U.S. patent number 3,926,906 [Application Number 05/081,156] was granted by the patent office on 1975-12-16 for dental filling package.
This patent grant is currently assigned to Johnson & Johnson. Invention is credited to Henry Lawrence Lee, II, Francis Fabian Smith, Michael Lawrence Swartz.
United States Patent |
3,926,906 |
Lee, II , et al. |
December 16, 1975 |
**Please see images for:
( Certificate of Correction ) ** |
Dental filling package
Abstract
Direct dental filling materials utilizing a crosslinkable binder
system and finely divided inorganic filler are packaged as two
component systems with each of the two package components
containing an intimate mix of unpolymerized resin binder and
inorganic filler in the proportions in which they will be present
in the cured dental filling. The contents of the two package
components are essentially the same with the exception that one
package component contains together with the resin binder and
filler, an accelerator for the resin binder and the other package
component contains a catalyst for the resin binder. In preparing a
filling a portion of the contents of one package component is mixed
with a portion of the content of the other package component. For
color blending one of the package components may be prepared in
different tints.
Inventors: |
Lee, II; Henry Lawrence (San
Marino, CA), Smith; Francis Fabian (Los Angeles, CA),
Swartz; Michael Lawrence (Encino, CA) |
Assignee: |
Johnson & Johnson (New
Brunswick, NJ)
|
Family
ID: |
24961998 |
Appl.
No.: |
05/081,156 |
Filed: |
October 15, 1970 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
736950 |
Jun 14, 1968 |
|
|
|
|
Current U.S.
Class: |
523/116; 106/35;
523/212; 524/786; 523/214; 524/854 |
Current CPC
Class: |
C08J
3/241 (20130101); C08F 20/16 (20130101); A61K
6/887 (20200101) |
Current International
Class: |
A61K
6/083 (20060101); A61K 6/02 (20060101); C08F
20/16 (20060101); C08F 20/00 (20060101); C08J
3/24 (20060101); C08K 003/36 () |
Field of
Search: |
;260/41,41R,42.53,42.15
;206/47,63.5 ;106/35 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Czaja; Donald E.
Assistant Examiner: Person; S. M.
Parent Case Text
This application is a continuation of our copending application
Ser. No. 736,950 filed June 14, 1968, entitled "Dental Filling
Package," and now abandoned.
Claims
Having thus described our invention, we claim:
1. A method of filling a tooth comprising the steps of:
a. providing a first quantity of paste-like material consisting
essentially of: a premixed unpolymerized resin binder system
containing active polyfunctional monomer having a central portion
which contains at least one aromatic ring and at least two acrylic
end groups; a finely-divided, organosilane keying agent-treated,
inorganic filler constituting at least 65 percent by weight of said
paste-like material; and a free radical generating catalyst for
said binder system in which the free radicals when generated in
sufficient quantities will produce relatively rapid polymerization
of said system;
b. providing a second quantity of paste-like material consisting
essentially of: substantially the same premixed unpolymerized resin
binder system which is in said first quantity of material; a
finely-divided, organosilane keying agent-treated, inorganic filler
constituting at least 65 percent by weight of said second quantity
of paste-like material; and an activator for said catalyst to cause
the aforesaid generation of free radicals in sufficient quantities
to produce relatively rapid polymerization of said binder
system;
c. extracting from each of said quantities of material
approximately equal amounts of the same sufficient to effect the
desired tooth restoration;
d. mixing said extracted quantities so that said activator of said
second quantity of material reacts with said catalyst of said first
quantity of material causing the generation of sufficient free
radicials to inititate relatively rapid polymerization of said
resin binder system; and
e. promptly filling a tooth with said mixture before it hardens due
to polymerization so that after said mixture is in a tooth it will
harden in a known and substantially uniform time to form a hard
dental filling.
2. A method of producing a hard dental filling comprising the steps
of:
a. taking a quantity of paste-like material consisting essentially
of: pre-mixed unpolymerized resin binder system containing active
polyfunctional monomer having a central portion which contains at
least one aromatic ring and at least two acrylic end groups;
finely-divided, organosilane keying agent-treated, inorganic filler
constituting at least 65 percent by weight of said materal; and
free radical generating catalyst for said system in which the free
radicals when generated in sufficient quantities will produce
relatively rapid polymerization of said system;
b. mixing an activator which is reactive with said catalyst to
cause generation of free radicals in sufficient quantities to cause
relatively rapid polymerization of said system into said quantity
of paste-like material so as to initiate relatively rapid
polymerization of said system, said activator being added in the
form of a paste-like composition in which the activator is
substantially uniformly dispersed throughout a mixture of
unpolymerized resin binder system and finely divided filler, said
activator when mixed in such form resulting in a more uniform
initiation of polymerization throughout the binder system and a
dental filling of greater initial hardness when said mixture is
placed in a tooth immediately after preparation.
