U.S. patent application number 11/387177 was filed with the patent office on 2007-01-11 for laser curable polymerisable composition for he protection of hard tissue.
This patent application is currently assigned to Dentsply Research and Development Corp.. Invention is credited to Andreas Facher, Joachim E. Klee, Rolf Mulhaupt, Martin Schmider, Christoph Weber.
Application Number | 20070010597 11/387177 |
Document ID | / |
Family ID | 34925995 |
Filed Date | 2007-01-11 |
United States Patent
Application |
20070010597 |
Kind Code |
A1 |
Klee; Joachim E. ; et
al. |
January 11, 2007 |
Laser curable polymerisable composition for he protection of hard
tissue
Abstract
One-component heat-curable sealant composition for the
protection of exposed dental surfaces, comprising (a) a
polymerisable monomer and/or oligomer which has at least two
polymerizable double bonds per molecule, and (b) an initiator
system comprising benzoylperoxide in an amount of at least 2 wt.-%
based on the total composition.
Inventors: |
Klee; Joachim E.;
(Radolfzell, DE) ; Facher; Andreas; (Konstanz,
DE) ; Weber; Christoph; (Konstanz, DE) ;
Mulhaupt; Rolf; (Freiburg, DE) ; Schmider;
Martin; (Freiburg, DE) |
Correspondence
Address: |
DENTSPLY INTERNATIONAL INC
570 WEST COLLEGE AVENUE
YORK
PA
17404
US
|
Assignee: |
Dentsply Research and Development
Corp.
Los Angeles
CA
|
Family ID: |
34925995 |
Appl. No.: |
11/387177 |
Filed: |
March 23, 2006 |
Current U.S.
Class: |
523/109 |
Current CPC
Class: |
A61K 6/20 20200101; A61K
6/20 20200101; C08L 33/00 20130101; C08L 33/00 20130101; C08L 63/00
20130101; A61K 6/20 20200101; C08L 63/00 20130101; A61K 6/20
20200101; A61K 6/20 20200101 |
Class at
Publication: |
523/109 |
International
Class: |
A61K 6/10 20060101
A61K006/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 30, 2004 |
EP |
04018112.5 |
Jul 29, 2005 |
WO |
2005/008268 |
Claims
1. One-component heat-curable sealant composition for the
protection of exposed dental surfaces, comprising (a) a
polymerisable monomer and/or oligomer which has at least two
polymerizable double bonds per molecule, and (b) an initiator
system comprising benzoylperoxide in an amount of at least 2 wt.-%
based on the total composition.
2. The one-component heat-curable sealant composition according to
claim 1 further comprising (c) a heat-curable step-growth
polymerization system.
3. The one-component heat-curable sealant composition according to
claim 1 further comprising (d) a filler or a precursor thereof.
4. The one-component heat-curable sealant composition according to
one of claims 1 to 3, further comprising (e) a solvent.
5. The one-component heat-curable sealant composition according to
any one of the preceding claims, wherein the polymerizable monomers
or oligomers are (meth)acrylate monomers or oligomers.
6. The one-component heat-curable sealant composition according to
any one of the preceding claims, which is polymerisable by locally
heating the composition at a temperature of between 120 and
250.degree. C., preferably between 160 to 220.degree. C.
7. The one-component heat-curable sealant composition according to
any one of the preceding claims, wherein the filler comprises fine
teflon particles.
8. The one-component heat-curable sealant composition according to
any one of the preceding claims, wherein the composition contains a
precursor for a filler which is an alkoxysilane compound undergoing
polycondensation reactions during heat curing of the composition,
thereby forming the filler.
9. The one-component heat-curable sealant composition according to
any one of the preceding claims, which is a pit and fissure sealant
or a cervical surface sealant.
10. The one-component heat-curable sealant composition according to
any one of the preceding claims, wherein the composition contains
the polymerisable monomer and/or oligomer in an amount of from 10
to 99 wt.-%.
11. The one-component heat-curable sealant composition according to
any one of the preceding claims, wherein the composition contains
benzoylperoxide in an amount of from 2.0 to 5.0 wt.-%.
12. The one-component heat-curable sealant composition according to
any one of claims 3 to 14, wherein the composition contains the
filler or precursor thereof in an amount of from 0 to 30 wt.-%.
13. The one-component heat-curable sealant composition according to
any one of claims 4 to 12, wherein the composition contains the
solvent in an amount of from 0 to 70 wt.-%.
