Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K6/00—Preparations for dentistry
  • A61K6/30—Compositions for temporarily or permanently fixing teeth or palates, e.g. primers for dental adhesives

Definitions

• Orthodontic treatment involves movement of malpositioned teeth to orthodontically correct positions.
• Tiny orthodontic appliances known as brackets are connected to exterior surfaces of the patient's teeth, and an arch wire is placed in a slot of each bracket.
• the archwire forms a track to guide movement of the teeth to desired positions for correct occlusion.
• End sections of the archwire are often received in appliances known as buccal tubes that are fixed to the patient's molar teeth. In recent years it has become common practice to bond orthodontic appliances directly to the surface of the tooth.
• Adhesive precoated brackets are known and offer significant advantages to the orthodontist.
• Adhesive precoated brackets have a bonding base upon which the manufacturer may apply a precise quantity of adhesive such as a photocurable adhesive. When it is desired to mount the bracket on a tooth, the bracket is simply removed from the package and placed directly onto the tooth surface.
• Photocurable adhesives offer advantages to orthodontic practitioners.
• the exact position of the bracket on the corresponding tooth is highly important in order to facilitate moving the teeth to the desired positions without the need to place bends or twists in the archwire.
• the use of a photocurable orthodontic adhesive is highly beneficial in that the practitioner can take time to position the brackets in precise, appropriate locations. Once the practitioner is satisfied with the bracket positions, the curing light can be activated to quickly harden the adhesive and secure the brackets in place.
• photocurable adhesives provide other desirable functional properties, including, for example, sustained fluoride release.
• it is also desirable that the adhesive have adequate hydrophilicity or moisture tolerance, as indicated, for example, by the ability of the adhesive to absorb water or saliva.
• brackets with adhesives used adhesives that were more viscous (i.e., less fluid) than other available orthodontic adhesives. Higher viscosity was used to ensure that the adhesive retained its shape and did not separate or distort when the bracket was lifted from the package for use.
• some orthodontists prefer the use of less viscous (i.e., more fluid) adhesives in order to facilitate manipulation of the bracket before the adhesive is cured.
• brackets with less viscous adhesives are relatively easy to slide along the tooth surface when an effort is made to align the bracket in a proper, precise orientation on the tooth before the adhesive is cured.
• the use of an adhesive with too low of a viscosity may be detrimental by causing the bracket to slip in the package or slip on the tooth (i.e., skating).
• Orthodontic brackets precoated with adhesive are commonly sold with a flexible release substrate in contact with the adhesive.
• many release substrates are not suitable for use with all adhesives.
• soft, tacky, less viscous, hydrophilic adhesives it has been found that a portion of the adhesive is sometimes left on the release substrate when an attempt is made to lift the appliance from the container and detach the adhesive from the release substrate. In those instances, sufficient adhesive may not remain on the bracket to provide adequate bond strength to retain the bracket on the tooth during the course of orthodontic treatment.
• adhesives having a relatively low viscosity tend to slowly flow across the release substrate and from the space beneath the bracket over extended periods of time, creating bracket removal and/or liner release problems.
• the shape of the adhesive may distort as the appliance is lifted from the container.
• detaching the adhesive from the release substrate may alter the configuration of the adhesive, resulting in unsatisfactory direct bonding unless additional steps are undertaken to shift the adhesive by hand back to its original, pillow-like shape.
• some of the adhesive may be shifted to one side of the appliance base, such that the opposite side of the base does not have a satisfactory amount of adhesive for bonding.
• the void space may result in premature, spontaneous debonding of the appliance from the tooth, a nuisance that is best avoided. Furthermore, in some instances the void space can establish a pocket that receives food and debris, facilitating the formation of caries.
• the present invention provides a packaged article including an orthodontic appliance.
• the orthodontic appliance has a base for bonding the appliance to a tooth, and an adhesive on the base of the appliance.
• the adhesive includes a polymerizable component, a fluoride-releasing material, a hydrophilic component, a hardener, an acidic component, and a filler including a fumed silica having a surface area of at least about 70 m /g.
• a container at least partially surrounds the orthodontic appliance having adhesive on the base thereof.
• the adhesive has a static yield stress at 28 °C of at least about 7000 dynes/cm 2 .
• the adhesive has a flow-out value of no greater than about 0.4 millimeters (mm) after one week at 40°C, wherein flow-out value is a measure of the tendency of an adhesive to flow on a liner as described herein.
• the fumed silica has a surface area of about 70 m 2 /g to about 1000 m 2 /g, more preferably about 90 m 2 /g to about 500 m 2 /g, and most preferably about 100 m 2 /g to about 150 m 2 /g.
• the packaged article may be provided in a kit that includes, for example, instructions for using the orthodontic appliance. Ln another aspect, the present invention provides a packaged article including an orthodontic appliance.
• the orthodontic appliance has a base for bonding the appliance to a tooth, and an adhesive on the base of the appliance.
• the adhesive includes a polymerizable component, a fluoride-releasing material, a hydrophilic component, a hardener, an acidic component, a filler, and a photobleachable dye.
• the hardener includes a sensitizing compound different from the photobleachable dye.
• the adhesive has an initial color prior to exposure to actinic radiation and a final color subsequent to exposure to actinic radiation, with the initial color being different than the final color.
• a container at least partially surrounds the orthodontic appliance having adhesive on the base thereof.
• the filler includes fumed silica having a surface area of at least about 70 m 2 /g.
• the packaged article may be provided in a kit that includes, for example, instructions for using the orthodontic appliance.
• the present invention provides a method of bonding an orthodontic appliance to a tooth.
• the method includes providing a packaged article including an orthodontic appliance having a base for bonding the appliance to a tooth, an adhesive on the base of the appliance, and a container at least partially surrounding the orthodontic appliance having adhesive on the base thereof.
• the adhesive includes a polymerizable component, a fluoride-releasing material, a hydrophilic component, a hardener, an acidic component, and a filler including fumed silica having a surface area of at least about 70 m 2 /g; removing the orthodontic appliance having adhesive on the base thereof from the container; applying the base of the appliance to the tooth surface; and exposing the adhesive to actinic radiation.
• the present invention provides a method of bonding an orthodontic appliance to a tooth.
• the method includes providing a packaged article including an orthodontic appliance having a base for bonding the appliance to a tooth, an adhesive on the base of the appliance, and a container at least partially surrounding the orthodontic appliance having adhesive on the base thereof, wherein the adhesive includes a polymerizable component, a fluoride-releasing material, a hydrophilic component, a hardener, an acidic component, a filler, and a photobleachable dye, and wherein the adhesive has an initial color prior to exposure to actinic radiation and a final color subsequent to exposure to actinic radiation, the initial color being different than the final color; removing the orthodontic appliance having adhesive on the base thereof from the container; applying the base of the appliance to the tooth surface; and exposing the adhesive to actinic radiation.
• the hardener includes a sensitizing compound different from the photobleachable dye.
• the present invention provides a packaged adhesive including an adhesive and a release substrate including a surface in contact with the adhesive.
• the adhesive includes a polymerizable component, a fluoride-releasing material, a hydrophilic component, a hardener, an acidic component, and a filler including a fumed silica having a surface area of at least about 70 m 2 /g, wherein the adhesive has a static yield stress at 28 °C of at least about 7000 dynes/cm 2 and a flow-out value of no greater than about 0.4 millimeters after one week at 40°C.
• the present invention provides a packaged adhesive including an adhesive and a release substrate including a surface in contact with the adhesive.
