Dental adhesive comprising an unsaturated monomer, a coupling agent, a crosslinker, leachable fluoride and a photoinitiator

A single package adhesive for tooth bonding applications which comprises a bulk-water-free solvent-based homogeneous liquid containing: PA1 1) An ethylenically unsaturated monomer that possesses a hygroscopic functional group that (a) is capable of chemically reacting with and through the ethylenic bond of the ethylenically unsaturated-functional monomer of 2) below, and (b) provides the capacity for chemical bonding to the surface to which the adhesive is applied. PA1 2) A mixture of soft, medium and hard crosslinkers (cross linking agents) that are polyfunctional molecules where the functionality is complementary to the ethylenic unsaturation of the ethylenically-unsaturated-functional monomer of 1) above; PA1 3) A measurable amount of a water/fluid leachable fluoride capable of being leached from the liquid in a metered amount, obtained from a fluoride source, such as a particulate siliceous fluoride containing filler suspended in the liquid, in which the fluoride therein is water leachable; and PA1 4) a photoinitiator system, i.e., comprises a free radical photoinitiator that induces addition polymerization of an ethylenically unsaturated compound. A method is described for using the adhesive in tooth bonding applications.

BRIEF DESCRIPTION OF THE INVENTION 
A single package adhesive for tooth bonding application comprising a 
bulk-water-free solvent-based homogeneous mixture of-- 
1) an ethylenically-unsaturated-functional monomer; 
2) a coupling agent; 
3) a crosslinker (cross linking agent); 
4) a measurable amount of a water/fluid leachable fluoride capable of (a) 
being leached from the adhesive in a metered amount; 
5) a photoinitiator; 
6) optionally, a radiopaquing agent; and, optionally, a buffering agent. 
Composite formation by adhesively interbonding with tooth components using 
this single package adhesive. 
BACKGROUND TO THE INVENTION 
GERISTORE.RTM., TENURE.RTM., and TENURE.RTM. QUIK .TM., sold by Den-Mat 
Corporation, Santa Maria, Calif., are promoted for certain uses in 
dentistry. U.S. Pat. Nos. 4,738,722, 5,334,625 and 5,151,453, incorporated 
herein by reference, describe GERISTORE.TM.. GERISTORE.TM. is a small 
particle composite provided as a two-package adhesive system that contains 
fluoride, is radiopaque and hydrophilic. It has low-cure shrinkage, low 
coefficient of thermal expansion and high strength. It aggressively bonds 
by chemical coupling to dentin, enamel, composites used in dentistry, 
porcelain and metal, such as stainless steel. It is a paste/paste 
formulation that is easy to mix. It is capable of rapid cure by exposure 
to room temperature and for more rapid cure, by exposure to light. In 
addition, though it contains a fluoride, which could be toxic when 
ingested in large dosages, it is biocompatible and safe to use within a 
human or other animal when applied topically. 
TENURE.TM. is a solvent based crosslinkable acrylic resin, provided as a 
solution/solution formulation, that is, a two-package system. Its 
composition is described in U.S. Pat. No. 4,964,911, patented Oct. 27, 
1990, and more effectively disclosed in U.S. Pat. No. Re 34,937, patented 
May 16, 1995, the disclosure of which is incorporated by reference. It is 
not an ionomer and does not release fluoride ion. It is less hydrophilic 
than GERISTORE.RTM.. It too is a crosslinkable resin. It contains a 
volatile solvent (typically acetone), which readily evaporates. After 
evaporation, a film of the resin rapidly cures in situ. The film is light 
and/or heat cured to a thermoset condition. TENURE.RTM. bonds by chemical 
coupling to dentin, enamel, porcelain, metal and the composites typically 
used in dentistry. It has been recommended for use with GERISTORE.RTM. in 
chemically bonding GERISTORE.TM. to dentin or enamel. 
TENURE.RTM. QUICK.TM. is a single package adhesive that is sold for the 
same applications as TENURE.RTM. and it is described in commonly assigned, 
patent application Ser. No. 08/515,185, filed Aug. 11, 1995, now 
abandoned, based on provisional application serial no. 60/000,804, filed 
Jul. 5, 1995. 
