Abstract:
A rapid palatal expansion device is provided having first and second housing parts joined by a threaded spindle which controls the relative position of those housing parts, the spindle incorporating a ratchet/stop system to prevent unwanted screw slippage or backwinding while exerting expansion force to the appliance. Each housing part includes at least one extending rod for transmitting the expansion force to the patient&#39;s teeth or body parts. The housing parts may be oriented with respect to each other by a pair of guide rods extending through them. Directional indicia may be formed on one or more of the housing parts to facilitate spindle adjustment by the orthodontist.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION  
         [0001]    The present invention relates generally to orthopedic devices and, more particularly, to rapid orthodontic/orthopedic palatal expansion or spreader appliances for dental arches.  
           [0002]    Various orthodontic and orthopedic devices are known to apply force to the teeth, jaw or related body parts. In general, one such type of appliance is referred to as an orthopedic expander which is mounted within a patient&#39;s mouth to expand the palate. Various prior patents, such as U.S. Pat. Nos. 3,835,540, 4,347,054, 4,482,318 and 5,281,133, show these devices, the latter showing at attempt at a rapid palatal expansion (RPE) device.  
           [0003]    Many of these prior devices, and RPEs in particular, include a threaded spindle for controllably separating two housing parts, each housing part having one or more force transmitting rods extending toward the teeth. Unfortunately, it is often the case with these prior devices that the threaded spindle is subject to slippage or backwinding (such as lengendary screw backwinding) once set in place for use, in part due, for example, to the countervailing forces exerted on it by the teeth, the high flex applied to the device from the patient&#39;s chewing of food, and/or from the high variations in sizing and fitting the devices into the patient&#39;s mouth (i.e., the tolerance changing from the bending to fit, etc.).  
           [0004]    Various attempts have been made to compensate for or reduce this slippage. Double threading of the spindle has been suggested, but that can significantly increase the spindle cost if done so within the manufacturing tolerances needed due to the small size constraints of dental and orthodontic components. Teflon coatings have been suggested, but due to the heat applied in the forming process, tolerances can be reduced and unpredictable results obtained, sometimes requiring removal and replacement of the appliance. In general, since these appliances are used within a patient&#39;s mouth for relatively long periods of time, dimensional constraints and durability are severe. Moreover, the mechanisms for activation and adjustment must be readily accessible to the orthodontist.  
           [0005]    Accordingly, it is an object of the present invention to provide an improved orthodontic appliance, especially one which:  
           [0006]    1. More reliably transmits desired force to the body parts for sustained periods of time in use,  
           [0007]    2. Is less prone to slippage and backwinding,  
           [0008]    3. Is relatively inexpensive to manufacture,  
           [0009]    4. Can be readily adjusted once mounted in place, and  
           [0010]    5. Can accommodate a variety of different applications and housing modifications.  
           [0011]    These and other objects of the present invention are attained by the provision of a rapid palatal expansion device having first and second housing parts joined by a threaded spindle which controls the relative position of those housing parts, the spindle incorporating a ratchet/stop system to prevent unwanted screw slippage or backwinding while exerting expansion force to the appliance. Each housing part includes at least one extending rod for transmitting the expansion force to the patient&#39;s teeth or body parts. The housing parts may be oriented with respect to each other by a pair of guide rods extending through them. Directional indicia may be formed on one or more of the housing parts to facilitate spindle adjustment by the orthodontist.  
           [0012]    Other objects, advantages and novel features of the present invention will now become readily apparent to those of skill in this art from the following drawings and detailed description. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 shows a top view of a RPE incorporating the present invention in the fully closed position.  
         [0014]    [0014]FIG. 2 shows a bottom view of the RPE of FIG. 1.  
         [0015]    [0015]FIG. 3 shows a top schematic view of the RPE of FIG. 1, illustrating internal components.  
         [0016]    [0016]FIG. 4 shows the view of FIG. 3 with the RPE in an opened position.  
         [0017]    [0017]FIG. 5 shows an enlarged view of the threaded spindle of the RPE of FIG. 1.  
         [0018]    [0018]FIG. 6 shows a cross-sectional view through line  6 - 6  of FIG. 5.  
         [0019]    [0019]FIG. 7 shows an left end view of the threaded spindle of FIG. 5.  