• the adhesive includes a polymerizable component, a fluoride-releasing material, a hydrophilic component, a hardener, an acidic component, a filler, and a photobleachable dye, wherein the adhesive has an initial color prior to exposure to actinic radiation and a final color subsequent to exposure to actinic radiation, the initial color being different than the final color, and wherein the adhesive has a static yield stress at 28 °C of at least about 7000 dynes/cm 2 .
• the hardener includes a sensitizing compound different from the photobleachable dye.
• orthodontic appliance refers to .any device intended to be bonded to the teeth, including, but not limited to, orthodontic brackets, buccal tubes, lingual buttons, and cleats.
• the term “orthodontic appliance” encompasses orthodontic bands.
• the appliance has a base for receiving adhesive and it can be made of metal, plastic, ceramic, and combinations thereof
• hardenable is descriptive of a material that can be cured or solidified, for example, by heating to remove solvent, heating to cause polymerization, chemical cross-linking, radiation-induced polymerization, or crosslinking.
• hardener means a system that initiates hardening of a resin.
• a hardener may include, for example, a polymerization initiator.
• photobleachable refers to loss of color upon exposure to actinic radiation.
• filler means a particulate material (e.g., an inorganic oxide) in dry powder form capable of being dispersed in a resin.
• a dental composite preferably includes a powder dispersed in a resin.
• silicon refers to the compound silicon dioxide. See Kirk- Othmer Encyclopedia of Chemical Technology, 4th Ed., Vol. 21, pp. 977-1032 (1977).
• amorphous silica refers to silica that does not have a crystalline structure as defined by x-ray diffraction measurements.
• examples of amorphous silica include silica sols, silica gels, precipitated silica, and pyrogenic silica.
• pyrogenic silica and “fumed silica” are used interchangeably and refer to amorphous silicas formed in the vapor phase.
• Pyrogenic silica may contain, for example, a few hundred primary particles fused into branched- chain, three-dimensional aggregates.
• Examples of pyrogenic silica include products available under the trade designations AEROSIL OX-50, AEROSIL-130, AEROSIL- 150, AEROSIL-200, and AEROSIL R-972 available from DeGussa AG, (Hanau, Germany) and CAB-O-SIL M5 and CAB-O-SEL TS720 available from Cabot Corp. (Boston, MA).
• base filler refers to fillers other than fumed silica fillers.
• Base fillers include, for example, non-reactive fillers (e.g., quartz fillers), reactive fillers (e.g., fluoroaluminosilicate glass), and combinations thereof.
• silane treated means that the surface of a particle has been modified by application of a silane (e.g., dichlorodimethylsilane).
• the silane may be a coupling agent that includes a reactive functionality (e.g., ⁇ - methacryloxypropyltrimethoxysilane, A 174) .
• aggregate length means the longest dimension of the aggregate.
• aggregate is descriptive of strongly associated primary particles often bound together by, for example, by residual chemical treatment, covalent chemical bonds, ionic chemical bonds, or hydrogen bonds.
• slump refers to the phenomenon of flow under the force of gravity. It is desirable that orthodontic adhesives do not slump because after they are placed in the mouth, the practitioner wants the imparted shape to remain unchanged until the materials are cured. It is also preferable that the adhesive can support the weight of the appliance without slumping. Slumping can lead to bracket drift and skating of the adhesive coated bracket on the tooth. Materials with a sufficiently high yield stress will not slump; that is, they will not flow under the stress of gravity. The yield stress of a material is the minimum stress required to cause the material to flow, and is described in Rheology Principles, Measurements, and Applications, C. W. Macosko, NCH Publishers, Luc, New York, 1994, p. 92.
• the yield stress of an orthodontic adhesive be sufficiently high that the material does not slump in all types and sizes of uses.
• the yield stress of an orthodontic adhesive will be sufficiently high that the material does not substantially slump when supporting a bracket on top of the adhesive. If the adhesive does flow out from underneath the bracket, preferably it will remain on a release substrate when the bracket is removed.
• the pre-cured adhesive be preapplied (e.g., with a syringe) to an orthodontic appliance and the resulting adhesive precoated appliance packaged for later use by a practitioner.
• the adhesive can be preapplied to a release substrate and then packaged for later use by a practitioner to adhere an orthodontic appliance to a tooth. Ln both cases, it is critical that the packaged adhesive (whether applied on an appliance or a release substrate) does not slump over time.
• the preapplied (or precoated) adhesive does not slump under typical package storage and shipping conditions, for example, storage for up to 6 months, preferably for up to about 1 year, and more preferably for up to about 3 years. Generally storage would be expected to be at or below ambient temperature (i.e., room temperature), however, in some cases, storage and shipping conditions could be at greater than ambient temperature.
• the adhesive can be evaluated for adhesive/bracket flow-out (or "flow-out”) and/or adhesive/bracket vertical slip (or “slip”) according to the test methods described herein.
• flow-out measures the tendency over time of an adhesive to flow outwardly on a horizontally mounted release substrate beneath an orthodontic bracket
• slip measures the tendency of an adhesive-coated bracket vertically mounted on a release substrate to slip downward over time.
• the flow-out (after one week at 40°C) and slip values are less than about 0.4 mm, more preferable less than about 0.25 mm, and most preferable 0 (zero).
• Flow-out or slip values greater than about 0.4 mm are readily apparent to the naked eye and can lead to significant problems during storage and/or shipping of the packaged adhesive. Such problems can include, for example, shape distortion of the adhesive on a release liner or, more seriously, separation of an orthodontic appliance from the adhesive when the appliance is removed from the package.
• the adhesive have a static yield stress at 28 °C of about 7000 dynes/cm 2 to about 100,000 dynes/cm 2 ; and have a steady state viscosity at 28°C of about 3 x 10 2 Pascal-seconds (Pa-s) to about 7 x 10 4 Pa-s.
• (meth)acrylate is a shorthand reference to acrylate, methacrylate, or combinations thereof
• (meth)acrylic is a shorthand reference to acrylic, methacrylic, or combinations thereof.
• Figure 1 is a fragmentary, side cross-sectional view of a packaged article according to one embodiment of the present invention.
• Figure 2 is a perspective view of an orthodontic appliance according to another embodiment of the present invention.
• the present invention provides packaged article 10 including an orthodontic appliance such as bracket 12.
• the bracket 12 has a base 14 for directly bonding the bracket 12 to a patient's tooth structure.
• An adhesive 16 extends across the base 14 of the bracket 12.
• the bracket 12 and the adhesive 16 are at least partially surrounded by a container 18.
• the exemplary container 18 illustrated in Fig. 1 includes an integrally-molded body with internal wall portions that define a recess or well 20.
• the well 20 includes side walls and a bottom 22.
• the side walls of the well 20 include horizontally extending recesses for engagement with edge structure of carrier 24. Additional information regarding a suitable carrier 24 is set out in U.S. Pat. No. 5,328,363 (Chester et al).
• the bottom 22 of the well 20 includes a release substrate 25.
• the article 10 also includes a cover 26 with a tab 28, with the cover 28 being connected to the container 18 by, for example, adhesive 30.
• the present invention provides packaged article 10 including orthodontic appliance 12 having a base 14 for bonding the appliance 12 to a tooth, an adhesive 16 on the base, and preferably, a release substrate 25 including a surface 27 in contact with the adhesive 16.
• the adhesive 16 includes a polymerizable component, a fluoride-releasing material, a hydrophilic component, a hardener, an acidic component, and a filler.
