Abstract:
A dental instrument for installing and removing dental prostheses which includes both a speed wrench and a ratchet wrench, each being independently geared to a row of teeth on a screwdriver mounted in the dental instrument. The dental instrument includes a housing having a first and a second chamber. The screwdriver is partially mounted within the first chamber and the speed and rachet wrenches extend into the second chamber. The speed and ratchet wrenches are coaxially mounted within a handle that extends outwardly away from the housing. The speed wrench is rotatable about the longitudinal axis of the handle. The ratchet wrench is slidable along the longitudinal bore of the handle and is rotatable about the handle&#39;s longitudinal axis through 180°. The screwdriver is mounted in such a manner that the driver bit is oriented substantially at ninety degrees to the wrenches.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    This invention generally relates to dental tools and instruments. More particularly, the invention relates to a dental instrument that is used for installing dental components relating to artificial teeth. Specifically, the invention relates to a universal dental wrench that includes a screwdriver and has both speed wrench and ratchet wrench capabilities. 
         [0003]    2. Background Information 
         [0004]    The advent of implant prosthodontics has brought about a paradigm shift in the way dentists secure artificial teeth in the oral cavity. In the early 1980&#39;s much of the fixed-detachable bridgework for full arch dental rehabilitation and restoration was attached by means of some type of retaining screw. Depending on the implant system used, the screws were torqued by hand to effect the clamping force necessary for retaining the implant in the jaw bone. Therefore, one of the early prosthetic complications was screw loosening that was caused by lack of initial pre-load of the screw, as well as poor fit and heavy bite forces. 
         [0005]    As the industry moved forward in the early 1990&#39;s, single tooth and partially endentulous applications became commonplace. Torque wrenches were introduced with or without torque controllers. Screw loosening was significantly reduced by utilizing torque values anywhere from 15-35 Ncm and changing the screw composition from gold to alloyed materials. Two retention philosophies grew out of the new protocol, firstly, screw-retained fixed implant prostheses that may involve one or more abutment and retention screws and, secondly, cement-retained prostheses that usually have an abutment screw under one or more cemented crowns. 
         [0006]    There are many competing implant systems currently available on the market for installing the retention and abutment screws and each has its own unique features. There are different size implants, abutments, abutment screws, thread orientations and screw-head driving types. Each manufacturer tends to produce their own types of screwdrivers and torque wrenches for installing and tightening these components. The wrenches and screwdrivers generally cannot be used for universal installation of these components. One of the more popular torque wrench systems on the market today is manufactured by Dentsply International, based in York, Pa. Dentsply International manufactures, amongst other products, both a torque screwdriver hub and a ratchet driver for loading dental components. 
         [0007]    The steps to install and torque a retainer screw are typically as follows: 
         [0008]    A cylindrical hole is drilled into the alveolar ridge of the patient and an implant bolt is inserted into that cylindrical hole. The implant bolt typically includes an external thread that allows it to bite into and grip the surrounding bone. The implant bolts generally also include an internally threaded bore that is adapted to receive a male portion of a prosthesis, i.e., an artificial tooth or a post for an artificial tooth. Once the implant bolt is installed in the jaw bone, it is covered and a period of time is allowed to pass so that the implant undergoes osseointegration, i.e., bone tissue infiltrates and surrounds the implant bolt to securely embed the same within the jaw bone. After this has occurred, the prosthesis is installed. This is accomplished as follows:
       1. A screw is placed on the end of a small manual screwdriver. The screws are typically only about ¼ inch long and are therefore difficult to handle.       
 
         [0010]    The prosthesis is inserted into position with respect to the implant bolt. 
         [0011]    The screw is placed into the hole on the prosthesis and the dentist tries to hold the screw and prosthesis on the implant bolt with one finger and with the other hand tries to line up and begin to engage the threads on the screw.