3. A storable and activatable paste-like material for use in
producing a hard dental filling material consisting essentially of:
an intimate mix of resin binder system containing active
polyfunctional monomer having a central portion which contains at
least one aromatic ring and at least two acrylic end groups;
finely-divided, organosilane keying agent-treated, inorganic filler
constituting at least 65 percent by weight of said material; and a
free radical generating catalyst which when activated will generate
free radicals in sufficient quantity to produce relatively rapid
polymerization of said system and which material will remain
substantially unpolymerized and ready to be activated for a period
of months.
4. A storable and activatable paste-like material for use in
producing a hard dental filling material consisting essentially of:
an intimate mix of resin binder system containing active
polyfunctional monomer having a central portion which contains at
least one aromatic ring and at least two acrylic end groups;
finely-divided, organosilane keying agent-treated, inorganic filler
selected from the group consisting of fused silica, aluminum oxide,
crystalline quartz and glass beads, said filler constituting at
least 65 percent by weight of said material; and a free radical
generating catalyst which when activated will generate free
radicals in sufficient quantity to produce relatively rapid
polymerization of said system and which material will remain
substantially unpolymerized and ready to be activated for a period
of months.
5. A storable and activatable paste-like material for use in
producing a hard dental filling material consisting essentially of:
an intimate mix of resin binder system containing active
polyfunctional monomer having a central portion which contains at
least one aromatic ring and at least two acrylic end groups;
finely-divided, organosilane keying agent-treated, inorganic filler
constituting at least 65 percent by weight of said material, in
which a small portion of said filler is replaced by an amount of
hydrophobic submicron silica sufficient to substantially eliminate
separation between said binder system and filler; and a free
radical generating catalyst which when activated will generate free
radicals in sufficient quantity to produce relatively rapid
polymerization of said system and which material will remain
substantially unpolymerized and ready to be activated for a period
of months.
6. A storable and activatable paste-like material for use in
producing a hard dental filling material consisting essentially of:
an intimate mix of resin binder system containing active
polyfunctional monomer having a central portion which contains at
least one aromatic ring and at least two acrylic end groups and
which resin binder system includes at least 85 percent by weight of
bis phenol A backbone monomer; finely-divided, organosilane keying
agent-treated, inorganic filler constituting at least 65 percent by
weight of said material; and a free radical generating catalyst
which when activated will generate free radicals in sufficient
quantity to produce relatively rapid polymerization of said system
and which material will remain substantially unpolymerized and
ready to be activated for a period of months.
7. A manufacture specifically for a dentist to use in producing
hard dental fillings in a substantially uniform manner, said
manufacture being composed of two paste-like materials disposed in
separate containers and from each of which containers a dentist may
extract necessary amounts of materials to produce a dental filling
to be made, the material in one of said containers consisting
essentially of: premixed unpolymerized resin binder system
containing active polyfunctional monomer having a central portion
which contains at least one aromatic ring and at least two acrylic
end groups; finely-divided, organosilane keying agent-treated,
inorganic filler constituting at least 65 percent by weight of said
paste-like material; and free radical generating catalyst for said
system in which the free radicals when generated in sufficient
quantities will produce relatively rapid polymerization of said
system; the material in the other of said containers consisting
essentially of: substantially the same premixed unpolymerized resin
binder system as in said first container; finely-divided,
organosilane keying agent-treated, inorganic filler constituting at
least 65 percent by weight of the material in said other container;
and activator reactive with the catalyst in the material of said
one container to cause generation of free radicals in sufficient
quantity to produce relatively rapid polymerization of said system;
the mixture of materials extracted from each of said containers
causing polymerization of said binder system to be initiated and
hardening of the mixture to occur in a known and substantially
uniform time to produce a hard dental filling after being placed in
a tooth.
