Orthodontic appliances (brackets) having a pre-applied or factory applied adhesive thereon presenting a non-tacky surface are described. The brackets, which may be plastic, metal or ceramic, have a bonding base surface to which an appropriate adhesive composition is pre-applied. The adhesive, which is uncured and generally presents a tacky outer surface, is protected from deterioration or disturbance by the attachment or adherence of particles, which may form a layer, on the outer surface of the adhesive, thereby presenting a non-tacky surface. Also included are articles consisting of a container with a cover and an orthodontic bracket having pre-applied adhesive received in the container. The adhesive on the bracket in the container presents a non-tacky surface by virtue of a layer of particles secured to the otherwise tacky adhesive surface.

FIELD OF THE INVENTION 
The invention relates to orthodontic appliances (brackets) having 
pre-applied adhesive and to methods of adhering orthodontic brackets to 
tooth surfaces. 
BACKGROUND OF THE INVENTION 
In the field of orthodontics, it has become increasingly important to 
enhance the bonding strengths achieved when adhering orthodontic 
appliances, particularly brackets, to patient's teeth. A competing 
concern, however, is the reduction of the cost of installing a set of 
brackets on a patient's teeth by reducing the amount of chair-side time 
spent by the orthodontist. One technique that has become increasingly 
popular is the use of pre-applied adhesives or factory-applied adhesives 
on the bonding surface of the orthodontic appliance or bracket. For 
example, U.S. Pat. Nos.4,978,007; 5,172,809; 5,015,180; 5,328,363; 
5,429,229; 5,183,403; 5,221,202; 4,948,367; 4,204,325; 5,575,645; 
5,538,129; 5,552,177; 3,797,115; and 5,354,199 all relate to orthodontic 
brackets having pre-applied adhesive thereon. 
By shipping orthodontic brackets with the adhesive already applied thereto, 
the clinician is saved the time normally spent in preparing the adhesive 
and applying it to the bracket. This serves to reduce the overall cost of 
the procedure of applying a set of brackets to a patient's teeth, and it 
also serves to enhance the consistency of the adhesive bonds achieved when 
the brackets are applied to the patient's teeth. This latter point can be 
critically important since inconsistent bonding strengths between the 
various brackets on a patient's teeth may result in debonding of one or 
more brackets during the treatment process. Factory-applied adhesives 
typically have more consistent compositional characteristics, thus 
resulting in more consistent adhesive bonding. 
One drawback associated with factory-applied adhesives is the limitation on 
how such brackets are packaged and shipped. It is important that the 
adhesive layer pre-applied to the bracket bonding surface not be disturbed 
or degraded at any time prior to application to the patient's tooth. This 
can present a number of problems since typically the adhesive surface is 
tacky. Disturbance or deterioration of the adhesive layer is undesirable 
as it may diminish the bonding capacity of the adhesive and/or cause 
inconsistent bonding properties. One technique that has been employed to 
attempt to protect the adhesive surface is a release layer or release tape 
covering the otherwise exposed adhesive surface on the bracket. When ready 
for use, the release tape is pulled away from the bracket, or vice versa. 
One drawback to such arrangements is that at least a portion of the 
adhesive may be removed with the tape, thereby deleteriously affecting the 
bonding integrity of the bracket. 
Therefore, what is needed is an orthodontic bracket having a 
factory-applied adhesive in which the adhesive surface is protected in 
such a manner that the adhesive surface is not disturbed or degraded, and 
wherein the bond strengths achieved using the brackets with 
factory-applied adhesive are enhanced. 
SUMMARY OF THE INVENTION 
In its broadest aspects, the present invention is directed to improvements 
in orthodontic appliances (brackets) wherein a pre-applied or 
factory-applied adhesive thereon presents a non-tacky surface. The 
invention also relates to methods of adhering orthodontic brackets with 
pre-applied adhesive to tooth surfaces. The appliances of the present 
invention are advantageous in that they can be shipped without the typical 
concern for suspending or otherwise keeping the pre-applied adhesive from 
contacting the container. This is because in the instant invention, the 
outer surface layer of the adhesive is non-tacky. Furthermore, the present 
invention obviates the use of release tapes and other such means for 
attempting to protect the adhesive surface. 