Bisco Inc., 1500 W. Thordal Ave., Itasca, Ill., 60143, sells a "one-step" 
adhesive bonding acrylic resin system called "One-Step" that uses a single 
solution to form the adhesive resin film. It is cited to yield the 
following physical data in bonding to certain substrates: 
______________________________________ 
Substrates SBS, MPa 
______________________________________ 
Dentin (using etchant) 
27.3 (0.6) 
Enamel (using etchant) 
30.4 (3.8) 
Metals: 
Gold Alloy 20.6 (5.0) 
Rexillium III (Ni--Cr) 
25.5 (2.3) 
Stainless Steel (316) 
29.2 (1.7) 
Set Amalgam (TYTIN .RTM. ) 
13.6 (1.5) 
______________________________________ 
There is a need for an adhesive composition with the properties of 
TENURE.RTM. that is designed to be used from a single package of 
ingredients.

THE INVENTION 
This invention relates to a single package adhesive that is superior for 
tooth bonding applications which comprises a bulk-water-free solvent-based 
homogeneous liquid containing: 
1) an ethylenically unsaturated-functional monomer that possesses a 
hygroscopic group that (a) is capable of chemically reacting with and 
through the ethylenic bond of the ethylenically unsaturated-functional 
monomer of 2) below, and (b) provides the capacity for chemical bonding to 
the surface to which the adhesive is applied. For example, the coupling 
agent may be an acrylic monomer that possesses acrylic unsaturation and 
contains a surface bonding group, such as one or more of the following 
groups: 
______________________________________ 
i) an alkylene polyether 
vi) phosphinyl 
ii) hydroxyl vii) stannoyl 
iii) quaternary ammo- viii) amide 
nium ix) alkylene amine 
iv) tertiary amine x) alkoxysilyl 
v) phosphoryl xi) acyloxysilyl 
______________________________________ 
2) a mixture of soft, medium and hard crosslinkers (cross linking agents) 
that are polyfunctional molecules where the functionality is complementary 
to the ethylenic unsaturation of the ethylenically-unsaturated-functional 
monomer of 1) above; 
3) a measurable amount of a water/fluid leachable fluoride capable of being 
leached from the liquid in a metered amount, obtained from a fluoride 
source, such as a particulate siliceous fluoride containing filler 
suspended in the liquid, in which the fluoride therein is water leachable; 
and 
4) a photoinitiator system, i.e., comprises a free radical photoinitiator 
that induces addition polymerization of an ethylenically unsaturated 
compound. 
An important facet of this invention is that the components of the 
formulation with the exception of the fluoride generating source, are 
sufficiently compatible with each other and the solvent of choice. This 
means that the combination of the ingredients used in making the invention 
form a stable homogeneous mixture, i. e., they form a stable solution that 
can be stored for an extended period of time. It is preferred in the 
practice of the invention that all of the components of the formulation 
with the exception of the fluoride source remain in solution at ambient 
conditions for months, without precipitation of any component. However, it 
is within the contemplation of this invention that one or more of the 
ingredients of the formulation may precipitate from the solution on 
standing. In those instances, the precipitate is a soft deposit that is 
readily redissolved by stirring. 
The expression "water-free" is intended to cover the exclusion of 
intentionally-added water and the expression "relatively water-free" and 
"essentially anhydrous" are intended to encompass a product in which water 
is not intentionally added in bulk form. In either of these circumstances, 
water may be present as molecular water that is bound to any of the 
materials that are used in formulating the adhesive of the invention. The 
molecular water that is bound to any of the adhesive reactants of the 
adhesive of the invention can be readily removed by heating the reactant 
at moderate temperatures and conditions below that which either degrades 
or polymerizes the adhesive reactant, at a temperature at or above the 
boiling point of the reactant if the reactant is lower boiling than water. 
Such allows separation of the formulation component from bound or freely 
associated water. Whether such bound water is present or removed plays an 
insignificant role in the performance of the adhesive of the invention to 
the extent that the water does not co-react with any of the component 
making up the adhesive formulation, including the source for fluoride. In 
general, the adhesive is made with a solvent that is water soluble, and as 
a result, the small quantity of water in the adhesive is fully diluted by 
the solvent. 
