indexed to the implant. Then, an open tray impression is taken of the patient&#39;s mouth, including the abutment analog. The impression, including the impression coping portion of the abutment analog, is removed from the patient&#39;s mouth. Then, the abutment base is removed from the patient&#39;s mouth. An implant analog is then attached to the abutment base, in an indexed angular position which is the same as the indexed position used for attaching the base to the implant, and the abutment base and implant analog are reattached and reindexed to the impression coping 
     According to another aspect of the present invention, the abutment base bears a plurality of unique angular indexing indicia which are registrable with a set of unique angular indexing indicia borne by the impression coping. 
     It is an advantage of the present method that an implant based dental restoration device may be fabricated completely in a dental laboratory, without the need for a dentist and patient to engage in cementing or fastening of angled abutment bases while working within the patient&#39;s mouth. 
     It is another advantage of a method according to the present invention that chair time of both the dentist and the patient will be saved because of the absence of the need to assemble angular correction hardware within the patient&#39;s mouth. 
     It is yet another advantage of a method according to the present invention that cost is controlled because it is more efficient to utilize a laboratory build a dental restoration device in its entirety, rather than requiring a dentist to do a portion of the construction, which is then handed off to the laboratory, and subject to errors of measurement and angularity. 
     Other advantages, as well as features of the present invention, will become apparent to the reader of this specification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partially schematic representation of a dental restoration device which is implant based and which is mounted to the mandible of a patient. 
         FIG. 2  is an abutment analog for use with a closed tray impression. 
         FIG. 3  is similar to  FIG. 2 , but shows the abutment analog in an exploded view. 
         FIG. 4  is similar to  FIGS. 2 and 3 , but shows an abutment analog, and a dental model, in a partially sectional view. 
         FIG. 5  illustrates an assembled abutment analog for use with an open tray impression. 
         FIG. 6  shows the abutment analog of  FIG. 5  in an exploded presentation. 
         FIG. 7  shows the abutment analog of  FIGS. 5 and 6  in section. 
         FIG. 8  is a process flow diagram for using the closed tray abutment analog of  FIGS. 2 ,  3  and  4 . 
         FIG. 9  is a process flow diagram for use with the open tray abutment analog of  FIGS. 5 ,  6  and  7 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in  FIG. 1 , an implant-based dental restoration includes an implant,  20 , which is shown as having been placed within a patient&#39;s mandible,  16 . As shown in  FIG. 1 , the center axis, A 1 , of implant  20  is not parallel to the center line, or more precisely, the central plane, C L , of the patient&#39;s mandible. In other words, implant  20  is at an angle to an imaginary central plane, C L , extending through the patient&#39;s mouth. This lack of parallelism is not desirable, and is typically corrected through the use of hardware further described herein. The dental restoration also includes an abutment base,  22 , which is threaded into internal threads,  24 , carried within implant  20 . Abutment base  22  provides a mounting location for a geometric compensator  32 , which corrects for the angular mismatch between axis A 1  of implant  20  and center line or plane C L  of the patient&#39;s mouth. Geometric compensator  32  allows the axis, A 2 , of a pressure sensitive fastening,  36 , which is attached to geometric compensator  32 , to be parallel with C L , thereby assuring the ease of attaching of a dental restoration device,  12 , including a prosthetic tooth,  18 , to the patient. 
     Plastic insert  35  holds geometric compensator  32  within a cup-shaped retainer,  34 , which is mounted permanently within dental restoration device  12 . Because geometric compensator  32  is itself an angle correction device, it is critical that the rotational orientation of abutment base  22  be accurately maintained throughout the process of fabricating and fitting restoration device  12 . This is accomplished by maintaining the thread timing of abutment base  22  according to the present invention. It will be appreciated that inadvertent rotation of abutment base  22  about its threaded axis would likely cause the angular correction otherwise produced by geometric compensator  32  to be lost, which would effectively destroy the function of compensator  32 , while rendering fitting of the completed restoration device a very difficult proposition for both the dentist and the patient. 
       FIGS. 2 ,  3  and  4  show a closed tray abutment analog,  69 , which includes an abutment base,  28 , having an internal thread  50 , which is engaged by a threaded fastener,  78 . Fastener  78  passes through a bore,  74 , formed in a closed tray impression coping,  70 , for the purpose of attaching impression coping  70  to abutment base  28 . Abutment base  28  has a shank,  40 , with threads  44 , which allow abutment base  28 , and, therefore, abutment analog  69 , to be threadedly fixed into a dental implant,  20 , contained in a patient&#39;s mouth ( FIG. 1 ). Because screw threads are used on shank  40 , as well as within implant  20 , the act of threadedly engaging abutment analog  69  with implant  20  will result in the abutment analog being angularly indexed to implant  20  once the threads are fully engaged and the head,  48 , of abutment  28  is in contact with implant  20 . 
     Impression coping  70  has a non-circular indentation,  82 , which prevents impression coping  70  from rotating within the finished impression. Note that impression coping  70  also has a number of unique, color-coded, angular indexing indicia  76   a  and  76   b , which are registrable with a similar set of unique, replicated, angular indexing indicia,  52   a  and  52   b , which are borne upon head  48  of abutment base  28 . Abutment base  28  has a male hexagonal antirotation feature,  68 , formed at the uppermost portion of head  48 , which engages a female hexagonal antirotation feature,  62 , formed in impression coping  70 , in much the same manner as a polygonal socket wrench engages a matching fastener head. Abutment analog  69  has an installed height which is less than the operational height of a closed impression tray, allowing an impression tray and impression to be removed from a patient&#39;s mouth without first disengaging either impression coping  70  or abutment base  28  from dental implant  20 . 