• the release substrate 25 may be selected from a number of materials including, for example, polyolefins, poly(vinyl chloride), polyurethanes, and poly(tetrafluoroethylene).
• the surface 27 of the release substrate 25 comprises a number of pores, and preferably no more than about 50% by weight of the adhesive 16 is within the pores.
• the article 10 is preferably packaged in a container that provides barriers to the transmission of light and/or water vapor. Ln some embodiments of the present invention, the article 10 is preferably provided as a kit. In some embodiments, the present invention preferably provides a method of bonding an orthodontic appliance 12 to a tooth.
• the adhesive preferably has a static yield stress at 28°C of at least about 7000 dynes/cm 2 .
• the adhesive preferably has a steady state viscosity of about 3 x 10 2 Pa-s to about 7 x 10 4 Pa-s at 28°C.
• the adhesive preferably has an initial color prior to exposure to actinic radiation and a final color subsequent to exposure to actinic radiation, with the initial color being different than the final color.
• the adhesive preferably includes a photobleachable dye
• the hardener preferably includes a sensitizing compound different from the photobleachable dye.
• the adhesive preferably includes a filler including a fumed silica having a surface area of at least about 70 m /g.
• the filler further includes a base filler.
• the adhesives used in the present invention are preferably substantially free of solvent, and substantially free of added water.
• substantially free of added water means that the composition does not contain water that is intentionally added as a non-complexed or coordinated entity. It is understood that many materials, such as metals or glasses, contain water that is taken up from the atmosphere or is present as a coordination complex in its normal state. Water taken up by hygroscopic materials or present as a hydrate is permissibly present in the compositions described herein. Any water that is present in the composition, regardless of source, should not be present in amounts such that the water will have a deleterious effect on the long term properties of the composition. For example, water should not be present in an amount that would facilitate reaction of an acid-reactive filler with an acidic component so that lumpiness or graininess of the material develops during commercially desired storage times.
• Orthodontic adhesives used in the present invention preferably have the ability to uptake water, and therefore are moisture tolerant. It has been surprisingly found that these adhesives retain their strength even when used in moisture contaminated conditions. In orthodontic bracket bonding procedures, for example, it is not necessary to dry the substrate, as long as a coating of moisture tolerant primer is applied to the tooth, prior to bonding the orthodontic appliance. Teeth primed with moisture tolerant primers may become recontaminated as in situations where bonding has been delayed, or where a patient secretes excessive crevicular fluid.
• the adhesives have the ability to absorb moisture from this recontamination situation.
• the primer may also include an etchant composition. Decreased bracket bond failures are expected using orthodontic appliances having these adhesives. ADHESIVE
• Adhesives used in the present invention include a polymerizable component, a fluoride-releasing material, a hydrophilic component, a hardener, and an acidic component as disclosed, for example, in U.S. Pat. No. 6,126,922 (Rozzi et al.) and International Patent Application Publication No. WO 00/69393 (Brennan et al.). Hydrophilic Component.
• Adhesives used in the present invention include a hydrophilic component.
• the hydrophilic component is a hydrophilic monomer, oligomer, or polymer.
• hydrophilic component is relatively lower in steady state viscosity than other ingredients of the composition so that it serves as a viscosity lowering function in the overall uncured material.
• exemplary hydrophilic components are disclosed, for example, in U.S. Pat. No. 6,126,922 (Rozzi et al.) and International Patent Application Publication No. WO 00/69393 (Brennan et al.).
• Preferred hydrophilic components include, for example, 2-hydroxyethyl acrylate, 2-hydroxyefhyl methacrylate (HEMA), hydroxypropyl (meth)acrylate, glycerol di(mefh)acrylate, poly(ethylene glycol) methacrylate, poly(ethylene glycol) di(meth)acrylate, poly(propylene glycol) (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, glycidyl (meth)acrylate, and combinations thereof.
• HEMA 2-hydroxyethyl acrylate
• HEMA 2-hydroxyefhyl methacrylate
• glycerol di(mefh)acrylate poly(ethylene glycol) methacrylate
• poly(ethylene glycol) di(meth)acrylate poly(propylene glycol) (meth)acrylate
• tetrahydrofurfuryl (meth)acrylate glycidyl (meth)acrylate
• hydrophilic monomers include glycerol (meth)acrylate, glycerol di(mefh)acrylate, ethylene glycol di(meth)acrylate, poly(ethylene glycol) di(meth)acrylate (where the number of repeating ethylene oxide units varies from 2 to 30, including, for example, tri(ethylene glycol) dimethacrylate (TEGDMA)).
• hydrophilic components include monomers and polymers such as pyrrolidone, a moiety containing hydroxy groups and polyether groups, a moiety containing a sulfonate group, a moiety containing a sulfinate group, N-oxysuccinimide, N- vinylacetamide, and acrylamide.
• the adhesive includes at least about 0.05% by weight, more preferably at least about 1% by weight, and most preferably at least about 3% by weight hydrophilic component, based on the total weight of the adhesive.
• the adhesive includes at most about 90% by weight, more preferably at most about 60% by weight, and most preferably at most about 20% by weight hydrophilic component, based on the total weight of the adhesive.
• Adhesives used in the present invention include an acidic component.
• the acidic component is an acidic monomer, oligomer, or polymer.
• the acidic component includes at least one acidic group.
• the acidic group is preferably selected from oxyacids or tbio-oxy acids of C and P. More preferably, the acidic component is a compound that is an acid of C or P.
• a precursor to the acid such as an acid anhydride, e.g., 4-methacryloxyethyl trimellitate anhydride (4-META), or ester can be used in place of the acid itself.
• the desired acid may be generated in situ.
• Preferred acids include, for example, carboxylic acids, sulfonic acids, and phenols, with carboxylic acids, alkylsulfonic acids, arylsulfonic acids, and phosphonic acids being more preferred.
• Exemplary hydrophilic components are disclosed, for example, in U.S. Pat. No. 6,126,922 (Rozzi et al.) and International Patent Application Publication No. WO 00/69393 (Brennan et al.).
• Preferred acidic groups are carboxylic acids, sulfonic acids, phosphoric acids, phosphonic acids, and boric acids, the salts of the foregoing acids or precursors of the foregoing acids that are easily converted to these acids in conditions encountered during an orthodontic procedure.
• acidic components include, for example, (meth)acryloyl substituted carboxylic acids; phosphoric acid esters of hydroxyethyl (mefh)acrylate, hydroxypropyl (meth)acrylate, and glycerol di(meth)acrylate; (meth)acrylates of pentaerythritol (e.g., pentaerythritol di(meth)acrylate); and (meth)acrylates of dipentaerythritol (e.g., dipentaerythritol penta(meth)acrylate), and combinations thereof.
• pentaerythritol e.g., pentaerythritol di(meth)acrylate
• dipentaerythritol e.g., dipentaerythritol penta(meth)acrylate
• Preferred acidic components include, for example, derivatives of amino acids, and acids such as tartaric acid, citric acid, malic acid that have been functionalized with an ethylenically unsaturated functionality.
• citric acid may be functionalized by incorporating an acryloyl or methacryloyl functionality.
• CDMA is the reaction product of citric acid and isocyanatoethyl methacrylate.
• the adhesive includes at least about 0.01% by weight, more preferably at least about 0.05% by weight, and most preferably at least about 1% by weight acidic component, based on the total weight of the adhesive.
• the adhesive includes at most about 90% by weight, more preferably at most about 60% by weight, and most preferably at most about 20% by weight acidic component, based on the total weight of the adhesive.
