Abstract:
A dental tool having a pair of releasably and pivotably connected opposing jaw members. A biasing mechanism connected to at least one of the jaw members biases the jaw members toward a proximate rest position. A separating mechanism is connected to at least one jaw member for separating the jaw members. An ultrasonic vibrator is connected to the jaw members for vibrating them. A fastening device may be used to connect the pair of opposing jaw members.

Description:
FIELD OF THE INVENTION 
     In one of its aspects, the present invention relates to a vibrating dental tool for the removal of crowns and bridges. 
     BACKGROUND OF THE INVENTION 
     Vibrating dental tools and, in particular, ultrasonic dental tools are known. 
     U.S. Pat. No. 5,320,532 (Farzin-Nia et al.) teaches an ultrasonic tool for fracturing the interface between dental structures and, specifically, for the removal of orthodontic bands or brackets from teeth after the completion of treatment. The working tip of the tool may be wedge-shaped, flat or needle shaped. In one embodiment, a pair of spaced projections are disposed on either side of an engaging surface to provided a receiving area for the bracket to minimize slipping off. In use, the tip of the tool is placed against a bracket and ultrasonic energy is transferred through the bracket to the adhesive layer. 
     U.S. Pat. No. 5,733,119 (Carr) teaches a microsurgical drill bit, which can be connected to an ultrasonic transducer. The drilling tips are angled and may have bent end portions to permit the tool to be held at a comfortable angle. 
     While drilling devices and simple devices for the removal of adhesively connected dental structures are known, there is a need for a dental tool adapted for the removal of crowns and bridges. 
     The crowning and bridging of teeth is a common practice in dentistry. There are a number of indications for crowns and bridges. Some of the more common indications are: heavily restored teeth with little of the original teeth left; following root canal treatments; and bridges for the replacement of missing teeth. Crowns and bridges may also be used for aesthetic reasons. 
     When a tooth is prepared for a crown, the practitioner removes or shaves off the surface of the tooth to a depth of approximately 1.5 millimeter (mm). The practitioner generally then cements a temporary crown to the tooth. The practitioner then generally awaits lab work on the tooth, before cementing in a permanent crown. 
     There are many instances where a practitioner must remove a crown or bridge. One common instance is the removal of a temporary crown. This may prove particularly challenging where the temporary crown fits tightly over the original tooth. Another common instance is the removal of a permanent crown that has been temporarily cemented. This might occur, for example, where the practitioner wishes to obtain approval of the crown from the patient before permanently securing it. This might also occur where the practitioner wishes to ensure that tooth sensitivity will subside before permanently securing a crown. 
     Other common instances may arise after a crown has been permanently secured. For example, removal of a crown is required where there is caries underneath it and the practitioner does not wish to cut the crown to provide treatment. Similarly, a crown may need to be removed where it is necessary to perform a root canal on the underlying tooth. Yet another instance might be where one crown of a bridge becomes loose and the practitioner must remove the other crowns of the bridge in order to re-cement the bridge. 
     Existing crown removal tools generally involve the application of a blunt force to the crown, which often results in broken or fractured crowns or teeth. This can add complexity and expense to a dental procedure and, in addition, may cause additional discomfort to a patient. The inventor is aware of an ultrasonic crown removal tool, the ATD Automatic Crown &amp; Bridge Remover by J. Morita, USA, Inc. This tool consists of ultrasonic steel string arranged as a loop and a pneumatic hook that attaches to a hand piece that causes slow movement of the hook. The steel string, while designed to assist with separating the crown from the root, suffers from a number of drawbacks. The steel string is difficult to position if the teeth are close together. Further, if the crown-tooth interface is smooth, the string will not catch at this position. The string also has trouble penetrating the crown-tooth junction. Finally, due to the application of pressure on one side of the crown or tooth-crown junction, the crown almost invariably breaks during the removal procedure, which adds to the complexity and expense of the procedure. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to obviate or mitigate at least one of the above-mentioned disadvantages of the prior art. 
     Accordingly, in one of its aspects, the present invention provides a dental tool, comprising: a pair of opposing jaw members; a biasing mechanism connected to a jaw member for biasing the jaw members toward a proximate rest position; a separating means connected to a jaw member for separating the jaw members; a vibrator connected to the jaw members for vibrating them; and securing means connecting the pair of opposing jaw members. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will be described with reference to the accompanying drawings, wherein like reference numerals denote like parts, and in which: 
         FIG. 1  illustrates a front view of an embodiment of the present dental tool in the rest position. 
         FIG. 2  illustrates a front view of an embodiment of the present dental tool in an open position. 
         FIG. 3  illustrates an enlarged partial front view of an embodiment of the present dental tool being positioned on a tooth. 
         FIG. 4  illustrates a magnified side view of a wedge portion of an embodiment of the present dental tool. 
         FIG. 5  illustrates a magnified front view of a wedge portion of an embodiment of the present dental tool. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to  FIG. 1 , dental tool  10  has a pair of opposed jaw members  12 . Jaw members  12   a  and  12   b  are connected to a handle  14  through a neck  16 . 
