WO2005094757A1

WO2005094757A1 - Dental sealant composition for the protection of hard tissue

Info

Publication number: WO2005094757A1
Application number: PCT/EP2005/002410
Authority: WO
Inventors: Joachim E. Klee; Andreas Facher; Christoph Weber; Rolf Mülhaupt; Martin Schmider
Original assignee: Dentsply De Trey Gmbh
Priority date: 2004-03-11
Filing date: 2005-03-07
Publication date: 2005-10-13

Abstract

A dental sealant composition for protection of an exposed dental surface, comprising a heatcurable step-growth polymerization system.

Description

Dental sealant composition for the protection of hard tissue

Field of the Invention

The present invention relates to a dental sealant composition for 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 an exposed dental surface of a tooth or heat sensitive dental product. The sealant composition is characterized by undergoing a rapid rate of cure by a laser without heat-damaging neighboring tissue, improved biological compatibility, high hardness, low long-term abrasion and high acid resistance.

Technical background

WO02/102909 discloses reactive oligomers for low shrinkage compositions useful in dental, molding applications or in any applications where accurate molding and/or registration is required. EP-A 0 673 637 discloses a dental filling composition containing at least 40 % by weight of a filler imparting a radioopacity of at least 3 mm/mm Al, and having a viscosity of less than 20.000 cps. The compositions disclosed by EP-A 0 673 637 and WO02/102909 are unsuitable as a dental sealant composition for protection of hard tissue, in particular a pit and fissure sealant or a cervical surface sealant.

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.

Dental materials can be divided into chemically (thermally) curable materials and materials polymerizing by exposure to light. Thermal polymerization is usually severely limited regarding applications on living tissue or other heat sensitive surfaces.

Conventional pit and fissure sealants are typically based on chain-growth polymerization systems such as radical polymerization systems comprising e.g. ethylenically unsaturated monomers such as (meth)acrylate monomers. Self-curing chain-growth polymerization compositions of such type are typically two-component systems including in a first component with one or more than one methacrylate monomer(s) and at least one component of a free radical liberating (redox) polymerization system for said monomer(s). This first monomer(s) component may further include a peroxide type catalyst (oxidant) which is later contacted with the 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. The operator has to watch the setting and working time of the sealant after mixing the two components, since after a certain period of time the system is (self-)cured and cannot be processed anymore. Further, there are light-curing chain-growth polymerization compositions containing generally (meth)acrylate 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. Moreover, a light-curing system has the disadvantage with regard to a dental sealant that light may not reach the sealant if applied into a fissure or intricate interdental space. As a result, incomplete curing occurs and the strength with regard to a wipe and scratch test tends to be low. Thus, dual-cure systems comprising a redox- and a light-curing catalyst have been proposed. However, these systems still have the problem that the redox-catalyst has to be divided into a two-component system, in order to prevent premature curing. Accordingly, these systems still suffer from the mixing and handling problems described above.

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.

Another object of the invention is to provide a polymerizable dental sealant composition capable of undergoing a rapid rate of cure to produce a polymer having strong adhesion to dentin or enamel and having excellent protective properties as a pit or fissure sealant or a sealant for an exposed cervical surface or an exposed surface of another dental product.

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 a catalyst is superfluous.

Yet a still further object of the invention is to provide a process of utilizing such compositions to prepare a high quality polymer.

Disclosure of the invention

The present invention provides a dental sealant composition for protection of an exposed dental surface, comprising a heat-curable step-growth polymerization system.

In particular, the present invention provides a dental sealant composition for protection of an exposed dental surface which is useful as a pit and fissure sealant or a cervical surface sealant, comprising

(a) a heat-curable step-growth polymerization system;

(b) optionally a solvent; and

(c) optionally up to 30 % by weight of a filler or a precursor thereof, whereby the composition has a viscosity of at most 5 Pa-s (23°C). In a specific embodiment, the dental sealant composition consists essentially of components (a), (b), and (c) and optionally colorants, fluorescent dyes or UV-stabilizers.

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 than two 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 prepolymeron the exposed dental surface.

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.

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.

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.

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.

