Abstract:
A device to be held in the mouth of a patient who has limited jaw opening and to assist in the therapy. The device has a frame with opposite side members having adjustable lengths. A rotatable knob drives a threaded screw to change the tension applied to a pair of springs. The springs activate a cam to raise or lower an upper mouthpiece with respect to a lower mouthpiece and to thereby adjust the jaw opening of the patient.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a device to assist in the therapy of a patient and, in particular, to a patient who has limited jaw opening due to any number of causes such as muscle injury, surgical procedures, radiation therapy, temporomandibular joint dysfunction, osteoarthritis, post infection, or trauma. 
     BACKGROUND OF THE INVENTION 
     There are many persons who are limited in the extent to which they are able to open their mouths. Some of the causes of this problem are listed above. This problem is frequently referred to as trismus. A person afflicted with trismus is not able to fully open their lower jaw. This is problematic in that, often, access to the interior of the afflicted person&#39;s mouth and throat is necessary to effectively treat the cause of the affliction. Approximately 75,000 to 100,000 persons in the United States require treatment for this ailment annually. 
     Additionally, there are other occasions, such as during an examination or any procedure performed with or without general or local anesthesia, when the patient&#39;s mouth must be propped open. 
     The applicants are aware of devices for dilating and/or propping open a human mouth. The Dingman Mouth Gag is a frame with coiled springs, tongue depressors, cheek retractors and movable tooth hooks which is positioned in front of the mouth. In U.S. Pat. No. 742,698 to Mason, a dental prop is disclosed which has pivoted jaws and tooth pads on the inner ends of the jaws. Arthur, in U.S. Pat. No. 972,983 discloses a dilator having a handle with four sockets in which are received four blades. The handle may be turned to move the blades. Koehler, in U.S. Pat. No. 976,812 discloses a mouth speculum having a pair of pivotally connected jaw bars which have ends to engage teeth within a mouth. Rotation of a bolt provides a means to open and close the jaws. In U.S. Pat. No. 1,025,265, Grindle discloses a cheek distender having two pivotally connected handles with bow-shaped arms and cheek plates on the ends of the arms. In U.S. Pat. No. 1,229,595, Du Brul discloses a dental appliance having a prop to hold the mouth open. The appliance has two sections connected by a spring hinge. A plate is attached to one section to engage the teeth. The other section has means to hold a clam roll in place. In U.S. Pat. No. 1,311,313 Brix discloses a retractor having two parallel bars spaced apart by an arm at one end and a plate at the other. A movable arm is carried by one of the parallel bars. Hooks are formed on the ends of the arms. A slidable bar is connected to the other parallel bar. On the end of the slidable bar is a hook which can be moved with respect to the parallel bars. In U.S. Pat. No. 2,061,936 issued to Engelfried, a mouth prop is disclosed that is inserted between a patient&#39;s teeth. This device includes a threaded bolt that carries a pair of bars thereon that, carrying tooth engagement means thereon, are linearly movable to prop a mouth open. In U.S. Pat. No. 2,182,390 issued to Reardon, a surgical device is disclosed for propping open the mouth of a patient, so as to permit access to and illumination of the area in back of the nose and above the palate. In U.S. Pat. No. 5,718,665, Stubbs discloses an animal speculum wherein first and second arms connected by a threaded rod are provided. By rotating the rod, the distance between the first and second arms may be selectively adjusted. In U.S. Pat. No. 5,846,212, Beeuwkes, III et al disclose a device for omnidirectional translation of the mandible of a human patient. The device provides for translation and lateral movement. Kastenbauer et al, in U.S. Pat. No. 5,897,491 disclose a device for endoscopic examination which includes a vertical frame with locking and vertical frame with locking and spreading instruments attached to the frame and extending horizontally from the frame. Esselbach, in UK Patent 17.220 discloses a mouth opening instrument having angularly bent levers hinged together. The ends of the arms of the levers carry mouthpieces which are spring actuated into an open position. Schranz, in UK Patent 674.272 discloses a retractor which has two curved arms which are pivotally connected to a bridge member. Each curved arm has a shortened arm which is received in a central traveling block. A gear box is mounted in the center of the bridge member. The curved arms open and close. 