More specifically, orthodontic brackets, which may be plastic, metal or 
ceramic, have a bonding base surface to which an appropriate adhesive 
composition is pre-applied by the manufacturer. The adhesive, which is 
uncured, generally presents a tacky outer surface. The means of protecting 
that tacky surface from deterioration, degradation or disturbance in the 
present invention is the attachment, adherence or partial embedding of 
particles, which may form a layer, to the outer surface of the adhesive. 
The particles, which may be any one or combination of different materials, 
including inorganic or organic particles, are secured to the exposed 
adhesive surface. Upon application of the particles, the surface presented 
is non-tacky and therefore not readily subjected to deterioration or 
disturbance by delamination, as would normally occur upon disturbance of a 
typical tacky adhesive, such as when release tapes or layers are utilized. 
In a preferred embodiment, an orthodontic bracket having pre-applied 
adhesive of the present invention is a metal bracket having a mesh bonding 
surface on the base thereof. The bracket has a first adhesive coating 
applied onto the bonding mesh and that first adhesive coating is 
pre-cured. Thereafter, a second adhesive layer is applied which remains 
uncured. It is preferable that this second adhesive have long-term shelf 
stability characteristics in the uncured state. The particles are then 
applied by either dipping or sprinkling. By way of example, but not 
limitation, the particles may be made of an inorganic material such as 
barium alumino borosilicate, quartz, or soda lime glass. Alternatively, 
the particles may be a synthetic organic polymer such as 
methylmethacrylate, ethylmethacrylate, or methyl/ethyl copolymers. 
Regardless of the particular material of the particles, those particles 
are secured to the outermost portion of the adhesive layer. In one 
embodiment, the particles are partially embedded in the adhesive. The 
particles ultimately become an integral part of the adhesive upon 
application of the bracket to a tooth, but since they may be only 
partially embedded at the time of application, there is presented a 
non-tacky outer surface. It is believed that the combination of a 
pre-cured adhesive layer and an uncured adhesive layer result in improved 
bond strength. 
Turning to application of the brackets of the present invention, it is 
desirable that a tacky surface be created at chair side to aid in 
application of the brackets to a patient's teeth. Achieving the desired 
tackiness may be dependent upon the adhesive consistency as well as the 
tooth primer (sealant). In particular, the primer should wet the particles 
effectively to allow the adhesive-particles-primer mixture to immediately 
become tacky when the bracket is placed; otherwise, the bracket may 
experience excessive drift or completely fall off the tooth when the 
bracket placement instrument is withdrawn. Upon application of the 
appropriate tooth primer and adherence of the bracket to the tooth, curing 
is effected by visible light radiation, as is well known in the art. 
These and other features and advantages of the present invention will 
become apparent to persons skilled in the art upon review of the detailed 
description and examples hereinbelow.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention is directed to orthodontic appliances, and 
particularly orthodontic brackets, which have an adhesive applied to the 
bonding surface thereof, wherein the adhesive has a non-tacky surface. In 
one preferred embodiment, the adhesive includes two distinct visible 
light-curable pastes and the non-tacky surface is the result of a layer of 
synthetic organic polymer particles partially embedded within the exposed 
adhesive surface. 
In one aspect of the present invention, the brackets are metal brackets 
which have a mesh bonding base. In this context, bond failure 
predominantly occurs at the mesh-adhesive interface because, during 
adhesive curing, the light is unable to fully penetrate the most shadowed 
area (i.e., the mesh interstices). As a means of addressing this problem, 
it is contemplated in the present invention that a first adhesive 
composition is applied to the bonding surface and mesh. This adhesive is 
worked into the mesh and then smeared level to the mesh surface using a 
spatula. This adhesive is cured using a Demetron 400 visible light curing 
light or equivalent (output of at least 300 mw/cm.sup.2) at a distance of 
5 mm or less, directly perpendicular to the mesh surface for approximately 
10 seconds. This first adhesive composition will hereinafter be referred 
to as Paste A. Pre-curing of Paste A yields a maximum monomer to polymer 
conversion allowing full bonding strength to develop within the mesh area. 