8. A manufacture specifically for a dentist to use in producinng
hard dental fillings in a substantially uniform manner, said
manufacture being composed of two paste-like materials disposed in
separate containers and from each of which containers a dentist may
extract necessary amounts of material to produce a dental filling
to be made, the material in one of said containers consisting
essentially of: premixed unpolymerized resin binder system
containing active polyfunctional monomer having a central portion
which contains at least one aromatic ring and at least two acrylic
end groups; finely-divided, organosilane keying agent-treated,
inorganic filler constituting at least 65 percent by weight of said
paste-like material; and free radical generating catalyst for said
system in which the free radicals when generated in sufficient
quantities will produce relatively rapid polymerization of said
system; the material in the other of said containers consisting
essentially of substantially the same premixed unpolymerized resin
binder system as in said first container; finely-divided,
organosilane keying agent-treated, inorganic filler constituting at
least 65 percent by weight of the material in said other container;
and activator reactive with the catalyst in the material of said
one container to cause generation of free radicals in sufficient
quantity to produce relatively rapid polymerization of said system;
the mixture of materials extracted from each of said containers
causing polymerization of said binder system to be initiated and
hardening of the mixture to occur in a known and substantially
uniform time to produce a hard dental filling after being placed in
a tooth; and the quantity of material containing the activator
being colored so that said mixture will substantially match the
color of the tooth in which it is to be placed.
9. A manufacture specifically for a dentist to use in producing
hard dental fillings in a substantially uniform manner, said
manufacture being composed of two paste-like materials disposed in
separate containers and from each of which containers a dentist may
extract necessary amounts of material to produce a dental filling
to be made, the mateial in one of said containers consisting
essentially of: premixed unpolymerized resin binder system
containing active polyfunctional monomer having a central portion
which contains at least one aromatic ring and at least two acrylic
end groups; finely-divided, organosilane keying agent-treated,
inorganic filler selected from the group consisting of fused
silica, aluminum oxide, crystalline quartz and glass beads, said
filler constituting at least 65 percent by weight of said
paste-like material; and free radical generating catalyst for said
system in which the free radicals when generated in sufficient
quantities will produce relatively rapid polymerization of said
system; the material in the other of said containers consisting
essentially of: substantially the same premixed unpolymerized resin
binder system a. in said first container; finely-divided,
organosilane keying agent-treated, inorganic filler selected from
the group consisting of fused silica, aluminum oxide, crystalline
quartz and glass beads, said filler constituting at least 65
percent by weight of the material in said other container; and
activator reactive with the catalyst in the material of said one
container to cause generation of free radicals in sufficient
quantity to produce relatively rapid polymerization of said system;
the mixture of material extracted from each of said containers
causing polymerization of said binder system to be initiated and
hardening of the mixture to occur in a known and substantially
uniform time to produce a hard dental filling after being placed in
a tooth; and the quantity of material containing the activator
being colored so that said mixture will substantially match the
color of the tooth in which it is to be placed.
10. A manufacture specifically for a dentist to use in producing
hard dental fillings in a substantially uniform manner, said
manufacture being composed of two paste-like materials disposed in
separate containers and from each of which containers a dentist may
extract necessary amounts of materials to produce a dental filling
to be made, the material in one of said containers consisting
essentially of: premixed unpolymerized resin binder system
containing active polyfunctional monomer having a central portion
which contains at least one aromatic ring and at least two acrylic
end groups; finely-divided, organosilane keying agent-treated,
inorganic filler constituting at least 65 percent by weight of said
paste-like material, in which a small portion of said filler is
replaced by an amount of hydrophobic submicron silica sufficient to
substantially eliminate separation between said binder system and
said filler; and free radical generating catalyst for said system
in which the free radicals when generated in sufficient quantities
will produce relatively rapid polymerization of said system; the
material in the other of said containers consisting essentially of:
substantially the same premixed unpolymerized resin binder system
as in said first containers; finely-divided, organosilane keying
agent-treated, inorganic filler constituting at least 65 percent by
weight of the material in said other container in which a small
portion of said filler is replaced by an amount of hydrophobic
submicron silica sufficient to substantially eliminate separation
between said binder system and said filler; and activator reactive
with the catalyst in the material of said one container to cause
generation of free radicals in sufficient quantity of produce
relatively rapid polymerization of said system, the mixture of
materials extracted from each of said containers causing
polymerization of said binder system to be initiated and hardening
of the mixture to occur in a known and substantially uniform time
to produce a hard dental filling after being placed in a tooth.