• Adhesives used in the present invention include a polymerizable component.
• the polymerizable component is a monomer, oligomer, or polymer that includes a polymerizable group.
• Exemplary polymerizable components are disclosed, for example, in U.S. Pat. No. 6,126,922 (Rozzi et al.) and International Patent Application Publication No. WO 00/69393 (Brennan et al.).
• the polymerizable component may also be selected from hydrophilic and acidic components disclosed herein that are polymerizable.
• Polymerizable groups may be selected from free radically polymerizable groups, cationically polymerizable groups, or combinations thereof. Ln a preferred aspect of the present invention, at least some of the polymerizable material is relatively lower in viscosity than other ingredients of the composition so that it serves a viscosity lowering function in the overall uncured material.
• Preferred polymerizable groups are free radically polymerizable groups.
• Preferred free radically polymerizable components are esters of (meth)acrylic acid, including, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate ("HEMA”), hydroxypropyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, glycidyl (meth)acrylate, the diglycidyl methacrylate of bisphenol A (“Bis-GMA”), glycerol mono(meth)acrylate, glycerol di(meth)acrylate, ethylene glycol di(meth)acrylate, poly(ethylene glycol) di(meth) acrylate (where the number of repeating ethylene oxide units vary from 2 to 30, including, for example, triethylene glyco
• the adhesive includes at least about 0.05% by weight, more preferably at least about 0.1% by weight, and most preferably at least about 0.5% by weight polymerizable component, based on the total weight of the adhesive.
• the adhesive includes at most about 90% by weight, more preferably at most about 60% by weight, and most preferably at most about 20% by weight polymerizable component, based on the total weight of the adhesive.
• Fluoride-Releasing Material Adhesives used in the present invention include a fluoride-releasing material.
• the fluoride-releasing material may be a filler.
• the fluoride- releasing material used in the present invention may be naturally occurring or synthetic fluoride minerals, fluoride glass such as fluoroaluminosilicate glass, simple and complex inorganic fluoride salts, simple and complex organic fluoride salts or combinations thereof.
• these fluoride sources can be treated with surface treatment agents.
• the fluoride-releasing material may optionally be a metal complex.
• fluoride-releasing material examples include fluoroaluminosilicate glasses as described, for example, in U.S. Pat. No. 3,814,717 (Wilson et al.), which may be optionally treated as described, for example, in U.S. Pat. No. 5,332,429 (Mitra et al.).
• Exemplary fluoride-releasing materials are disclosed, for example, in U.S. Pat. No. 6,126,922 (Rozzi et al.) and International Patent Application Publication No. WO 00/69393 (Brennan et al.).
• the adhesive includes at least about 10% by weight, more preferably at least about 45% by weight, and most preferably at least about 75% by weight fluoride-releasing material, based on the total weight of the adhesive.
• the adhesive includes at most about 87% by weight, more preferably at most about 85% by weight, and most preferably at most about 83% by weight fluoride-releasing material, based on the total weight of the adhesive.
• Adhesives used in the present invention include a hardener.
• the hardener will induce hardening upon exposure to actinic radiation (e.g., the hardener includes a photoinitiator).
• the polymerizable component includes free radical polymerizable groups
• the hardener is preferably selected to be a free radical initiator.
• Exemplary hardeners are disclosed, for example, in U.S. Pat. No. 6,126,922 (Rozzi et al.) and International Patent Application Publication No. WO 00/69393 (Brennan et al.).
• Preferred free radical photoinitiators include ternary photoinitiator systems as disclosed, for example, in U.S. Pat. No. 5,545,676 (Palazzotto et al.).
• Useful visible light induced ternary photoinitiator systems preferably include a sensitizing compound (e.g., camphorquinone), an electron donor (e.g., sodium benzene sulfinate, amines, and amino alcohols), and an iodonium salt (e.g., diphenyliodonium chloride, bromide, iodide, or hexafluorophosphate).
• a sensitizing compound e.g., camphorquinone
• an electron donor e.g., sodium benzene sulfinate, amines, and amino alcohols
• an iodonium salt e.g., diphenyliodonium chloride, bromide, iodide, or hexafluorophosphate
• Useful ultraviolet light-induced polymerization initiators preferably include ketones (e.g., benzyl and benzoin), acyloins, and acyloin ethers.
• Preferred ultraviolet light-induced polymerization initiators include 2,2-dimethoxy-2-phenylacetophenone available under the trade designation IRGACURE 65 and benzoin methyl ether (2- methoxy-2-phenylacetophenone), both available from Ciba Specialty Chemicals, Basel, Switzerland.
• the photoinitator is preferably capable of promoting hardening of the polymerizable components on exposure to light of a suitable wavelength and intensity.
• the photoinitiator is also preferably sufficiently shelf stable and free of undesirable coloration to permit its storage and use under typical orthodontic conditions. Nisible light photoinitiators are preferred.
• the photoinitiator should be present in an amount sufficient to provide the desired rate of hardening. This amount will be dependent in part on the light source, the thickness of the layer to be exposed to radiant energy, and the extinction coefficient of the photoinitiator.
• the photoinitiator components will be present at a total weight of about 0.001% to about 5%, more preferably about 0.01% to about 1%, based on the total weight of the composition.
• the adhesive preferably has an initial color remarkably different than dental structures. Color is preferably imparted to the adhesive through the use of a photobleachable dye.
• the adhesive preferably includes at least about 0.001% by weight photobleachable dye, and more preferably at least about 0.002% by weight photobleachable dye, based on the total weight of the adhesive.
• the adhesive preferably includes at most about 1% by weight photobleachable dye, and more preferably at most about 0.1% by weight photobleachable dye, based on the total weight of the adhesive.
• the amount of photobleachable dye may vary depending on its extinction coefficient, the ability of the human eye to discern the initial color, and the desired color change.
• the color formation and bleaching characteristics of the photobleachable dye varies depending on a variety of factors including, for example, acid strength, dielectric constant, polarity, amount of oxygen, and moisture content in the atmosphere.
• the bleaching properties of the dye can be readily determined by irradiating the adhesive and evaluating the change in color.
• at least one photobleachable dye is at least partially soluble in the hardenable resin.
• Exemplary classes of photobleachable dyes are disclosed, for example, in U.S. Pat. No. 6,331,080 (Cole et al.) and U.S. Pat. Application Serial Nos. 09/489,612, filed January 21, 2000, and 09/689,019, filed October 12, 2000.
• Preferred dyes include, for example, Rose Bengal, Methylene Violet, Methylene Blue, Fluorescein, Eosin Yellow, Eosin Y, Ethyl Eosin, Eosin bluish, Eosin B, Erythrosiri B, Erythrosin Yellowish Blend, Toluidine Blue, 4',5'-Dibromofluorescein, and combinations thereof.
• the color change in the inventive adhesive is initiated by light.
• the adhesive 's color change is initiated using actinic radiation using, for example, a dental curing light which emits visible or near infrared (LR) light for a sufficient amount of time.
• the mechanism that initiates the color change in the compositions of the invention may be separate from or substantially simultaneous with the hardening mechanism that hardens the resin.
• an adhesive may harden when polymerization is initiated chemically (e.g., redox initiation) or thermally, and the color change from an initial color to a final color may occur subsequent to the hardening process upon exposure to actinic radiation.
• the change in adhesive color from an initial color to a final color is preferably quantified by a Color Test as described below. Using the Color Test, a value of ⁇ E* is determined, which indicates the total color change in a 3-dimensional color space. The human eye can detect a color change of approximately 3 ⁇ E* units in normal lighting conditions.
