U.S. patent application number 09/804940 was filed with the patent office on 2001-08-09 for abrasion resistant dental composition product and process.
Invention is credited to Liu, Andrew T. C..
Application Number | 20010012861 09/804940 |
Document ID | / |
Family ID | 27359349 |
Filed Date | 2001-08-09 |
United States Patent
Application |
20010012861 |
Kind Code |
A1 |
Liu, Andrew T. C. |
August 9, 2001 |
Abrasion resistant dental composition product and process
Abstract
Dental composition, product and process using a silicon
containing abrasion resistant material. The dental products formed
are abrasion resistant and self-lubricating across their entire
cross sections. Dental compositions useful for forming dental
products in accordance with the invention preferably includes an
ethylenically unsaturated silane. The composition is formed into a
dental prosthesis, such as an artificial tooth, inlay, onlay,
facing, crown or bridge.
Inventors: |
Liu, Andrew T. C.; (York,
PA) |
Correspondence
Address: |
DALE R. LOVERCHECK
DENTSPLY INTERNATIONAL INC.
570 West College Avenue
York
PA
17405-0872
US
|
Family ID: |
27359349 |
Appl. No.: |
09/804940 |
Filed: |
March 14, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09804940 |
Mar 14, 2001 |
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08391282 |
Feb 21, 1995 |
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08391282 |
Feb 21, 1995 |
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08097541 |
Jul 27, 1993 |
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08097541 |
Jul 27, 1993 |
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08011038 |
Jan 29, 1993 |
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08011038 |
Jan 29, 1993 |
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07979093 |
Nov 19, 1992 |
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08011038 |
Jan 29, 1993 |
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07729018 |
Jul 12, 1991 |
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Current U.S.
Class: |
523/118 ; 424/49;
433/202.1 |
Current CPC
Class: |
C08F 2/02 20130101; C08L
51/085 20130101; C08L 51/085 20130101; A61K 6/17 20200101; C08F
255/02 20130101; A61K 6/887 20200101; A61K 6/887 20200101; C08F
265/06 20130101; A61K 6/896 20200101; C08F 265/06 20130101; A61K
6/887 20200101 |
Class at
Publication: |
523/118 ; 424/49;
433/202.1 |
International
Class: |
A61K 007/16; C08L
001/00; C08J 003/00; C08K 003/00; A61C 013/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 23, 1992 |
AU |
18520/92 |
Jun 24, 1992 |
CA |
2072205 |
Jul 10, 1992 |
EP |
92111787.5 |
Jul 12, 1992 |
JP |
185532/1992 |
Claims
What is claimed is:
1. An artificial tooth comprising an enamel and a body, at least
one of said enamel and said body comprising a matrix polymer having
silicon containing moieties said silicon containing moieties being
without hydroxy or alkoxy groups.
2. The artificial tooth of claim 1 wherein said silicon containing
moiety is formed from a polymerizable composition comprising a
compound of at least one of the general formulas: 9and 10wherein
R.sub.1 and R.sub.2 each independently is hydrogen or a lower
alkenyl having from 1 to 6 carbon atoms R.sub.3 and R.sub.4 each
independently is hydrogen or a lower alkyl having from 1 to 6
carbons atoms, and j and 1 each independently is an integer from 1
to 6.
3. The artificial tooth of claim 1 wherein said silicon containing
moiety is formed from a polymerizable composition comprising a
compound within the scope of at least one of the general formulas:
11and 12wherein R.sub.5, R'.sub.5R.sub.6, R'.sub.6, R.sub.7 and
R.sub.8, independently are hydrogen or a lower alkyl of from 1 to 6
carbons and m and n each independently is an integer from 1 to
6.
4. An artificial tooth comprising an enamel and a body, said enamel
being integrally connected to said body, said tooth comprising
self-lubricating polymer particles and a matrix polymer having
silicon containing moieties.
5. The tooth of claim 4 wherein said silicon containing moieties do
not comprise hydroxy or alkoxy groups and are covalently bonded to
crosslink said matrix polymer.
6. The tooth of claim 4 wherein said self-lubricating polymer
particles comprise polymer formed compounds of the general formula:
13wherein p is an integer from 100 to 1,000,000, (--) is a single
or a double bond, when (--) is a double bond R, R', and R.sub.11
independently are hydrogen, or a lower alkyl of from 1 to 6
carbons, and R and R.sub.10 are not present; when (--) is a single
bond R, R', R.sub.9, R.sub.10, and R.sub.11 independently are
hydrogen, fluorine or a lower alkyl of from 1 to 6 carbons and said
matrix polymer, said matrix polymer comprising acrylate or
methacrylate polymer or copolymer.
7. The tooth of claim 6 wherein said self-lubricating polymer
particles comprise polyethylene having a molecular weight of at
least 1,000,000, said polyethylene having a coefficient of friction
less than about 0.25.
8. The tooth of claim 7 wherein said polyethylene has a molecular
weight greater than 1,000,000 and is in the form of particles
having a particle size less than 80 microns, and are chemically
bonded to said polymeric matrix.
9. The tooth of claim 6 wherein said particles are retained in a
matrix of an interpenetrating polymer network.
10. The tooth of claim 6 wherein said lubricating abrasion
resistant polymer particles have been treated by gas plasma
treatment.
11. A dental composition for dental use comprising: polymer matrix
forming composition, said composition comprising a polymerizable
silicon containing compound of the general formula: 14wherein
R.sub.1 and R.sub.2 each independently is hydrogen or a lower
alkenyl having from 1 to 6 carbon atoms and n is an integer from 1
to 6 and self-lubricating abrasion resistant particles, said matrix
forming composition being adapted to form a polymer matrix and said
abrasion resistant particles being adapted to be covalently bonded
to said polymer matrix.
12. The dental composition of claim 11 wherein said polymer matrix
forming composition has the form of a dental prosthesis and said
self-lubricating abrasion resistant particles are substantially
evenly distributed in said polymer matrix forming composition.
13. The dental composition of claim 11 wherein said
self-lubricating particles comprise a polymer of the general
formula: 15wherein p is an integer from 100 to 1,000,000, (--) is a
single or a double bond; when (--) is a double bond R, R', and
R.sub.11 independently are hydrogen, or a lower alkyl of from 1 to
6 carbons, and R.sub.9 and R.sub.10 are not present; when (--) is a
single bond R, R', R.sub.9, R.sub.10, and R.sub.11 independently
are hydrogen, fluorine or a lower alkyl of from 1 to 6 carbons.
14. A dental composition of claim 11 wherein said self-lubricating
abrasion resistant particles have a coefficient of friction less
than about 0.25.
15. The dental composition of claim 11 wherein said composition has
a form of an artificial tooth, inlay, onlay, facing, crown or
bridge and said particles are covalently bonded to crosslink said
polymeric matrix material.
16. The dental composition of claim 11 wherein said polymer matrix
forming composition comprises a blend of particulate material and
liquid polymerizable monomers, said liquid polymerizable monomers
comprising a) said polymerizable silicon containing compound b)
monofunctional polymerizable monomer, and c) di- or polyfunctional
crosslinking agent reactive with said polymerizable monomer, said
particulate material comprising from about 10% to about 70% by
weight of said dental composition, said particulate material
comprising said self lubricating polymer particles and crosslinked
polymer particles having average diameters up to about 500 microns,
said crosslinked polymer particles being sufficiently crosslinked
as to maintain substantially their structural identity when exposed
to said monomers, said crosslinked polymer particles being capable
of swelling with or imbibing at least 10% by weight of said
crosslinked polymer particles of said monomers, said crosslinked
polymer particles being substantially swollen by said monomers, and
said dental composition being capable of being hardened into a
water insensitive object.
17. The tooth of claim 16 wherein said self-lubricating particles
comprise a polymer of the general formula: 16wherein p is an
integer from 100 to 1,000,000, (--) is a single or a double bond;
when (--) is a double bond R, R', and R.sub.11 independently are
hydrogen, or a lower alkyl of from 1 to 6 carbons, and R.sub.9 and
R.sub.1o are not present; when (--) is a single bond R, R',
R.sub.9, R.sub.10, and R.sub.11 independently are hydrogen,
fluorine or a lower alkyl of from 1 to 6 carbons.
18. The tooth of claim 17 wherein said dental composition comprises
from about 15 to about 55% by weight of said crosslinked polymer,
and at least about 50% by weight of said crosslinked polymer
particles have average diameters below about 150 microns.
19. A process for producing a dental prosthesis comprising: molding
a polymerizable composition to form a dental prosthesis, said
polymerizable composition comprising a polymerizable silicon
containing compound which does not have hydroxy or alkoxy
groups.