11. A manufacture specifically for a dentist to use in producing
hard dental fillings in a substantially uniform manner, said
manufacture being composed of two paste-like materials disposed in
separate containers and from each of which containers a dentist may
extract necessary amounts of material to produce a dental filling
to be made, the material in one of said containers consisting
essentially of: premixed unpolymerized resin binder system
containing active polyfunctional monomer having a central portion
which contains at least one aromatic ring and at least two acrylic
end groups and in which said resin binder system includes at least
85 percent by weight of bis phenol A backbone monomer;
finely-divided, organosilane keying agent-treated, inorganic filler
constituting at least 65 percent by weight of said paste-like
material; and free radical generating catalyst for said system in
which the free radicals when generated in sufficient quantities
will produce relatively rapid polymerization of said system; the
material in the other of said containers consisting essentially of:
substantially the same premixed unpolymerized resin binder system
as in said first container; finely-divided, organosilane keying
agent-treated, inorganic filler constituting at least 65 percent by
weight of the material in said other container; and activator
reactive with the catalyst in the material of said one container to
cause generation of free radicals in sufficient quantity to produce
relatively rapid polymerization of said system, the mixture of
materials extracted from each of said containers causing
polymerization of said binder system to be initiated and hardening
of the mixture to occur in a known and substantially uniform time
to produce a hard dental filling after being placed in a tooth.
Description
BRIEF DESCRIPTION OF THE INVENTION
Direct filling materials utilizing a finely divided filler and a
resin binder have heretofore been proposed. Such a direct filling
material is described, for example, in Bowen U.S. Pat. No.
3,066,112. One of the difficulties in marketing such direct filling
materials is the problem of packaging. In any filling system
utilizing a polymerizable organic binder and finely divided
inorganic filler it is necessary for the dentist to blend together
the components just prior to placing the filling in the tooth
cavity. Accordingly, any packaging systems for fillings of this
type should be such as to reduce the chance of error on the
dentist's part with respect to the proper proportioning of
ingredients in preparing the filling. It should also simplify the
mixing procedure, as the time permitted for mixing and inserting
the dental filling material is limited. Furthermore, in packaging
dental filling materials the ingredients must be so packaged that
reaction and deterioration is minimized over relatively long
periods of storage otherwise the ingredients will have been found
to have deteriorated by the time the dentist is ready to use the
same.
In direct filling systems such as described in Bowen U.S. Pat. No.
3,066,112 the binder system is composed of the monomer ##SPC1##
Hereinafter referred to as BIS-GMA, admixed with other active
monomers referred to by Bowen as reactive diluents. The binder
resin system is activated through the inclusion of both an
activator and a catalyst. In marketing such systems it has
heretofore been the practice to prepare a paste of the BIS-GMA
monomer and the finely divided filler, as a paste is much easier
for the dentist to handle when making the final mix, than is a dry
powder such as the filler itself would present. Portions of the
other active monomers have heretofore been packaged separately from
the BIS-GMA in order to avoid premature reaction. This packaging
has been thought necessary in order to obtain the extended life
required for any such prepackaged system. As a result, although
stable prepackaged materials for making fillings of the type
described in Bowen Pat. No. 3,066,112 have been made commercially
available, stability has been obtained by careful separation of
many of the component parts to avoid prepolymerization with the
result that the package made available to the dentist contained
four separate package components.
Of these package components, package component (1) contained a
paste comprising a mixture of BIS-GMA and inorganic filler, package
component (2) contained reactive liquid diluent monomer, package
component (3) contained the reactive liquid diluent monomer
together with an activator for the system, and package component
(4) contained the catalyst, benzoyl peroxide.
When using this prepackaged system in making his fillings it was
first necessary that the dentist activate a portion of his diluent
monomer. This was done by taking a small amount of catalyst from
package component (4) and adding it to some reactive diluent
monomer taken from package component (2). The activated monomer so
prepared because of its short storage life of about thirty days,
had to be prepared periodically by the dentist. When preparing the
filling the dentist then mixed together premeasured proportions of
the paste from package component (1), the catalyzed reactive
diluent monomer which had been previously prepared by the dentist
and a portion of the reactive monomer containing activator from
package component (3). As the ratio of BIS-GMA to reactive diluent
monomer is critical for obtaining the maximum binder strength as
well as is the ratio of filler to binder resin, substantial care
had to be exercised by the dentist in order to be sure that proper
proportions were admixed according to the directions contained with
the prepackaged system.