• the dental compositions of the present invention are preferably capable of having a color change, ⁇ E*, of at least about 20; more preferably, ⁇ E* is at least about 30; most preferably ⁇ E* is at least about 40.
• the components and component levels used in the adhesive may be selected as desired with guidance from the accompanying specification and examples.
• the selection of the hardener to include high levels of iodonium salt, the selection of the acidic component to include high levels of CDMA, and the selection of low levels of photobleachable dye may all tend to reduce the degree of color return.
• Adhesives used in the present invention may optionally include reactive or non-reactive fillers.
• the filler can have a unimodal or polymodal (e.g., bimodal) particle size distribution.
• the filler can be an inorganic material. It can also be a crosslinked organic material that is insoluble in the polymerizable resin, and is optionally filled with inorganic filler.
• the filler is preferably non-toxic and suitable for use in the mouth.
• the filler can be radiopaque, radiolucent, or non-radiopaque.
• Reactive fillers include those that are commonly used with ionomers to form ionomer cements.
• suitable reactive fillers include metal oxides such as zinc oxide and magnesium oxide, and ion-leachable glasses including, for example, those described in U.S. Pat. Nos. 3,655,605 (Smith); 3,814,717 (Wilson et al.); 4,143,018 (Crisp et al.); 4,209,434 (Wilson et al.); 4,360,605 (Schmitt et al.), and 4,376,835 (Schmitt et al.).
• Such reactive fillers may be incorporated to modify the handling characteristics or to affect the setting properties of the ultimate composition.
• the reactive filler is preferably a finely divided reactive filler.
• the filler should be sufficiently finely divided so that it can be conveniently mixed with the other ingredients and used in the mouth.
• Average particle sizes for the filler are preferably at least about 0.2 micron and more preferably at least about 1 micron.
• Average particle sizes for the filler are preferably at most about 15 microns and more preferably at most about 10 microns. Average particle sizes may be measured by using, for example, a sedimentation analyzer.
• Preferred fillers for use in adhesives used in the present invention include acid- reactive fillers.
• Suitable acid-reactive fillers include metal oxides, metal salts, and glasses.
• Preferred metal oxides include barium oxide, calcium oxide, magnesium oxide, and zinc oxide.
• Preferred metal salts include salts of multivalent cations including, for example, aluminum acetate, aluminum chloride, calcium chloride, magnesium chloride, zinc chloride, aluminum nitrate, barium nitrate, calcium nitrate, magnesium nitrate, strontium nitrate, and calcium fluoroborate.
• Preferred glasses include borate glasses, phosphate glasses, and fluoroaluminosilicate glasses.
• acid reactive fillers are those that release fluoride.
• Fluoride releasing glasses in addition to providing good handling and final composition properties as discussed herein, provide the benefit of long-term release of fluoride in use including, for example, use in the oral cavity. Fluoroaluminosilicate glasses are particularly preferred.
• Suitable acid reactive fillers are also available from a variety of commercial sources familiar to those skilled in the art. Mixtures of fillers can be used if desired.
• acid reactive fillers can be subjected to a surface treatment. Suitable surface treatments include acid washing, treatment with phosphates, treatment with chelating agents such as tartaric acid, and treatment with a silane or silanol coupling agent. Particularly preferred acid reactive fillers are silanol treated fluoroaluminosilicate glass fillers, as described in U.S. Patent No. 5,332,429 (Mitra et al.).
• Non-acid reactive fillers may be selected from one or more of any material suitable for incorporation in compositions used for medical applications, such as fillers currently used in dental restorative compositions and the like.
• suitable non-acid reactive inorganic fillers are naturally-occurring or synthetic materials such as quartz, nitrides (e.g., silicon nitride), glasses derived from, for example Ce, Sb, Sn, Zr, Sr, Ba, and Al, colloidal silica, feldspar, borosilicate glass, kaolin, talc, titania, and zinc glass; low Mohs hardness fillers such as those described in U.S. Pat No.
• submicron silica particles e.g., pyrogenic silicas such as the "Aerosil” Series “OX 50", “130", “150” and “200” silicas sold by Degussa and "Cab-O-Sil M5" and “Cab-O-Sil TS720" silicas sold by Cabot Corp., Boston, MA.
• suitable non-reactive organic filler particles include filled or unfilled pulverized polycarbonates, polyepoxides, and the like.
• Preferred non-acid reactive filler particles include quartz, submicron silica, and non-vitreous microparticles of the type described in U.S. Patent No. 4,503,169 (Randklev). Mixtures of non-acid reactive fillers are also contemplated, as well as combination fillers made from organic and inorganic materials.
• the surface of the filler particles is treated with a coupling agent in order to enhance the bond between the filler and the polymerizable resin.
• suitable coupling agents include, for example, gamma- methacryloxypropyltrimethoxysilane, gamma-mercaptopropyltriethoxysilane, gamma- aminopropyltrimethoxysilane, and combinations thereof.
• the adhesive preferably includes one or more fumed silica fillers having a surface area of at least about 70 m 2 /g, more preferably at least about 90 m 2 /g, and most preferably at least about 100 m 2 /g. Ln some embodiments of the present invention, the adhesive preferably includes one or more fumed silica fillers having a surface area of at most about 1000 m"/g, more preferably at most about 500 m 2 /g, and most preferably at most about 150 m 2 /g.
• the adhesive includes at least about 10% by weight, more preferably at least about 45% by weight, and most preferably at least about 75% by weight, based on the total weight of the adhesive, of a base filler.
• the adhesive includes at most about 87% by weight, more preferably at most about 85% by weight, and most preferably at most about 83% by weight, based on the total weight of the adhesive, of a base filler.
• the adhesive includes at least about 0.1% by weight, more preferably at least about 0.2% by weight, and most preferably at least about 0.5% by weight, based on the total weight of the adhesive, of a fumed silica filler having a surface area of at least about 70 m 2 /g.
• the adhesive includes at most about 50% by weight, more preferably at most about 15% by weight, and most preferably at most about 3% by weight, based on the total weight of the adhesive, of a fumed silica filler having a surface area of at least about 70 m 2 /g.
• base filler will preferably allow lower levels of fumed silica fillers to reach the desired Theological properties, and likewise lower levels of base filler will preferably allow higher levels of fumed silica fillers to reach the desired rheological properties.
• the adhesive includes a fumed silica filler having an average aggregate length of at least about 0.01 micron, more preferably at least about 0.05 micron, and most preferably at least about 0.1 micron.
• the adhesive includes a fumed silica filler having an average aggregate length of at most about 1 micron, more preferably at most about 0.5 micron, and most preferably at most about 0.4 micron.
• adhesives used in the present invention may optionally include adjuvants.
• adjuvants include, for example, cosolvents, pigments, inhibitors, accelerators, viscosity modifiers, surfactants, rheology modifiers, colorants, medicaments, adhesion promoters and other ingredients that will be apparent to those skilled in the art.
• the compositions may contain stabilizers.
• Suitable adjuvants include, for example, those disclosed in International Patent Application Publication No. WO 00/69393 (Brennan et al.).
• Adhesives used in the present invention preferably have physical properties that are desired for precoated and/or packaged orthodontic appliances and/or adhesives. Desirable properties include, for example, adequate handling properties, no slump that would be observable by a practitioner, suitable operatory light stability, no observable slip when placed on liner or tooth, suitable aesthetic color, color stability under office light conditions (e.g., white light stability), and sufficient tack such that the precoated bracket does not fall off the tooth when placed there prior to curing
• Adhesives used in the present invention preferably have no substantial flow-out.
