Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-10-12
2003-03-04
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S115000, C523S117000, C523S118000, C523S120000, C524S492000, C524S493000, C524S494000
Reexamination Certificate
active
06528555
ABSTRACT:
TECHNICAL FIELD
The present invention relates adhesive suitable for use in the oral environment, such as a patient's mouth. In particular, the adhesive has a vibrant initial color and having the capability of changing to a final color upon exposure to actinic radiation. The initial and final colors are different.
BACKGROUND
Orthodontic treatment involves movement of malpositioned teeth to orthodontically correct positions. Tiny orthodontic appliances, known as brackets, are connected to anterior, cuspid and bicuspid teeth, and an archwire forms a track to guide movement of the teeth to desired positions. In previous years, the orthodontic appliances were connected to teeth by welding or brazing each appliance to a metal band, which was then placed on the desired tooth. But, more recently, it has been preferred to bond the brackets directly to the tooth surface. The direct bonding method minimized the use of metal band thus eliminating the “metallic mouth” appearance that is often associated with orthodontic treatment.
The use of a bonding method can typically require, among other steps, placing an amount of adhesive on the bracket, applying the brackets to the desired, preferably preconditioned teeth, and removing excess adhesive. Conventional orthodontic adhesives are typically clear or contain pigment, which gives the adhesives a white or tooth color. It is desirable that a sufficient but not an excess amount of adhesive is used to bond the brackets to the teeth surface. Excess adhesive on the teeth will eventually be a site for bacteria accumulation. Because orthodontic treatment can last from 18 to 36 months, the bacteria accumulation may damage the teeth and may lead to discoloration of the adhesive, both of which are very undesirable. Removal of the excess adhesive from teeth surfaces can be difficult if there is similarity in the adhesive color and the teeth color, i.e., due to a lack of a contrasting color in the adhesive.
Some skilled in the art have explored the use of color changing adhesive, in particular for orthodontic applications. For example, an orthodontic adhesive having color changing capabilities upon curing by a light source is commercially available from the Orec® Corporation, San Marcos, Calif. The company supplies a product identified as CRYPSIS Color Change Orthodontic Bonding Adhesive (Photocure). As of the filing date, the adhesive is described at Orec's web site (www.orec.com/Pg21.htm) as having an initial yellow color, which allows easy visualization and removal of excess adhesive prior to curing. Once cured, the adhesive turns to tooth-like color.
U.S. Pat. No. 5,545,676 (Palazzotto et al.) discloses a composition useful as a photocurable adhesive, e.g., for orthodontics. The composition comprises (a) free-radically polymerizable monomer and (b) photoinitiator system, soluble in the monomer, comprising photochemically effective amounts of (i) diaryliodonium salt (“iodonium salt”), (ii) sensitizing compound (“sensitizer”) capable of absorbing light within the range of wavelengths between about 300 and 1000 nanometers and capable of sensitizing 2-methyl-4,6-bis-(tricholormethyl)-s-triazine, and (iii) electron donor compound. The donor is different from the sensitizer. It is further specified that the donor oxidation potential is 0<E
ox
(donor)≦E
ox
(p-dimethoxybenzene). Although the patent describes a very useful photoinitiator system, it does not disclose a system or a composition that has color changing capabilities.
A need remains for adhesives that exhibits effective color changing capabilities within a practical working time to aid a dental practitioner in applying orthodontic appliances to a patient's teeth.
SUMMARY
The present invention provides a new adhesive suitable for use in the oral environment. The adhesive is used in orthodontic application. It contains a colorant and optionally a sensitizer to impart color-changing capability. The adhesive provides a vibrant initial color (before actinic radiation exposure) that is remarkably different than dental structures, such as teeth, thereby aiding the practitioner in using a sufficient amount and in placing it in and on areas of the dental structure. Useful initial colors include pink, red, blue, orange, and green, which tends to provide better color contrast against the dental structures, as compared to a yellow colored adhesive. Methods of making and using the color-changing adhesive are also provided.
In brief summary, the present invention is directed to an adhesive for use in the oral environment, the adhesive comprising a filler, a hardenable resin, a hardener, and a colorant, the adhesive having an initial color prior to exposure to actinic radiation and a final color after exposure to actinic radiation. The initial and final colors are different. The inventive adhesive is capable of undergoing a change in color of &Dgr;E* greater than about 10 as a result of actinic radiation exposure. In one inventive embodiment, a dye or a combination of dyes can be used to impart a desired initial color.
Advantageously, the adhesive's final color preferably closely matches the dental structures that surrounds it. Alternatively, it is able to transmit the color of the underlying dental structure, i.e., the final color is substantially clear. By formulating the adhesive so that it results in a tooth-like hue, the adhesive can form an “aesthetic” layer upon the tooth surface. Dental materials that match normal tooth color and shades (i.e. tooth-like) are often considered to have high aesthetic quality, especially when the dental material is indistinguishable from the normal tooth surface when viewed from only a short distance.
Another advantage of the present invention is ease of use because the adhesive cures quickly. A practitioner such as an orthodontist can easily cure it using a conventional dental curing light.
The present invention also provides for orthodontic appliances that are precoated with the adhesive, the appliance packaged conveniently in capsule-like containers. The precoated appliance typically has a precise amount of adhesive on its base. Precoated appliances represent a significant advantage to the orthodontists. For example, when it is desired to mount the appliance on a tooth, the appliance is simply removed from the package and directly placed on the tooth surface. There is little need, if any, to remove excess adhesive.
The packaging components used to store the adhesive and precoated orthodontic appliances preferably minimize, if not nearly eliminate, the transmission of visible and near infrared light to the appliances. In this way, the stability of the adhesive, and thus the orthodontic appliance can be maintained for a long period of time, on the order of years.
As used herein the following terms are intended to have the following definitions:
“aesthetic layer”, means a layer that is customarily positioned in a visible location on teeth (e.g., the tops of molars, labial surfaces of incisors and cuspids) and is either visible due to the layer being the outermost layer or can be seen through any overlying layer;
“hardenable” is descriptive of a material that can be cured or solidified e.g., by heating to remove solvent, heating to cause polymerization, chemical cross-linking, radiation-induced polymerization or crosslinking, or the like;
“photo-bleach(able)” means a loss of color upon exposure to actinic radiation;
“hardener” means a system that initiates hardening of a resin, and can be used synonymously with “initiator system”;
“orthodontic appliance” means any device intended to be bonded to the teeth, including, but not limited to, orthodontic brackets, buccal tubes, lingual buttons, and cleats. The appliance has a base for receiving adhesive and it can be made of metal, plastic, ceramic, and combinations thereof; and
“tooth-like” color refers to the broad range of colors and shades of naturally occurring teeth, which can be quantified for example, using the Vita™-shade system (covering the range A1 through D4), a tooth color/shade guide freque
James Darrell S.
Nikutowski Enrique A.
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