One distinction between this adhesive from other adhesives is the fact that 
it is an essentially anhydrous composition. It is anhydrous in that 
essentially no free water is added to the formulation. Any water in the 
formulation is bound water, i.e., water that is chemically bound to one of 
the ingredients in the formulation, as noted above. For example, the 
hydroxylated acrylates and/or the solvents may contain from about 0 to 
about 5 weight percent bound water, that is, water that is hydrogen bonded 
to the hydroxylated acrylate or the solvent structures. The overall 
adhesive formulation may be hygroscopic, and absorb water on standing. 
Such water is bound to the various adhesive formulation's chemicals' 
structures. For example, glycerol methacrylate, a preferred hydroxylated 
reactant, is hygroscopic and will absorb water on standing. However, the 
amounts of water in the formulation based on bound water will not, in any 
case, exceed about 2 weight percent of the weight of the adhesive 
formulation. 
The inventive adhesive comprises a resin based on an ethylenically 
unsaturated-functional monomer that contains a hygroscopic group and 
exhibits hydrophilicity. Typical of such groups are hydroxyl, amide, 
amine, aliphatic ether, pyrrolidone, ureyl, and the like. 
Another feature of the inventive adhesive is that it tenaciously bonds to 
surfaces onto which it is coated as well as securely ties up any inorganic 
filler that is included in its formulation. This is accomplished by virtue 
of the presence of fluoride and by the presence in the adhesive 
formulation of the invention of a plurality of crosslinking agents. The 
same formulation without the fluoride does not adhere as tenaciously and 
the same formulation without the plurality of crosslinking agents does not 
have the consistently high adhesion levels. 
Chemical bonding means strong and weak bonding forces. Strong bonding 
forces, as used herein, refers to covalent, ionic, hydrogen bonding and 
complexation, and weak bonding forces, encompasses the other forms of 
bonding. Where weak bonding forces are employed, the extent of such 
bonding is such that the adhesion to the surface is of the nature of a 
stronger bonding force. For example, van der Waal forces are weak bonding 
forces. In the case of the invention, the amount of such forces existing 
between the adhesive and the surface will be sufficient to give the 
performance of a stronger bonding force. 
Desirable crosslinking agents are materials, such as a molecule, that are 
functionally complementary to the ethylenically-unsaturated-functional 
monomer. Desirably, the crosslinking agent contains a functional group 
that is reactable with the ethylenic unsaturation. Preferably, the 
functional group is an acrylic ethylenic unsaturation. At another part of 
at least one of the crosslinking agent molecules is a surface bonding 
group that can impart one or more properties to the adhesive coating: 
1) chemical bonding capabilities to the substrate surface to which the 
adhesive coating is applied; and/or 
2) wetting agent properties in that it reduces the surface tension of the 
adhesive coating, causing the adhesive to spread across or penetrate more 
easily the surface of the substrate onto which the adhesive coating is 
applied. 
In addition, the adhesive of the invention contains at least three 
different crosslinking agents. The crosslinking agent are a polyfunctional 
molecules where the functionality is complementary to the ethylenic 
unsaturation of the ethylenically-unsaturated-functional monomer. In one 
category of crosslinking agent, the functional groups are separated by an 
organic moiety that is wholly aliphatic, thus forming a soft crosslinker. 
In the second category of crosslinking agent, the functional groups are 
separated by an organic moiety that is partially aliphatic and partially 
aromatic, thus forming a medium crosslinker. In the third category of 
crosslinking agent, the functional groups are separated by an organic 
moiety that is essentially wholly aromatic, thus forming a hard 
crosslinker. 
The soft crosslinker typically contains an organic moiety that separates 
the two ethylenically unsaturated groups that is an aliphatic group of up 
to 10 aliphatic carbon atoms. Preferably, the functional groups of the 
crosslinking agent are bonded to a central moiety that is aliphatic in 
nature. Illustrative of such flexible groups are the residues of ethylene 
glycol, diethylene glycol, propylene glycol, dipropylene glycol, and the 
like. The medium crosslinker typically contains an organic moiety that 
separates the two ethylenically unsaturated groups that is a mixture of 
aliphatic and aromatic groups. In the case of the medium crosslinker, the 
ethylenically unsaturated functional groups are bonded to a central group 
that has the flexibility of an alkane or an alkyl benzene containing 
compound, such as 2,2-bis(4-hydroxyphenyl)propane, 
2,2,-bis(4-hydroxyphenyl)fluoroalkanes, and the like. Typically, the 
aromatic group of the medium crosslinker is a central moiety of the 
molecule. The hard crosslinker comprises an essentially rigid aromatic 
organic group that separates the two ethylenically unsaturated groups. 