         [0020]    [0020]FIGS. 8 a - 8   e  show an enlarged left end view of the left housing part of the RPE of FIG. 1 at various consecutive positions of the threaded spindle. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0021]    The present invention is illustrated in the drawings as incorporated within an RPE appliance. Such appliances can be used in a variety of implementations, such as rapid maxillary expansion, distalization, upper or lower palatal expansion, space closure, etc. at the instance of the attending orthodontist or surgeon.  
         [0022]    As shown in FIG. 1, the RPE  10  includes left housing part  20  and right housing part  30 . Each such housing part is, for example, formed from a top and bottom portion which is welded, clamped, brazed or otherwise joined together in a conventional manner. Thus, left housing part  20  includes top portion  22  and bottom portion  24 , and right housing part  30  likewise includes top portion  32  and bottom portion  34 . The formation of the housing parts in this manner is suggested for manufacturing efficiency rather than as a requirement of the present invention. The structure of the housing parts used in the present invention could alternatively be formed by other means, such as machining of solid parts, but likely at a greater cost.  
         [0023]    Left housing part  20  includes an internal passageway  26 , preferably formed with an enlarged region  27  connecting to a constricted region  28 . Another enlarged region  29  is preferably connected to constricted region  28  opposite the connection to enlarged region  27 . In certain embodiments, passageway  26  can extend completely through left housing part  20 , but it is not necessary that it do so in all applications. It is advantageous to form left housing part  20  with a portion A of enlarged region  27  exposed for external access to the passageway. This can be done, for example, by forming a notch or cut-out area on top portion  22  that is not present on bottom portion  24 .  
         [0024]    Right housing part  30  includes an internal passageway  36  that is preferably threaded along at least a portion of its length. If passageway  36  is not threaded along its entire length, the unthreaded portion is preferably formed of greater dimension than the threaded portion so as not to constrain threading movement of an object through the threaded portion.  
         [0025]    Each housing part is formed to receive at least one extending rod  40 . These rods are preferably fixed to their respective housing parts and are used to transmit force from the housing parts to the teeth or body areas in a conventional manner. That force will typically be used to expand the teeth or body areas, such as the palate. In especially preferred embodiments, housing parts  20  and  30  can be maintained in a desired orientation with respect to each other through the use of one or more guide rods  42 . These guide rods are, for example, each fixed at one end or portion thereof to one of the housing parts and slidably received by the other housing part. Use of two or more guide rods can serve to prevent twisting motion of the housing parts with respect to each other if the guide rods are formed of conventional cylindrical rods. In other embodiments, that same result may be achieved by a single guild rod if the rod is configured differently, such as to have a rectangular cross section rather than circular. The guide rods may be fixed to either housing part as desired in a given application. As shown in the drawings, both guide rods  42  are fixed to housing part  20  and slidably received within housing part  30 .  
         [0026]    By way of example, housing parts  20  and  30  as shown in the drawings are approximately 11 mm wide (width being measured in the direction across rods  40 ) and approximately 6 mm in length (length being measured along the length of rods  40 ). Housing parts  20  and  30  and rods  40  and  42  may, for example, be formed from conventional materials used in orthodontic appliances.  
         [0027]    Housing parts  20  and  30  are joined by a threaded spindle  50  which controls the relative position of those housing parts. Spindle  50  is movably mounted within both passageway  26  and passageway  36 , preferably for rotational movement within passageway  26  and rotational and longitudinal movement (via threading) withing passageway  36 . Spindle  50  includes a threaded portion  52  which is formed to be matingly received within passageway  36  by the threads in that passageway. Rotation of threaded portion  52  within passageway  36  serves to apply expansion or contraction force to housing part  30 , moving it away from or toward housing part  20  according to the direction of rotation of spindle  50 .  
         [0028]    Spindle  50  also includes sprocket portion  54  which is formed so as to be rotatably received with width-wise clearance within enlarged region  27 . Sprocket portion  54  includes, for example, a plurality of recesses  56  therein. As shown in FIG. 6, these recesses can be formed by two intersecting passageways  58  passing laterally through spindle  50  to create four recesses  56 . Any other number of recesses can be used as desired for a given application or embodiment. Recesses  56  are dimensionally formed so as to received a tool for insertion therein to turn spindle  50 . In the embodiment shown in the drawings, that tool can be a cylindrical rod of conventional nature. Enlarged region  27  and exposed area A are formed so as to allow such rods to have sufficient access to recesses  56  for insertion and a measure of turning (width-wise relative to housing part  20 ) that exposes the next adjacent recess of sprocket portion  54  for similar insertion and turning. In alternative embodiments, sprocket  54  may alternatively be formed with projections, rather than recesses  56 , which can be engaged to rotate spindle  50 .  