     While being useful for their purpose, most of these patented devices have particular drawbacks, especially where the patient is afflicted with trismus. In particular, the jaw supporting portions move away from and towards one another in a straight linear fashion. Unfortunately, the mandible does not move in such a linear fashion. The jaw joint is a ginglimoarthroidial joint and, as such, moves in a sliding pivotal articulation (where the lower jaw joins the skull), such that the lower jaw pivotally moves away from and towards the skull in a substantially arcuate path. Thus, if the devices such as disclosed in Engelfried and Reardon would be utilized to open a jaw afflicted with trismus, the tooth engaging portions thereof, while moving linearly, would slip or ride over the teeth of the jaw, which moves arcuately. Such an arrangement can result in breaking and/or other damage occurring to the teeth and/or jaw of the patient. 
     U.S. Pat. No. 5,035,420 to Beeuwkes, III et al, disclose a jaw exerciser which has curvilinear guide tracks to guide movement of a carriage which provides corresponding movement of a mandibular jaw member. The mandibular jaw member is supported by the carriage. 
     U.S. Pat. Nos. 4,991,566 and 5,097,820 to Shulman et al address the arcuate movement of the jaw and disclose devices which move similarly to the natural movement of the jaw. However, the devices can be substantially improved and the present application discloses improvements to these devices. 
     BRIEF SUMMARY OF THE INVENTION 
     It is a primary object of the present invention to provide a device for opening the jaw of a patient in therapy of the patient. 
     It is a further object to provide a jaw opening device in which the tension applied to the jaw can be varied quantitatively and in small, controllable increments. 
     In accordance with the teachings of the present invention, there is disclosed a device to assist in the therapy of a patient who has limited jaw opening. The device has a rectangular frame having two opposite side members. The side members have adjustable lengths. Means are provided to adjust the lengths of the side members concurrently. Each side member has a first end and an opposite second end. An upper mouthpiece and a lower mouthpiece are connected between the respective first end of the side members of the frame. The upper mouthpiece and the lower mouthpiece have a distance therebetween wherein adjusting the lengths of the side members of the frame changes the distance between the upper mouthpiece and the lower mouthpiece. When the mouthpieces are received in the mouth of the patient, the jaw opening of the patient is adjustable. 
     In further accordance with the teachings of the present application, there is disclosed a device to assist in the therapy of a patient who has limited jaw opening. The device has a frame having two side members, the side members having adjustable lengths. Each side member has a first end and an opposite second end. Means are provided to adjust the lengths of the side members concurrently. An upper mouthpiece and a lower mouthpiece are connected between the respective first ends of the side members of the frame, the upper mouthpiece and the lower mouthpiece having a distance therebetween. Each side member has a center bore formed longitudinally therethrough. A spring is disposed in each bore, the spring having a first end and a second end. An adjusting means is connected to the first end of each spring. A chuck tip is connected to the second end of each spring. Two heads are provided, the first end of each side member being connected to a respective one of the heads. Each head has an opening therein. A respective joint is received in each opening in the respective heads. A cam surface is formed on each joint, the respective chuck tip bearing on the cam surface. Two spaced-apart sleeves are provided, the respective second ends of each side member being telescopically received in the respective sleeve. Changing the adjusting means on the first end of each spring changes the tension of the respective springs with respect to the cam surface and telescopically moves the respective side members with respect to the sleeves. In this manner, the distance between the upper mouthpiece and the lower mouthpiece is changed, such that the jaw opening of the patient is adjustable in controllable increments. 
     These and other objects of the present invention will become apparent from a reading of the following specification taken in conjunction with the enclosed drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the device of the present invention. 
     FIG. 2 is a side elevation view with the counterbalance rod not shown. 
     FIG. 3 is a top plan view. 
     FIG. 4 is a bottom plan view. 
     FIG. 5 is an exploded view of a portion of the device including the housing and knob. 
     FIG. 6 is an exploded view of a second portion of the device showing all of the components exterior of the housing. 
     FIG. 7 is a side elevational view of the control shaft. 
     FIG. 8 is a top plan view of the cross brace knuckles and cross brace rod. 