20. The process of claim 19 wherein said polymerizable silicon
containing compound is within the general formula 17wherein R.sub.1
and R.sub.2 each independently is hydrogen or a lower alkenyl
having from 1 to 6 carbon atoms and n is an integer from 1 to
6.
21. The process of claim 19 wherein said polymerizable composition
is capable of being hardened into said water insensitive object;
and said process further comprises shaping said polymerizable
composition; and exposing said polymerizable composition to heat or
to electromagnetic radiation to harden said polymerizable
composition into a shaped article.
22. The process of claim 19 wherein said polymerizable composition
comprises from about 15 to about 55% by weight crosslinked polymer
particles, and at least about 50% by weight of said crosslinked
polymer particles have average diameters below about 150
microns.
23. The process of claim 19 wherein said polymerizable composition
comprises a compound of the general formula: 18wherein R.sub.14 and
R.sub.15 independently are hydrogen or alkyl having from 1 to 6
carbon atoms and A is an aromatic moiety selected from the group
consisting of (a) biphenyl, diphenyl alkylidene having from 1 to
about 6 carbon atoms in its alkylidene moiety, diphenyl sulfone,
diphenyl sulfoxide, diphenyl ether, and diphenyl sulfide; (b) the
diglycidyl derivatives of subgroup (a); and (c) the diurethane
derivatives of either subgroup (a) or sub-group (b).
24. The process of claim 19 wherein said polymerizable composition
further comprises one or more members selected from the group
consisting of free radical initiators, photochemical initiators,
activators, pigments, fillers and radiopaquing agents.
25. The procedure of claim 19 wherein said dental prosthesis is a
molded tooth, inlay, onlay, facing, crown, bridge or denture.
Description
[0001] This is a continuation-in-part of U.S. patent application
Ser. No. 08/011,038 filed Jan. 29, 1993 which is incorporated
herein by reference in its entirety, and which is a
continuation-in-part of U.S. patent application Ser. No. 07/979,093
filed Nov. 19, 1992 which is incorporated herein by reference in
its entirety, and a continuation-in-part of U.S. patent application
Ser. No. 07/729,018, filed Jul. 12, 1991 which is incorporated
herein by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] The invention relates to self-lubricating abrasion resistant
compositions useful for a wide range of applications. Particular
utility is found in the dental and medical arts where such
compositions are suitable for the formation and construction of
dental prosthesis such as artificial teeth, inlays, onlays, and
facings, crowns and bridges and artificial bone parts and medical
prosthetic body parts, such as knee joints and/or other bone
engaged surfaces and the like where abrasion resistance,
polishability and aesthetics are important. Artificial teeth should
exhibit certain physical and physicochemical characteristics to be
suitable for use. They should be hard and resistant to chipping,
durable, and stable to solvents, water, and heat. In addition, they
should be of an aesthetically acceptable color, i.e., close to that
of natural teeth, or be amenable to artificial coloration. The
teeth should not cause excessive wear to opposing natural or
artificial teeth, should not wear out of occlusion, and should be
capable of being bonded firmly to supportive structures. They
should also be amenable to ordinary means of physical shaping,
grinding, and polishing, so as to minimize production costs.
[0003] Various metals and ceramics as used in the formation of
prior art artificial teeth and other dental appliances possess
certain inherent deficiencies which lessen their desirability in
dental applications. Thus, the metallic color of gold, amalgam, and
other metallic species serves as an aesthetic detraction to the
wearer of appliances made therefrom. In addition, the high cost of
most noble metals from which many such appliances are commonly made
leads to a cost consideration whenever their use is contemplated.
Ceramic materials, another common alternative, are often difficult
to form into acceptable shapes, and may tend to be abrasive
resulting in excessive wear upon contacting hard tissue, enamel and
dentin. Such materials are also difficult to polish satisfactorily.
These reasons together with factors related to cost, to consumer
preference, to the technical skills of dental practitioners, and to
convenience have motivated a search for alternative compositions
suitable for the construction of dental appliances, inlays, onlays,
crown and bridge material, artificial teeth and the like. Of the
presently available organic compositions used for the construction
of artificial teeth, most are composed of acrylics, often
crosslinked by polyfunctional moieties.
[0004] As used herein "self-lubricating material" means a material
which is adapted to increase the lubricity of a product surface
reduce friction, and consequently reduce wear.
[0005] As used herein "water insensitive" means that water does not
have a material effect upon the material so characterized.
[0006] It is to be understood that the term "bisphenol-A" is
commonly utilized in the art to indicate the chemical compound
2,2-bis(4-hydroxyphenyl)propane. It is also to be understood that
the term "bis-GMA" is commonly used to indicate the chemical
compound
2,2-bis(4-(2-hydroxy-3-methacryloxypropoxy)-phenyl)propane,
otherwise referred to as "digycidyl methacrylate ester of
bisphenol-A."
[0007] Dentsply in U.S. Pat. Nos. 4,396,476, 4,396,377 and
4,698,373 (the disclosures of which are incorporated herein by
reference) discloses interpenetrating network teeth, but does not
disclose self-lubricating abrasion resistant compositions as
required by the present invention.
[0008] Thornton U.S. Pat. No. 2,345,305 discloses making artificial
teeth comprised of different plastic materials for the face
("enamel") and body portions. Note FIG. 17, and page 4, column 2,
lines 21-24. Another composite plastic tooth structure is disclosed
by Cornell U.S. Pat. No. 3,488,846.
[0009] Rosenkranz et al. U.S. Pat. No. 3,928,299 discloses an
organic homopolymer or random copolymer containing urethane
groups.
[0010] Michl et al. in U.S. Pat. Nos. 4,267,097 and 4,281,991 (the
disclosures of which are incorporated herein by reference) disclose
artificial teeth prepared from (a) particle/bead PMMA, (b) a liquid
monomer such as the adduct of hydroxymethacrylates and
diisocyanates or difunctional esters of (meth)acrylic acids or
mixtures thereof, and (c) micro-fine inorganic fillers. Michl et al
do not disclose self-lubricating abrasion resistant hardenable
compositions as required by Applicants' invention.
[0011] Walkowiak et al. in U.S. Pat. Nos. 4,308,190 and 4,369,262
disclose dental paste materials of a polymerizable acrylic ester, a
crosslinked bead polymer, and a particulate inorganic filler and do
not disclose self-lubricating abrasion resistant hardenable
compositions, or interpenetrating network compositions for making
artificial teeth as required by Applicants' invention.
[0012] Simpson in U.S. Pat. No. 4,361,676 discloses a
sag-resistant, pumpable composition comprising a liquid material
dispersed throughout a synthetic, continuous crosslinked polymer
matrix.
[0013] Wright et al. in U.S. Pat. No. 4,598,111 disclose the use of
various divinyl compounds, including divinyl dimethylsilane (column
6, line 35) as a crosslinking agent for (meth)-acrylate -monomer
systems. Other patents of this general type include, for example,
Kohno et al. U.S. Pat. No. 4,761,436; dimethyldivinylsilane as a
comonomer; column 3, line 29); Feinberg et al. U.S. Pat. No.
4,894,315; column 3, lines 37-38); Fryd et al. U.S. Pat. No.
4,956,252; column 5, lines 43-44); and Kafka et al. U.S. Pat. No.
4,970,037; column 9, lines 16-17).
[0014] Yamazaki et al. in U.S. Pat. No. 4,826,893 disclose a dental
composition comprising (a) a siloxane polymer, (b) a monomer
copolymerizable with the siloxane polymer, (c) a polymerization
catalyst, e.g. benzoyl peroxide, and optionally, (d) a filler.
[0015] Laundry in U.S. Pat. No. 3,084,436 discloses soft dental
materials manufactured from mixtures of methacrylate monomers.
Monofunctional esters together with vinyl-acetate or vinyl stearate
are crosslinked with polyfunctional esters of acrylic or
methacrylic acid. The resulting product is disclosed as being three
dimensionally crosslinked.
[0016] Graham et al. in U.S. Pat. No. 3,087,875 disclose
preparation of graft copolymers. Alkyl methacrylate and analogous
polymers are dissolved in monomers such as alkyl acrylates, alkyl
thioacrylates, and N-vinyl lactams. The monomers are subsequently
grafted to the preformed polymers via photochemical initiation.
[0017] Cornell in U.S. Pat. No. 3,427,274 discloses hardenable
materials formed from a mixture of methyl methacrylate homopolymer
and styrenebutadiene copolymer latex coated with methyl
methacrylate polymer which may be incorporated in a
methacrylate-crosslinking agent composition to form hardenable
compositions.
[0018] Chang in U.S. Pat. No. 3,452,437 discloses a dental
restorative material formed from the "diglycidyl methacrylate of
bisphenol-A" (bis-GMA) to which a quantity of methyl methacrylate
may be added.
