Patent Publication Number: US-2021169615-A1

Title: Reinforced ceramic orthodontic bracket

Description:
BACKGROUND 
     1. Field 
     The present disclosure relates to orthodontic brackets, and in particular, to a reinforced ceramic orthodontic bracket, the bracket being reinforced with a metal backing. 
     2. Description of the Related Art 
     Orthodontics is a specialized field of dentistry that involves the application of mechanical forces to urge poorly positioned or crooked teeth into correct alignment and orientation. Orthodontic procedures can be used for cosmetic enhancement of teeth, as well as medically necessary movement of teeth to correct an underbite or an overbite. For example, orthodontic treatment can improve the patient&#39;s occlusion and/or enhanced spatial matching of corresponding teeth. 
     The most common form of orthodontic treatment involves the use of orthodontic brackets and wires, which together are commonly referred to as “braces.” Orthodontic brackets are small slotted bodies configured for direct attachment to the patient&#39;s teeth, or alternatively, for attachment to bands, which are, in turn, cemented or otherwise secured around the teeth. Once the brackets are affixed to the patient&#39;s teeth, such as by means of glue or cement, a curved arch wire is inserted into slots in the bracket. The arch wire acts as a template or track to guide movement of the teeth into proper alignment. End sections of the arch wire are typically captured within tiny appliances known as tube brackets or terminal brackets, which are affixed to the patient&#39;s bicuspids and/or molars. The remaining brackets typically include open arch wire slots and apply orthodontic forces by means of ligatures attached to the brackets and arch wire (e.g., by means of tie wings on the brackets). 
     Orthodontic treatment is traditionally performed using metallic brackets. With the continuously increasing demand for orthodontic treatment among adults, the aesthetic preferences of orthodontic applicants have received increased emphasis. Accordingly, more aesthetic orthodontic appliances, including ceramic brackets and clear aligners, have been recently introduced. 
     Although ceramic is biocompatible, rigid, and has greater aesthetic appeal than metal appliances, it is a brittle material with low ductility. These characteristics may result in enamel damage or bracket fracture when removing/debonding the ceramic bracket from the tooth. 
     Thus, an orthodontic bracket solving the aforementioned problems is desired. 
     SUMMARY 
     The reinforced ceramic orthodontic bracket includes a ceramic body reinforced with a metal backing. The bracket attaches to a user&#39;s tooth and accepts an alignment wire for adjusting the orientation of the tooth based on forces provided by the alignment wire. A tooth contacting side of the bracket may include a metal plate to counteract the relatively low tensile strength and ductility of the ceramic. An opaque layer may be included between the ceramic and the metal plate to mask the color of the metal so that the bracket blends in with the natural color of the tooth. 
     A method of making the orthodontic bracket includes sintering the ceramic body, the opaque layer, and the metal plate together, resulting in bonds between the layers that do not rely upon adhesive. 
     These and other features of the present disclosure will become readily apparent upon further review of the following specification and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a front view of a reinforced ceramic orthodontic bracket. 
         FIG. 2  shows a back view of the orthodontic bracket of  FIG. 1   
         FIG. 3  shows a perspective view of the orthodontic bracket of  FIG. 1  as seen from the side of the bracket. 
         FIG. 4  shows an exploded perspective view of an alternative embodiment of a reinforced ceramic orthodontic bracket. 
     
    
    