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. 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.

A preferred example of a carboxylic acid derivative-amine system comprises an aromatic tetra- carboxylic 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 polyimide.

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.

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.

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.

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.

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.

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.

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.

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. Preferably, the dental sealant composition of the present invention is a one-component system. A "one-component system" means in this specification that the growth-step polymerization system of the present invention is 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 only at 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.

On the other hand, a "two-component system" means in the present specification, that the step- growth polymerization system is not shelf stable at room temperature for an extended period of time, such that the reactive ingredients of the polymerization system have to be separated during storage in individually packaged containers.

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. 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:

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.

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:

III

IV

The sealant composition according to the invention may advantageously be polymerized by locally heating the composition at a temperature of between 100 and 250 °C, preferably between 160 to 220 °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.

An amine in the sealant composition according to the invention is preferably a di- or polyamine and may be a substituted or unsubstituted aliphatic, alkyl, aryl, or cycloalkyl primary amine, secondary amine, primary-secondary amine, primary-tertiary amine or secondary-tertiary amine. A primary-secondary amine comprises a primary amine functionality and a secondary amine functionality, such as diethylenetriamine. A primary-tertiary amine comprises a primary amine functionality and a tertiary amine functionality, such as N,N-diethylethylendiamine. A secondary-tertiary amine amine comprises a secondary amine functionality and a tertiary amine functionality.

The dental sealant composition of the invention may further comprise a filler or a precursor thereof. The filler may be an inorganic filler or an organic filler or a mixture thereof. The dental 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 orsubmicron 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 μm, 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.

In a further preferred embodiment of the present invention, the filler comprises a nanofiller, particularly modified silica according to the following formula:

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.

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.-%. Further, the dental sealant composition according to the invention may contain the filler or precursor thereof in an amount of from 0 to 30 wt.-%, more preferably in an amount of from 0 to 15 wt.-%. In a specific embodiment, the dental sealant composition of the invention does not contain any filler. In a preferred embodiment of the present invention, the dental sealant composition according to the invention has a viscosity of at most 5 Pa-s at 23°C. In a preferred embodiment, the dental sealant composition according to the invention has a viscosity of at most 4 Pa-s at 23°C, more preferably at most 3Pa-s at 23°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.

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.

The present invention further provides a process for the protection of an exposed dental surface of a tooth or heat sensitive dental product, whereby such method may comprise the following steps:

(a) applying the dental sealant composition according to one of the above described embodiments, particularly according to one of claims 1 to 15, to said exposed dental surface for providing a coating on said exposed dental surface, and

(b) heating the coating obtained in step (a) to a temperature of at least 100 °C for curing the coating and forming a protective sealant coating.

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°C), although the outside of the tooth may heated up to 250°C, preferably up to 180°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°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.

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.

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.

The following examples and comparative examples are illustrative of embodiments of the invention. All parts and percentages are by weight.

Example 1

5.000 g (10.13 mmol) of compound II (prepared by reaction of bis(hexamethylene) triamine and carbonyl bis caprolactam (CBC)), 0.984 g (5.06 mmol) 3,(4),8,(9)-Bis(aminomethyl)-tricyclo- 5.2.1.0 ^2,e -decane were dissolved in CHCI₃.

In order to dry dentin surface the Laser was applied in a pulse sequence of 10 x 4 pulses (F up = 0.5 J/cm²; f_up= 100 Hz; f= 1 Hz) Thereafter, approximately two times 10 μl of a mixture prepared above were applied homogeneously on dentin that prior was etched for 45 s by using of 37%age H₃PO₄. Then this layer was irradiated by the following pulses: 5 x, 10 x 4 pulses (F_up = 0.9 J/cm²; f_up= 100 Hz; f=1 Hz) and 1 x and 5 x 4 pulses (F_up = 1.2 J/cm²; f_up=100 Hz; f= 1 Hz). The formed layer had a thickness of approximately 12 μm. It withstood a wipe test and scratch test. Comparative Example 1

In order to dry dentin surface the Laser was applied in a pulse sequence of 10 x 4 pulses (F_up = 0.5 J/cm²; f_up= 100 Hz; f= 1Hz) Thereafter, Seal & Protect (Dentsply De Trey) was applied homogeneously on dentin that prior was etched for 45 s by using of 37%age H₃PO₄. Then this layer was irradiated by the following pulses: 5 x, 10 x 4 pulses (F_up = 0.9 J/cm²; f_up= 100 Hz; f=1 Hz) and 1 x and 5 x 4 pulses (F_up = 1.2 J/cm²; f_up=100 Hz; f= 1 Hz). The formed layer had a thickness of approximately 10 μm. It did not withstand a wipe and a scratch test.