14. The one-component heat-curable sealant composition according to
any one of the preceding claims, which has a viscosity of at most 5
Pas (23.degree. C.).
15. A process for the protection of exposed dental surfaces or heat
sensitive dental products, which comprises the following steps: (a)
applying the one-component heat-curable sealant composition
according to any one of the preceding claims to an exposed surface
of a tooth for providing a coating on the exposed surface of the
tooth, and (b) heating the coating obtained in step (a) to a
temperature of at least 100.degree. C. for curing the coating and
forming a protective sealant coating.
16. The process according to claim 15, wherein the heating is
performed by irradiation of laser light.
17. The process according to claim 15 or 16, wherein the protective
sealant coating is formed on pits or fissures of a tooth.
18. The process according to claim 15 or 16, wherein the protective
sealant coating is formed on a cervical surface of a tooth.
19. Kit-of-parts comprising a one-component heat-curable sealant
composition according to any one of claims 1 to 14 and a laser.
20. Use of a composition according to any one of claims 1 to 14 for
the protection of a tooth.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a one-component
heat-curable sealant composition typically having a viscosity of at
most 5 Pas (23.degree. C.) for the protection of hard tissue, in
particular exposed dental surfaces. The present invention also
relates to a process for the protection of hard tissue, in
particular exposed dental surfaces. The sealant composition is
capable of undergoing a rapid rate of cure by a laser without
heat-damaging neighboring tissue. The sealant composition of the
invention has improved biocompatibility, high hardness, low
long-term abrasion and high acid resistance.
TECHNICAL BACKGROUND
[0002] WO02/078646 discloses a dental composition containing
benzoyl peroxide and for use as a root canal sealant.
[0003] Protective dental treatment for avoiding mechanical,
bacterial or chemical trauma, in particular primary and secondary
caries, is of increasing importance in the dental field. Pit and
fissure sealants are known as compositions used in protective
treatments of occlusal surfaces. Sealant materials for protective
treatment of cervical surfaces exposed by gingival retraction
caused by long-standing periodontitis are also known. However, such
materials are characterized by high abrasion and require frequent
replacements.
[0004] Dental materials can be divided into chemically (thermally)
curable materials and materials polymerizing by exposure to light.
Thermal polymerization is usually severly limited for applications
on living tissue or other heat sensitive surfaces. Highly reactive
initiators and the presence of amine accelerators are usually
required whereby the shelf-life of a one-component composition is
deteriorated or multi-component systems are required.
[0005] Pit and fissure sealants are typically based on methacrylate
monomers. Self-curing compositions are typically two-component
systems including in a first component one or more methacrylate
monomers and at least one component of a free radical liberating
(redox) polymerization system for said monomer(s). The monomer
composition may include the peroxy type catalyst (oxidant) which is
later contacted with a second component including the reducing
agent (reductant) shortly prior to dental use. In case of a sealant
composition, the viscosity of the composition must be low enough to
allow thorough penetration of fissures and intricate interdental
spaces with no air bubbles prior to polymerisation. The handling of
a two-component system for providing a low-viscosity composition is
highly problematic.
[0006] Light-curing compositions contain methacrylate monomers and
an initiator system in a single pack. However, the storage
stability of such compositions depends on the absence of light and
the careful handling of the composition prior to
polymerisation.
[0007] A primary object of the invention is to provide
polymerizable dental sealant compositions wherein the foregoing and
related disadvantages are eliminated or at least mitigated to a
substantial extent.
[0008] Another object of the invention is to provide polymerizable
dental sealant compositions capable of undergoing a rapid rate of
cure to produce a polymerizate having strong adhesion to dentin or
enamel and having excellent protective properties as a pit or
fissure sealant or a sealant for exposed cervical surfaces.
[0009] Yet another object of the invention is to provide such a
sealant composition having good structural stability within the
environment of the human oral cavity. Still another object of the
invention is to provide such a composition wherein any requirements
for using higher catalyst concentrations to achieve effective rate
and degree of cure are obviated.
[0010] Yet a still further object of the invention is to provide a
process of utilizing such compositions to prepare a high quality
polymerizate.
DISCLOSURE OF THE INVENTION
[0011] The present invention provides a one-component heat-curable
sealant composition having a viscosity of at most 5 Pas (23.degree.
C.) for the protection of exposed dental surfaces, comprising
[0012] (a) a polymerisable monomer and/or oligomer, and [0013] (b)
an initiator system comprising benzoylperoxide.