• Flow-out value is a measure of the tendency of an adhesive to flow on a liner, and is measured by a test method as described in the Examples. Ln brief, flow-out is measured by coating an adhesive on an orthodontic bracket, placing the adhesive on the coated bracket in contact with a release substrate, and holding for a specified time at a specified temperature (e.g., one week at 40°C). The flow-out is measured as flow out of the adhesive from the edge of the bracket in millimeters.
• Adhesives used in the present invention preferably have a steady state viscosity at 28°C of at least about 3 x 10 2 Pa-s, more preferably at least about 5 x 10 3 Pa-s, and most preferably at least about 1 x 10 4 Pa-s.
• Adhesives used in the present invention preferably have a steady state viscosity at 28°C of at most about 7 x 10 4 Pa-s, more preferably at most about 2.5 x 10 4 Pa-s, and most preferably at most about 2 x 10 4 Pa-s.
• Adhesives used in the present invention preferably have a static yield stress at 28°C of at least about 7,000 dynes/cm 2 , more preferably at least about 8,000 dynes/cm 2 , and most preferably at least about 9,000 dynes/cm 2 .
• Adhesives used in the present invention preferably have a static yield stress at 28°C of at most about 100,000 dynes/cm 2 , more preferably at most about 60,000 dynes/cm 2 , and most preferably at most about 25,000 dynes/cm 2 .
• the adhesives used in the present invention may be applied to the base of the orthodontic appliance by methods known in the art. Suitable methods include, for example, application with a syringe or other suitable dispensing devices as disclosed, for example, in U.S. Pat. No. 5,552,177 (Jacobs et al.). RELEASE SUBSTRATE
• Articles of the present invention preferably include a release substrate in contact with the adhesive.
• a surface of the release substrate includes a number or pores, and no more than about 50% by weight of the adhesive is in the pores.
• the release substrate includes a foam.
• Suitable release substrates are disclosed, for example in U.S. Pat. No. 6,183,249 (Brennan et al.).
• the release substrate is a crosslinked polyethylene foam available under the trade designation MLNICEL (e.g., MLNICEL M200) from Noltek (Lawrence, MA).
• the release substrate provides for easy release of the appliance and reduced slip and flow-out.
• the release substrates used in the present invention may be applied to the adhesive on the base of the orthodontic appliance by methods known in the art. Suitable methods include, for example, placing the release substrate on the bottom of a container well and then lightly inserting the bracket in the well such that the adhesive is in contact with the release substrate.
• a robotic arm may be used, for example, as described in U.S. Pat. No. 5,552,177 (Jacobs et al.).
• the articles of the present invention are preferably packaged in a container for storage and distribution.
• Suitable containers include, for example, those disclosed, for example, in U.S. Pat. Nos. 4,978,007 (Jacobs et al.), 5,172,809 (Jacobs et al), 5,328,363 (Chester et al.), 5,354,199 (Jacobs et al.), 5,538,129 (Chester et al.), 5,575,645 (Jacobs et al.), and in coassigned U.S. Pat. Application Serial No. 10/126804 entitled "CONTAINERS FOR PHOTOCURABLE MATERIALS".
• the container may include a release substrate.
• the release substrate may optionally be part of the container, but preferably the release substrate is a release liner.
• kits may include additional components including, for example, instructions for using the orthodontic appliance, etching compositions, swabs or brush tips for etching compositions, appliance placement guides or jigs, extra quantities of adhesive, primer, sealant, and mix pads.
• Methods of using the presently disclosed article include separating the orthodontic appliance from the release substrate, wherein the adhesive preferably remains on the base of the orthodontic appliance.
• the orthodontic appliance is then applied to the tooth surface and positioned properly by the practitioner so that the adhesive is in intimate contact with the surface of the tooth.
• the adhesive is hardened by exposure to actinic radiation.
• the surface of the tooth may be etched and dried before adhering the adhesive-coated bracket to the tooth.
• a coating of primer may be applied to the tooth prior to adhering the adhesive-coated bracket to the tooth.
• the drying step may or may not be required, depending upon the type of primer applied.
• the etchant may include a primer.
• the appliance is bonded to the tooth with a bond strength of at least about 7 MPa, more preferably at least about 9 MPa, and most preferably at least about 11 MPa.
• the appliance is bonded to the tooth with a bond strength of at most about 25MPa.
• the rheometer was then programmed to wait for 10 minutes for the temperature to stabilize at 28°C before beginning the measurement. The rheometer was then programmed to shear the adhesive sample at a shear rate of 0.01 second "1 for 30 seconds followed by shearing at 0.1 second "1 for 4.5 minutes. During each of these periods the rheometer collected stress measurements.
• the yield stress of an adhesive sample was defined as the point at which the stress vs. time curve deviated from an initially linear trajectory. Practically, this was determined by constructing a tangent to the stress vs. time curve. The tangent was then shifted by 0.06 seconds to the right and the intercept with the stress vs. time curve determined. This intercept, being very close to the point of deviation from linearity, was defined as the static yield stress (or as the transition from elastic deformation to viscoelastic flow) and reported as dynes/cm 2 for the adhesive sample. Reported values were from single measurements of the samples. The adhesive samples were thixotropic, meaning that the viscosity under constant shear rate changes with time.
• the viscosity of an adhesive sample was defined as the viscosity measured after a given time under shear. This time was chosen such that any yield stresses would have been overcome. A period of 3.5 minutes at 28°C under a shear rate of 0.1 second "1 ) was chosen since by that time all of the adhesive samples measured were well beyond yielding. The results were reported as steady state viscosity values (from single measurements) in units of Pa-s (Pascal-seconds). WATER UPTAKE
• the Adhesive/Bracket Flow-Out Test Method was used to determine the tendency of an adhesive to flow on a liner beneath an orthodontic bracket, a phenomenon called "flow-out". If an adhesive exhibits flow-out on a specific liner in this test, then the adhesive would be expected to flow-out within a blister package containing the adhesive precoated on a bracket and covered with the same liner. Flow-out can produce stringing of the adhesive away from the bracket base as the adhesive precoated bracket is removed from the liner. This result can cause difficulties for a practitioner who must then make adjustments to the shape of the adhesive pad (or pillow) prior to placement of the adhesive precoated bracket on the tooth. Ln the worst case, flow-out prevents full release of the adhesive from the liner, which may even cause separation of the adhesive from the precoated bracket.
• Mini Twin V-slot brackets (3M Unitek, Ref # 017-333 or 017-334) were coated by application from a syringe with about 8 mg of adhesive placed on a SCOTCHPAK 1022 release liner (3M Company) with the adhesive in contact with the liner, and held for one week in a 40°C oven. (Time and temperature of the test was varied depending upon the test sample.) The adhesive precoated brackets were placed on liners that were held to cardboard via double stick tape in order to keep the brackets in a horizontal position in the oven. Special precaution was taken to ensure that no adhesive was visible beyond the bracket base at the start of the test.
• the Adhesive/Bracket Vertical Slip Test Method was developed to determine if adhesive precoated brackets using specific adhesive compositions would slip on specific release liners in blister packages. If an adhesive exhibits slippage on a specific liner in this test, then the adhesive would be expected to slip (e.g., during transit to the customer) within a blister package containing the adhesive precoated on a bracket and covered with the same liner. In the worst case, the adhesive precoated brackets may slip entirely off the liner, destroying the product functionality. Or, the adhesive precoated bracket may rotate in the package, which would result in improper orientation for placement of the bracket on the tooth by the practitioner.