[0019] Bruckmann et al. in U.S. Pat. No. 3,468,977 disclose the
formulation of dental compositions from a mixture of a polymer and
a monomer. The preformed uncrosslinked polymer beads are allowed to
swell with monomer which may contain a crosslinking agent. Acrylic
materials may be used for both the monomer and the polymer.
[0020] Petner in U.S. Pat. No. 3,470,615, teaches the formulation
of a material suitable for use in the construction of dental
appliances. A mixture of an uncrosslinked homopolymer and
crosslinked copolymer is dissolved in a liquid polyglycol
dimethacrylate to form a suspension which may be brushed on a
substratum and subsequently hardened by heat to build up layers of
polymeric material. A similar teaching may be found in U.S. Pat.
No. 3,471,596, also to Petner et al. A thick liquid is provided
which is useful in the building up of dental crowns and the like.
The difunctional monomer may contain various thickening agents
including poly(methyl methacrylate). In some embodiments, the
poly(methyl methacrylate) may be supplemented with additional
polymer which may be partially crosslinked with allyl
methacrylate.
[0021] Lee in U.S. Pat. No. 3,539,533 discloses a filling material
including a monomer solution filled with inorganic particulate
filler. The monomer solution may be a mixture of methacrylate
monomers containing bisphenol-A dimethacrylate.
[0022] Taylor in U.S. Pat. No. 3,597,389 discloses polyfunctional
methacrylate monomers, including "bisphenol-A glycidyl
dimethacrylate" (bis-GMA), polymerized with an inorganic filler to
yield dental compositions.
[0023] Waller in U.S. Pat. No. 3,629,187 discloses the use of the
isocyanate or diisocyanate adducts of bisphenol-A type compounds.
These adducts are employed together with various inorganic fillers
and liquid monomers to form liquid or paste compositions which are
polymerizable either thermally or photochemically.
[0024] Dougherty in U.S. Pat. No. 3,647,498 discloses dental
compositions which are composed of liquid-solid mixtures. The solid
phase is an acrylate or methacrylate polymer in bead form.
[0025] Logemann in U.S. Pat. No. 3,649,608 discloses dental
compositions which comprise solid bead polymers or copolymers of
methacrylate type materials.
[0026] Lee in U.S. Pat. No. 3,751,399 discloses compositions for
dental use comprising aromatic and alicyclic polyacrylates which
are mixed together with other polyacrylate compounds especially
those containing bisphenol-A structures.
[0027] Sperling in U.S. Pat. No. 3,833,404 discloses elastomers,
especially acrylates, urethanes, butadienes, natural rubbers, and
polyvinyl alcohol, are formulated which possess interpenetrating
polymeric network type structures. These materials are disclosed as
being "hard", but are used as vibration and sound damping
insulators.
[0028] Highgate in U.S. Pat. No. 3,961,379 discloses an article
manufactured from a crosslinked polymer which is swollen with a
monomer containing a crosslinking agent.
[0029] Temin in U.S. Pat. No. 4,197,234 discloses dental
restorative composite compositions and filler therefor.
[0030] Engel in U.S. Pat. No. 4,288,221 discloses durable
polishable direct filling material.
[0031] Jarby in U.S. Pat. No. 3,469,317 discloses material for
filling cavities.
[0032] Crowell in U.S. Pat. No. 2,315,503 discloses art of molding
composite resins.
[0033] Crowell in U.S. Pat. No. 2,403,172 discloses art of molding
resins of vinyl type.
[0034] Van Beuren Joy in U.S. Pat. No. 3,532,502 discloses
dentures, compositions, and methods Michl et al in U.S. Pat. No.
4,281,991 discloses dental prostheses.
[0035] Bauman et al in U.S. Pat. No. 4,771,110 discloses polymeric
materials having controlled physical properties and processes for
obtaining these.
[0036] Muramoto et al in U.S. Pat. No. 4,829,127 discloses
composite resin particles, its preparation and resinous composition
for coating use containing the same.
[0037] Bauman in U.S. Pat. No. 4,880,879 discloses abrasion
resistant composite material and process for making the same.
[0038] Podszun et al in U.S. Pat. No. 4,937,144 discloses dental
fillers. r Lee in Australian Patent Specification 50,674 discloses
dental adhesive composites.
[0039] Mark et al in Encyclopedia of Polymer Science and Technology
1967, Volume 6, pages 627-628 discloses alkoxy silane coupling
agents for glass. Page in Silane coupling agents, discloses alkoxy
silane compling agents.
[0040] None of the foregoing patents discloses the novel
compositions and prostheses having matrix material bonded or
adapted to form self-lubricating abrasion resistant material in
accordance with the invention.
OBJECTS OF THE INVENTION
[0041] It is an object of the invention to provide abrasion
resistant dental compositions especially useful as dental
appliances, dentures and other prostheses, inlays, onlays, facings,
crowns and bridges and the like.
[0042] It is the object of the invention to provide an abrasion
resistant polymer composition comprising polymerizable vinyl silane
or siloxane monomers useful as a dental prosthesis.
[0043] It is an object of the invention to provide a dental
composition which can be polymerized to form an abrasion resistant
prosthesis such as an artificial tooth comprising the addition of
polymerizable vinyl silane or siloxane monomers.
[0044] It is the object of the invention to provide an abrasion
resistant dental prosthesis such as an artificial tooth comprising
polymerizable vinyl dialkyl silane or siloxane monomers.
[0045] It is an object of the invention to provide a dental
composition comprising polymerizable vinyl silane or siloxane
monomers which can be polymerized to form an abrasion resistant
prostheses such as an artificial tooth.
[0046] It is an object of the invention to provide a dental
composition comprising polymerizable dimethyl divinyl silane or
siloxane monomers which can be polymerized to form an abrasion
resistant prosthesis such as an artificial tooth comprising
polymerizable dimethyl divinyl silane or siloxane monomers.
[0047] It is an object of the invention to provide an abrasion
resistant dental composition that can be molded to form an
artificial tooth comprised of copolymers of polymerizable dimethyl
divinyl silane or siloxane monomers and acrylate or methacrylate
monomers.
[0048] It is an object of the invention to provide an abrasion
resistant dental composition that can be molded to form an
artificial tooth comprised of copolymers of polymerizable dimethyl
divinyl silane or siloxane monomers and acrylate or methacrylate
monomers interpenetrating swellable crosslinked copolymers of
esters of acrylic and/or methacrylic acid.
[0049] It is an object of the invention to provide a dental
product, such as, a dental prosthesis, artificial tooth, inlay,
onlay, facing, crown or bridge which is wear resistant across its
entire cross section.
[0050] It is an object of the invention to provide compositions
which are useful in the construction of artificial teeth and other
dental appliances, which compositions lead to products having
superior physical and aesthetic characteristics.
[0051] "Ambient temperature" as used herein unless otherwise a
specified refers to a temperature of 23.degree. C.
[0052] Unless otherwise specified blends disclosed herein are
formed by stirring at ambient temperature until a homogeneous
solution is produced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0053] FIGS. 1 and 2 are cross-sectional side view and a front view
respectively of a posterior tooth in accordance with the
invention.
BRIEF SUMMARY OF THE INVENTION
[0054] The dental composition of the invention preferably includes
a polymerizable silicon containing monomer especially vinyl
siloxane and vinyl silane monomers. The dental composition is used
to form dental products having reduced wear. The dental products
formed are abrasion resistant across their entire cross-sectioned
surface. The composition is adapted to be formed into dental
prostheses, such as an artificial tooth, inlay, onlay, facing,
crown or bridge.
DETAILED DESCRIPTION OF THE INVENTION
[0055] The invention is now discussed with more particular
reference to FIGS. 1 and 2 in which like numerals refer to the same
component. FIGS. 1 and 2 show an artificial posterior tooth 30
having a tooth body 32 and an enamel coating 34. Tooth 30 includes
ridge lap 36, buckle face 38, occlusal face 40 and lingual face 42.
In a preferred embodiment tooth body 32 includes vinyl silane or
siloxane polymers and/or copolymers within an interpenetrating
polymer network (IPN) composition. In enamel 34 includes
self-lubricating abrasion resistant vinyl silane or siloxane
polymers and/or copolymers within an interpenetrating network
composition.
[0056] The dental compositions of the invention are molded and
polymerized to form dental prosthesis having reduced abrasive wear.