[0014] The polymerizable monomers or oligomers in the one-component
heat-curable sealant composition according to the invention are
capable of free-radical polymerization and are preferably
(meth)acrylate monomers or oligomers. The (meth)acrylate monomer or
oligomer or is selected from materials having at least two, and
preferably two to four polymerizable double bonds per molecule so
that the cured sealant composition be crosslinked and thus better
suited for use in the oral cavity. The most preferred monomers are
those having two polymerizable double bonds per molecule. Monomers
with a single polymerisable double-bond may be used in order to
adjust the viscosity of the composition. (Meth)acrylate monomer
materials useful herein are well known in the art. The preferred
materials generally include monomers having a central portion
containing an organic moiety and at least two (meth)acrylic end
groups. Preferable monomers are ethyleneglycol dimethacrylate,
diethyleneglycol dimethacrylate, dodecanediol dimethacrylate,
trimethylolpropane tri(meth) acrylate, hydroxyethyl methacrylate,
triethyleneglycol dimethacrylate, trimethylolpropane triacrylate,
glycerine dimethacrylate, and methacrylic acid. Desirable
characteristics for such monomers and/or oligomers include good
film forming properties, low viscosity, low polymerization
shrinkage, low water sorption and the ability to cure rapidly and
completely in the mouth when irradiated with a laser. It is also
desirable that the monomers be low in volatility and non-irritating
to the tooth pulp. An example of preferred oligomers is a
condensation product of methacryloyloxypropyl oxycarbonylamido
propyltriethoxy silane. A mixture of two or more appropriate
methacrylate monomers is within the scope of this invention. In
fact, depending on the choice of monomers, mixture are often highly
desirable to optimize the characteristics of the resulting dental
composition.
[0015] Thus, it is preferred that the monomer or oligomer or
monomer or oligomer blend have a viscosity of at most 5 Pas at
23.degree. C.
[0016] In a preferred embodiment, the cured composition is not
biodegradable based on the presence of biodegradable segments
selected from the group of poly(lactide), poly(glycolide) and
poly(caprolactone). If the cured composition is biodegradable based
on the presence of biodegradable segments, the acid resistance of
the cured composition will also be insufficient.
[0017] The initiator system comprises benzoylperoxide for
initiating polymerization of the monomers and/or oligomers.
Preferably, component (b) comprises benzoylperoxide as the only
initiator. The one-component heat-curable sealant composition
according to the invention preferaby contains benzoylperoxid in an
amount of from 0.01 to 5.0 wt.-%, preferably in an amount of from
0.1 to 2 wt-%. In a specific embodiment, the one-component
heat-curable sealant composition according to the invention
preferaby contains benzoylperoxid in an amount of at least 2.0
wt.-% more preferably from 2.0 to 5.0 wt.-%, still more preferably
in an amount of from 2.5 to 5 wt-%. If desired, peroxide
stabilizers such as ascorbic acid, maleic acid and the like may be
included in small amounts.
[0018] In a further embodiment of the present invention, the
one-component heat-curable sealant composition may further comprise
a heat-curable step-growth polymerization system. The step-growth
polymerization system utilized in the present invention may be an
addition polymerization system (without separation or delivery of a
leaving molecule) leading upon addition polymerization reaction to
a polyadduct and/or a condensation polymerization system (with
separation or delivery of a leaving molecule) leading upon
condensation polymerization reaction to a polycondensate. Further,
the step-growth polymerization system may comprise one, two or more
different type(s) of monomer(s) and/or oligomer(s). In a
step-growth polymerization system, monomers form in initial
reaction steps intermediates or oligomers having a rather low
molecular mass. These intermediates or oligomers form in the
further course of reaction macromolecules. Thus, a step-growth
polymerization system differs from a chain-growth polymerization
system such as a free radical polymerization system in which
monomers react only with a growing polymer chain. The step-growth
polymerization system has the advantage that a coating having
improved mechanical strength and durability may be provided. An
advantage of another embodiment of the present invention of a
step-growth polymerization system is that linear polymer chains may
be provided, and hence a thermoplastic polymer may be provided. In
a further embodiment of the present invention the dental sealant
composition of the present invention comprises such thermoplastic
prepolymers which may be used for forming a coating on an exposed
dental surface, and thermal condensation or addition to the polymer
occurs upon heating of the prepolymer on the exposed dental
surface.