Illustrative of such rigid groups are aromatic or aromatic rings such as 
benzene, biphenyl anthracyl, benzophenone, norbornyl, and the like. Such 
hard crosslinkers raise the T.sub.g of the cured coating. Such softer 
crosslinkers toughen the cured adhesive and can raise the T.sub.g of the 
cured coating, but not as high as other crosslinking agents that are 
classed as the medium and hard crosslinkers. 
In order to cure the adhesive of the invention, its formulation is provided 
with a conventional free-radical photoinitiator. The invention also 
contemplates, as an optional feature, the use of free radical scavengers 
in the formulation. 
A primary advantage of the invention is that the adhesive composition is an 
essentially anhydrous homogeneous liquid single-package system. This means 
that the adhesive composition is an essentially anhydrous solution that 
can be stored in and used from a single container, such as a glass or 
plastic bottle. Quite surprisingly, the adhesive of the invention yields a 
performance when used that is similar to the TENURE.RTM. two package 
system adhesive, described in U.S. Pat. No. Re 34,937 and superior to 
single package adhesives used in this art. 
In particular, the invention relates to the improvement where the adhesive 
composition is an essentially anhydrous homogeneous liquid single-package 
system comprising: 
1) an ethylenically-unsaturated-functional monomer, such as 
2-hydroxyethyl-methacrylateand,1,2-dihydroxypropyl methacrylate, the like; 
2) a soft crosslinking agent, such as triethylene glycol dimethacrylate, 
diethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and 
the like; 
3) a medium crosslinker such as 2,2-bis(4-methacryloxy 2-ethoxy-phenyl) 
propane; 
4) a hard crosslinker that is characterized by one or more compounds of the 
following formulae: 
##STR1## 
wherein n is 0 or 1; preferably mixture of such crosslinker; and 
4) A fluoride source for water leachable fluoride, such as fluoride 
component that is present in the adhesive as a component of a non-resinous 
component of the formulation. The fluoride component may be, but need not 
be soluble in the resin component of the adhesive. In the preferred 
practice of the invention, the fluoride component in the adhesive 
formulation will dissolve in water and to the extent the water is removed 
from the fluoride source, fluoride is carried with it. As noted above, the 
particularly desirable form of the fluoride component, is an inorganic 
fluoride in which the fluoride is present, e.g., in the form of an 
fluorosilicate structure or an alumina fluoride structure. The fluoride 
source of U.S. Pat. No. 5,360,770 is a glass composition in which the 
fluoride content is derived from an alkaline earth metal fluoride such as 
calcium fluoride, barium fluoride and strontium fluoride. A most preferred 
fluoride source is described in U.S. Pat. No. 5,360,770 which is 
incorporated herein by reference, particularly the examples and 
illustration of the patent that show how to make the fluoride source. The 
fluoride is leachable from the adhesive over a three to four month period. 
5) a photoinitiator; and 
6) a water soluble organic solvent such as acetone. 
In the preferred embodiment of the invention, the adhesive formulation is 
an essentially anhydrous solution comprising: 
a) 2-Hydroxyethylmethacrylate or Glycidyl methacrylate; 
b) Triethylene glycol dimethacrylate; 
c) Ethoxylated bisphenol A dimethacrylate, i. e., 2,2-bis(4-methacryloxy 
2-ethoxy-phenyl) propane; 
d) The dimethacrylate of pyromellitic dianhydride; 
e) A fluorosilicate structure or an alumina fluoride structure suspended 
therein; 
f) A photoinitiator such as ethyl 4-dimethylamino benzoate and 
camphoquinone (i.e., 2,3-bornanedione); and 
g) Acetone. 
The use of the adhesive composition of the invention to form a composite 
structure, involves, in one preferred embodiment, the steps of-- 
(a) optionally, contacting the adherend surface with an aqueous solution 
comprising at least one strong acid or acidic salt in order to condition 
the surface, followed by rinsing and drying the surface; 
(b) coat the surface with the essentially anhydrous adhesive of the 
invention: 
(c) cure the adhesive with light; 
(d) apply a compositing material to the coating; and 
(e) cure the compositing material in contact with the coating. 