While not wishing to be held to any theory describing the mechanism
operative by which additions of self-lubricating monomer improves
abrasion resistance, it is believed that silicon containing polymer
or copolymers form domains upon polymerization and molding. It is
hypothesized that as the dental composition is worn away new
domains of the self-lubricating polymer or copolymer are exposed
which smear over the surface of the molded article to occlude voids
and provide a modified surface with lower friction and consequent
improved abrasive wear resistance. Self-lubricating domains are
small with particle sizes less than 3 .mu.m, preferably less than 1
.mu.m, may be sub-microscopic in dimension and are bonded to the
matrix material. The dental products formed show improved abrasion
resistance across their entire cross sections, that is, whether or
not they are cut or sectioned. In a preferred embodiment material
preferably is formed into a dental prosthesis, artificial tooth,
inlay, onlay, facing, crown or bridge.
[0057] Artificial teeth and other dental prostheses which are
prepared from hardenable dental compositions in accordance with one
preferred embodiment of the invention have outer face(s) which
include polymeric self-lubricating material. For example, occlusal
portions, i.e. "enamel", of artificial teeth are molded from
compositions of the invention and are laminated over the tooth body
(32 of FIG. 1) which may be made from a different or less abrasion
resistant prior art material. Alternatively, enamel and body
portion may be molded from the material of the invention.
[0058] In general, the novel compositions of this invention are
useful for the formation, construction and repair of dental
appliances, artificial teeth, oral prosthesis, and similar
articles. In addition, compositions in accordance with the
invention are utilized especially as inlay or onlays cemented into
or onto teeth, and in the preparation of dental crowns and
bridges.
[0059] The hardenable dental molding compositions of the invention
comprise a blend of powder and liquid components which are combined
in certain proportions to form a precursor blend are permitted to
reach a moldable consistency and are then molded and polymerized by
heat and/or light into a useful desired form. In a preferred
interpenetrating network embodiment of the invention include blends
of powder and liquid components which are combined in certain
proportions and permitted to age or mature to produce a precursor
blend that is moldable into prosthetic teeth and other dental
devices. The precursor blend is formed by combining polymer and
monomer which is then polymerized. The resulting form may be the
finished dental device or it may be machined or otherwise
subsequently post-formed to produce the desired'shape, as for
example a dental inlay formed from a computer assisted design and
machining device. In a preferred embodiment of the invention
product compositions include copolymers or polymers of
self-lubricating silicon containing monomers within an
interpenetrating polymer network. Product compositions are formed
from precursor blends. Precursor blends are formed by combining a
crosslinked polymer, a silicon containing monomeric compound such
as a vinyl polymerizable silane or siloxane compound, a
monofunctional monomer and/or a crosslinking monomer and/or
oligomer. Optionally precursor blends include uncrosslinked polymer
and a polymerization catalyst system. Precursor blends are allowed
to age or mature and then are molded and polymerized.
[0060] In a preferred embodiment the polymerizable silicon
containing compounds include two or more ethylenically
polymerizable groups per molecule and are soluble in the
polymerizable monomer blend. Unlike coupling agents typically used
for silanation of inorganic filler, these silicon containing
compounds do not bond to inorganic filler and do not include
hydroxy or alkoxy groups. Self-lubricating abrasion resistant
material are preferably formed from silicon containing monomeric
compounds within the scope of general formula I and IA: 1
[0061] or 2
[0062] wherein R.sub.1 and R.sub.2 independently are hydrogen or a
lower alkenyl having from 1 to 8 carbon atoms, R.sub.3 and R.sub.4
independently are hydrogen or lower alkyl having from 1 to 6 carbon
atoms and j, and 1 each independently is an integer from 1 to 6.
Preferably R.sub.1 and R.sub.2 are independently lower alkenyl
having from 2 to 8 carbon atoms. More preferred silicon containing
monomeric compounds are within the scope of the general formula II
and IIA: 3
[0063] or 4
[0064] wherein R.sub.5, R'.sub.5, R.sub.6, R'.sub.6, R.sub.7 and
R.sub.8 each independently is hydrogen or a lower alkyl of from 1
to 6 carbons; and R.sub.6 and R.sub.7 are unsaturated polymerizable
moieties or a lower alkyl having from 1 to 6 carbon atoms; and n
and m each independently is an integer of from 1 to 6. Most
preferably the monomeric material is divinyldimethyl silane or
divinyldimethyl siloxane.
[0065] Exemplary of silicon containing compounds within the scope
of the general formulas I, IA, II, and IIA are the following:
1,4-divinyl-1,1,4,4-tetramethyldisilyethane; 3-methacryloxypropyl
tris-(vinyldimethylsiloxy) silane; divinyldimethylsilane;
methacryloxypropyltrimethoxysilane; 3-methacryloxypropyl
tris-(vinyldimethylsiloxy) silane;
1,3-divinyltetramethyldisiloxane;
methacryloxypropyltrimethoxysilane and divinyldimethylsilane. In a
preferred embodiment of the invention the silicon containing
compound is divinyl dimethyl siloxane and/or divinyl dimethyl
siloxane.
[0066] In a preferred embodiment of the invention a tooth has an
enamel coating which includes a silicon containing moiety and a
tooth body which is prepared from compositions including
self-lubricating particles for example ultrahigh molecular weight
polyethylene particles (described in my copending patent
application Ser. No. 07-979,093 filed Nov. 19, 1992 which is
incorporated herein by reference). The self-lubricating polymer
particles preferably are within the scope of general formula (III):
5
[0067] wherein p is an integer from 100 to 1,000,000,
[0068] (--) is a single or a double bond,
[0069] R, R', R.sub.9, R.sub.10, and R.sub.11 independently are
hydrogen, fluorine or a lower alkyl having from 1 to 6 carbon
atoms,
[0070] when (--) is a double bond R, R', and R.sub.11 independently
are hydrogen, or a lower alkyl having from 1 to 6 carbon atoms, and
R.sub.9, and R.sub.10 are not present,
[0071] Crosslinked polymer particles are preferably included in
compositions in accordance with the invention. They have average
diameters ranging from about 0.001 micron to about 500 microns.
Preferably, at least 50% by weight of the particles have diameters
less than about 150 microns, and more preferably, less than 100
microns. A mixture of two or more different crosslinked polymers
may be used. A characteristic of the crosslinked polymer is that it
will be insoluble in, but will be swollen by the liquid components
used in the preparation of the precursor blend. Uncrosslinked
polymer of the precursor blend may be characterized as being
capable of dissolving in or being dispersed by the liquid
components of the blend.
[0072] The liquid polymerizable monomer blend comprises polymerable
silicon containing monomers, a polymerizable monomer, and di- or
polyfunctional crosslinking monomers or ogligomers or prepolymers
having the capacity to dissolve or disperse said uncrosslinked
polymer, and, in a preferred embodiment swell particles of
crosslinked polymer. A mixture of two or more polymerizable mono
and polyfunctional polymerizable monomers which dissolve or become
miscible with crosslinking agent and the polymerizable silicone
containing monomer are used in a one preferred embodiment.
[0073] Crosslinked powder used in a preferred embodiment of the
invention is prepared from polyfunctional and/or monofunctional
monomers which are polymerized, e.g. by bulk, solution, suspension
or emulsion techniques and comminuted to the preferred size ranges
if necessary.
[0074] Monofunctional Monomers for Preparation of Crosslinked
Polymer Powder
[0075] Exemplary of monomers for the production of the crosslinked
polymers useful in the practice of some of the preferred
embodiments of the invention are methyl-, ethyl-,
isopropyl-,tert-butyloctyl-, dodecyl-, cyclohexyl-, chloromethyl-,
tetra-chloroethyl-, perfluoro-octyl-, hydroxyethyl-,
hydroxy-propyl-, hydroxybutyl-, 3-hydroxy-phenyl-,
4-hydroxy-phenyl-, aminoethyl-, aminophenyl-, and thiophenyl-,
acrylate, methacrylate, ethacrylate, propacrylate, butyl acrylate
and chloromethacrylate, as well as the homologous mono-acrylic acid
esters of bisphenol-A, dihydroxydiphenyl sulfone, dihydroxydiphenyl
ether, dihydroxybiphenyl, dihydroxydiphenyl sulfoxide, and 2,2
bis(4-hydroxy-2, 3,5, 6-tetraf luorophenyl) propane. Other suitable
species will be apparent to those skilled in the art, some of which
are later recited below.