[0019] In another embodiment of the present invention, the dental
sealant composition of the present invention comprises a
step-growth polymerization system consisting essentially of
monomer(s). Thus, the viscosity is advantageously low and allows
easy application of the dental sealant application and provides a
highly reliable sealing property of the composition. According to a
preferred embodiment of the present invention the dental sealant
composition provides the above described thermoplastic prepolymers
upon application of the composition to an exposed dental
surface.
[0020] Examples of the step-growth polymerization systems of the
present invention comprise epoxide-amine, epoxide-thiol,
epoxide-carboxylic acid, epoxide-carboxylic acid anhydride,
epoxide-phenol, isocyanate-amine, isocyanate-alcohol,
isocyanate-thiol, isothiocyanate-amine, isothiocyanate-alcohol,
isothiocyanate-thiol, carboxylic acid derivative-amine, carboxylic
acid derivative-alcohol, carboxylic acid derivative-thiol,
acrylate-amine, acrylate-thiol, acrylamide-amine, acrylamide-thiol,
maleinimide-amine, maleinimide-thiol, acrylate-malonic acid
derivative, acrylamide-malonic acid derivative, blocked
isocyanate-amine, blocked isocyanate-alcohol, SiH-En addition, and
siloxane systems.
[0021] An epoxide-amine system may comprise a monomer/oligomer
having at least one epoxide and one amine functionality, or it may
comprise at least two different monomers/oligomers of which one
monomer/oligomer comprises at least two epoxide moieties and the
other monomer/oligomer comprises at least two amine groups. An
epoxide-thiol system may comprise a monomer/oligomer having at
least one epoxide and one thiol functionality, or it may comprise
at least two different monomers/oligomers of which one
monomer/oligomer comprises at least two epoxide moieties and the
other monomer/oligomer comprises at least two thiol groups. An
epoxide-carboxylic acid system may comprise a monomer/oligomer
having at least one epoxide and one carboxylic acid functionality,
or it may comprise at least two different monomers/oligomers of
which one monomer/oligomer comprises at least two epoxide moieties
and the other monomer/oligomer comprises at least two carboxylic
acid groups. An epoxide-carboxylic acid anhydride system may
comprise a monomer/oligomer having at least one epoxide and one
carboxylic acid anhydride functionality, or it may comprise at
least two different monomers/oligomers of which one
monomer/oligomer comprises at least two epoxide moieties and the
other monomer/oligomer comprises at least two carboxylic acid
anhydride moieties. An epoxide-phenol system may comprise a
monomer/oligomer having at least one epoxide and one phenol moiety,
or it may comprise at least two different monomers/oligomers of
which one monomer/oligomer comprises at least two epoxide moieties
and the other monomer/oligomer comprises at least two phenol
moieties.
[0022] An isocyanate-amine system may comprise at least two
different monomers/oligomers of which one monomer/oligomer
comprises at least two isocyanate moieties and the other
monomer/oligomer .comprises at least two amine groups. An
isocyanate-alcohol system may comprise a monomer/oligomer having at
least one isocyanate and one alcohol functionality, or it may
comprise at least two different monomers/oligomers of which one
monomer/oligomer comprises at least two isocyanate moieties and the
other monomer/oligomer comprises at least two alcohol groups. An
isocyanate-thiol system may comprise a monomer/oligomer having at
least one isocyanate and one thiol functionality, or it may
comprise at least two different monomers/oligomers of which one
monomer/oligomer comprises at least two isocyanate moieties and the
other monomer/oligomer comprises at least two thiol groups.
[0023] An isothiocyanate-amine system may comprise at least two
different monomers/oligomers of which one monomer/oligomer
comprises at least two isothiocyanate moieties and the other
monomer/oligomer comprises at least two amine groups. An
isothiocyanate-alcohol system may comprise a monomer/oligomer
having at least one isothiocyanate and one alcohol functionality;
or it may comprise at least two different monomers/oligomers of
which one monomer/oligomer comprises at least two isothiocyanate
moieties and the other monomer/oligomer comprises at least two
alcohol groups. An isothiocyanate-thiol system may comprise a
monomer/oligomer having at least one isothiocyanate and one thiol
functionality, or it may comprise at least two different
monomers/oligomers of which one monomer/oligomer comprises at least
two isothiocyanate moieties and the other monomer/oligomer
comprises at least two thiol groups.