     Abutment analog  69  is employed according to the method shown in  FIG. 8 , wherein prior to the start at block  800 , the dentist or other operator attaches an abutment base,  28 , to an impression coping  70 , using fastener  78 . Indices  52   a  and  52   b  are aligned with indices  76   a  and  76   b , respectively, as part of this assembly step. Those skilled in the art will appreciate in view of this disclosure that abutment  28  may be an actual abutment employed later to attach the completed dental restoration device to the patient, or, alternatively, may be a surrogate for such a device, and used only for the purpose of processing and fabricating a dental restoration device. 
     After the abutment and impression coping are attached to one another, the assembled abutment analog  69  is attached to implant  20  with angular indexing at block  804 . In a preferred embodiment, angular indexing is achieved at block  804  by torquing abutment analog  69  to implant  20  according to a predetermined torque value. This may be accomplished by applying a torque wrench to a polygonal upper portion of abutment analog  69 . Then, the processor moves to block  808 , where an impression is taken using conventional impression materials. Subsequently, at block  812 , the impression is removed, leaving abutment analog  69 , including the impression coping, affixed within the patient&#39;s mouth. After removing the impression, abutment  28  and impression coping  70  are removed at block  814 , and an implant analog,  38 , is threadedly attached to abutment base  28  at an indexed position which is the same indexed position at which abutment analog  69 , including abutment base  28 , was attached to implant  20 . This is achievable by torquing implant analog  38  to abutment base  28  with the same torque value employed earlier to torque abutment base  28  to implant  20 . These two uses of measured torque tightening assure that accurate thread timing is established for use in the laboratory to fabricate the patient&#39;s restoration device. 
     Those skilled in the art will appreciate in view of this disclosure that the present invention may be practiced without employing a torque wrench by using manually applied tightening torque to achieve a thread lock between abutment analog  69  and implant  20  in the first case, and between abutment analog  69  and implant analog  38  at a subsequent step of the present process. Relying upon the presence of a thread lock condition, which is manually discernable by a steep rise in tightening torque, although not as precise as using a torque wrench to achieve indexing in a repeatable manner, is believed to be an acceptable alternative in many cases. 
     At block  820 , abutment analog  69  and implant analog  36  are installed in the impression in the precise orientation established during the impression making step. Torquing of implant analog  36  to abutment analog  69  prior to re-insertion of the abutment analog into the impression avoids subjecting the abutment analog to excessive torques which could cause undesirable rotational shifting of abutment analog  69  within the impression. As noted above, this assures that the thread timing of implant analog  38  replicates the thread timing of implant  20 . 
     At block  824 , a model of the patient&#39;s dentition or mouth is fabricated, for example, with plaster-of-paris (item  37  at  FIG. 4 ), followed by fabrication of a dental restoration device at block  828 . Because the present method allows the spatial location and thread timing of implants  20  to be accurately replicated by implant analogs  38  in the model made of the patient&#39;s mouth, the worker in a dental laboratory is able to accurately produce and implement all of the angularity changes required to construct a dental restoration device which is easily installed in the patient&#39;s mouth. In other words, the laboratory implements the angle corrections, described in connection with  FIG. 1 , which were formerly the responsibility of the dentist to both determine and partially implement, and which depended ultimately upon a less than satisfactory system for handing off angle corrections to the laboratory. 
     Once the fabrication is completed at block  828 , the completed restoration device is transferred, including any abutments supplied by the laboratory, to the patient, and the method ends at block  836 . 
     The method shown at  FIG. 9 , which applies to an open tray impression, is similar to the method disclosed in  FIG. 8 , except that following a start at block  900 , and the attachment of the abutment coping to the implant with angular indexing at block  904  using either a torque wrench, or manual tightening until thread lock is sensed, and the impression taking at block  908 , the impression removed at block  912  includes the open tray impression coping,  56 , ( FIGS. 5-7 ) which has a non-circular section,  60 , formed therein to prevent unwanted rotation of impression coping  56  within the impression. This means that once the impression is taken, threaded fastener  64  will be removed, so as to allow the impression coping  56  to be separated from abutment base  28 . In essence, abutment analog  26  has an installed height which is at least proximate the operational height of an open impression tray, so that an impression tray and impression bearing impression coping  56  may be removed from a patient&#39;s mouth after disengaging impression coping  56  from base  28 . As an additional part of block  912 , once the impression containing impression coping  56  has been removed from the patient&#39;s mouth, abutment base  28  will be removed from implant  20  and implant analog  36  will be torqued to abutment base  28  at block  916 . This assures that implant analog  36  has been attached at the correctly indexed position. Then, at block  920 , abutment base  28 , bearing implant analog  36 , will be reattached to impression coping  56 , using indices  52   a , and  52   b  indexed with indices  66   a  and  66   b , to re-establish the indexed position which was used to make the impression. As before, a model will be fabricated at block  924  followed by fabrication of the dental restoration device at block  928  and transfer of the fabricated restoration device, including appropriate abutments, at block  932 , followed by the end of the process at block  936 . The abutments  28  used in the final steps of the restoration could be the original ones used in making the impression, or yet other abutments which provide necessary fastening features for the dental restoration device. 
     The foregoing invention has been described in accordance with the relevant legal standards, thus the description is exemplary rather than limiting in nature. Variations and modifications to the disclosed embodiment may become apparent to those skilled in the art and fall within the scope of the invention. Accordingly the scope of legal protection afforded this invention can only be determined by studying the following claims.