       2. Once the screw is started and there is no danger of dropping the screw and prosthesis, the dentist will use a speed wrench to turn the screw. A speed wrench is a 90° screwdriver with a rotary knob on its outer end that allows the dentist to turn the screw the required number of turns until it seats. It would seem obvious to try and use a small ratcheting-style wrench to tighten the screw, but for two issues. There is no room to swing the end of a ratcheting wrench in many areas of the mouth. Furthermore, the screw is so small and has so little resistance until it is properly seated that it would not allow the ratcheting wrench to properly ratchet the screw.   3. Once the screw has been seated with the speed wrench, the dentist will change his tool and will use a torque wrench to engage and properly tighten the screw according to the manufacturer&#39;s specifications.       
 
         [0014]    The oral cavity is a relatively small space in which to work. Consequently, it is difficult and inconvenient for the dentist to have to keep switching tools, engaging miniaturized screws and then manipulating the tools in such a confined area. 
         [0015]    There is therefore a need in the art for a dental implant instrument that enables a dentist to perform both a speed wrench type function and a ratchet wrench type function without having to change tools. 
       SUMMARY OF THE INVENTION 
       [0016]    The device of the present invention is a dental instrument that may be used to install and remove dental prostheses. The dental instrument includes both a speed wrench and a ratchet wrench, each being independently geared to a row of teeth on a screwdriver mounted in the dental instrument. The dental instrument includes a housing having a first and a second chamber which communicate with each other. The screwdriver is partially mounted within the first chamber and one end of each of the speed and rachet wrenches extends into the second chamber. The speed and ratchet wrenches are coaxially mounted within a handle that extends outwardly away from the housing. The speed wrench is rotatable in either direction about the longitudinal axis of the handle and, as it moves, it causes a corresponding rotation of the screwdriver. The ratchet wrench is slidable along the longitudinal bore of the handle to release it from engagement with the associated row of teeth on the screwdriver. The ratchet wrench is also rotatable about the handle&#39;s longitudinal axis through 180° once released, so as to correctly positioned to perform a ratcheting function, no matter which direction the screwdriver is rotated. The screwdriver is mounted in such a manner that the driver bit is oriented substantially at ninety degrees to the longitudinal axes of the wrenches. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The preferred embodiments of the invention, illustrative of the best mode in which applicant has contemplated applying the principles, are set forth in the following description and are shown in the drawings and are particularly and distinctly pointed out and set forth in the appended claims. 
           [0018]      FIG. 1  is a perspective view of the universal dental wrench in accordance with the present invention; 
           [0019]      FIG. 2  is an exploded perspective view of the dental wrench of  FIG. 1 ; 
           [0020]      FIG. 3  is a top view of the dental wrench; 
           [0021]      FIG. 4  is a cross-sectional side view of the dental wrench; 
           [0022]      FIG. 5  is a cross-sectional top view through line B-B of  FIG. 4 ; 
           [0023]      FIG. 6  is a bottom view of the dental wrench with the main body and outer handle removed; and 
           [0024]      FIG. 7  is a side view of the dental wrench as shown in  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    Referring to  FIGS. 1-7 , there is shown a universal dental implant wrench in accordance with the present invention and generally indicated at  10 . Wrench  10  is a device that includes a dental screwdriver  12  in combination with a speed wrench and a ratchet wrench as will be hereinafter described. 
         [0026]    Wrench  10  is designed to be used in conjunction with any suitable dental screwdriver known in the art. There are essentially two kinds of screwdrivers presently used in implant systems. Both screwdrivers look the same externally, but differ internally. The most common screwdriver is essentially a solid piece of stainless steel with knurling or teeth on its exterior surface to provide a grip when used by hand. These screwdrivers can also be used in conjunction with a dental ratchet which engages the teeth on the screwdriver. The second type of screwdriver is not a solid device and includes an internal slip clutch that slips when the correct torque setting is obtained. These torqued screwdrivers may also be used in conjunction with ratchet wrenches. One such suitable torque screwdriver is manufactured as part #45732 by Dentsply International. It is this torque screwdriver that is depicted as screwdriver  12  in the attached figures. 