         [0029]    Spindle  50  further includes neck portion  60  which is closely and rotatably received within constricted region  28 . Spindle  50  also includes ratchet portion  62  which is rotatably received within enlarged portion  28 . Ratchet portion  62  is, for example, of greater cross sectional dimension than neck portion  60  such that constricted region  60  serves to retain spindle  50  within left housing part  20  while permitting its rotational motion.  
         [0030]    Ratchet portion  62  is, for example, formed with a plurality of indentations or notches  64  about its circumference. An actuation slot  66  may also be formed across the end face of ratchet portion  62 . The number of notches shown in FIGS. 7 and 8 are four, but that is by way of example only. Any number of notches can be employed as desired in a given application or embodiment, according to the degree of spindle slip rotation permissible and the dimensional constraints of a given appliance.  
         [0031]    Left housing part  20  includes a stop member  70 , mounted at enlarged region  29 . Stop member  70  is, for example, clamped at one end  72  between top portion  22  and bottom portion  24 . Stop member  70  is, for example, secured to left housing part  20  by a locating pin  71 , welded or brazed though an opening in the housing. A free end  74  of stop member  70  extends into enlarged portion  29  and is, for example, placed to abut ratchet portion  62 .  
         [0032]    In the example shown in FIGS. 8 a - 8   e , free end  74  extends into notches  64  as spindle  50  is rotated within left housing part  20 . Stop member  70  is preferably formed from a durable and resilient metal material, such as a titanium alloy (nickle or copper titanium alloys of a type used for memory wire will often suffice). Stop member  70  bends within enlarged region  29  as spindle  50  is rotated between notches, as seen in FIGS. 8 b - 8   d . Stop member  70  extends back to its straight length when spindle  50  is rotated such that it aligns with and into a notch  64 , as seen in FIGS. 8 a  and  8   e . When stop member  70  aligns with and into a notch  64 , it resists bending. Thus, stop member  70  serves to restrict rotation of spindle  50  that would remove it from that notch.  
         [0033]    Accordingly, stop member  70  acts with spindle  50  to restrict undesired motion of spindle  50 , such as would otherwise be caused by slippage or backwinding once RPE  10  is mounted within the patient. The application of intended rotational force through recesses  56  of sprocket portion  54  can readily overcome the bending resistance of stop member  70 . However, unintended rotation is of sufficiently less force that the stop member remains unbent. In order to facilitate utilization of RPE  10 , an arrow indicia  80  is, for example, formed on top portion  22  which informs the orthodontist or installer of RPE  10  of the direction of rotation of spindle  50  needed for expansion of the RPE (movement of right housing part  30  away from left housing part  20 ).  
         [0034]    In especially preferred embodiments, notches  64  are formed symetricly, that is, with the same degree of slope (or other applicable dimensional change) on each side of the notch so that the resistance of stop member  70  to bending is the same regardless of the direction of rotation of spindle  50 . Thus, the ratchet/stop arrangement would work in either direction of rotation. By encapsulating spindle  50  and stop member  70  in the manner of the present invention, operation of the features thereof does not detrimentally impact the patient in any significant manner, as for example, by interfering with eating or cleaning of the appliance.  
         [0035]    In the embodiment shown in the drawings, enlarged region  29  is open at one end so as to allow access to actuation slot  66  for more rapid rotation of spindle  50  during initial application or final removal of the appliance if that is desired by the orthodontist or installer. Also, the nature of the threading used by spindle  50  can be altered as needed. For example, threaded portion  52  can be formed with a spiral threading or multiple threading to further increase the threading friction and reduce the amount of slippage and back threading or backwinding and/or to increase the installation efficiency in making the initial setting of the appliance. Also, the present invention has been illustrated in a RPE appliance, but can be readily adapted to other orthodontic and orthopedic devices as needed in both temporary and permanent applications.  
         [0036]    Therefore, although the present invention has been illustrated and describe above in specific embodiments, those are by way of illustration and example only and are not to be taken as a limitation to the scope of the invention. The spirit and scope of the present invention are limited only by the terms of the claims below.