Orthodontic appliance having continuous shape memory

Abstract

Continuous adjustment appliances are provided that can store a large number of geometries that can be successively accessed throughout orthodontic treatment, with each geometry can correspond to an arrangement of the patient's teeth. An appliance according to the present disclosure can be stimulated to transition among the myriad geometries, which can include changes to the overall shape of the appliance as well as the position and geometry of the cavities corresponding to a patient's teeth. Methods of creating the continuous adjustment appliances and methods of treatment using the continuous adjustment appliances are also revealed.

1 . A polymeric shell dental appliance for placement on a dental arch comprising
 a concave trough having a cavity configured to be positioned on a plurality of teeth in the dental arch and having a first approximate shape, wherein the concave trough comprises a crosslinked shape memory polymer, and wherein the crosslinked shape memory polymer is a semicrystalline, non-segmented polymer configured to restore the concave trough to   (a) a second approximate shape on application of a first external energy stimulus; and   (b) a third approximate shape on application of a second external energy stimulus of a greater magnitude than the first energy stimulus.   
     
     
         2 . The polymeric shell dental appliance of  claim 1 , wherein the third approximate shape represents a prescribed final arrangement of the teeth in the dental arch. 
     
     
         3 . The polymeric shell dental appliance of  claim 1 , wherein the second approximate shape represents an intermediate arrangement of teeth in the dental arch. 
     
     
         4 . The polymeric shell dental appliance of  claim 1 , wherein each external energy stimulus is an increase in temperature. 
     
     
         5 . The polymeric shell dental appliance of  claim 4 , wherein each external energy stimulus represents a transition temperature, and wherein each transition temperature is greater than 37° C. 
     
     
         6 . The polymeric shell dental appliance of  claim 1 , wherein the crosslinked shape memory polymer is further configured to restore the concave trough to a fourth approximate shape on application of a fourth external energy stimulus of a greater magnitude than the second or third energy stimuli. 
     
     
         7 . The polymeric shell of  claim 1 , wherein the polymer contains physical crosslinks, chemical crosslinks, or combinations thereof. 
     
     
         8 . The polymeric shell appliance of  claim 1 , wherein the semicrystalline polymeric material includes a number of crystalline structures, and wherein a portion of crystalline structures are irreversibly disrupted on application of the first external energy stimulus to transition the shell to the second approximate shape. 
     
     
         9 . The polymeric shell appliance of  claim 8 , wherein the remaining portion of crystalline structures are irreversibly disrupted on application of the third external energy stimulus. 
     
     
         10 . The polymeric shell appliance of  claim 1 , wherein the polymer includes a crystallization temperature range, and wherein recovery of the second and third approximate shapes occurs when the temperature of the shell is increased to a corresponding temperature within the crystallization temperature range. 
     
     
         11 . The polymeric shell appliance of  claim 10 , wherein the semicrystalline polymeric material includes a number of crystalline structures, wherein an increasing number of crystalline structures are irreversibly disrupted as the temperature of the shell is increased through the crystallization temperature range, and wherein irreversibly disrupting the crystalline structures changes at least one of the approximate shape of the shell, the cavities within the trough, and a combination thereof. 
     
     
         12 . A method for manufacturing polymeric shell dental appliances configured to conform to one or more teeth of a patient, the method comprising:
 providing a first positive model of the patient's dentition, the model representing a repositioned arrangement of the patient's teeth;   forming over the model at a first molding temperature a sheet of crosslinkable, crystallizable polymeric material having a crystallization temperature range having an upper limit and a lower limit;   crosslinking the polymer to create an appliance having a first stored geometry;   providing a second model representing a first intermediate arrangement of the patient's teeth, the arrangement including one or more teeth in different orientations than the first model;   subjecting the appliance to a second molding temperature within the crystallization temperature range and being less than the first molding temperature to create a shell having a second stored geometry;   providing a third model representing a second intermediate arrangement of the patient's teeth, the second arrangement including one or more teeth in different orientations than the first intermediate arrangement   subjecting the appliance to a third molding temperature within the crystallization temperature range to create a third stored geometry, the third molding temperature being less than either the first or second molding temperatures; and   cooling the shell below the lower limit of transition temperature range.   
     
     
         13 . The method of  claim 12 , wherein heating the sheet comprises heating for a period of time sufficient to selectively melt at least portion of the crystalline structures in the shape memory material. 
     
     
         14 .- 15 . (canceled) 
     
     
         16 . The method of  claim 12 , wherein the first model comprises a plurality of reconfigurable tooth models arranged relative to a physical arch, and wherein providing the second model comprises moving at least one of the tooth objects to create the second arrangement. 
     
     
         17 . The method of  claim 16 , wherein the forming a sheet of crosslinkable polymeric material over the model includes the act of applying pressure to the model, and wherein the tooth model is moved along a treatment path segment while the pressure is applied to the model. 
     
     
         18 . The method of  claim 12 , wherein the polymeric material forms an increasing number of crystalline structures as the temperature is reduced from the upper limit of the crystallization temperature range to the lower limit. 
     
     
         19 .- 21 . (canceled)