         [0027]    Referring to  FIG. 2 , screwdriver  12  has a body  12   a  that includes two rows of drive teeth thereon. The first row of drive teeth are speed wrench teeth  14  and the second row of teeth are ratchet drive teeth  16 . Screwdriver  12  also includes an elongated shaft  18  and a driver bit  20  which are configured to engage a dental component such as a retainer screw  21  ( FIG. 4 ). 
         [0028]    In accordance with a specific feature of the present invention there is provided a housing  22  that receives an upper portion of screwdriver  12  in a first chamber  24  and a first end  26  of a handle  28  in a second chamber  30 . First and second chambers  24 ,  30  are interconnected with each other. The upper portion of screwdriver body  12   a  disposed within first chamber  24  includes the rows of speed wrench teeth  14  and ratchet driver teeth  16 . The top end  32  of screwdriver  12  protrudes out of first chamber  24  ( FIG. 1 ). A cover  34  is screwed into position over second chamber  30  to protect the components retained therein. 
         [0029]    Referring to  FIG. 4 , and in accordance with a specific feature of the present invention, handle  28  comprises an elongated cylindrical pipe  36  with a speed wrench  46  and ratchet wrench  38  concentrically received therein. A first end  36   a  of pipe  36  threadably engages housing  22  proximate second chamber  30 . Handle  28  is a non-moving component that the dentist can hold to manipulate the instrument. A tubular speed wrench shaft  46  is disposed within the bore  40  of pipe  36 . Shaft  46  extends into second chamber  30  of housing  22  and terminates inwardly from the threaded first end  36   a  of pipe  36 . A bevel gear  54  is mounted on the inward end  46   a  of shaft  46 . Shaft  46  extends through bore  40  and terminates slightly outwardly of second end  36   b  of pipe  36  in a speed wrench knob  48 . Knob  48  is rotatable by hand and when knob  48  is so rotated, speed wrench shaft  46  rotates within bore  40  and thereby rotates bevel gear  54 . The teeth on bevel gear  54  engage the teeth on an intermediate gear  56  that is disposed within second chamber  30  and is mounted substantially at right angles to bevel gear  54 . Intermediate gear  56  engages the speed wrench teeth  14  on screwdriver  12 . 
         [0030]    A ratchet bar  38  is received through the bore  47  of speed wrench shaft  46  and extends into second chamber  30  of housing  22 . A first end  38   a  of ratchet bar  38  is chisel-shaped ( FIGS. 2 &amp; 5 ) having first and second faces  50 ,  52  that are differently profiled. First face  50  is substantially arcuate and J-shaped, while second face  52  is substantially linear and angled. It should be understood, however, first and second faces  50 ,  52  can be shaped in a different manner without departing from the spirit of the present invention. 
         [0031]    First end  38   a  of ratchet bar  38  is designed to engage ratchet drive teeth  16  on screwdriver  12 . The second end  38   b  of ratchet bar  38  is of a reduced diameter and a coil spring  42  is disposed around this second end  38   b.  Coil spring  42  is compressed between the larger diameter portion of ratchet bar  38  and speed wrench knob  48  and urges first end  38   a  of ratchet bar  38  into engagement with ratchet drive teeth  16 . A control knob  44  is provided on the second end  38   b  and this knob  44  enables the dentist to partially withdraw ratchet bar  38  from within the bore  40  of outer pipe  36  and to rotate ratchet bar  38  through 180°. When ratchet bar  38  is in a first position, first face  50  is presented for engagement with drive teeth  16 . When ratchet bar  38  is rotated through 180°, then ratchet bar  38  presents a second face  52  for engagement with drive teeth  16 . 
         [0032]    Dental wrench  10  is also provided with a ball bearing  58  and an associated spring  60  and screw  62  which urges the ball bearing  58  between speed wrench teeth  14  and ratchet drive teeth  16 . 