Claims

1. A dental sealant composition for protection of an exposed dental surface which is useful as a pit and fissure sealant or a cervical surface sealant, comprising (a) a heat-curable step-growth polymerization system; (b) optionally a solvent; and (c) optionally up to 30 % by weight of a filler or a precursor thereof, whereby the composition has a viscosity of at most 5 Pa-s (23°C).

2. The dental sealant composition according to claim 1 , wherein said heat-curable step- growth polymerization system is selected from the group consisting of 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.

3. The dental sealant composition according to claim 1 or 2, which is a one-component system.

4. The dental sealant composition according to one of the preceding claims, wherein said heat-curable step-growth polymerization system is selected from the group consisting of epoxide-arylamine, epoxide-cycloalkylamine, isocyanate-alcohol, blocked isocyanate-amine, and blocked isocyanate-alcohol systems.

5. The dental sealant composition according to one of the preceding claims wherein said step-growth polymerization system is a condensation polymerization system.

6. The dental sealant composition according to claim 5, wherein said condensation polymerization system which 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.

The dental sealant composition according to one of the preceding claims, wherein said blocked isocyanate system may comprise a monomer and/or oligomer having a terminal moiety of the following formula:

wherein n is an integer of from 3 to 15, preferably 5 to 7.

8. The dental sealant composition according to one of the preceding claims, which may comprise at least one blocked isocyanate selected from the group of compounds having the following formulae I to IV:

III

IV

9. The dental sealant composition according to one of the preceding claims, which is polymerizable by locally heating the composition at a temperature of between 120 and 250 °C, preferably between 160 to 220 °C.

10. The dental sealant composition according to one of the preceding claims, wherein said step-growth polymerization system may comprise a di- or polyamine which is a substituted or unsubstituted aliphatic, alkyl, aryl, orcycloalkyl primary amine, secondary amine, primary-secondary amine, primary-tertiary amine or secondary-tertiary amine.

11. The dental sealant composition according to one of the preceding claims, which may comprise a filler or a precursor for a filler, said precursor being an alkoxysilane compound undergoing polycondensation reactions during heat curing of the composition, thereby forming the filler.

12. The dental sealant composition according to one of the preceding claims, wherein said filler may comprise fine polytetrafluoroethylene particles.

13. The dental sealant composition according to one of the preceding claims which may comprise a solvent, preferably in an amount of from 0 to 70 wt.-%.

14. The dental sealant composition according to one of the preceding claims, wherein the composition contains the heat-curable step-growth polymerization system in an amount of from 10 to 99 wt.-%.

15. The dental sealant composition according to one of the preceding claims which is a pit and fissure sealant or a cervical surface sealant.

16. A process for the protection of an exposed dental surface of a tooth or heat sensitive dental product, which may comprise the following steps: (a) applying the dental sealant composition according to one of claims 1 to 15 to said exposed dental surface for providing a coating on said exposed dental surface, and (b) heating the coating obtained in step (a) to a temperature of at least 100 °C for curing the coating and forming a protective sealant coati ng.

17. The process according to claim 16, wherein said heating is performed by exposure to laser light.

18. The process according to claim 16 or 17, wherein the protective sealant coating is formed on pits or fissures of a tooth.

19. The process according to claim 16 or 17, wherein the protective sealant coating is formed on a cervical surface of a tooth.

20. Kit-of-parts comprising a dental sealant composition according to one of claims 1 to 15 and a laser.

21. Use of a dental sealant composition according to one of claims "1 to16 for protection of a tooth.