     Similar reference characters denote corresponding features consistently throughout the attached drawings. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The reinforced ceramic orthodontic bracket is a ceramic bracket reinforced with a metal backing. The bracket may be dimensioned and configured similar to orthodontic brackets known in the art for attachment to a user&#39;s teeth that receive an alignment wire for aligning the teeth. A tooth-contacting side of the bracket includes a metal reinforcement to counteract the relatively low tensile strength and ductility of the ceramic for bonding/debonding the bracket to and from the teeth. An opaque layer may be included between the ceramic and metal reinforcement for masking the color of the metal so that the bracket blends in with the natural color of the tooth. 
       FIGS. 1-3  show a first embodiment of the bracket  10 , which includes a ceramic body  20  defining a base  22  and a wire guide  24 . The wire guide  24  provides two parallel walls  26  having aligned slots  28  for accepting an alignment wire. The base  22  of the bracket  10  provides an arcuate tooth-facing surface (shown in  FIG. 3 ). The arcuate tooth-facing surface of the base  22  may be designed to match the shape of the tooth for which it is intended to be attached. The ceramic body  20  is a unitary component made of crystalline alumina. The crystalline alumina may be polycrystalline when a more opaque body is desired or monocrystalline when a more translucent body is desired. 
     A metal base  30  is attached to the tooth-facing side of the ceramic body  20 . The metal base  30  may completely cover the tooth facing surface of the ceramic body  20 . In some embodiments, as shown in  FIGS. 2 and 3 , the metal base  30  may have a larger area than the tooth-facing surface of the ceramic body  20 , resulting in the metal base extending past the peripheral edge of the ceramic body  20  (shown in  FIGS. 1 and 3 ). The metal base  30  may be a plate, a surface coating, a pad, or other metal reinforcement. A tooth-facing side of the metal base  30  may define a cross-hatched, mesh, or knurled pattern (shown in  FIG. 2 ) and/or may be provided with micro-roughness by grinding, milling, etching with hydrogen fluoride or other strong acid, or other abrading processes to increase surface area for bonding. The cross-hatched pattern may be provided by indentations or projections of the cross-hatching. The metal base  30  may be made from any biocompatible metal with sufficient hardness that it may be bonded to a tooth and removed without damaging tooth enamel and without fracturing, e.g., stainless steel. The metal base  30  reinforces the ceramic base  20  to allow for removal from a user&#39;s tooth using conventional orthodontic removal pliers without damaging the bracket or the tooth enamel, thereby allowing rebonding and recycling the bracket  10  (if needed) using conventional techniques known in the art. 
       FIGS. 3-4  show a second embodiment of a bracket  12 . The bracket  12  includes a ceramic body  20  and metal base  30 , similar to the first embodiment. An opaque pad  40  is provided between the ceramic body  20  and the metal base  30 . The opaque pad  40  may prevent the color of the metal base  30  from being transmitted through the ceramic body  20 , thereby improving the aesthetic appearance of the bracket  12 . The opaque pad  40  may completely cover the ceramic body-facing surface of the metal base  30 . The opaque pad  40  may be made of zirconia or a polymer. If a polymer is used, it may enhance the removal/debonding force transition from metal to ceramic referring to polymer flexibility. 
     The ceramic body  20  and metal base  30  may be bonded together using both chemical and physical bonds. A method of making the bracket  12  may include roughening the tooth-facing surface of the ceramic body  20  and the ceramic body-facing surface of the metal base  30 . The ceramic body  20  may be roughened using acid etching, sand blasting, or other methods known in the art. The metal base  30  may be roughened using sand blasting, acid etching, or other methods known in the art, followed by heat treatment for oxidizing the metal surface. The roughened surfaces may be bonded by forcing the surfaces together while heating in a sintering process. During the sintering process, the ceramic will partially dissolve and be saturated with the metal oxide, resulting in a chemical bond between the two surfaces. As a result, the metal base  30  and the ceramic body  20  will be bonded without the use of an adhesive that may be susceptible to failure and degradation. In embodiments using zirconia as an opaque layer  40 , a thin layer may be painted on the roughened and oxidized metal base  30  and heated under a vacuum to prevent voids. The metal base  30  and zirconia/polymer  40  component may then be attached to the ceramic body  20  using the previously discussed sintering process. 
     It is to be understood that the reinforced ceramic orthodontic bracket is not limited to the specific embodiments described above, but encompasses any and all embodiments within the scope of the generic language of the following claims enabled by the embodiments described herein, or otherwise shown in the drawings or described above in terms sufficient to enable one of ordinary skill in the art to make and use the claimed subject matter.