[0076] Polyfunctional Monomers for Preparation of Crosslinked
Polymer Powder
[0077] Crosslinking agents which are useful in the production of
the crosslinked polymer component of a preferred embodiment of the
invention include a wide variety of di- or polyfunctional moieties
which are capable of crosslinking monomer species, for example,
acrylic and lower alkyl acrylic acid diesters, acrylic and lower
alkyl acrylic acid esters formed from alcohols having a second
reactive function such as allyl methacrylate, urethane diacrylates
and dimethacrylates, polyvinylic compounds, divinyl aromatic
compounds, esters of di- or polyfunctional unsaturated acids, e.g.,
maleic, fumaric, citraconic, mesaconic, itaconic, malonic, or
aconitic, etc., acids preferably reacted with either monohydric or
poly-hydroxylic saturated and unsaturated alcohols to form esters
which are effective polyfunctional crosslinking agents useful in
the formulation of the crosslinked polymers of the invention. In
general, these alcohols have one or more hydroxylic functionalities
and have from 2 to about 30 carbon atoms. Thus, useful alcohols
include allyl, methallyl, crotyl, vinyl, butenyl, isobutenyl and
similar unsaturated alcohols as well as polyols such as ethylene
glycol, propylene glycol, butylene glycol, diethylene glycol,
triethylene glycol, tetraethylene glycol, penta-ethylene glycol,
glycerol, 1,3, 3-tri-methylolpropane, pentaerythritol,
dihydroxyphenol, and alkylidene bis-phenols such as bisphenol-A,
1,1-bis(4-hydroxy-phenyl)-methane, 4,4'dihydroxybiphenyl,
4,4,-dihydroxydiphenyl sulfone, dihydroxydiphenyl ether,
dihydorxydiphenyl sulfoxide, resorcinol, hydroquinone, etc. and
esters of a mono- or dibasic unsaturated acid with an unsaturated
monohydroxylic alcohol such as allyl acrylate, allyl methacrylate,
vinyl acrylate (methacrylate and C.sub.1 to C.sub.20 homologs),
dimethallyl fumarate, N-allyl acrylamide, crotyl acrylate, allyl
crotonate, allyl cinnamate, diallyl maleate, etc. di-, tri-, and
higher esters of polyhydroxylic alcohols such as ethylene "glycol"
diacrylate (dimethacrylate and C.sub.2-C.sub.40 homologs),
trimethylolpropane trimethacrylate, the diacrylate and
dimethacrylate esters of bisphenol-A, as well as acrylate and alkyl
acrylate esters which correspond to the general formula (IV): 6
[0078] where R.sub.12 and R.sub.13 may be the same or different and
are hydrogen or alkyl groups containing from 1 to about 6 carbon
atoms and n is a whole number from 1 to about 10. Alternatively,
the crosslinking agent may conform to the formula (V) 7
[0079] where R.sub.14 and R.sub.15 may be the same or different and
are hydrogen or alkyl groups containing from 1 to about 6 carbon
atoms and A is an aromatic moiety selected from the group
consisting of (a) biphenyl, diphenyl alkylidene having from 1 to
about 6 carbon atoms in the alkylidene portion thereof, diphenyl
sulfone, diphenyl sulfoxide, diphenyl ether, and diphenyl sulfide;
(b) the diglycidyl derivatives of group (a); and (c) the diurethane
derivatives of either group (a) or group (b). Additional examples
include allyl acrylate, divinyl (trivinyl or higher homologs)
benzene, substituted divinyl benzenes, and analogous compounds.
Compounds such as bis-GMA and the urethane diacrylate formed by
reacting hydroxyethyl acrylate, hydroxypropyl acrylate and their
methacrylic homologs with 2,4,4-trimethylhexyl-1,6-diisocyanate are
especially useful, as are diallyl maleate, ethylene glycol
dimethacrylate, trimethylolpropane trimethacrylate and the
dimethacrylate ester of bisphenol-A. In one embodiment a
polymerizable silicon containing monomer, for example vinyl silane
or siloxane monomer, may be included.
[0080] Mixtures of two or more crosslinking agents and silicon
containing monomers are useful in the practice of the
invention.
[0081] Preparation of Crosslinked Polymer Powder
[0082] Crosslinked polymer which may be prepared from the
ingredients above or others which are useful in the practice of a
preferred interpenetrating network embodiment of the invention are
formed from monomers or blends of monomers together with
crosslinking agents as hereinbefore described. The monomers
suitable for use in the production of the crosslinked polymers
include acrylic and lower alkyl acrylic acid esters, N-vinyl
lactams, acrylamides, acrylonitriles, styrenes, alkenes, and
urethanes. Preferred monofunctional monomeric species useful in the
preparation of the composition of the invention include acrylic and
lower alkyl acrylic acid esters which generally conform to the
general formula (VI): 8
[0083] wherein R.sub.16 is hydrogen or an alkyl group including
from 1 to about 6 carbon atoms, and where R.sub.17 is either (a) an
alkyl or cycloalkyl group including from 1 to about 20, and
preferably from 1 to about 6 carbon atoms; (b) phenyl and (c) alkyl
substituted phenyl in which the alkyl groups include from 1 to
about 6 carbon atoms. Various substituents may be present on either
or both of the groups R.sub.16 and R.sub.17. Thus, hydroxyl,
carboxyl, amino, thiol and halogen (e.g., fluorine, chlorine, etc.)
functionalities may be present, with the latter being preferred.
Fluorine is an especially suitable and useful substituent.
[0084] The crosslinked polymer powders are produced by polymerizing
a mixture of the monomer or monomers and crosslinking agent or
agents described above. The amount of crosslinking agent employed
in the production of the crosslinked polymers used in the practice
of the invention is a critical factor. It has been found that the
capacity of particles of polymers so produced to swell with or to
imbibe the liquid components forming the precursor blend of the
invention, is directly related to the amount of crosslinking agent
used in the production of such crosslinked polymers.
[0085] The physicochemical properties of the crosslinked polymer
fillers useful in the preferred interpenetrating network embodiment
of the invention determine the relative proportions of monomer and
crosslinking agent used to formulate said suitable crosslinked
polymers. Such crosslinked polymers must be sufficiently well
crosslinked as to maintain substantially their structural identity
when exposed to the liquid components of the precursor blend of the
invention. At the same time, they must not be so thoroughly
crosslinked as to be incapable of swelling with or imbibing such
liquid components. Thus, it is convenient to describe the
proportion of crosslinking agent by what it does rather than by
what it is. In view of the fact that the crosslinked polymers are
utilized in finely particulate form, as will be more fully
explained, it is convenient to define the -minimum amount of
crosslinking agent used therein as being that amount which is
sufficient to cause the particulate crosslinked polymer not to lose
its particulate discreteness upon exposure to the liquid components
of the invention. Similarly, the maximum amount of crosslinking
agent used therein is that amount beyond which the resulting
crosslinked polymer particles are unable to swell with or further
imbibe a significant portion of liquid components upon exposure
thereto. In this regard, a quantity of crosslinked polymer
particles would be said to swell with or imbibe a significant
portion of liquid components if it swelled with or has imbibed at
least 10% of its own weight of such liquid. Preferably, an amount
of crosslinking agent is used to provide a crosslinked polymer
having the capacity to imbibe from about 10 to about 500 percent of
its own weight of liquid components.
[0086] It will be clear to those skilled in the art that the
minimum and maximum values for the proportions of crosslinking
agents suitable for inclusion in the crosslinked polymers of this
invention will vary depending upon the chemical identity of the
component monomers and crosslinking agents. In general, however,
the crosslinking agents may comprise from as low as about 0.01% to
as high as about 100 and preferably from about 0.2% to about 40 by
weight of the resulting crosslinked polymer. The production of the
crosslinked polymer useful in the preferred interpenetrating
network embodiment of the invention from monomers and crosslinking
agents may be performed by any of the many processes known to those
skilled in the art. Thus, the polymers may be formed by heating a
mixture of the components to a temperature sufficient to cause
polymerization, either with or without the addition of initiators.
For this purpose, peroxy type initiators such as benzoyl peroxide,
dicumyl peroxide and other materials familiar to those skilled in
the art may be employed and the use of activators may be
advantageous in some formulations. Alternatively, the crosslinked
polymers of the invention may be formed from the constituents by
photochemical or radiant initiation utilizing light or high energy
radiation.
[0087] The polymerization of the crosslinked polymers may be
accomplished in a wide variety of ways all of which are known to
those skilled in the art. Thus, they may be formed by suspension
polymerization (as taught by Grim in U.S. Pat. No. 2,673,194),
emulsion polymerization, block polymerization. The crosslinked
particles preferably have an average particle size should be from
about 0.001 micron to about 500 microns. It is preferred that at
least 50% by weight of the particles have diameters below 150
microns and more preferably below 100 microns.