The problems confronting a dentist in preparing a filling using
such a prepackaged system can be readily seen. It is necessary for
him to remember to keep on hand a fresh batch of catalyzed reactive
diluent monomer, to carefully measure out the proportional parts
from the different containers to obtain the proper ratio of
monomers and the proper ratio of binder to inorganic filler and to
completely blend the mixture. All of this had to be done
immediately prior to placing the filling in the cavity. The
blending must be done rapidly otherwise the binder would polymerize
to too hard a mass prior to the dentist being able to place the
blended filling in the tooth and work it into the cavity. Blending
must also be uniform otherwise the filling will vary in consistency
depending on the ratio of binder to filler found in the final
filling. Furthermore, considerable care must be exercised in
measuring out the proper quantities from the respective package
components. All of these factors place a substantial strain on the
dentist preparing the filling with the result that dental fillings
so prepared may vary substantially with the best results not being
obtained. Also, substantial waste is encountered as it is extremely
difficult to measure accurately the small quantities needed to fill
one or two teeth with the result that substantially more filling
material is blended than is actually needed.
It has been discovered that in dental restorative systems such as
that of Bowen Pat. No. 3,066,112 where an inorganic filler is
present in amounts substantially greater than the binder resin and
an activator and catalyst are employed that the monomers comprising
the binder resin can all be premixed with the finely divided
inorganic filler and be kept in this premixed state for many months
even in the presence of a catalyst or an activator without undue
deterioration of the binder system occurring. It has further been
discovered that where the catalyst for the system is included in
one premixed lot of binder and filler and the activator for the
system is included in the other premixed lot of binder and filler
that when portions of the lot containing the catalyst and portions
of the lot containing the activator are then blended, excellent
polymerization is obtained. As a result, when packaging is done in
accordance with the present invention the dentist is supplied with
a two component package system. All critical blending has been
predone by the manufacturer. As it is only necesary to have
sufficient amounts of catalyst and activator present to initiate
polymerization, not even the proportionate amount taken and blended
from the two package components is critical. As a result the
dentist can take quite small amounts for blending thus avoiding
waste. All critical blending is accurate as it is done by the
manufacturer with the result that more consistent fillings are
obtained. Furthermore, time for mixing, on the part of the dentist,
is substantially reduced.
Direct filling mterials of the type utilizing a binder system
composed of unreacted monomers, an inorganic filler, and an
activator and cataylst, particularly of the type where one of the
reactive monomers is a bis phenol A containing monomer are packaged
in a two component package wherein each of the package components
contains a mixture of the unpolymerized resin binder and the
inorganic filler in substantially the proportions in which they
will be present in the final cured filling and one of the package
components contains, together with the premixed nonpolymerized
binder and filler, an accelerator for the binder system while the
other package component contains together with the premixed
nonpolymerized binder and inorganic filler a catalyst for the
binder system.
As the binder and inorganic filler are premixed in the proper ratio
and the catalyst and activator serve to initiate the reaction but
are not highly critical with respect to amounts present, the dental
filling can be readily prepared by taking approximately equal
portions of each of the two components of the package and blending
together. Also, the packaging system is ideally suited for
providing the dentist with several base shades which he then can
blend to obtain the particular shade which he may desire for the
filling. One of the package components, where tinting is desired,
is made up in several of the basic shades. The dentist then blends
various proportions of the basic shades together to get the shade
desired and then blends this mix, which is still unreactive, with a
substantially equal portion of the other package components which
contain the missing catalyst or activator depending on which was
used in preparing the various basic shade mixes.
DETAILED DESCRIPTION OF THE INVENTION
In direct filling systems wherein the filling consists essentially
of a finely divided inorganic filler bonded together by a
polymerized resin binder substantial difficulty has been
encountered in prepackaging the necessary ingredients to make the
filling in such a form that they can be easily and conveniently
handled by the dentist and will not deteriorate prior to use. A
filling material of this type is well illustrated by the filling
system described by Bowen in his U.S. Pat. No. 3,066,112. The
filling system of Bowen utilizes as a binder system a monomer
having a bis phenol A backbone having the structure ##SPC2##
and terminal acrylate group. Bowen suggests than an active monomer
be added as a diluent to control the viscosity of his bis phenol A
backbone monomer. One of the advantages of using a monomer system
of this type is the large amount of finely divided inorganic filler
with which the same can be blended in making a filling. Inorganic
filler can be blended in with the binder resin in amounts as high
as 78 percent by weight of the dental filling material. Substantial
difficulty has, however, been encountered in the packaging of the
necessary ingredients for making fillings of this general type,
that is, a difficulty in prepackaging in such manner that the work
and responsibility on the part of the dentist for handling and
obtaining accurate blend is substantially reduced.