     FIG. 9 is a side elevational view of the cross brace knuckles and the cross brace rod. 
     FIG. 10 is a side elevational view of the head. 
     FIG. 11 is a front elevational view of the head. 
     FIG. 12 is a side elevational view of the joint with the stem rod. 
     FIG. 13 is a front view of the joint with the stem rod. 
     FIG. 14 is a bottom plan view of the subassembly for the upper mouthpiece. 
     FIG. 15 is a side elevational view of FIG.  14 . 
     FIG. 16 is a top plan view of the subassembly for the lower mouthpiece. 
     FIG. 17 is a cross-sectional view taken across the lines  17 — 17  of FIG.  16 . 
     FIG. 18 is a top plan view of the subassemblies for holding the mouthpieces with the mouthpieces not shown. 
     FIG. 19 is a side elevation view of the subassemblies of FIG. 18 with the mouthpieces attached and showing pivotal movement of the mouthpieces. The plate cap of the head is not shown. 
     FIG. 20 is a cross-sectional view of the loading screw connected to the loading shaft and mounted in the housing. 
     FIG. 21 is a partial cross-sectional view showing the spring extended and chisel tip disposed in the bore in the side members and contacting the cam surface in the joint. 
     FIG. 22 is the same as FIG. 21 with the spring compressed. 
     FIG. 23 is a top plan view showing the indicia when the distance between the mouthpieces is relatively small. 
     FIG. 24 is a perspective view of the device of the present invention in the mouth of a patient. 
     FIG. 25 is a partial cut-away side view showing the present invention engaging the teeth in the patient&#39;s mouth. 
    
    
     DESCRIPTION 
     Referring now to FIGS. 1-6, the device  10  has a frame which has a pair of opposite side members  12  which are adjustable in their effective length with respect to the size of the frame. Each side member  12  has a respective first end  14  and second end  16 . The second ends  16  are each received in a respective sleeve  18  wherein the second ends  16  may telescope within the sleeve  18  as the side member  12  moved to lengthen or shorten the frame. Each sleeve  18  is connected to a housing  20 , the sleeves  18  being spaced apart. Within the housing  20 , there are two drive means  22 , and two sets of sprockets  24 ,  24 ′. One pair of sprockets  24  are keyed to, and rotated by, a control shaft  26 . These sprockets  24  drive both drive means  22  which, in turn, drive the other pair of sprockets  24 ′. The sprockets  24 ′ are driven by the drive means  22  in a first direction and an opposite second direction as selected. The driven sprockets  24 ′ are connected to means to move the side members  18  as will be described. The control shaft  26  (FIG. 7) extends out of the housing  20  away from the side members  12 . A knob  28  or control means is mounted on the control shaft  26  externally of the housing  20  and distally of the side members  12 . Rotation of the knob  28  in a first direction produces concomitant rotation of drive means  22  and rotation of the knob  28  in an opposite second direction reverses the direction of rotation of the drive means  22 . Thus, rotation of the knob  28  produces lengthening or shortening of the side members  12  by telescoping the side members into the respective sleeves  18  as will be described. As the knob  28  is rotated, the side members  12  both move concurrently and equidistantly. 
     The preferred embodiment is a plurality of sprockets  24 ,  24 ′ and two pitch chain drive means  22 . However, other means known to persons skilled in the art may be disposed in the housing  20  to lengthen and shorten the side members  12 . 
     The first end  14  of each side member  12  is connected to a respective cross brace knuckle  30  (FIGS.  8  and  9 ). Preferably, the side member  12  is received in an opening in the respective cross brace knuckle  30  and extends outwardly on both sides of the opening. A lower stem rod  33  is connected to the cross brace knuckle  30  and extends oppositely from the housing  20  and is disposed under the head  34 . A cross brace rod  32  connects the cross brace knuckles  30  and is opposite from the housing  20 . Thus, the device  10  has a frame formed by the two side members  12 , the housing  20  and the cross brace rod  32 . Preferably, the frame is square or rectangular with the side members  12  being parallel to one another and the housing  20  and cross brace rod  32  being approximately perpendicular to the side members  12 . However, the device  10  is not limited to a rectangle or square and may be other configurations including triangular and trapezoidal. 