[0088] Uncrosslinked Polymer Powders
[0089] In addition to the crosslinked polymers described above, the
polymer component of the precursor blend of a preferred embodiment
of the invention may comprise an uncrosslinked polymer. Such
uncrosslinked polymer include those formed from any of the
monofunctional monomer species which have been disclosed above as
being useful for the preparation of the crosslinked polymers used
in the practice of the invention. Thus, monomer species conforming
to the formula above, the acrylic and C.sub.1 to C.sub.6 lower
alkyl acrylic esters of aliphatic alcohols having from 1 to about
20 carbon atoms, or mixtures thereof, are suitable as is vinylidene
fluoride. Polymeric methyl methacrylate and copolymers thereof are
preferred. The uncrosslinked polymers may be formed from the
monomers through any of the polymerization procedures known to
those skilled in the art. Thus, thermal or photochemical
polymerization, either with or without initiators, sensitizers,
activators or chain transfer agents may be employed. Similarly,
either bulk, suspension or emulsion polymerization may be utilized.
Preferably, the uncrosslinked polymers should be characterized as
having average molecular weight of from about 100,000 to about
2,000,000 g/mole, and especially of from about 500,000 to about
900,000 g/mole. While the polymers are used in particulate form,
they differ from the crosslinked polymer filler in that, unlike the
crosslinked polymers, the uncrosslinked polymers do not have a
critical particle size distribution. Thus, polymer particles or
beads of any conveniently small size such as about 50 microns, may
be utilized. Smaller sizes are preferred since they imbibe monomers
and will dissolve therein more readily, but larger sizes may be
used as well.
[0090] Polymerizable Liquid Monomer Blend
[0091] Polymerizable monomers suitable for use in the formulation
of the precursor blend of a preferred embodiment of the invention
may comprise any of a wide variety of monomers including those
previously described examples provided in the preparation of
crosslinked and uncrosslinked polymer powder. Thus, acrylic and
lower alkyl acrylic acid esters, N-vinyl lactams, acrylimides,
acrylamides, acrylonitriles, styrenes, alkenes, urethane acrylate
or methacrylate and other monomeric species may be employed in the
practice of the invention.
[0092] Especially preferred examples of polymerizable monomers
useful in the practice a preferred embodiment of the invention
include methyl-, ethyl-, isopropyl-, t-butyl-, octyl-, dodecyl-,
cyclohexyl-, chloromethyl-, tetrachloroethyl-, perfluorooctyl-,
hydroxyphenyl-, hydroxypropyl-, hydroxybutyl-, 3-hydroxyphenyl-,
4-hydroxyphenyl-, aminoethyl-, aminophenyl-, and thio-phenyl-,
acrylate, methacrylate, ethacrylate, propacrylate, butacrylate and
chloromethacrylate, as well as the homologous mono-acrylic acid
esters of bisphenol-A, dihydroxydiphenyl sulfone, dihydroxydiphenyl
ether, dihy-droxybiphenyl, dihydorxydiphenyl sulfoxide, and
2,2-bis(4-hydroxy-2,3,5,6-tetrafluorophenyl)-propane. Other
suitable species will be apparent to those skilled in the art who
will further recognize that mixtures of two or more different
polymerizable monomers may be used.
[0093] Polyfunctional Monomers and Oligomer Components of
Polymerizable Liquid Blend
[0094] Preferably, the crosslinking agents for the polymerizable
monomers comprise esters of unsaturated acids, e.g., acrylic,
methacrylic, ethacrylic, propacrylic, butacrylic, etc. maleic,
fumaric, citraconic, mesaconic, itaconic, malonic, or aconitic,
etc., acids. Other unsaturated acids will be readily apparent to
those skilled in the art. These acids are preferably reacted with
either unsaturated or polyhydroxylic alcohols to form esters which
are effective polyfunctional crosslinking agents for the monomeric
species useful in the practice of the invention. Thus, useful
alcohols include allyl, methallyl, crotyl, vinyl, butenyl,
isobutenyl and similar unsaturated alcohols as well as polyols such
as ethylene glycol, propylene glycol, butylene glycol, diethylene
glycol, triethylene glycol, tetraethylene glycol, pentaethylene
glycol, glycerol, trimethylolpropane, pentaerythritol,
dihydroxyphenol, alkylidene bisphenols such as bisphenol-A;
1,1-bis(4-hydroxyphenyl)methane; 4,4'-dihydroxy-biphenyl;
4,4'-dihydroxydiphenyl sulfone; dihydroxydi-phenyl ether;
dihydroxydiphenyl sulfoxide; resorcinol; hydroquinone; etc.
[0095] Preferred crosslinking agents used in the practice of the
invention include those previously described examples provided for
in preparation of crosslinked and uncrosslinked polymer powders as
well as, the esters of a monomeric dibasic unsaturated acid with an
unsaturated monohydroxylic alcohol such as allyl acrylate, allyl
methacrylate, vinyl acrylate (methacrylate and homologs),
dimethallyl fumarate, N-allyl acrylamide, crotyl acrylate, allyl
crotonate, allyl cinnamate, diallyl maleate, etc. Other preferred
species are the di-, tri-, and higher esters of polyhydroxylic
alcohols such as ethylene "glycol" diacrylate (dimethacrylate and
C.sub.2-C.sub.6 homologs), trimethlolpropane trimethacrylate, and
the dimethacrylate ester of bisphenol-A as well as other acrylate
and allyl acrylate esters. In addition, the crosslinking agent for
the polymerizable monomers may be a glycidyl acrylate or allyl
acrylate, divinyl (trivinyl or higher homologs) benzene,
substituted divinyl benzenes, or analogous compounds. Furthermore,
mixtures of crosslinking agents are useful in the practice of the
invention.
[0096] Compounds such as those described herein above as
crosslinking agents and bis-GMA and the urethane dimethacrylate
formed from the reaction of hydroxyethyl acrylate, hydroxypropyl
acrylate and their methacrylate homologs with
2,4,4-trimethylhexyl-1,6-diisocyanate (hereinafter referred to as
"urethane dimethacrylate" or "di-acrylate") are especially useful,
as are ethylene glycol dimethacrylate, trimethylolpropane
trimethacrylate and the dimethacrylate ester of bisphenol-A. The
corresponding acrylates are similarly useful as is diallyl
maleate.
[0097] Silicon Containing Monomer Components of the Polymerizable
Liquid Blend
[0098] Silicon containing monomers of the liquid polymerizable
blend include those of the general formula I, IA, II and IIA. These
compounds do not include hydroxy or alkoxy moieties. In a preferred
embodiment of the invention the silicon containing monomer includes
two ethylenically polymerizable groups per molecule and are soluble
in the polymerizable monomer blend in the concentrations used.
These silicon containing monomers are adapted to form crosslinks in
the polymer formed by polymerization of the polymerizable monomer
blend. In a preferred embodiment of the invention the silicon
containing monomer is divinyl dimethyl siloxane, divinyl dimethyl
silane, and mixtures thereof.
[0099] Additional Ingredients
[0100] In addition to the components described above, (i.e.,
crosslinked polymer, uncrosslinked polymer, polymerizable monomer)
the precursor blend may contain additional, optional, ingredients,
such as, initiators, activators, pigments, fillers, radiopaquing
agents, adhesion modifiers, free radical or photochemical
initiators. In this regard, peroxy type initiators such as dicumyl
or benzoyl peroxide are useful. Similarly, pigments and fillers may
be added to modify the appearance, density, and physical
characteristics of the resultant dental appliances. Inorganic
materials, especially silica and titania, silicates and aluminates,
glasses and ceramics are useful fillers and pigments, and a wide
variety of other useful pigments and fillers will be apparent to
those skilled in the art. The fillers and radiopaquing agents may
constitute a major part by weight of the compositions of the
invention. According to a preferred embodiment, the precursor blend
of this invention may comprise admixtures of organic resin
components and particulate, inorganic filler in weight ratios of
from about 1:2 to about 2:1 or more depending on the specific
gravity of inorganic ingredients included.
[0101] Precursor Blends
[0102] The precursor blends in accordance with a preferred
embodiment of the invention are formulated by a mixing together of
the constituent species in proper proportion, followed by aging or
maturing. Several techniques are available for this and others will
be apparent to those skilled in the art. Thus, it is possible to
combine crosslinked polymer filler, polymerizable vinyl silicon
containing monomers, uncrosslinked polymer and polymerizable liquid
blend in proper proportions including therewith, for example, a
peroxide initiator and a pigment. This combination is then
thoroughly mixed and aged to result in a precursor blend which has
a uniform appearance. This blend may have the consistency of dough
or may be more or less mobile depending upon the desired use
thereof. Particulate inorganic fillers or other modificants may be
preferably added at this stage in the formulation of the
compositions if desired. The compositions thus formed may be
alternatively molded, extruded, brushed, formed, worked or
otherwise shaped in any conventional manner and caused to
polymerize or cure to result in hard dental appliances having
superior properties. The application of heat or radiant energy is
usually required for this polymerization or curing.