[0024] A carboxylic acid derivative-amine system may comprise a
monomer/oligomer having at least one carboxylic acid derivative and
one amine functionality, or it may comprise at least two different
monomers/oligomers of which one monomer/oligomer comprises at least
two carboxylic acid derivative moieties and the other
monomer/oligomer comprises at least two amine groups. A carboxylic
acid derivative-alcohol system may comprise a monomer/oligomer
having at least one carboxylic acid derivative and one alcohol
functionality, or it may comprise at least two different
monomers/oligomers of which one monomer/oligomer comprises at least
two carboxylic acid derivative moieties and the other
monomer/oligomer comprises at least two alcohol groups. A
carboxylic acid derivative-thiol system may comprise a
monomer/oligomer having at least one carboxylic acid derivative and
one thiol functionality, or it may comprise at least two different
monomers/oligomers of which one monomer/oligomer comprises at least
two carboxylic acid derivative moieties and the other
monomer/oligomer comprises at least two thiol groups. The
carboxylic acid derivative may be an carboxylic acid, a carboxylic
acid anhydride, a carboxylic acid ester or a carboxylic acid halide
or nitrile. The halide in the carboxylic acid halide is preferably
a bromide or chloride. In case of a carboxylic acid halide, the
dental sealant composition of the present invention comprises
preferably also a hydrogen halide scavenger, e.g. a tertiary amine.
In case of a nitrile, it is preferred that the nitrile is not
harmful.
[0025] A preferred example of a carboxylic acid derivative-amine
system comprises an aromatic tetracarboxylic acid dianhydride, e.g.
pyromellitic dianhydride or pyrazine tetracarboxylic dianhydride,
as a carboxylic acid derivative and an aliphatic or aromatic
diamine, e.g. 4,4'-oxydianiline or diaminothiadiazole, as an amine.
Such a system leads upon a condensation polymerization to a
pblyimide.
[0026] A further preferred example of a carboxylic acid
derivative-amine system comprises an aromatic dicarboxylic acid
halide, e.g. terephthalic acid dichloride, as a carboxylic acid
derivative and an aromatic diamine, e.g.
4,4'-diamino-biphenyl-3,3'-diol (or 3,3'-dihydroxybenzidine), as an
amine. Such a system leads upon a condensation polymerization to a
polybenzoxazole.
[0027] An acrylate-amine system may comprise at least two different
monomers/oligomers of which one monomer/oligomer comprises at least
two acrylate moieties and the other monomer/oligomer comprises at
least two amine groups. An acrylate-thiol system may comprise a
monomer/oligomer having at least one acrylate and one thiol
functionality, or it may comprise at least two different
monomers/oligomers of which one monomer/oligomer comprises at least
two acrylate moieties and the other monomer/oligomer comprises at
least two thiol groups.
[0028] An acrylamide-amine system may comprise a monomer/oligomer
having at least one acrylamide and one amine functionality, or it
may comprise at least two different monomers/oligomers of which one
monomer/oligomer comprises at least two acrylamide moieties and the
other monomer/oligomer comprises at least two amine groups. An
acrylamide-thiol system may comprise a monomer/oligomer having at
least one acrylamide and one thiol functionality, or it may
comprise at least two different monomers/oligomers of which one
monomer/oligomer comprises at least two acrylamide moieties and the
other monomer/oligomer comprises at least two thiol groups.
[0029] A maleinimide-amine system may comprise at least two
different monomers/oligomers of which one monomer/oligomer
comprises at least two maleinimide moieties and the other
monomer/oligomer comprises at least two amine groups. A
maleinimide-thiol system may comprise a monomer/oligomer having at
least one maleinimide and one thiol functionality, or it may
comprise at least two different monomers/oligomers of which one
monomer/oligomer comprises at least two maleinimide moieties and
the other monomer/oligomer comprises at least two thiol groups.
[0030] An acrylate-malonic acid derivative system may comprise a
monomer/oligomer having at least one acrylate and one malonic acid
derivative functionality, or it may comprise at least two different
monomers/oligomers of which one monomer/oligomer comprises at least
two acrylate moieties and the other monomer/oligomer comprises at
least two malonic acid derivative groups. An acrylamide-malonic
acid derivative system may comprise a monomer/oligomer having at
least one acrylamide and one malonic acid derivative functionality,
or it may comprise at least two different monomers/oligomers of
which one monomer/oligomer comprises at least two acrylamide
moieties and the other monomer/oligomer comprises at least two
malonic acid derivative groups.