The adhesives of the invention are suitable for a variety of dental 
application, ranging from restorations to the teeth, bonding to and with 
enamel, dentin, porcelain, plastics and metal prosthesis (precious and 
non-precious metals), and the like. 
DETAIL DESCRIPTION OF THE INVENTION 
The adhesive coating based on the adhesive formulation of the invention is 
typically a crosslinked light set resin that contains hygroscopic groups 
that attract water to the coating. When the crosslinking is not too 
extensive, the adhesive coating can absorb enough water that it can swell. 
The amount of water that the adhesive can absorb can be as high as 25 
weight percent. However, the degree of crosslinking of the adhesive 
coating is typically high enough that water absorption will not exceed 
about 5 weight percent. The backbone of the polymer providing the 
hygroscopic groups of the resin phase of the adhesive coating is typically 
aliphatic and may contain groups therein that enhance the hydrophilicity 
of the resin phase. The adhesive coating's resin is typically the in situ 
reaction product of one or more of a polymerizable ethylenically 
unsaturated organic monomer containing groups that are attractive to 
water. Thus the components of the adhesive formulation may be-- 
An ethylenically unsaturated-functional monomer that contains a hygroscopic 
group. Typical of such groups are hydroxyl, amide, amine, aliphatic ether, 
amine, hydroxyalkyl amine, hydroxyalkyl amide, pyrrolidone, ureyl, and the 
like. Illustrative of such monomers are the following: 
##STR2## 
A particularly desirable ethylenically unsaturated-functional monomer is 
an acrylic-monomer having the following structure: 
##STR3## 
wherein R' and R", individually, are hydrogen, alkyl of 1 to about 4 
carbon atoms, monocyclic aryl, such as phenyl, alkyl phenyl where the 
alkyl is 1 to about 3 carbon atoms, cyclohexyl, and the like; R.sup.2 is 
hydrogen, alkyl of 1 to about 3 carbon atoms, and the like; X is O, S and 
N--R.sup.3, where R.sup.3 is hydrogen, alkyl of 1 to about 4 carbon atoms, 
--R.sup.1 --Y, and the like; R.sup.1 is a divalent radical connecting Y to 
X, and may be one of the following: 
##STR4## 
wherein each R.sup.4 is hydrogen or alkyl of 1 to about 3 carbon atoms; 
and Y is OH, NR.sup.5, SH, OR.sup.6, where R.sup.5 is hydrogen, methylol, 
methylol methyl ether, R.sup.6 is alkyl of 1 to about 3 carbon atoms 
provided that R.sup.1 is --CH.sub.2 --, and the like; q is 0 or 1 and p is 
0 or 1, and p is 0 when q is 1 and 1 when q is 0; and Z is hydrogen. 
A particularly desirable thermosetting adhesive is based on 2-hydroxyethyl 
methylmethacrylate ("HEMA"), 2-hydroxyethyl acrylate, 2,3-dihydroxypropyl 
methacrylate, acrylamide, methacrylamide, hydroxyalkyl acrylamide, 
hydroxyalkyl methacrylamide, and the like materials, and includes 
generally, acrylic monomer that possesses acrylic unsaturation and 
contains a surface bonding group possessing one or more of the following 
groups: 
______________________________________ 
1) an alkylene polyether; 
7) alkoxysilyl 
2) hydroxyl 8) phosphoryl 
3) carboxyl 9) phosphinyl 
4) carboxylic acid salt 
10) stannoyl 
5) quaternary ammonium 
11) amide 
6) tertiary amine 12) alkylene amine 
13) acyloxysilyl 
______________________________________ 
These coupling agents interreact with the polymerization of the 
aforementioned diethylenically unsaturated-functional monomer that serve 
to crosslink the adhesive. 