• brackets were coated by application from a syringe with about 8 mg of adhesive (with the exception of buccal tubes which were coated with about 16 mg of adhesive).
• the adhesive precoated brackets were placed on MLNICEL M200 foam liner (Voltek Corp, Division of Sekisui America, Lawrence, MA). Each liner containing the adhesive precoated bracket was held to a piece of cardboard via double stick tape. Special precaution was taken to ensure that no adhesive was visible beyond the bracket base at the start of the test.
• a "starting line” was drawn near the top edge of the bracket to ensure measurement of the exact distance of slippage.
• the cardboard containing the brackets was held vertically in an oven (set at a predetermined temperature, typically 40°C or 50°C) for predetermined period of time (typically 3 to 14 days).
• Slippage of the adhesive coated bracket on the liner was measured as flow-out beyond the top edge of the bracket base and was measured using RAM Optical Instrumentation as described in the preceding test method.
• the slippage values reported (in mm) were an average of at least 3 adhesive precoated bracket samples per test.
• Fluoride release was measured by first forming sample compositions into disks 20- mm in diameter and 1-mm thick. Both sides of each disk were covered with polyethylene terephthalate film and light-cured for 60 seconds on each side using two oppositely disposed VISLLUX 2 Visible Light Curing Units (3M Company) with about a 1-cm distance between the output end of the light guide and the sample disk. The film was then removed from both sides of the disks and the samples allowed to cure for 1 hour at 37° C/95% relative humidity ("RH"). Each disk was weighed and placed in a glass jar to which was added 25 ml of deionized water. The sample solutions were maintained at 37° C for specified time periods at which times the incremental fluoride release was measured as follows.
• a fluoride-selective electrode Orion Model 96-09-00 (Orion Research Inc., Cambridge, MA) was used to quantify the amount of fluoride ion released from the sample disks in water.
• the electrode was calibrated using Fluoride Activity Standards #940907 and #040908, at 100 parts per million ("ppm") and at 10 ppm, respectively, fluoride standard fluid (both from Orion Research Lnc).
• Bond strength was tested by adhering metal orthodontic brackets with mesh bases to bovine teeth using an adhesive sample.
• the adhesive sample was applied by syringe to VICTORY SERIES REF 017-401 (or equivalent) upper central brackets (3M Unitek).
• the bovine teeth were first cleaned with a pumice aqueous slurry and rinsed.
• the teeth were then etched with 37% phosphoric acid etching solution, rinsed with water and dried with moisture-free and oil-free air.
• the teeth were then treated with TRANSBOND MIP moisture insensitive primer (3M Unitek) according to manufacture's directions.
• the metal brackets with applied adhesive were seated onto the teeth and pressed firmly to extrude any excess adhesive. The excess was cleaned away.
• the adhesive was then cured with 10- second exposures on both the mesial and distal sides of the brackets using an ORTHOLUX XT Curing Unit.
• the samples of teeth and bonded brackets were stored overnight in 37°C water. Bond strength testing was performed by engaging a 0.50-mm round stainless steel wire loop under the occlusal tie wings. Using an Lnstron universal load frame, a load was applied in a shear/peel mode until debonding of the bracket from the tooth occurred. The wire attached to the Lnstron was pulled at a rate of 5 mm minute. The maximum force (in units of pounds) was recorded as bond strength per bracket and the reported value was an average of 10 measurements using 10 different adhesive-coated brackets. This average was then converted to units of MPa by dividing by the bonding base area (10.9 mm 2 ) and multiplying by 4.4.
• Quantification of initial and bleached color of adhesive samples was performed with a StellarNet Portable Spectrometer Model EPP2000C equipped with a 400-micron fiber reflectance probe and SpectraWiz CLELAB colorimeter software (StellarNet, Inc., Oldsmar, FL).
• an adhesive sample was extruded onto a polyester release liner, a metal ring was placed around the adhesive, and a second release liner was placed on top of the adhesive.
• the resulting construction was then pressed between two Plexiglas plates with the metal ring controlling the adhesive thickness to 0.51 mm.
• the adhesive sample between the two release liners was placed on top of a white reflectance standard (Part No. RS50, 50-mm diameter, Halon type >97% reflectance, 300-1500 nm, StellarNet, Inc.).
• the fiber optic probe of the spectrometer was positioned 6.3 mm above the sample at a 45° angle.
• Color measurements were taken through the top release liner at an exposure time of 1000 milliseconds and with the center of the adhesive under the beam.
• the software captured the reflectance spectrum and converted the input to L*, a* and b* values.
• the a* value was indicative of the redness of the sample with higher numbers indicative of greater redness.
• Cured adhesive samples were prepared in the same manner described herein, except that the adhesive pressed between the two polyester release liners was cured for 3 minutes in a TRIAD 2000 light curing oven (Dentsply International, Inc., York, PA). The cured adhesive sample with the polyester liners intact was placed directly onto the white reflectance standard. The light source of the spectrometer was switched on and L*, a* and b* values were measured as described herein with each reported value representing the average of 3 measurements. WHITE LIGHT STABILITY
• Adhesive samples were prepared as described herein for the Color Test Method. Five samples were made by pressing the adhesive between polyester release liners to a disk shape having a thickness of 0.51 mm. One adhesive disk was measured immediately and used as the zero point. The remaining four disks were placed onto a sheet of white paper and placed at desk height directly below a fluorescent light fixture at standard ceiling height. The distance between the fluorescent light and the adhesive samples was approximately 2.0 meters. Adhesive samples were removed from fluorescent light exposure after 2, 5, 10 and 20 minutes exposure and moved to a dark room. Colors of the samples were then measured as described herein for the Color Test Method. Results for a* could then be reported as a function of exposure to fluorescent lighting with each reported value representing a single measurement.
• CDMA is defined as the reaction product of citric acid and LEM as prepared according to the following procedure.
• Citric acid (1870 g; 9.733 moles citrate, 29.2 moles carboxylate) was dissolved in tetrahydrofuran (5.9 liters) in a reaction vessel fitted with a mechanical stirrer, condenser, addition funnel, and air inlet tube.
• BHT 4.69 g
• TPS 4.68 g
• DBTDL DBTDL
• Filler A was a silane-treated quartz filler prepared according to the following procedure.
• a 58.3-g portion of deionized water was weighed into a 1000-ml beaker. The water was preheated to about 29° to 33° C.
• 105 g of quartz filler Cold Quartz, Jessieville, AK
• AEROSIL R-972 fumed silica was added to the water followed by the slow addition of 1.7 g of AEROSIL R-972 fumed silica.
• the pH of the resulting slurry was adjusted to between about 2.5 and 3.0 with 1% trifluoroacetic acid (Sigma-Aldrich).
• Filler B was a silane-treated fluoroaluminosilicate glass (FAS) filler prepared according to the following procedure.
• a 6,420-g portion of deionized water was weighed into a 23-liter polyethylene pail.
• the water was stirred with a Premier electric mixer (Premier Mill, Reading, PA) so as to create a vortex of about 2.5 mm in depth about the mixer shaft and adjusted to a pH of about 3.0 with the addition of about 90 g of glacial acetic acid.
• To the resulting acidic solution was added 521 g of 3- methacryloxypropyltrimethoxysilane (United Chemical Technologies, Inc.).