[0031] A blocked isocyanate-amine system may comprise a
monomer/oligomer having at least one blocked isocyanate and one
amine functionality, or it may comprise at least two different
monomers/oligomers of which one monomer/oligomer comprises at least
two blocked isocyanate moieties and the other monomer/oligomer
comprises at least two amine groups. A blocked isocyanate-alcohol
system may comprise a monomer/oligomer having at least one blocked
isocyanate and one alcohol functionality, or it may comprise at
least two different monomers/oligomers of which one
monomer/oligomer comprises at least two blocked isocyanate moieties
and the other monomer/oligomer comprises at least two alcohol
groups.
[0032] A SiH-En addition system is preferably a silane-acrylate,
silane-allylether, silane-vinylether, silane-acrylamide, or
silane-maleinimide system. A silane-acrylate system may comprise a
monomer/oligomer having at least one silane and one acrylate
functionality, or it may comprise at least two different
monomers/oligomers of which one monomer/oligomer comprises at least
two silane moieties and the other monomer/oligomer comprises at
least two acrylate groups. A silane-allylether system may comprise
a monomer/oligomer having at least one silane and one allylether
functionality, or it may comprise at least two different
monomers/oligomers of which one monomer/oligomer may comprise at
least two silane moieties and the other monomer/oligomer may
comprise at least two allylether groups. A silane-vinylether system
may comprise a monomer/oligomer having at least one silane and one
vinylether functionality, or it may comprise at least two different
monomers/oligomers of which one monomer/oligomer may comprise at
least two silane moieties and the other monomer/oligomer may
comprise at least two vinylether groups. A silane-acrylamide system
may comprise a monomer/oligomer having at least one silane and one
acrylamide functionality, or it may comprise at least two different
monomers/oligomers of which one monomer/oligomer may comprise at
least two silane moieties and the other monomer/oligomer may
comprise at least two acrylamide groups. A silane-maleinimide
system may comprise a monomer/oligomer having at least one silane
and one maleinimide functionality, or it may comprise at least two
different monomers/oligomers of which one monomer/oligomer may
comprise at least two silane moieties and the other
monomer/oligomer may comprise at least two maleinimide groups.
[0033] A siloxane system may comprise at least one siloxane having
at least two alkoxy groups, preferably selected from methoxy,
ethoxy, and propxy groups, bonded to one or more than one Si-atom;
most preferred are methoxy groups.
[0034] According to a preferred embodiment of the present
invention, the dental sealant composition may comprise a
step-growth polymerization system which is a condensation
polymerization system. Preferably, the condensation polymerization
system is selected from the group consisting of carboxylic acid
derivative-amine, carboxylic acid derivative-alcohol, carboxylic
acid derivative-thiol, blocked isocyanate-amine, and blocked
isocyanate-alcohol systems as described above.
[0035] In a particular preferred embodiment of the present
invention, the dental sealant composition may comprise a blocked
isocyanate system comprising a monomer and/or oligomer having a
terminal moiety of the following formula: ##STR1## wherein n is an
integer of from 3 to 15, preferably 5 to 7. The step-growth
polymerization systems including a blocked isocyante have the
advantage that they are suited as a one-component system. When a
blocked isocyanate is reacted with an amine a urea linkage is
formed. In other words a blocked isocyanate-amine system leads to a
polyurea. When a blocked isocyanate is reacted with an alcohol a
urethane linkage is formed. In other words a blocked
isocyanate-alcohol system leads to a polyurethane. Most preferred
is a blocked isocyanate system wherein n is 5. In such a system
caprolactam is separated or delivered upon condensation
polymerization.
[0036] The dental sealant composition of the present invention
may-comprise preferably at least one blocked isocyanate selected
from the group of compounds having the following formulae I to IV:
##STR2##
[0037] Desirable characteristics of the monomer(s) and/or
oligomer(s) of the step-growth polymerization system of the present
invention include good film forming property, low viscosity, low
polymerization shrinkage, low water sorption and the ability to
cure rapidly and completely in the mouth when irradiated with a
laser. It is also desirable that the monomers/oligomers are low in
volatility and non-irritating to the tooth pulp. Thus, the dental
sealant composition according to present invention contains the
heat-curable step-growth polymerization system preferably in an
amount of from 10 to 99 wt.-%.