[0103] Procedure
[0104] It is especially useful to mold the compositions of this
invention into artificial teeth for inclusion in prosthetic
devices. It is to be understood, however, that the precursor blends
are suitable for a very wide range of dental uses, including
fillings, teeth, bridges, crowns, veneers, facings, denture base
and denture reline materials, and orthodontic splint materials, and
the like. The materials of the invention may also be utilized for
prosthetic replacement or repair of various hard body structures
such as bone and may be utilized for reconstructive purposes during
surgery.
[0105] The nature of the chemical and physical relationships among
the components of the precursor blends of the invention is
important to the practice of the invention. Among these
relationships is the necessity that the crosslinked polymer
particles be capable of swelling by imbibing the liquid components.
Of similar importance is the requirement that the uncrosslinked
polymers, when included, be capable of dissolving in the liquid
components. The precursor blend formed by any of the useful
techniques described above is aged for a period of time sufficient
to insure that in one embodiment the crosslinked polymer has become
substantially fully swollen with, interpenetrated by or has
substantially imbibed the liquid crosslinking blend and that the
uncrosslinked polymer, if used, has at least partially been
dissolved therein. Thus, as used herein, "aged" or "aging" refer to
the maintenance of the components of the precursor blend in
association with one another in the blend for a period of time
sufficient to substantially fully swell the crosslinked polymer
particles with the mixture of polymerizable monomer and
crosslinking agent dissolved therein. Frequently, aging is
manifested by a change in the consistency of the mixture as
equilibrium is approached. The time necessary to approach such
equilibrium will vary depending upon the blending techniques, the
relative proportions of materials, the particle sizes and molecular
weights of the polymers and the temperature extent in the mixtures.
In general, aging time of from one to seven days has been found to
be adequate to approach the desired equilibrium. It is to be
understood that it lies well within the abilities of those skilled
in the art to ascertain the optimum aging time for a formulation in
view of the foregoing considerations. In accordance with this
preferred technique, powder components including self-lubricating
abrasion resistant particles are blended with a polymerizable
liquid blend. The precursor blend is then aged for a period of time
sufficient to permit the crosslinked polymer particles to be
substantially fully swollen with, or interpenetrated by
polymerizable blend. Precursor blends thus formed may be
alternatively molded, brushed, extruded, formed, worked or
otherwise shaped to form useful dental devices and articles. Other
techniques are presented in the examples which follow, and still
others will be apparent to those skilled in the art.
[0106] Upon polymerization of the precursor blends in one
embodiment a three dimensional structure is believed to be formed
which may be denominated as an interpenetrating polymeric network.
The interpenetrating network structure which is believed to form is
a major contributing factor to the serendipitous combination of
superior chemical and physicochemical properties which is exhibited
by the articles constructed according to the practice of the
invention. Interpenetrating polymeric networks are related to, but
distinct from, traditional graft polymers.
[0107] Interpenetrating Network Moldings
[0108] In accordance with a preferred embodiment of the invention a
self-lubricating interpenetrating network may be viewed as being
composed of ultra high molecular weight polyethylene dispersed
within two or more crosslinked, and hence three dimensionally
arrayed, polymeric networks which do not necessarily have any
covalent bonds in common. While the two networks may, indeed, be
independent in the sense that they need possess no covalent
linkages between them; they are physically trapped one "within" the
other and cannot disassociate by any physical manipulation without
the rupture of covalent bonds. Particulate crosslinked polymer is
allowed to swell with or imbibe monomer mixed with crosslinking
agent, and when the imbibed mixture of monomer and crosslinking
agent is subsequently caused to polymerize, an interpenetrating
polymeric network may be seen to be formed within the confines of
the particulate crosslinked polymer. It is believed that the aging
process employed in the preparation of the precursor blends of the
invention is required to accomplish substantially full swelling
with interpenetration by or substantially complete imbibition of
crosslinking agent by the crosslinked polymer particles, and to
approach an equilibrium thereof.
[0109] The American Dental Association specification number 15
specifies, "the strength of the bond between tooth and resin is
tested in tension. The minimum bond strength is 30.9 MN/M.sup.2
(4,480 psi; 315 Kg/cm.sup.2), which is sufficient to prevent
separation of the teeth from the resin denture base in use." This
pertains to "acrylic denture base resin polymerized by the heat
processing technique." The compositions of this invention meet or
exceed this specification.
[0110] A unique, heterogeneous microstructure is exhibited by one
embodiment, the preferred interpenetrating network embodiment of
the invention. One exemplary method for observing this
microstructure is as follows:
[0111] 1. The tooth, or molded article, is sectioned and one
section potted in epoxy against a flat surface.
[0112] 2. The sectioned surface of the potted specimen is polished
to a smooth surface using nos. 320, 400 and 600 grit silicon
carbide papers wet continuously with water.
[0113] 3. A final polish is obtained using an aqueous slurry of 0.3
micron A1.sub.2O.sub.3 on a chamais.
[0114] 4. The polished surface of the section is exposed for four
minutes to the vapors of boiling concentrated nitric acid; the
microstructure is oxidatively exposed by this-etching procedure and
is best captured by photomicrography at 260.times.
magnification.
[0115] The microstructure thus observed is heterogeneous and
comprises what may best be described as particles suspended in a
matrix. The particles are believed to be identifiable with the
particulate crosslinked polymers of the precursor blend which have
been swollen by and interpenetrated with the monomer and
crosslinking agent. By comparison with conventional composite
compositions containing only rigid inorganic fillers, the articles
formed according to the present invention exhibit a micro-structure
in which the structure is much more closely packed. It is to be
understood that this methodology, while of wide application in the
examination of the micro-structure of the novel compositions of the
invention, is not exclusive. Other techniques involving greater or
lesser magnification and other means of visualization are also
useful in disclosing the structure. Distributed throughout this
structure is particulate self-lubricating particles.
[0116] Preferably teeth and other molding formed in accordance with
a preferred embodiment of the invention are prepared from 0.05 to
50 percent by weight polymerizable silicon containing
self-lubricating monomer compound. Especially preferred are such
teeth prepared from 0.5 to 40 percent by weight of a silicon
containing compound. More preferably such teeth are from 0.5 to 20
percent by weight of a silicon containing compound. Most preferably
such teeth are from 1 to 10 percent by weight silicon containing
compound. Most preferably the self-lubricating silicon containing
monomer is divinyldimethyl silane or divinyldimethyl siloxane.
[0117] The following examples describe certain representative
embodiments of this invention and will serve further to illustrate
the nature thereof. It is to be understood that the examples are
merely illustrative, and do not in any way limit the scope of the
invention as defined by the claims. All percentages are by weight
and unless otherwise specified correspond to the amount in grams of
a component used in a composition.
COMPARATIVE EXAMPLE 1
[0118] Prior Art Tooth
[0119] A precursor blend is prepared having the following
composition:
1 Weight Percent of Blend Methyl Methacrylate (MMA) 43.30 Ethylene
glycol dimethacrylate 2.30 benzoyl peroxide (BPO) 0.23
polymethylmethacrylate (PMMA) 54.00
[0120] The polymethyl methacrylate polymer has an average molecular
weight of 800,000 g/mole, and is in the form of particles with
diameters 46% by weight of which are below 74 microns in size, the
balance (54%) being below about 500 microns.
[0121] All ingredients of the precursor blend composition except
polymer are added to a planetary mixer and stirring until a
homogeneous solution is produced. The polymer is then added and
stirred to form a uniform dough. Prosthetic teeth are molded from
the precursor blend composition in heated metal molds after the
precursor blend composition is aged at ambient temperature for
seven days.
EXAMPLE 2
[0122] Prior Art Tooth
[0123] A precursor blend is prepared having the following
composition.
2 Weight Percent Methyl Methacrylate 37.33 Bisphenol A
Dimethacrylate 8.43 Benzoyl peroxide 0.24 Polymethyl methacrylate
54.00
[0124] All ingredients of the precursor blend composition except
polymer are added to a planetary mixer and stirring until a
homogeneous solution is produced. The polymer is then added and
stirred to form a uniform dough. Prosthetic teeth are molded from
the precursor blend composition in heated metal molds after the
precursor blend composition is aged at ambient temperature for
seven days. The teeth are clear and comply with ADA/ANSI
Specification 15.
EXAMPLE 3
[0125] Prior Art Interpenetrating Network Tooth C
[0126] A precursor blend is prepared having the following
composition:
3 Weight Percent of blend 35.35% methyl methacrylate 0.21% benzoyl
peroxide 7.44% 2,2-bis(4-methacryloxyphenyl)propane 38.00%
poly(methyl methacrylate-co-ethylene dimethacrylate) (99.2:0.8)
19.00% poly(methyl methacrylate) 100.00%
[0127] The crosslinked polymer is in the form of particles, 46% by
weight of which were below 74 microns in size, the balance being
below about 500 microns in size. The poly-(methyl methacrylate)
have an average molecular weight of 800,000 g/mole.