A number of acrylic adhesive resins rely on polyacrylyl substituted 
monomers to crosslink and chain extend the polymer that comes into 
existence on polymerization in the presence of an polymerization 
initiator. For example, the pure forms of HEMA typically contain small 
amounts of ethylene glycol dimethacrylate which will crosslink a polymer 
based on HEMA. The degree of crosslink may be so minuscule as to have 
little effect on the ultimate properties of the polymer. Crosslinking 
agents are frequently added to HEMA based resins to impart a particular 
quality of crosslinking and toughness to the cured resin. For example, 
diethylene or triethylene glycol dimethacrylate can otherwise lower the 
crosslink density of the resin which may impart toughness to the resulting 
cured polymer. Those types of crosslinkers would be considered a soft 
crosslinker, as defined above. However, in the practice of this invention, 
it is desired to use three type of crosslinkers, one that is hard, one 
that is medium hard, and one that is soft. In this respect, one may 
include the above crosslinker, in its normal impurity concentrations, as 
part of the soft crosslinker, but in the preferred embodiment, it is 
desirable to employ hard, medium and soft crosslinkers that contain at 
least two acrylyl groups bonded to aromatic containing moiety(ies) and two 
acrylyl groups bonded to an aliphatic moiety. A desirable hard crosslinker 
is characterized by the following formulae: 
##STR5## 
wherein n is 0 or 1. The preferred hard crosslinking agent is one of (i) 
the esters or imides of pyromellitic acid dianhydride and 2-hydroxyethyl 
methacrylate or 2-aminoethyl methacrylate, or the corresponding acrylates, 
as illustrated in group B above, (ii) the ester or imides of 
3,3',4,4'-benzophenonetetracarboxylic dianhydride and 
2-hydroxyethylmethacrylate or 2-aminoethyl methacrylate, or the 
corresponding acrylates, as illustrated in group A above, (iii) the esters 
and imide/amides of 4-trimellitic acid anhydride and 
2-hydroxyethylmethacrylate or 2-aminoethyl methacrylate, or the 
corresponding acrylates, as illustrated in group C above, (iv) the ester 
or imides of 2,2-bis(3,4,-dianhydridophenyl)-1,1,1,3,3,3-hexafluoropropane 
and 2-hydroxyethyl methacrylate or 2-aminoethyl methacrylate, or the 
corresponding acrylates, as illustrated in group D above, and (v) other 
compounds containing at least one group or moiety capable of free radical 
polymerization and at least one aromatic ring or moiety containing 
electron-withdrawing substituents that do not interfere with free radical 
polymerization. The medium crosslinker is typically an diacrylic or 
dimethacrylic ester or ether of the ethylene oxide adduct of bisphenol A. 
The soft crosslinkers are the other glycol dimethacrylates and diacrylates 
mentioned herein. Preferred medium crosslinkers are ethoxylated bisphenol 
A dimethacrylate and the adduct of glycidylmethacrylate and bisphenol A, 
The fluoride component is present in the adhesive as a component of a 
non-resinous component of the formulation. The fluoride component may be, 
but need not be soluble in the resin component of the primary coating. In 
the preferred practice of the invention, the fluoride component in the 
adhesive will dissolve in water and to the extent the water is removed 
from the fluoride source, fluoride is carried with it. As noted above, the 
particularly desirable form of the fluoride component, is an inorganic 
fluoride in which the fluoride is present, e.g., in the form of an 
fluorosilicate structure or an alumina fluoride structure. The fluoride 
source of the patent is a glass composition in which the fluoride content 
is derived from an alkaline earth metal fluoride such as calcium fluoride, 
barium fluoride and strontium fluoride. A most preferred fluoride source 
is described in U.S. Pat. No. 5,360,770 which is incorporated herein by 
reference, particularly the examples and illustration of the patent that 
show how to make the fluoride source. As noted above, the adhesive is 
optionally provided with a leachable fluoride component. The fluoride is 
leachable from the coating over a three to four month period. This means 
that after many days and even months, the coating should be able to 
release small measured amounts of fluoride into the wound area. The 
longevity of the fluoride in the coating and the ability to meter it from 
the coating are dependent on a number of factors, such as: 
the concentration of fluoride in the coating; 
the nature of the chemical bond of the fluoride within the coating 
composition; 
the level of hygroscopicity of the coating; 
if the fluoride is part of a solid, the degree of particulateness of the 
solid, coupled with the rate at which fluoride can be leached from the 
solid; 
if the fluoride is part of a liquid molecule, the rate at which the 
fluoride is cleaved from the molecule to form a leachable fluoride; and 
if the fluoride is part of a polymer, the rate at which fluoride in the 
polymer can be solubilized and leached from the polymer. 