[0038] In case that a particularly low viscosity is desired, it is
preferred that the step-growth polymerization system of the present
invention contains mostly monomer(s) and only a small amount of
oligomer(s). In case that polymerization shrinkage should be
optimized the amount of oligomer(s) may be increased.
[0039] The sealant composition according to the invention may
advantageously be polymerized by locally heating the composition at
a temperature of between 100 and 250.degree. C., preferably between
160 to 220.degree. C. without damage of hard tissue whereby a
dental/medical coating is obtained. Preferably such local heating
is conducted by exposure to laser light, microwave energy, or
ultrasound.
[0040] The one-component heat-curable sealant composition may
further comprise (d) a filler or a precursor thereof. The filler
may be an inorganic filler or an organic filler or a mixture
thereof. The one-component heat-curable sealant composition may
contain a precursor for a filler, namely preferably one or more
alkoxysilane compounds undergoing polycondensation reactions during
heat curing of the composition, thereby forming the filler. The
inorganic particulate filler employed in the compositions of this
invention include fused silica, quartz, crystalline silica,
amorphous silica, soda glass beads, glass rods, ceramic oxides,
particulate silicate glass, radiopaque glasses (barium and
strontium glasses), and synthetic minerals. It is also possible to
employ finely divided materials and powdered hydroxyl-apatite,
although materials that react with silane coupling agents are
preferred. Also available as a filler are colloidal or submicron
silicas coated with a polymer. Small amounts of pigments to allow
matching of the composition to various shades of teeth can be
included. The filler particles would be generally smaller than
about 5 microns in diameter and preferably smaller than 3 .mu.m,
preferably in a range of from 3 to 500 nm. The filler in the dental
sealant composition according to the invention may preferably
comprise fine polytetrafluoroethylene particles. The dental sealant
composition according to the invention may contain the filler or
precursor thereof in an amount of from 0 to 30 wt.-%.
[0041] The dental sealant composition according to the invention
has a viscosity of at most 5 Pas at 23.degree. C. Such a
composition has the advantage that it allows thorough penetration
of fissures and intricate interdental spaces with no air bubbles
prior to polymerization. Hence, in a particular preferred
embodiment of the present invention, the dental sealant composition
is a pit and fissure sealant or a cervical surface sealant.
[0042] In a further preferred embodiment of the present invention,
the filler comprises a nanofiller, particularly modified silica
according to the following formula: ##STR3##
[0043] The one component heat-curable sealant composition may
further comprise a solvent, preferably in an amount of from 0 to 70
wt.-%. Suitable solvents are selected from organic solvents such as
acetone, ethanol, tert-butyl alcohol, ethylmethylketone, and/or
chloroform.
[0044] The dental sealant composition of the present invention is a
one-component system. A "one-component system" means in this
specification that the chain and optionally growth-step
polymerization systems of the present invention are rather
shelf-stable at room temperature, such that a polymerization
reaction of the monomer(s) and/or oligomer(s) of such a
one-component system does essentially not occur at room
temperature, but requires elevated temperatures. Therefore, the
one-component system according to the present invention may
comprise only one type of monomer/oligomer as a reactive ingredient
having at least two functional groups of which one functional group
is reactive with the other functional group. Alternatively, a
one-component system according to the present invention may
comprise e.g. at least two monomers/oligomers as reactive
ingredients of which one monomer/oligomer comprises at least two
functional groups that are reactive with at least two functional
groups of the other monomer. Preferably, a one-component system of
the present invention is shelf-stable at room temperature for an
extended period of time, preferably for at least 3 months, more
preferably at least 6 months, most preferably for a period of at
least 12 months, without substantial polymerization reaction of the
ingredient(s) of the one-component system. Such a one-component
system has the advantage that mixing prior to use is not necessary.
Thus, accuracy and reliably curing is improved and mixing errors
are avoided. Moreover, a time consuming mixing step and equipment
for mixing during a chair-side application is eliminated.
Preferably, such a one-component system comprises a heat-curable
step-growth polymerization system that is selected from the group
consisting of epoxide-arylamine, epoxide-cycloalkylamine,
isocyanate-alcohol, blocked isocyanate-amine, and blocked
isocyanate-alcohol systems.
[0045] The present invention further provides a process for the
protection of exposed dental surfaces or heat sensitive dental
products, which comprises the following steps: [0046] (a) applying
the one-component heat-curable sealant composition having a
viscosity of at most 5 Pas (23.degree. C.) of the invention to an
exposed surface of a tooth for providing a coating on the exposed
surface of the tooth, and [0047] (b) heating the coating obtained
in step (a) to a temperature of at least 100.degree. C. for curing
the coating and forming a protective sealant coating.