[0128] The benzoyl peroxide and
2,2-bis(4-methacryloxy-phenyl)propane are dissolved in the methyl
methacrylate at ambient temperature to form a monomer solution. The
polymers and pigment are charged to a planetary dough mixer
containing the monomer solution and the charge is stirred until
visibly homogeneous. Prosthetic teeth (C) are molded from the
resultant precursor blend mixture after it is aged at ambient
temperature for seven days. The resulting teeth grind with a dusty,
fine debris, bond to denture base and are impact and wear
resistant.
EXAMPLE 4
[0129] Abrasion Resistant Silane Monomer Containing IPN Tooth D
[0130] A precursor blend is prepared having the following
composition:
4 Weight Percent of Blend methyl methacrylate 34.55 benzoyl
peroxide 0.22 2,2-bis (4-methacryloxyphenyl)propane 7.08
poly(methyl methacrylate-co-ethylene dimethacrylate) (99.2:0.8)
37.00 poly(methyl methacrylate) 19.00 divinyl dimethyl silane 2.15
100.00
[0131] The crosslinked polymer is in the form of particles, 46% by
weight of which were below 74 microns in size, the balance being
below about 500 microns in size. The poly-(methyl methacrylate)
have an average molecular weight of 800,000 g/mole.
[0132] The benzoyl peroxide and divinyl dimethyl silane, and
2,2-bis(4-methacryloxy-phenyl)propane are dissolved in the methyl
methacrylate at ambient temperature to form a monomer solution. The
polymers and pigment are charged to a planetary dough mixer
containing the monomer solution and the charge is stirred until
visibly homogeneous. Prosthetic teeth (D) are molded from the
resultant precursor blend mixture after it is aged at ambient
temperature for seven days. The resulting teeth grind with a dusty,
fine debris, bond to denture base and are impact and wear
resistant.
[0133] The teeth (C) formed in Example 3 showed a volume loss of
0.0316 mm.sup.3 determined by the method of Douglas, for wear
testing in an artificial mouth as described in Dental Materials
1986: 2: 235-240; Dental Materials 1985: 6: 238-242; J. Dent. Res.
1983: 62: 32-36; J. Prosthet Dent 1985: 54(2): 273-280 and Dent
Mater 1985: 1: 115-119. The teeth (D) formed in Example 4 in
accordance with the invention have a volume loss of 0.0243 mm.sup.3
as determined by Douglas wear testing in an artificial mouth, which
amounts to about 23% improvement over the prior art teeth (C) of
Example 3.
EXAMPLE 5
[0134] One-Component Filled Radiation Curable Material
[0135] The following precursor blend, containing an inorganic
filler and prepared as described in Example 1 by adding all
ingredients except polymer to a planetary mixer and stirred until a
homogeneous solution is produced. The polymer is then added and
stirring is continued to form a uniform dough.
5 Weight Percent of Blend 21.21% methyl methacrylate 3.00%
divinyl-dimethyl silane 2.96% butyl methacrylate 0.27%
camphorquinone 0.43% dimethylamino benzoic acid ethyl ester 2.08%
2,2-bis(4-methacryloxyethoxyphenyl)-propane 1.13% tetraethylene
"glycol" dimethacrylate 1.13% neopentyl "glycol" dimethacrylate
19.45% poly(methyl methacrylate-co-2,2-bis-
(4-methacryloxyphenyl)propane) (99.8:0.2) 12.23% poly(methyl
methacrylate) 35.66% gamma methacryloxypropyl trimethoxy silane
treated, fine (12 micron) particle quartz 0.45% pigment 100.00%
[0136] The dough is polymerized by visible light radiation using a
Caulk MAX photocure lamp (registered trademark of Dentsply
International).
EXAMPLE 6
[0137] Dental Veneers
[0138] A two step presswell process is used to mix a one part
dental veneer material. A blend is prepared from the following:
6 Step 1 3.00% divinyldimethyl silane 2.99% methyl methacrylate
0.51% benzoyl peroxide 45.26% reaction product off hydroxypropyl
methacrylate with 2,2,4-trimethylhexyl- 1,6-disocyanate(2:1)
(urethane dimeth- acrylate) (UDMA) 48.24% poly(methyl
methacrylate-co-ethylene dimethacrylate) (99.8:0.2) 100.00%
[0139] The benzoyl peroxide is dissolved in the methyl methacrylate
and blended with the urethane dimethacrylate and silane monomer.
This solution is then mixed with the poly(methyl
methacrylate-co-ethylene dimethacrylate) (99.8:0.2). The mixture is
stored in the dark in a sealed jar to become the "pre-swell" blend.
The crosslinked polymer i.e. poly(methyl
methacrylate-co-ethylenedimethacrylate) (99.8:0.2) is in the form
of fine particles at least 50% by weight are below 100 microns in
size, and the balance below 500 microns in size. After one month
storage the fully swollen crosslinked polymer "preswell" blend is
admixed as follows:
7 Step 2 48.84% "preswell" blend from Step 1 51.03% gamma
methacryloxpropyl trimethoxy silane treated microfine silica (the
silane used) 0.13% acrylic acid 100.00%
[0140] These components are mixed on a three roll mill with minor
amounts of pigments as required until a uniformly shaded paste is
obtained.
[0141] A veneer is prepared on an opaqued crown by the well known
build up method. A dentin shade veneer paste is built up on the
crown by hand and instrument modelling. Next, an incisor shade
veneer paste is built on top of the dentin. The veneer is
polymerized by immersion in a 90.degree. C. water bath under three
bars air pressure. Veneers are also polymerized by immersion in
glycerin in a similar manner. The finished veneer has a high gloss
and good aesthetic appearance. The veneer has three times the wear
resistance of conventional acrylic veneers by a prophy abrasion
test. The veneer can be readily shaped by grinding, yielding a
dusty debris, and then is readily polished to a smooth, high gloss
finish. The veneer is resistant to chemicals and stains, has good
impact strength and is repairable. The veneer paste is stable at
ambient conditions. The veneer paste is stable for nine months at
ambient temperature and seventy days at 50.degree. C.
EXAMPLE 7
[0142] Self-Lubricating Tooth Material
[0143] A precursor blend is prepared from the following
composition. All ingredients of the precursor blend composition are
added to a planetary mixer and stirred until a homogeneous solution
is produced. The polymer is then added and stirred to form a
uniform dough. Powder components are intimantly mixed in a high
shear blender before adding to prepared liquid components.
8 3.0% divinyldimethyl silane 17.9% microfine silica (Degussa 0
.times. 50) 29.4% methyl methacrylate 0.4% benzoyl peroxide 6.2%
ethylene glycol dimethacrylate 43.1% poly(methyl methacrylate)
100.0
[0144] Thus ingredients are mechanically mixed in a closed
container until a viscous paste (dough) is obtained. This paste is
introduced into a tooth mold and polymerized for 4 minutes at
110.degree. C. The artificial tooth thus obtained shows clear
opalescence, i.e. it appears yellowish in transmitted light and of
a blue-white transparency in incident light.
EXAMPLE 8
[0145] Self-Lubricating Abrasion Resistant IPN Tooth
[0146] A precursor blend is prepared from the following
composition:
9 18.16% high molecular weight poly(methyl meth-acrylate) polymer
38.23% poly(methyl methacrylate-co-ethylene dimethacrylate)
(99.2:0.8) 7.45% 2,2-bis(4-methacryloxyphenyl)pro- pane 6.82%
reaction product of hydroxypropyl methacrylate with
2,2,4-trimethylhexyl- 1,6-disocyanate(2:1) (urethane dimeth-
acrylate) (UDMA) 26.52% methylmethacrylate 0.21% benzoyl peroxide
2.28% divinyl dimethyl silane 0.33% pigments 100.00%
[0147] The polymers are in the form of particles, 46% by weight of
which were below 74 microns in size, the balance being below about
500 microns in size. The poly(methyl methacrylate) has an average
molecular weight of 800,000 g/mole. All ingredients of the
precursor blend composition are added to a planetary mixer and
stirred until a homogeneous solution is produced. The polymer is
then added and stirred to form a uniform dough. This material is
aged 14 days and then is molded into IPN teeth in heated metal
molds.
[0148] It should be understood that while the present invention has
been described in considerable detail with respect to certain
specific embodiments thereof, it should not be considered limited
to such embodiments but may be used in other ways without departure
from the spirit of the invention and the scope of the appended
claims.
* * * * *