It has now been discovered that where the ratio of finely divided
inorganic filler to resin binder is such that the filler is present
in amounts of at least 65 percent by weight of the total mix that
the unpolymerized components of the binder resin will remain
unpolymerized for extended periods of time. This permits the binder
resin to be premixed with the filler in substantially the
proportions in which the binder resin and filler will occur in the
cured filling with the same remaining stable and unpolymerized for
many months. It has further been discovered that such premixed
inorganic filler and unpolymerized resin binder can have blended
therewith either the activator for the system or the catalyst for
the system and still remain in an unpolymerized state for many
months. However, when a portion of the premixed resin and inorganic
filler containing the activator is blended with a portion of the
premixed binder and inorganic filler containing a catalyst for the
system, the binder then polymerizes and cross-links to give a
strong, useful filling.
Although the packaging system of the present invention may be used
for the prepackaging of any cement formed of an inorganic filler
and binder therefor where the inorganic filler is present in
amounts at least equal to the weight of the unpolymerized binder,
the same is particularly suitable for the prepackaging of cement
systems suitable for filling teeth utilizing as the primary binder
monomer or one of the primary binder monomers a bis phenol A
backbone monomer with terminal acrylic groups. As the dental
filling materials described in Bowen Pat. No. 3,066,112 are good
examples of filling materials of this type, the same will be used
in more specifically describing the practice of the present
invention.
The dental filling system of Bowen Pat. No. 3,066,112 comprises in
essence a finely divided inorganic filler bonded together by a
cross-linked resin binder. The ingredients in unpolymerized system
which when blended together on polymerization give the
aforementioned filling are the binder system, an activator for the
binder system, a catalyst for the binder system, and a finely
divided inorganic filler.
THE BINDER SYSTEM
The binder system, as used herein, refers to the unreacted monomers
which copolymerize to give the binder in the final filling. The
binder system of U.S. Pat. No. 3,066,112 contains as the primary
reactive monomer the bis phenol A backbone monomer having the
chemical formula ##SPC3##
this particular monomer is hereinafter referred to as BIS-GMA. The
BIS-GMA may be the only bis phenol A backbone containing monomer in
the system or the system may be modified through the inclusion of
other bis phenol A backbone monomers.
A bis phenol A backbone monomer is the primary monomer in the
binder system. BIS-GMA, the bis phenol A backbone monomer of Bowen,
may be prepared, for example, by any of the methods described in
U.S. Pat. No. 3,066,112. The viscosity of the bis phenol A backbone
monomer, which may be a mixture of bis phenol A backbone monomers,
is adjusted to a medium viscosity syrup by addition of reactive
diluent monomers such as methyl methacrylate and the glycol
dimethacrylate such as ethylene glycol dimethacrylate through
tetraethylene glycol dimethacrylate with the preferred reactive
diluent monomer being triethylene glycol dimethacrylate. Other
suitable reactive diluent monomers may be used. The bis phenol A
backbone monomer will generally comprise about 80 percent or more
of the binder system with the active diluent monomer or monomers
making up the rest of the interpolymerizable monomers present.
In order to obtain reasonably rapid curing an activator is used for
the binder system. Suitable activators are, for example,
N,N-dimethyl-para-toluidine and para-toluenesulfinic acid. However,
the activator is not limited to these particular ones, but other
amine activators may be used. Also, in order to initiate the
polymerization a suitable catalyst is employed, such as benzoyl
peroxide. Other activators are described, for example, in U.S. Pat.
No. 2,558,139. The activator reacts with the peroxide catalyst to
produce free radicals. The amount of activator will depend on the
particular activator used and the working time needed prior to the
commencement of hardening after the binder and finely divided
filler have been mixed ands catalyzed. The activator will generally
be present in amounts of about 0.1 to 2 percent by weight of the
reactive monomers in the binder system. Where a catalyst such as
benzoyl peroxide is used it would generally be present in amounts
of about 1 to 2 percent by weight of the binder system. The
activator and catalyst are not considered as a part of the binder
system as the term is used herein, as the same are used to catalyze
and control the rate of polymerization of the monomers which
interact to give the final cured binder in the dental filling.