One contemplated composition for Paste A that provides suitable results is 
the Sequence.TM. adhesive available from Ormco Corporation, Glendora, 
Calif. (Part No. 740-0148). The composition of Sequence is as follows: 
______________________________________ 
Component Weight Percent 
______________________________________ 
camphorquinone 0.20% 
barium aluminum borosilicate 
71.97% 
hydroxy ethyl methacrylate 
6.13% 
benzoyl peroxide 0.30% 
titanium dioxide 0.04% 
mercaptobenzothiazole 
0.30% 
ethoxylated bisphenol A dimethacrylate 
10.13% 
diethylaminoethylmethacrylate-BF.sub.3 
0.80% 
Sybron ATPU 10.13% 
______________________________________ 
It will be appreciated that a variety of adhesives may be suitable 
substitutes for the above-described Paste A; however, the choice of 
composition will result in variations of ultimate bond strength. The 
reason for this is that different adhesives possess differing abilities to 
couple with the stainless steel mesh (wetting characteristics, chemical 
affinity, etc.), the strength of the adhesive material (this is a 
mechanical bond that requires reinforced anchoring of adhesive tangs), and 
the ability of Paste A to couple with the Paste B adhesive discussed 
below. Finally, it should be noted that utilizing a pre-cured Paste A may 
not be necessary at all for brackets, particularly clear brackets, or 
other bonding base configurations that do not utilize a metallic mesh. 
The present invention further contemplates a second adhesive dispensed 
directly onto the mesh bonding pad. This second adhesive formulation will 
be referred to hereinafter as Paste B. Preferably, Paste B is a 
shelf-stable, high viscosity paste which is capable of maintaining its 
handling, curing and aesthetic characteristics while on a bracket in a 
package for at least one year at room temperature. It is contemplated that 
Paste B is dispensed directly onto the mesh bonding base of a metal 
bracket which has the pre-cured Paste A thereon. The consistency of the 
material may be such that Paste B is not self-leveling when applied to the 
bracket, in which case it may require teasing to form a desired geometry. 
It will be appreciated that as an alternative, Paste A may not be used at 
all and Paste B is the sole adhesive. Furthermore, although bond strength 
is found to be higher when a pre-cured Paste A is present within the mesh 
bonding surface, it is contemplated that the Paste B would be utilized by 
itself even on metal brackets having mesh bonding surfaces. 
One preferred Paste B composition which has demonstrated satisfactory 
results is as follows: 
______________________________________ 
Component Weight Percent 
______________________________________ 
camphorquinone 0.03% 
ethyl-4-(dimethylamino)benzoate 
0.12% 
barium aluminum borosilicate 
69.83% 
ethoxylated bisphenol A dimethacrylate 
15.01% 
Bis GMA 15.01% 
2,6-di-t-butyl-4-methylphenol 
0.003% 
______________________________________ 
The above formulation can be modified through filler selection if different 
handling characteristics are required. Ideally, paste dispensing onto the 
bracket should be automated and therefore the flow characteristics may 
require adjustment. 
An alternative Paste B composition contemplated for use in the present 
invention has the following composition: 
______________________________________ 
Component Weight Percent 
______________________________________ 
camphorquinone 0.03% 
ethyl-4-(dimethylamino)benzoate 
0.12% 
barium aluminum borosilicate 
62.50% 
silica 6.25% 
ethoxylated bisphenol A dimethacrylate 
21.80% 
trimethylopropane trimethacrylate 
9.30% 
2,6-di-t-butyl-4-methylphenol 
0.003% 
______________________________________ 
The above formulation may provide improved stability vis-a-vis the first 
described Paste B formulation. 