[0048] Heating may be performed by exposure to laser light,
microwave energy, infrared light or ultrasound, whereby exposure to
laser light is preferred. The process of the present invention has
the advantage that the temperature inside a tooth to which the
dental sealant composition of the present invention is applied is
increased only by 5 Kelvin units (5.degree. C.), although the
outside of the tooth may heated up to 250.degree. C., preferably up
to 180.degree. C., upon heating. Thus, no uncomfortable heat is
recognized by a patient, e.g. during a chair side application,
since e.g. the temperature of the pulp of a tooth is increased only
by up to 5 Kelvin (5.degree. C.). Furthermore, no danger of
destruction arises in case of an application of the dental sealant
composition of the present invention to an artificial tooth having
heat sensitive portions inside or in case of application of the
dental sealant composition of the present invention to another heat
sensitive dental product. According to a preferred embodiment of
the invention heating is conducted by applying a laser. Thus, the
intensity of irradiation and the amount of applied energy may be
easily adjusted, preferably by adjusting the pulses of the
laser.
[0049] In preferred embodiments of the present invention, the
protective sealant coating is formed on pits or fissures of a tooth
or on a cervical surface of a tooth by the process according to the
invention. Therefore, the one-component heat-curable sealant
composition according to the invention preferably is a pit and
fissure sealant or a cervical surface sealant.
[0050] The present invention further relates to a kit-of-parts
comprising a dental sealant composition according to the invention
and a laser. The present invention further relates to the use of a
dental sealant composition according to the invention for the
protection of a tooth.
[0051] The following examples and comparative examples are
illustrative of embodiments of the invention. All parts and
percentages are by weight. Dynamic viscosities may be measured by
using a Bohlin CS50 rheometer at 23.degree. C.
EXAMPLE 1
[0052] 5.820 g resin matrix composed of dodecanediol dimethacrylate
and a condensation product of methacryloyloxypropyl
oxycarbonylamido propyltriethoxy silane, 3.880 tetraethoxy silane,
0.300 g dibenzoyl peroxide were homogeneously mixed for obtaining a
mixture.
[0053] In order to dry a dentin surface, laser light was applied in
a pulse sequence of 10.times.4 pulses (F.sub.up=0.5 J/cm.sup.2;
f.sub.up=100 Hz; f=1 Hz). Subsequently, approximately 10 .mu.l of
the mixture prepared above were applied homogeneously on dentin
that was previously etched for 45 s by using of 37% age
H.sub.3PO.sub.4. Then this layer was irradiated by the following
pulses: 5.times., 10.times.4 pulses (F.sub.up=0.9 J/cm.sup.2;
f.sub.up=100 Hz; f=1 Hz) and 1.times. and 5.times.4 pulses
(F.sub.up=1.2 J/cm.sup.2; f.sub.up=100 Hz; f=1 Hz).
[0054] The formed layer had a thickness of approximately 7 .mu.m.
It withstand a wipe test and scratch test. Furthermore, the
material was thermocycled for 2400 cycles at 4 and 65.degree. C.
After that treatment the material layer withstands a tooth-brush
abrasion test.
COMPARATIVE EXAMPLE 1
[0055] In order to dry dentin surface the Laser was applied in a
pulse sequence of 10.times.4 pulses (F.sub.up=0.5 J/cm.sup.2;
f.sub.up=100 Hz; f=1 Hz) Thereafter, Seal & Protect (Dentsply
De Trey) was applied homogeneously on dentin that prior was etch
for 45 s by using of 37% age H.sub.3PO.sub.4. Then this layer was
irradiated by the following pulses: 5.times., 10.times.4 pulses
(F.sub.up=0.9 J/cm.sup.2; f.sub.up=100 Hz; f=1 Hz) and 1.times. and
5.times.4 pulses (F.sub.up=1.2 J/cm.sup.2; f.sub.up=100 Hz; f=1
Hz).
[0056] The formed layer has a thickness of approximately 10 .mu.m.
It do not withstand a wipe and a scratch test. Furthermore, the
material was thermocycled for 2400 cycles at 4 and 65.degree. C.
After that treatment the material layer withstands not a
tooth-brush abrasion test and was flaking form the tooth
surface.
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