A particularly desirable form of the fluoride component, is an inorganic 
fluoride in which the fluoride is present, e.g., in the form of an 
fluorosilicate structure or an alumina fluoride structure. Illustrative of 
such fluoride structures are fluorite (or fluorspar), CaF.sub.2, 
BaF.sub.2, SrF.sub.2, cryolite, Na.sub.3 AlF.sub.6, and fluorapatite, 
3Ca.sub.3 (PO.sub.4).sub.2 Ca(F,Cl).sub.2. A preferred fluoride source is 
described in U.S. Pat. No. 5,360,770. The fluoride source of the patent is 
a glass composition in which the fluoride content is derived from an 
alkaline earth metal fluoride such as calcium fluoride, barium fluoride 
and strontium fluoride. A particularly preferred glass composition that 
provides fluoride is the following: 
TABLE 1 
______________________________________ 
Component Mole % Component Mole % 
______________________________________ 
SiO.sub.2 17.6-21.6 P.sub.2 O.sub.5 
0.8-3.5 
Al.sub.2 O.sub.3 
9.0-11.0 Na.sub.2 O 
0.5-3.0 
MO 7.9-19.7 F 42.2-56.1 
______________________________________ 
in which M is an alkaline earth metal and MO is barium oxide and barium 
oxide binary and ternary mixtures with other alkaline earth metal oxides, 
such as BaO, BaO--CaO, BaO--SrO and CaO--BaO--SrO. Such preferred source 
of fluoride not only provides long term fluoride release from the adhesive 
but it also provides an essentially uniform release of fluoride over that 
period of time. FIGS. 1 and 2 illustrate the long term fluoride 
leachability of this fluoride source. FIG. 1 illustrates the release of 
fluoride by placing the aforementioned barium oxide based glass in water 
and determining the release of fluoride over an extended period of time. 
As can be seen, the fluoride release follows a straight line showing 
uniform release over 550 days, about 11/2 years. FIG. 2 shows area plots 
of ingredients in order to optimize the glass formulation for maximizing 
the fluoride release over an extended period, e.g., 11/2 years. 
Also included in the formulation, as an optional ingredient, is a 
photoinitiator. According to one aspect this invention, the 
light-initiated curing of a polymerizable matrix material involves 
photosensitization of light-sensitive compounds by ultraviolet or visible 
light, which, in turn, initiates polymerization of the matrix material. 
The photoinitiator to be used in this invention comprises a combination of 
a photosensitive ketone and a tertiary amine. Typical photosensitive 
ketones include benzophenone, acetophenone, thioxanthen-9-one, 
9-fluorenone, anthraquinone, 4'-methoxyacetophenone, diethoxyacetophenone, 
biacetyl, 2,3-pentadione, benzyl, 4,4'-methoxybenzil, 4,4'-oxidibenzil, 
and 2,3-bornadione (dl camphroquinone). Typical tertiary amines include 
ethyl-4-dimethyl amino benzoate, ethyl-2-dimethyl amino benzoate, 
4,4'-bis(dimethylamino) benzophenone, N-methyldiethanolamine, and 
dimethylaminobenzaldehyde. A preferred combination of the photoinitiators 
is 2,3-bornanedione with ethyl-4-dimethyl amino benzoate. Other suitable 
initiator are illustrated in U.S. Pat. No. 4,674,980 to Ibsen, et al., the 
disclosure of which is incorporated by reference. Alternatively, any known 
photosensitizing system which can function effectively in a one package 
composition when exposed to light may substitute for the above-named 
compounds or combinations. The amount of the photoinitiator should be 
sufficient to initiate polymerization in a selected resin and complete it 
in depth within about half a minute when the filler-resin composition is 
exposed to a visible-light output of at least 5,000 foot candles. In 
addition, any known free-radical scavenger (anti-oxidants) such as 
butylated hydroxytoluene can be used to scavenge small amounts of free 
radicals generated during extended shelf storage. 
The polymerization system of the adhesive may depend on effecting cure with 
either the photoinitiator or by use of a thermal initiator, which is a 
typical thermal curing agent known in the art. Illustrative of these are 
benzoyl peroxide, dicumyl peroxide, ditertiary butyl peroxide, tertiary 
butyl hydroperoxide, cumyl hydroperoxide, or other suitable peroxides may 
initiate polymerization of the polymerizable ethylenically unsaturated 
components of the primary coating. Addition of such thermal initiators is 
desirable to insure complete polymerization. Even when light alone does 
not cure the matrix material, the peroxide initiates curing of the uncured 
material thermally upon standing. Benzoyl peroxide may be used together 
with 2-hydroxyethyl-p-toluidine. 