     Preferably, handle  14  contains a vibrator, preferably in the form of an ultrasonic transducer for vibrating jaw members  12   a  and  12   b . In an alternate embodiment, handle  14  may be connected to an ultrasonic transducer and handle  14  may contain means for transferring movement or vibrations to jaw members  12   a  and  12   b . A power source for the ultrasonic transducer may be housed in handle  14 , preferably in the form of batteries. In an alternate embodiment, handle  14  may have means for connecting to an external power source. Ultrasonic dental handles or transducer heads are commonly used in the art in conjunction with cleaning tips. The particular configuration of the handle is not restricted and is within the purview of a person skilled in the art. Generally speaking handle  14  must have a motor (not shown) connected to the power sources (e.g. batteries), to the jaw members  12  for driving them, and to switching means for controlling the operation of the motor. 
     Preferably, manually operable control buttons  17   a ,  17   b , and  17   c  are provided on handle  14  for powering dental tool  10  on and off and for varying the power supplied to jaw members  12   a  and  12   b , thereby varying their amplitude of vibration. Preferably, one control button provides a high power setting, while a second control button provides a low power setting. The number of power settings is not particularly restricted and is within the purview of a person skilled in the art. Rather than discrete power settings, the power may be adjustable along a spectrum. 
     Suitable vibrational frequencies are within the purview of a person skilled in the art. The vibrator may suitably vibrate at between about 15,000 and about 40,000 Hertz. More preferably, the vibrator vibrates between about 20,000 and about 30,000 Hertz. Most preferably, the vibrator vibrates between about 25,000 and 28,000 Hertz. 
     Jaw members  12   a  and  12   b  are biased toward each other by biasing means, preferably in the form of a spring  18 . As will be apparent to a person skilled in the art, the position and number of biasing means is not particularly restricted, there may, for example, be a pair of biasing means, one operating on each of jaw members  12   a  and  12   b . Generally, in the proximate rest position there will be a small space between jaw members  12   a  and  12   b , typically of about 1 mm (although the space may be larger or jaw members  12   a  and  12   b  may be touching). 
     Neck  16  preferably has a hollow tubular portion  20  for slidably receiving a rear leg portion  22  of a first jaw member  12   a  having a substantially L-shape. The rear leg portion  22  extends longitudinally from the neck  16  having the same longitudinal axis. Preferably, adjustment and securing means are provided for adjusting the position of rear leg portion  22  within tubular portion  20  and for securing it in position, once the desired position is obtained. Suitable adjustment and securing means include a screw  24  that can be tightened to frictionally engage rear leg portion  22 . Tubular portion  20  may have one or more apertures or a continuous slot for receiving screw  24 . Similarly, rear leg portion  22  could have apertures therein for receiving securing means. In an alternate embodiment, screw  24  may be replaced by a biased pin (now shown) receivable in one of a series of apertures for securing leg portion  22  is a desired position. 
     Various adjustment and securing means will be apparent to a person skilled in the art. It will be apparent that the securing mechanisms must be fairly strong and reliable to maintain the position of jaw member  12   a  during operation. 
     A second jaw member  12   b  having a substantially C-shape is pivotally attached to an exterior of neck  16  at pivot point  26  substantially perpendicular to the longitudinal axis of the neck  16  and rear leg portion  22 . In the embodiment shown, second jaw member  12   b  has an extended rear leg portion  28  extending rearward substantially parallel to the longitudinal axis of the neck  16  when the first and second jaw members  12   a ,  12   b  are in a substantially closed position. Spring  18  is secured between extended rear leg portion  28  and neck  16  and has a longitudinal axis substantially perpendicular to the longitudinal axis of the neck  16 . Spring  18  may be secured to one or both of neck  16  and extended rear leg portion  28 . Various mechanisms for securing spring  18  will be apparent to persons skilled in the art and include for example hooking the ends to small apertures in the respective parts. In a preferred embodiment, neck  16  may have protruding walls  29  connected by a freely rotating pin  31  which in turn passes through a portion of extended rear leg portion  28 , permitting rear leg portion  28  to freely rotate about the pin. 
     With reference to  FIG. 2 , extended rear leg portion  28  preferably has a manually depressible actuator  30 . Depression of actuator  30  downward in the direction toward the neck  16  overcomes spring  18 , permitting jaw members  12   a and  12   b  to open. Upon release of actuator  30 , spring  18  forces jaw members  12   a and  12   b  toward a proximate rest position. In practice, generally a practitioner will depress actuator  30  using his or her thumb. 
     Neck  16  is preferably detachably secured to handle  14 . Neck  16  may be secured to handle  14  by any suitable means. The securing means is preferably in the form of a threaded socket in handle  14  (not shown) with corresponding threads on neck  16 . Other suitable securing means include, for example, a bayonet lock or a tool chuck. Jaw members  12   a  and  12   b  may also be detachably secured to neck  16 . This arrangement facilitates cleaning of dental tool  10 . In particular, neck  16 , rear leg portions  22  and  28  and jaw members  12   a  and  12   b  can advantageously be sterilized as a single unit. 