THE FILLER
The filler may be any finely divided solid which when dispersed
through the binder system will give improved structural strength
when the binder system is polymerized into a cured resin. The best
fillers are finely divided inorganic materials such as fused
silica, aluminum oxide, crystalline quartz, small glass beads and
the like. The finely divided filler has a particle size generally
in the range of about 2 to 85 with the preferred size being within
the range of about 5 to 75 microns. The best results are obtained
where the inorganic filler is treated with a keying agent to
improve the bond between the organic polymer binder and the surface
of the finely divided filler particles. Keying agents which have
been found highly suitable are the ethylenically unsaturated
organosilane finishing or keying agents where the filler is fused
silica, glass, aluminum oxide, or crystalline quartz and the binder
system is of the type described. The finely divided filler may be
treated with the keying agent, for example, in the manner described
in U.S. Pat. No. 3,066,112 wherein an aqueous solution of
tris(2-methoxy ethoxy) vinyl silane is catalyzed with sodium
hydroxide to give a pH of 9.3 to 9.8, and the filler treated with
this solution, for example, one-half percent of the silane being
used per weight of fused quartz. A slurry so formed is dried at
about 125.degree.C. and cooled.
The binder system is then blended with the inert filler into a
paste comprising from about 65 to 75 percent by weight filler with
the remainder being the binder system. The binder system, as
previously indicated, is the blend of active monomers which later
polymerize to give the cured organic polymer forming the binder in
the filling. In the preferred systems the inert filler is present
in amounts of at least 70 percent. The paste comprising the binder
system and the finely divided filler is divided into substantially
equal portions and to one portion is added an accelerator for the
binder system while to the other portion is added a catalyst for
the binder system. Although as described the catalyst and
accelerator are added after the paste of binder system and finely
divided filler has been prepared, one could add the catalyst and
the accelerator during the blending of the finely divided filler
and binder system the same being proportioned prior to blending
rather than afterwards.
In order to simplify the description the binder system inert filler
paste containing the activator will hereinafter be called package
component A and the blend of binder system and finely divided
filler containing the catalyst will be referred to as package
component B. Package component A and package component B are both
found to be quite stable over many months storage under normal room
conditions. This is quite surprising when it is considered that if
the catalyst is added to the binder system, polymerization of the
binder system will be found to occur after a few days. Also, the
binder system itself even without the addition of the catalyst
where it contains a mixture of active monomers is found to be
unstable and tend to polymerize, particularly where such active
monomer diluents as methyl methacrylate are present. Thus, it is
quite surprising that the binder system-inorganic filler paste with
the catalyst present is stable and may still be used after many
months.
Package component A and package component B may be placed in any
type of container formed of a material that is inert to the system.
Thus the container may be a tube formed of such materials as
chemically inert plastics such as polyethylene, polypropylene,
tin-lined metal and the like or small dishes formed of such
materials, as well as glass containers and the like. It is
generally preferred to include in the paste small amounts of
ultraviolet light absorbers and inhibitors to further assure
stability of the system. A suitable inhibitor, for example, is
butylated hydroxy-toluene which may be added in amounts of .01 to
.03 percent by weight based on the total binder system filler paste
and ultraviolet absorbers such, for example, as
2-hydroxy-4-methoxy-benzophenone in amounts of .2 to .3 percent
based on the weight of the binder system finely divided filler
paste. Also, in packaging the pastes of package component A and
package component B in glass or other light-permeable containers,
it is generally desirable to have the same tinted to exclude
ultraviolet light.
It is found that in some instances some separation between the
binder system and the finely divided filler may occur after several
months storage. Where such separation does occur it is also found,
particularly in package component B, that some polymerization may
also occur in the liquid phase of the separation. Where such
separation occurs, the contents can be again mixed and are found to
be still suitable for preparing dental fillings. However, this is
undesirable as it requires a periodic remixing by the dentist, and
as previously indicated, there is also the danger of some
polymerization occurring in the liquid phase if permitted to stand
too long. It has been discovered that this slight separation of
binder system from the finely divided filler can be prevented if a
small amount of submicron particles are added. Thus, where the
filler is aluminum oxide having a particle size of 10 to 50
microns, in the preferred practice of the present invention 1 to 4
percent by weight of submicron floculated silica are added.
Interestingly, no evidence of this separation or settling is found
to occur in smaller masses, 20 to 30 grams, of either package
component A or package component B even after storage as much as 3
months at room temperature. However, with larger masses such, for
example, as more than 50 grams of fused alumina in the particular
mass some settling, as previously indicated, has been found to
occur. The submicron silica may be mixed with the resin binder
before the same is mixed with the fused alumina or other finely
divided filler. Thus, for example, the addition of 2 percent
hydrophobic submicron silica to a resin binder system blended with
70 percent by weight fused alumina gave a consistency in the final
formula which was little changed from a formula identical with the
exception that the hydrophobic submicron silica was not added.