     A respective head  34  (FIGS. 10 and 11) is connected to the first end  14  of each side member  12 . Each head  34  has an opening  36  formed in one side thereof, the side being oriented outwardly from the device  10 . A plate cap  38  is attached to each head  34  to enclose the opening  36 . Preferably, a threaded screw is received in a hole in the plate cap to attach the plate cap  38 . An inverted L-shaped slot  40  is formed in the front surface of the head  34 , the slot communicating with the opening  36  in the head  34 . A joint  42  with a stem rod  44  extending outwardly therefrom is received in the opening  36  in the head  34 . The stem rod  44  is received in the slot  40  and is directed angularly upwardly away from the housing. The joint  42  has a cam surface  74  formed opposite from the stem rod  44 . 
     As shown in FIGS. 14 and 15, L rods  46  are connected to each of the stem rods  44 , the L rods  46  being directed toward each other. An upper pivot rod  48  extends between and beyond the L rods  46  and is connected to the L rods  46 . The upper mouthpiece  50 , preferably formed from plastic, has a notch formed in each sidewall of the upper mouthpiece  50  wherein the upper pivot rod  48  is frictionally received and retained in the respective notches. 
     The subassembly for the lower mouthpiece  52  is shown in FIGS. 16 and 17. Lower L rods  54  are connected to each of the lower stem rods  33 . A lower pivot rod  56  is connected to each of the lower L rods  54  and extends outwardly from each lower L rod  54 . The lower mouthpiece  52 , preferably formed of plastic has a notch formed in each sidewall of the lower mouthpiece  52  wherein the lower pivot rod  56  is frictionally received and retained in the respective notches. 
     Although the above retention means for the upper mouthpiece  50  and the lower mouthpiece  52  is preferred, other retention means known to persons skilled in the art may be used. It is understood that the upper mouthpiece  50  and the lower mouthpiece  52  are both pivotally attached to the respective upper pivot rod  48  and lower pivot rod  56  such that the mouthpieces may move about the respective pivot rods when held between the teeth or the jaws of the patient. This pivoting mounting provides a more comfortable and natural interface between the device  10  and the patient. 
     It is also preferred that a replaceable mouthpiece pad  58  be used with each mouthpiece  50 ,  52  to cushion the teeth and jaws of the patient as well as for hygienic reasons (FIG.  25 ). The mouthpiece pad  58 , preferably, is adhesively attached to the respective mouthpieces  50 ,  52  and is made of a resilient foam material. 
     As shown in FIGS. 18 and 19, the subassembly for the upper mouthpiece  50  is disposed above the subassembly for the lower mouthpiece. The lower subassembly is stationary and the upper subassembly may be elevated and lowered to change the distance d between the upper mouthpiece  50  and the lower mouthpiece  52 . 
     Two loading shafts  60  are connected to the rear surface of the housing  20  in a spaced-apart manner. The method of connection is not critical. In a preferred embodiment, each loading shaft  60  has circumferential channel formed near the end of the shaft. As shown in FIG. 20, each shaft  60  is mounted in an opening in the housing so that the end with the channel extends exteriorly of the housing  20  and a retainer such as an E ring is received in the channel. The major portion of the loading shaft extends interiorly into the housing  20 . Each loading shaft  60  is connected to a loading screw  62 . Each loading screw  62  extends through the housing  20  and passes through a respective opening in the front surface  64  of the housing. Each loading screw extends into a respective sleeve  18  without contacting the sleeve  18 . A loading nut  68  is threadingly engaged on the loading screw  62  as shown in FIGS. 21 and 22. The first end of a resilient means such as a coil spring  70  is connected to the loading nut  68  through a spring spacer  64 . The second, opposite, end of the spring  70  is connected to a chisel tip  72  or nose. The chisel tip  72  bears on a cam surface  74  which is formed on the joint  42 . The cam surface is an arcuate cavity formed between two flat surfaces. The tip of the chisel  72  engages the cavity and the flat surfaces act as a stop when the joint  42  has moved to a position wherein the respective flat surface contacts the respective side of the chisel  72 . As the chisel tip  72  is urged forwardly or backwardly by the resilient spring  70 , the cam surface  74  is urged clockwise or counterclockwise. The action is referred to herein as cam action for ease of expression although it is concentric planetary rotation. Each spring  70  is disposed in a longitudinal bore  76  in the respective side members  12 . Preferably, the entire spring  70  and loading nut  68  are received within the bore  76  in the side member  12 . The second end  16  of the side member  12  is telescopically received within the sleeve  18  and remains within the sleeve through the movement of the side member  12 . The spring, chisel tip and cam action have been disclosed in U.S. Pat. Nos. 5,558,624 and 5,645,521 issued to Hepburn et al. 
