Adjustable orthodontic band
BACKGROUND AND OBJECTIVES 
     Orthodontic bands have long been used in dentistry to serve as anchoring means for archwires and other dental appliances. The primary purpose of these bands and the appliances they hold is to exert pressure through wires on misplaced or misspaced teeth. It is necessary that the bands fit snugly on the teeth to which they are attached to prevent dislodging under pressure and also to prevent accumulation of food beneath the band and the teeth. Adjustable bands to fit a variety of tooth sizes were first constructed by a French orthodontist in 1841. It was found difficult to obtain conformance to the barrel-shaped contour of many teeth when using these adjustable types; much handwork was necessary to make the band conform and it was also necessary to use large amounts of cement to fill in the areas of non-conformance between the band and the tooth to which it was attached. The adjustable band, for these reasons, gave way to the individually-fitted one. The latter is fashioned by the orthodontist from a ribbon of metal which is formed around the tooth and then welded separately. In a later development preformed bands became available. These could be adapted to individual teeth but the orthodontist needed to stock a large number of bands of differing sizes. 
     The adjustablility concept was however not forgotten. Boyd et al (U.S. Pat. No. 2,007,517) and Lazarus (U.S. Pat. No. 3,138,872) describe improved adjustable bands but these still require preforming of a metal strip to the approximate shape of the tooth to be banded. Again the orthodontist needs to stock a supply of band sizes and will need to do a considerable amount of fitting for each band. 
     It is one objective of the present invention to provide an adjustable band which automatically conforms to the shape of the tooth when it is tightened above and below the widest contour. 
     It is a second objective of the present invention to provide a band having a wide adaptability of differing sizes of teeth so that only two or three sizes need to be stocked. It is a third objective of the present invention to permit continuous adjustment of the band diameter during the course of the treatment to allow changes in applied force or force angle or to compensate for slippage. 
     These and other objectives of the present invention will be explained in the description with reference to the drawings of which the following is a listing. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view of a band made according to the present invention showing the band tightening mechanism and an attached bracket. 
     FIG. 2 is a cut-away, partial view of the band showing details of the tightening and locking mechanism. 
     FIG. 3 is a cross section of the band taken along A-A&#39; of FIG. 1. 
     FIG. 4 is an isometric view of the band of FIG. 1 cylindrically formed and tightened as it would be around a tooth. 
     FIG. 5 is an isometric view of a second embodiment of the invention as it would be applied to a tooth. 
    
    
     DESCRIPTION OF THE INVENTION 
     The new band will be described with reference to FIGS. 1 through 4 which illustrate various features of one embodiment of the invention. The body 1 of the band is constructed of a metal which can be annealed to a &#34;dead soft&#34; condition. Gold and silver, for example can be used in alloys having this property. One end of the band is formed into the tang 2. A tightening assembly, shown in FIG. 2 is made up of the vertical shafts 15 and 15&#39;, the pinions 6 and 6&#39;, the driving heads 7 and 7&#39; and the locking means 24, 24&#39;, 25 and 25&#39;. The tightening assembly is mounted in a frame 14 which is welded or otherwise joined to the band. The racks 9 and 9&#39; are also welded to the band as is the archwire bracket 12, FIG. 1. 
     The band assembly is first formed into a cylindrical shape by passing tang 2 through the frame 14 until the racks 9 and 9&#39; engage the pinions 6 and 6&#39;, respectively, FIG. 4. The drive heads 7 and 7&#39; are raised and individually turned with tool 8 until the assembly just slips over the tooth to be banded. After the proper vertical and radial adjustments have been made, the upper and lower portions of the band are tightened by means of the driving heads 7 and 7&#39;. As each pinion is turned, the incisal and gingival portions of the band decrease in diameter to conform to the contour of the tooth. The central portion of band also decreases in diameter but not as rapidly. The slot 3 isolates the forces being exerted in the upper and lower halves of the band so that more compliance to the shape of the tooth is achieved. This is further aided by the variation in cross section of the band, FIG. 3. The thickness of the band at the at the incisal and gingival edges is a minimum and increases to a maximum 5 near and at the tooth contour edge. A distinct advantage of the present invention over preformed bands and previously available adjustable bands is the fact that allowance for differences in incisal and gingival diameters is made automatically. 
     When the band is snug, the driving heads are locked. The locking method is shown in detail in FIG. 2. The drive shafts 15 and 15&#39; pass through the hexagonal openings in the bottom plate 11 of the frame 14. Upward movement of each drive shaft frees the shaft and its pinion for turning because the lower portion of the shaft is cylindrical and smaller than the hexagonal opening. Downward movement places the hexagonal portions 24 and 24&#39; of the drive shafts into their respective hexagonal openings thus preventing further movement of the pinions. The racks 9 and 9&#39; are of sufficient width so that the permitted range of vertical movement of the pinions does not result in disengagement. 
     When the band has been properly adjusted with the bracket 12 at the desired position, the excess of tang 2 can be ground off by the orthodontist. Exposed slot area is filled in with cement. The band can be loosened or tightened for further adjustment during the course of the treatment. 
     In some applications the bracket 12 may be mounted on the frame 14 to minimize the number of protruding structures in the mouth. 
     A second embodiment of the invention is shown in FIG. 5. The tightening mechanism consists of the screws 20 and 20&#39; interacting with the threaded stanchions 21 and 21&#39;. The screws pass through the unthreaded bearing blocks 22 and 22&#39; and terminate in the screw heads 23 and 23&#39; which contain angularly spaced holes to permit the insertion of a drive pin for turning. Lock nuts 27 and 27&#39; are tightened to prevent subsequent loosening of the band. Excess screw length can be ground off. 
     In some cases additional friction between the inner surface of the band and the tooth can be achieved by welding a fine mesh 26 to the band as shown in FIG. 5.