Although the presence of the submicron silica substantially
eliminated the settling, its incorporation was found to have no
adverse effects on the properties of the system with respect to
curing and on the properties of the finally cured material.
In preparing the dental filling substantially equal portions of
package component A and package component B are blended together.
Polymerization is found to occur in about 1 to 3 minutes depending
on the particular activator and amount present. The same results
are obtained even though the proportions of package component A and
package component B used in the mixture are varied to as much as 2
parts of one to the other, thus indicating the noncriticality of
the proportionate amounts used.
As the binder is colorless and as most of the preferred filler
materials are white, it may be desirable to include some pigment.
However, unless the dentist is himself able to blend to the
particular shade in which he is interested, pigmented filling mixes
are not too desirable. It has heretofore been proposed to use
various blends of inert filler to optically match the tooth
structure so as to permit some of the underlying color of the tooth
to pass through. This may by achieved by selecting the proper blend
of glass beads and quartz to give the proper light index to the set
filling material. The present package system, however, blends
itself ideally to where pigmented fillings are desired as either
package component A or package component B can be put up in several
separate containers each having a different base color shade thus,
as base color shades, one may use brown, gray, yellow, universal
and unpigmented. The dentist then in preparing the filling would
take small proportions of different ones of the base colored
package components A and blend the same to obtain the desired shade
which he was seeking. There would be no pressure on the dentist
with respect to the binder setting while he was selecting and doing
his blending as all of the material blended would be package
component A. If desired, the basic color shades could be prepared
in package component B rather than A. However, whichever one is
selected that should be the one which contains all of the pigmented
mixes so that the same can be blended as previously indicated
without polymerization. After the desired shade is obtained then
the blended material is admixed with the binder resin-inorganic
filler mix of the other component package.
The practice of the invention is further illustrated by the
following Example which is given for purposes of illustration only,
the invention not being limited thereto.
EXAMPLE
A binder system is prepared by blending together 95 parts BIS-GMA
and 17 parts triethylene glycol dimethacrylate. Fourteen parts by
weight of submicron silica are blended in with the binder system.
The binder system so prepared containing the submicron silica is
then divided into two equal parts. One part is then blended with
fused alumina having a particle size range of 10-15 microns in the
proportion of 25 parts by weight binder to 75 parts by weight of
fused alumina. Two parts by weight of benzoyl peroxide are added to
the mix and blended therein.
The remaining portion of binder system containing the submicron
silica is divided into five parts. Organic dyes are then added to
give one part of brown tint, one a gray, one a yellow, one a
universal tint and the other is left unpigmented. Prior to adding
the dye an activator N,N-dimethyl-p-toluidine is added to the
binder mix prior to dividing into the five parts as above
described. The activator is added in an amount of 2 parts activator
to 98 parts by weight total monomer present. Each of the pigmented
and unpigmented portions of the monomer mix are then blended with
the fused alumina in the proportion of 25 parts by weight monomer
to 75 parts by weight fused alumina. The mix prepared with the
catalyst benzoyl peroxide is referred to as package component B and
the mixes prepared with the activator are referred to as package
component A. The color blending is first done by using small
amounts of different colors from the package components A. Thus, in
preparing a filling having a slightly warm tint, a small amount of
brown paste from a package component A (brown) is blended with a
small amount of paste from package component A (gray) and paste
from a package component A (neutral). If it is found that a slight
bit of yellow is needed to more closely approach the shade desired,
a small amount of yellow from package component A (yellow) is then
added, the yellow being added in the amounts needed to reach the
desired shade. The mix so obtained having the desired shade is then
blended with an approximately equal proportion of material taken
from package component B. The two pastes are mixed by spatula on a
mixing slab. The mix so obtained is placed in a preprepared cavity
of a tooth where it hardens in approximately 2 minutes from the
time that the material from package components A is blended with
the material from package component B.
The contents of package component A and package component B are
found to still be active and exhibit no separation after several
months storage under ordinary room conditions.
Particular embodiments of the invention have been used to
illustrate the same. The invention, however, is not limited to
these specific embodiments. In view of the foregoing disclosure,
variations and modifications thereof will be apparent, and it is
intended to include within the invention all such variations and
modifications except as do not come within the scope of the
appended claims.
* * * * *