         [0033]    The dental wrench  10  is used in the following manner. The dentist positions the retainer screw  21  on the prosthesis (not shown), and starts the threads by hand with a manual screwdriver (not shown). Once the threads have taken sufficiently, wrench  10  is engaged with screw  21  by inserting driver tip  20  into a recess  60  in the head  62  of screw  21 . The dentist then sets ratchet bar  38  for clockwise movement of speed wrench shaft  46 . The dentist can tell if the ratchet bar  38  is oriented correctly by observing the arrow marker  64  ( FIG. 1 ) on control knob  44 . If the dentist determines that the ratchet bar  38  is not oriented correctly, he will pull knob  44  outwardly in the direction of arrow “X” ( FIGS. 3 &amp; 4 ). This slides ratchet bar  38  part-way through bore  47  of speed wrench shaft  46 , and compresses coil spring  42  against control knob  48 . Ratchet bar  38  is then rotated through 180° by turning knob  44  in either a clockwise or anticlockwise direction. Then knob  44  is released when the marker  64  faces in the opposite direction. This allows the compressed coil spring  42  to revert to its original size and position, thereby forcing ratchet bar  38  to slide along bore  47  in the direction of arrow “Y” ( FIG. 4 ). First end  38   a  of ratchet bar  38  is thereby forced back into engagement with ratchet driver teeth  16 . When ratchet bar  38  is set for speed wrench shaft  46  to rotate in a clockwise direction, then first face  50  of ratchet bar  38  is presented for engagement driver teeth  16 . The dentist turns the speed wrench knob  48  in a clockwise direction the number of turns needed to seat screw  21 . The rotation of speed wrench knob  48  and thereby speed wrench shaft  46  drives bevel gear  54  which in turn drives intermediate gear  56 . The teeth of intermediate gear  46  engage speed wrench teeth  14  causing screwdriver  12  to rotate in a first direction. The screwdriver  12  will rotate in one direction only and as it does so, ratchet bar  38  will ratchet the screw during this process. The dentist will turn speed wrench knob  46  the required number of turns to finger tighten screw  21 . Once screw  21  is finger-tightened, the dentist will move handle  28  in a small arc in the direction of arrow “Z” ( FIG. 3 ) to torque screw  21  to the manufacturer&#39;s recommended specifications. Since screwdriver  12  is a torque screwdriver, it is pre-calibrated and will therefore slip when the correct preset torque limit is attained. 
         [0034]    If the dentist wishes to remove a prosthesis, the direction of rotation of screwdriver  12  and the ratcheting of rachet bar  38  can be reversed to unscrew screw  21 . This is achieved by pulling control knob  44  outwardly in the direction of arrow “X”, rotating ratchet bar  38  in the opposite direction, as indicated by arrow marker  64 , releasing knob  44  and then rotating speed wrench knob  48  in an anticlockwise direction. Rotation of ratchet bar  38  through 180° brings face  52  into engagement with ratchet drive teeth  16 . Rotating speed wrench shaft  46 , by turning speed wrench knob  48  in the opposite direction, causes bevel gear  54  and therefore intermediate gear to rotate in the opposite direction. Consequently, screwdriver  12  rotates in the opposite direction and unscrews the screw  21 . 
         [0035]    Dental wrench  10  therefore provides a bidirectional ratcheting function and a bidirectional speed wrench function in the same device. Both the ratchet bar  38  and speed wrench shaft  46  are disposed at approximately 90° to the directions in which the screw  21  is being inserted or withdrawn. Consequently, the dentist does not have to work within the limited confines of the patient&#39;s mouth, but can perform both the screwing and ratcheting functions in a more easily accessible location. 
         [0036]    In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed. 
         [0037]    Moreover, the description and illustration of the invention is an example and the invention is not limited to the exact details shown or described.