     In operation of the device  10 , when the knob  28  is rotated in a clockwise direction, the control shaft  26  is rotated clockwise. The sprockets  24  which are keyed to the control shaft  26  are rotated clockwise and move the drive means  22 . The drive means  22  drive the sprockets  24 ′ in a clockwise direction. The sprockets  24 ′ which are keyed to the loading shafts  60 , advance the screws  62  against the loading nuts  68 , spring spacers  69  and springs  70 . The chisel tips  72  are moved forwardly against the cam surface  74  and the joints  42  are moved clockwise to elevate the stem rods  44  and the upper mouthpiece  50 . 
     As the knob  28  is rotated, a quantifiable force is applied which extends the spring  70 . In turning the knob  28  and, ultimately, the screw  62 , greater compression is applied to the spring  70  which, in turn, exerts greater force on the chisel tip  72  and the cam surface  74  to exert a one way tension. The tension capability can range from 0, when the spring  70  is not compressed, up to the maximum tension capability of the spring. 
     When the knob  28  is rotated in a counterclockwise direction, the above movement is reversed and the upper mouthpiece  50  is depressed with respect to the lower mouthpiece  52 . 
     A plurality of spaced-apart indicia  78 , such as numerals, are provided on the outer surface of at least one, and preferably on both, of the side members  12 . The indicia  78  are located where the side member  12  is telescopically received in the sleeve  66  such that movement of the side members  12  can be easily gauged by observing which indicia are visible. As shown in FIG. 23, the indicia reading is approximately “3” and the distance between the mouthpiece is approximately 82% of the maximum. In FIG. 3 the indicia reading is approximately “1” and the distance between the mouthpiece is approximately 10% of the maximum. Through the use of the indicia, an adjustment means is provided to quantify the tension and force applied to the springs to adjust the effective lengths of the side members  12 . The term “effective length” is used because, although the actual length of each side member is not changed, the telescoping of the side member  12  in the respective sleeves  18  produces an effective length of each side member. This effective length is dependent upon the rotation of the knob  28  and effectively varies the distance between the housing and the mouthpieces while simultaneously varying the distance between the upper mouthpiece  50  and the lower mouthpiece  52 . Also, the indicia provide a means to reproduce the distance between the mouthpieces. The user of the device can vary the distance between the mouthpieces in small, controllable, increments. 
     A pair of counter balance weights  80  are provided to be removably attached to the device  10 . Preferably, each weight  80  is connected to a respective rod  82 . The rods  82  are threaded at the end opposite from the weight  80  and each is received in a cooperatively threaded opening  84  formed in the frame, preferably in the cross brace knuckle  30  on opposite sides of the frame. The rods  82  are oriented toward the mouthpieces  50 ,  52  with the respective weights  80  on opposite sides of the patient&#39;s head and distal from the housing  20 . The counterbalance weights  80  are particularly useful when the patient is in a standing or sitting position (FIG.  24 ). The weights  80  are of a mass to balance the weight and leverage of the frame and housing  20  which extends from the patient&#39;s mouth. The counterbalance weight  80  reduce stress on the teeth and jaws of the patient. When the patient is lying down, with device  10  extending upwardly from the patient&#39;s mouth, the counterbalance weights are not necessary. 
     Obviously, many modifications may be made without departing from the basic spirit of the present invention. Accordingly, it will be appreciated by those skilled in the art that within the scope of the appended claims, the invention may be practiced other than has been specifically described herein.