The adhesive may contain pigments such as iron oxide or titanium oxide and 
a color stabilizing agent such as 2,2-hydroxy-5-tert. octyl 
phenylbenzotriazole. 
In formulating the primary coating, the selection of the ingredients in 
formulating the coating is narrowly critical. Illustrative of such a 
formulation are the adhesive compositions as set forth in Table 2. 
TABLE 2 
______________________________________ 
Percentage 
Preferred Composition 
Ingredients by Weight 
% by weight 
______________________________________ 
Glass, fluoride source (e.g.. the Cal- 
5-20 9.0909 
cium fluoroaluminosilicate of Table 
2, supra. 
Ethylenically unsaturated monomer, 
3-15 8.9533 
e.g., 
2-hydroxyethyl methacrylate 
Soft Crosslinker, e.g., Triethylene 
2-10 8.9533 
glycol dimethacrylate 
Medium Crosslinker, e.g., Ethoxy- 
3-15 8.9533 
lated bisphenol A dimethacrylate 
Hard Crosslinker, e.g., PMDM 
2-20 6.9533 
Acetone 20-65 52.2779 
2,3-bornanedione 0.03-0.30 
1.409 
Ethyl 4-dimethylaminobenzoate 
0.01-3 1.409 
______________________________________ 
The preferred formulation was transferred to a small, black dropper bottle 
and tested as follows: 
Bovine teeth are prepared to expose the dentin surface and are mounted in 
an acrylic mold to support them during preparation and testing. The teeth 
are etched with a dental etchant for 15 seconds containing 37% Phosphoric 
Acid and are rinsed and blotted dry. Three coats of the adhesive are 
applied, and gently air-dried to remove solvent and form a thin film. If 
the surface does not appear glossy, an additional coat is applied and 
air-dried. Once a glossy surface is achieved, the material is light-cured 
for 15 seconds. using a Marathon 2000 curing light. Next, a ring mold with 
an inner diameter of 3.21 mm and a depth of approximately 2 mm was 
positioned on the light-cured adhesive. This was filled with Dual-Cured 
Marathon Composite and light-cured for 45 seconds. The ring mold was 
carefully excised using a scalpel and the samples were placed into 
37.degree. C. water. 
After 55 minutes, the samples were taken from the 37.degree. C. water and 
tested on an Instron Model 1011 for shear bond strength using a 1000 # 
Load Cell with 0.2 in/min. crosshead speed on a knife edge tester set at 
the 100# Load Range. The adhesion obtained averaged 12.0 Mpa (x=3). 
A typical restorative procedure for using the adhesive of the invention on 
dentin would encompass the following: 
Prepare and clean dentin surface as is customary. Apply 37% phosphoric acid 
etchant to the tooth's surface and allow to sit for 15 seconds. Thoroughly 
rinse and gently blot or air-dry the area treated. Completely immerse a 
brush tip in the adhesive composition of the invention. Using a fully 
saturated brush tip each time, apply three consecutive coats of the 
adhesive to the phosphoric prepared tooth. Allow the adhesive to lie on 
the tooth for 15 seconds. Remove solvent from the adhesive by directing a 
gentle stream of dry, oil-free air from an air syringe onto the adhesive. 
The force of the air should be strong enough to extract the adhesive's 
solvent while not so forceful as to force the adhesive from the 
preparation. If the dentin surface is not glossy after drying, re-apply 
the adhesive and gently re-dry. Light-cure the adhesive for 15 seconds 
then apply another thin coat using adhesive remaining on the brush. 
Position and cure the restorative material as directed by the 
manufacturer. 
Light having a wave length of about 480 .eta.M at an intensity of about 
5000 foot-candles is preferred. 
Typical surfaces for use of the adhesives of the invention include the 
following: 
bovine bone tissue, 
dentin, 
stainless steel, 
enamel, 
porcelain, 
nonprecious (NP) metals 
titanium and 
hydroxyapatite (the principal bone salt, Ca5(PO4)3OH, which provides the 
compression strength of vertebrate bone).