Yet another contemplated alternative Paste B has the following composition: 
______________________________________ 
Component Weight Percent 
______________________________________ 
camphorquinone 0.3% 
ethyl-4-(dimethylamino)benzoate 
0.12% 
barium aluminum borosilicate 
63.8% 
silica 5.3% 
Bis GMA 20.60% 
trimethylopropane trimethacrylate 
10.15% 
2,6-di-t-butyl-4-methylphenol 
0.003% 
______________________________________ 
Subsequent to application of the adhesive to the bonding surface of the 
bracket, a non-tacky exposed surface is provided by applying a layer or 
coating of particles to the exposed adhesive surface. In a preferred 
embodiment of the invention, the particles, which may be spherical or any 
other suitable shape, become partially embedded in the outermost portion 
of the Paste B adhesive. The particles form an integral part of the 
adhesive; however, the exposed surfaces of the particles are free of 
monomeric resin, thereby rendering a dry, plastic-like, non-tacky exposed 
surface. One suitable type of particles are commercially available Polymer 
82.TM., available from Sybron Chemicals. Polymer 82.TM. is a 50/50 
copolymer of poly(ethyl/methylmethacrylate) with a trace of a peroxide 
initiator. The particles are solid, plastic spheres, non-agglomerating, 
individual and free-flowing. The size range is approximately 0.001 to 
0.0005" in diameter. The bracket assembly having Paste B thereon is dipped 
into Polymer 82.TM. powder, or the powder is sprinkled onto the exposed 
Paste B. The paste will only accept a layer or coating because the small 
mass of a sphere immediately sticks to any exposed resinous surface, and 
when all spaces are occupied, excess spheres freely flow over the 
non-tacky surface, unable to attach. 
As an alternative to the Polymer 82.TM. particles, another product, Polymer 
65CLC (also available from Sybron Chemicals) provides good results. 
Polymer 65CLC is approximately 95% polymethylmethacrylate and 5% 
diacrylate cross-linker. The polymer spheres have a diameter size range of 
about sit 3 to 100 microns. The particle layer or coating may also 
comprise solid soda lime glass spheres, such as are available from Potters 
Industries under the designation Product 3000CP-01. These glass spheres 
are believed to have a diameter in the range of 5-45 microns. 
In use and application, the brackets of the present invention having an 
adhesive composition and a layer or coating of particles to present a 
non-tacky surface, are applied to a tooth surface which has been treated 
with a primer (sealant). Generally speaking, the primer should be 
hydrophilic. The primer essentially becomes the coupling agent for 
attaching the non-tacky surface of the Paste B adhesive to a porous, 
slightly moist tooth enamel. The primer should be light curable and shelf 
stable in conventional packaging. One contemplated primer composition is 
as follows: 
______________________________________ 
Component Weight Percent 
______________________________________ 
camphorquinone 0.10% 
ethyl-4-(dimethylamino)benzoate 
0.42% 
hydroxy ethyl methacrylate 
26.5% 
Bis GMA 73.0% 
2,6-di-t-butyl-4-methylphenol 
0.01% 
______________________________________ 
The above primer, which is a low viscosity, clear liquid, is painted onto 
dry, etched enamel. The bracket of the present invention with a non-tacky 
pre-applied adhesive is then positioned on the primed tooth and a light 
cure affixes the appliance. It is believed that the mechanism involved 
includes pressing the particles into the adhesive and there is presented 
an intermixed zone wherein the adhesive and the primer are intermixed at 
their interface. At that intermixed zone, the particles become scattered 
or dispersed in the adhesive/primer intermix. Upon light curing utilizing 
well known light curing techniques, the adhesive and primer are 
copolymerized into a cross-linked network or matrix that encompasses the 
particles. 
While the invention has been described in particularity and with reference 
to specific examples, the invention is not intended to be limited to such 
particulars. It will be appreciated by persons skilled in the art that 
various modifications can be made to the invention without departing from 
the scope thereof as defined in the appended claims.