     Preferably, neck  16  has an internal pivot point  32  to selectively secure the first and second jaw members  12   a  and  12   b  at a predetermined angled position. Neck  16  may have a plurality of pivot points. The number and position of internal pivot points in neck  16  is not particularly restricted and is within the purview of a person skilled in the art. Internal pivot point  32  facilitates placement of jaw members  12   a  and  12   b , within the mouth of a patient. In particular, this facilitates use of tool  10  on posterior upper molars and posterior lower molars. Neck  16  may further include releasable locking means for locking the position of internal pivot point  32  so as to impart a specific angle to neck  16  for use. The amount of force required to pivot about internal pivot point  32  may be selected so that pivoting can be performed manually or with the assistance of a tool. A locking mechanism (not shown) can be provided to prevent pivoting of neck  16  during use of dental tool  10  is unlikely. Various suitable locking mechanisms will be apparent to a person skilled in the art. Suitable mechanisms include a pin and sprocket mechanism (not shown) whereby an actuator is provided for disengaging the pin from the sprocket and permitting free pivoting and where upon release of the actuator, the pin engages the sprocket, thereby securing neck  16  at a desired internal angle. Another suitable locking mechanism would be interlocking members (not shown) that may be secured in a number of angled positions and that can be locked in a desired position using an actuable mechanism. 
     With reference to  FIGS. 2 and 3 , there is shown a tooth  34 , having a crown  36  thereon. Dental tool  10  is positioned so as to effect removal of a crown  36 . In practice, the practitioner depresses actuator  30  so as to open jaw members  12   a  and  12   b . The position of rear leg portion  22  of first jaw member  12   a  may be adjusted to accommodate a crown  36  that is longer on one side than the other, as shown in  FIG. 3 . The practitioner places open jaw members  12   a  and  12   b  about tooth  34  so that front wedge portions  38   a  and  38   b  are positioned at tooth-crown interface  40   a  and  40   b . Each front wedge portion  38   a  and  38   b  preferably has a substantially flat inner surface  42   a  and  42   b  for engaging the underside of crown  36  at tooth-crown interface  40   a  and  40   b . Once tool  10  is positioned, the practitioner turns on the ultrasonic vibrations using the appropriate control button(s)  17   a ,  17   b  and/or  17   c.    
     Preferably, tips  44   a  and  44   b  of wedge portions  38   a  and  38   b  are sharp edges. Alternately, tips  44   a  and  44   b  may taper to a sharp point. Tips  44   a  and  44   b  of wedge portions  38   a  and  38   b  are shaped to facilitate wedging of wedge portions  38   a  and  38   b  between crown  36  and tooth  34 . The shape of tips  44   a  and  44   b  also helps wedge portions  38   a  and  38   b  to chip into cement at tooth-crown interface  40   a  and  40   b . Spring  18  applies pressure to tips  44   a  and  44   b  of wedge portions  38   a  and  38   b  as it forces jaw members  12   a  and  12   b  toward the proximate rest or closed position. 
     The outer surfaces  46   a  and  46   b  of wedge portions  38   a  and  38   b  are angled. This angled outer surfaces  46   a  and  46   b  facilitates prying into cement and the forcing of crown  36  from tooth  34 . 
     Preferably, wedge portion  38  is about 0.5 to 2.5 mm thick, as shown by the letter T in  FIG. 4 . More preferably, wedge portion  38  is about 1 mm thick. Preferably, inner surface  42  of wedge portion  38  is between about 4 and 8 mm in length and more preferably about 6.5 mm in length, as shown by the letter L in  FIG. 5 ; this length generally being slightly longer than the thickness of a typical crown. The height of wedge portion  38 , as shown by the letter H in  FIGS. 4 and 5  is preferably between about 0.5 and about 2 mm, and more preferably about 1 mm. 
     Preferably, in use, a low power setting would be used initially to insert wedge portions  38   a  and  38   b  between tooth  34  and crown  36  in order to provide a good grip into tooth-crown interface  40   a  and  40   b  and then a high power setting would preferably be used to remove crown  36 , thereby minimizing the amount of trauma caused by the procedure. 
     Jaw members  12   a  and  12   b  are preferably formed of a strong, durable, substantially rigid and substantially heat-resistant medical grade material, such as stainless steel or a titanium alloy. 
     Preferably, the surfaces of wedge portions  38   a  and  38   b  are relatively smooth to facilitate sliding placement of wedge portion  38  into tooth-crown interface  40   a  and  40   b . It is, however, known in the art to coat the surfaces of dental tools with a fine layer of material that imparts additional strength and/or abrasiveness. In particular, a thin layer of diamonds is preferred for this purpose. In the case of dental tool  10 , such a fine diamond layer is suitably applied to tips  44   a  and  44   b  and/or outer surfaces  46   a and  46   b  for chipping away of the cement. Such a thin layer of diamonds might also suitably be applied to flat inner surfaces  42   a  and  42   b  to facilitate engagement of inner surfaces  42   a  and  42   b  against crown  36 . 
     While this invention has been described with reference to illustrative embodiments and examples, the description is not intended to be construed in a limiting sense. Thus various modifications of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to this description.