Orthodontic appliances with dissolvable coatings

A method of providing a fast dissolving and humidity-resistant marking on an orthodontic appliance having an elongated archwire slot extending in a generally mesial-distal direction thereon, the method comprising:

• compounding
• a water-insoluble pigment or water-soluble dye,
• a water-soluble binder selected from a polyamide, cellulose derivative, or homopolymer/copolymer of poly(ethylene oxide), and
• a volatile solvent to form a dispersion or solution;
• applying the dispersion or solution on a surface of the orthodontic appliance;
• and evaporating the volatile solvent to provide the marking,
• wherein the polyamide is selected from the group consisting of
• (i) polylactams which comprise monomers having the following functional group:
• (R1)(R2)-N—C(O)—R3,
• where R1, R2 and R3 each are independently aliphatic or aromatic hydrocarbon moieties optionally substituted with one or more of N, O, and S with the understanding that R1, R2 or both may form a ring with R3 such as a pyrrolidone ring, and at least one of R1, R2, and R3 comprises a polymerizable group;
• (ii) polymers based on amides from primary amines which comprise monomers having the following functional group:
• (R1)H—N—C(O)—R3
• where R1 and R3 are each independently aliphatic or aromatic hydrocarbon moieties optionally substituted with one or more of N, O, and S with the understanding that R1 may form a ring with R3 such as a pyrrolidone ring, and at least one of R1 and R3 comprises a polymerizable group:
• and
• (iii) acrylamides which comprise monomers having the following functional group:
• H2N-C(O)—R3,
• where R3 is as defined above,
• the cellulose derivative is selected from the group consisting of carboxymethylcellulose, hydroxypropylmethylcellulose, and hydroxyethylcellulose,
• and wherein at least 60 percent of the dried coating is removed when the appliance is subjected to the Dissolution Test, the steps of which are:
• 1) weighing 10-11 brackets to obtain the weight of coated brackets;
• 2) placing the brackets on a tacky surface of a bonding prep tray and cutting the tray to fit snugly inside a 150 milliliter beaker;
• 3) placing the beaker in a shaker bath containing water at 37° C. and a circular motion of 150 rpm;
• 4) adding 20 milliliters of distilled water to the beaker at t=0 covering the brackets on the tray to start dissolution;
• 5) removing the brackets on the tray from water after 120 seconds, drying the brackets in an oven heated to 100° C., and weighing the brackets;
• and
• 6) dissolving any residual coatings by rinsing the brackets with water and for coatings that are hard to be rinsed off by water, additionally sonicating the brackets in water, 5% ammonium hydroxide aqueous solution, or detergent solution to completely remove the coatings, drying the brackets, and weighing the uncoated brackets.

An orthodontic appliance comprising:

• a base, the base having a lingual-facing surface;
• a body extending outwardly from the base, the body having an elongated archwire slot extending in a generally mesial-distal direction;
• a water-dissolvable coating adhering to and extending over at least a portion of the tiewing bracket facial surfaces furthest from the lingual-facing surface of the base, the coating comprising:
• a colorant;
• and
• a water-soluble binder selected from a polyamide, cellulose derivative, or homopolymer/copolymer of poly(ethylene oxide),
• wherein the polyamide is selected from the group consisting of
• (i) polylactams which comprise monomers having the following functional group:
• (R1)(R2)-N—C(O)—R3,
• where R1, R2 and R3 each are independently aliphatic or aromatic hydrocarbon moieties optionally substituted with one or more of N, O, and S with the understanding that R1, R2 or both may form a ring with R3 such as a pyrrolidone ring, and at least one of R1, R2, and R3 comprises a polymerizable group;
• (ii) polymers based on amides from primary amines which comprise monomers having the following functional group:
• (R1)H—N—C(O)—R3
• where R1 and R3 are each independently aliphatic or aromatic hydrocarbon moieties optionally substituted with one or more of N, O, and S with the understanding that R1 may form a ring with R3 such as a pyrrolidone ring, and at least one of R1 and R3 comprises a polymerizable group;
• and
• (iii) acrylamides which comprise monomers having the following functional group:
• H2N-C(O)—R3,
• where R3 is as defined above,
• the cellulose derivative is selected from the group consisting of carboxymethylcellulose, hydroxypropylmethylcellulose, and hydroxyethylcellulose, and
• wherein at least 60 percent of the dried coating is removed when the appliance is subjected to a Dissolution Test, steps of which are:
• 1) weighing 10-11 brackets to obtain the weight of coated brackets;
• 2) placing the brackets on a tacky surface of a bonding prep tray and cutting the tray to fit snugly inside a 150 milliliter beaker;
• 3) placing the beaker in a shaker bath containing water at 37° C. and a circular motion of 150 rpm;
• 4) adding 20 milliliters of distilled water to the beaker at t=0 covering the brackets on the tray to start dissolution;
• 5) removing the brackets on the tray from water after 120 seconds, drying the brackets in an oven heated to 100° C., and weighing the brackets;
• 6) dissolving any residual coatings by rinsing the brackets with water and for coatings that are hard to be rinsed off by water, additionally sonicating the brackets in water, 5% ammonium hydroxide aqueous solution, or detergent solution to completely remove the coatings, drying the brackets, and weighing the uncoated brackets.