• the solution was stirred for 1 hour and then charged with 5990 g of finely powdered, FAS glass (Schott Glas, Landshut, Germany). The resulting slurry was stirred for 30 minutes and then poured evenly into a tray lined with polyester sheeting. The filled tray was placed in a convection drying oven for 16 hours at about 80° C, followed by an additional 2 hours at 100° C to yield a dry cake. The dried cake was crushed using a mortar and pestle and the crushed filler was screened though a 74 micrometer nylon screen to afford the powder filler designated as Filler B.
• a resin precursor was first prepared by charging the resin components shown in Tables 1A and IB into a vessel. The resulting mixture was heated to 45°C and stirred using an electric stirring motor (Fisher Scientific, model #47) fitted with a glass stirring rod and 2.54-cm Teflon stirring blade. Mixing speed was adjusted so as to create a vortex of about 6 mm. The mixing vessel was shielded from light and the mixing continued for 4 hours to dissolve all solid components. Each resin precursor was then combined with the filler components shown in Tables 1 A and IB mixed until a homogeneous, paste like composition was achieved.
• Example 2 3 and 5-9 mixing of the resin precursor with the filler components was accomplished using a planetary mixer (Charles Ross and Co, Hauppauge, NY) of sufficient size (0.95 to 3.785 liters) to accommodate the amounts of materials charged.
• Example 10 and Comparative Example 3 were mixed using a 15-liter planetary mixer (Premier Mill, Reading PA).
• the resin precursor was charged first to the mixing vessel followed by the filler components.
• the entire filler amount was charged at once and then mixed until the desired, paste-like consistency was achieved; or, alternatively, a portion of the total filler was withheld from the initial mixture and incorporated in subsequent mix cycles. Typically, a total of 1 to 4 additional filler mix cycles was utilized.
• Homogeneity of the paste depended on several factors, e.g., mix time, planetary mix speed, resin viscosity, and total amount of filler added. For the examples mixed in a planetary mixer, all were done at 45°C and at a mixing speed of 10 to 12 rpm.
• compositions of Examples 1-10 and Comparative Examples 1 (CE-1) and 2 (CE-2) contained more than one filler component.
• CE-1 and CE-2 filler components could be added independently in the amounts shown in Tables 1 A and IB.
• the filler components could be combined to form a filler precursor prior to charging to the resin precursor in the mixing vessel.
• Such filler precursors were prepared and used to make the compositions of Examples 2-5 and 9-10.
• Such admixing was accomplished by mixing small amounts by hand in a convenient sized beaker or, alternatively, for larger amounts of materials, blending was accomplished using, a Patterson Kelley Twin Shell Blender (Harsco Corp., Camp Hill, PA) as was done for Example 10.
• Examples 11-15 were prepared by blending small quantities of various fumed silica materials of high surface area into the composition designated Comparative Example 1.
• Examples 16-20 were prepared by blending small quantities of various fumed silica materials of high surface area into the composition designated Comparative Example 2.
• the specific fumed silica materials used and the quantities of fumed silica added are shown in Table 2. In each case, the addition of high surface area fumed silica caused a significant change in the physical characteristics of the compositions and the degree of this change was dependent on the amount and type of fumed silica added.
• Static Yield Stress and Steady State Viscosity The Static Yield Stress and Steady State Viscosity were measured for Examples 11-20, Comparative Examples 1-3, and the commercial product TRANSBOND XT orthodontic adhesive (3M Unitek) according to the Test Method described herein. Results are reported in Table 3 and show that the addition of low levels of various high surface area fumed silica materials to adhesive compositions CE-1 and CE-2, which contained the fumed silica OX-50 at levels of 3.95% and 7.90%, respectively, afforded compositions (Examples 11-20) with increased yield stress (with the exception of Example 13 which contained 0.25% fumed silica) and viscosity.
• Water Uptake was measured for Examples 2-3 and 5-6, Comparative Example 3, and the commercial product TRANSBOND XT orthodontic adhesive (3M Unitek) according to the Test Method described herein. Results in terms of percent increase in water uptake at Day 2 and Day 10 are reported in Table 4 and show (at Day 2) a significantly greater uptake of water by Examples 2-3 and 5-6 in comparison to the Comparative Example 3 or to the TRANSBOND XT.
• the enhanced water uptake can be attributed to the presence of substantially more hydrophilic polymers in the invention Examples 2-3 and 5-6.
• the hydrophilic nature of the adhesives used in the present invention facilitates fluoride transport and promotes the uptake of moisture or saliva so as to decrease the likelihood of bond failure (e.g., in the case of adhesive coated brackets bonded to moisture or saliva contaminated teeth).
• Adhesive/Bracket Flow-Out The Adhesive/Bracket Flow-Out of Examples 12-15, 17-20, and Comparative Examples 1-3 was measured according to the Test Method described herein. Results are reported in Table 5 and show that the addition of low levels of various fumed silica materials to the adhesive compositions CE-1 and CE-2, which contained the fumed silica OX-50 at levels of 3.95% and 7.90%, respectively, afforded compositions (Examples 12-15 and 17-20) with rheological properties such that little or no flow-out was measured from underneath the coated bracket. In contrast, significant flow-out was measured for Comparative Examples 1-3. Adhesive compositions that possess such rheological properties (i.e., minimal or no flow-out over time) are highly desirable for use as adhesives in adhesive-coated, packaged orthodontic appliances.
• Adhesive/Bracket Vertical Slip The Adhesive/Bracket Vertical Slip of Examples 2 and 5, and Comparative Examples 1-3 was measured according to the Test Method described herein. Results are reported in Table 6 and show that brackets coated with the inventive adhesive compositions (Examples 2 and 5 that contained a high surface area fumed silica material, i.e., CAB-O-SIL TS-720, with a surface area of about 105 to about 130 m 2 /g) exhibited essentially no bracket slippage. In contrast, significant bracket slippage was measured for brackets coated with Comparative Examples 1-3 that contained only a fumed silica material of low surface area, i.e.
• Adhesive compositions that possess such rheological properties (i.e., minimal or no slippage over time) are highly desirable for use as adhesives in adhesive-coated, packaged orthodontic appliances.
• Fluoride Release The Fluoride Release of Examples 2-5 and 9 and the commercial product F2000 restorative (3M Company) was measured according to the Test Method described herein. Results in terms of micrograms of fluoride per gram of test sample at Days 1, 2, and 21 are reported in Table 7 and show cumulative fluoride release for Examples 2-5 and 9 and the F2000 restorative product. These results can be attributed to the presence of a fluoride releasing component (i.e., a FAS glass component) in both the inventive Example(s) and in F2000 restorative. Table 7. Cumulative Fluoride Release Results
• Bond Strength for Moisture Tolerance The Bond Strength under different moisture conditions for Example 1 and the commercial product TRANSBOND XT orthodontic adhesive (3M Unitek) was measured according to the Test Method described herein. Results in terms of Bond Strength under dry and moist conditions are reported in Table 8 and show, under dry conditions, comparable values for both Example 1 and for the TRANSBOND XT samples. However, under moist conditions, Example 1 showed significantly greater Bond Strength than the commercial product. This enhanced Bond Strength (in comparison to TRANSBOND XT) can be attributed to the presence of hydrophilic polymers in Example 1 of the present invention. This hydrophilic property of Example 1 promotes the uptake of moisture or saliva so as to decrease the likelihood of bond failure (e.g., in the case of adhesive coated brackets bonded to moisture or saliva contaminated teeth).

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• 2002
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