WO2003013379A2

WO2003013379A2 - Dental compositions

Info

Publication number: WO2003013379A2
Application number: PCT/IL2002/000639
Authority: WO
Inventors: Hanna Dodiuk-Kenig; Irena Eppelbaum; Kira Lizenboim; Barry Zalsman
Original assignee: B.J.M. Laboratories Ltd.
Priority date: 2001-08-08
Filing date: 2002-08-06
Publication date: 2003-02-20
Also published as: WO2003013379A3; AU2002321808A1

Abstract

There are provided polymerizable compositions comprising at least one polymerizable monomer, a polymerization initiator, at least one filler, a polymerizable resin comprising a thermoplastic resin, and a dendritic molecule, wherein said composition contains at least about 40-95 wt.% of said filler, and from about 0.1 to about 10.0 wt.% of said dendritic molecule. Preferably, the dendritic molecule is a hyperbranched molecule which is a branched condensation polymer containing ester groups and at least one amide group in the polymer backbone, having at least one hydroxyalkyl amide end group,. Also provided are dental materials formed from such compositions.

Description

DENTAL COMPOSITIONS

This application is a continuation of U.S. Provisional Patent Application Serial No.60/205,267.

Field of the Invention

The present invention relates to polymerizable compositions useful in dentistry, to products formed by the polymerization of such compositions and to processes for forming such products.

Background of the Invention

Polymerizable compositions have various uses in dentistry, for example as materials for reconstructing teeth or as adhesives for holding reconstructive elements in place. Such compositions generally include a hydrophobic resin and an inert filler, such as quartz, silica-glass containing strontium, barium, zinc, boron, yttrium and others, alurninoborosilicate glass, colloidal silica. Often the filler particles are coated with a coupling agent to bond to the resin matrix. The strength of composites is dependent on chemical and Van der Waals interfacial forces between the polymer matrix and filler particles. These forces may be enhanced by the presence of polar functional groups on the polymer and/or by the treatment of filler surfaces with silanes, titanates, or other surface-active agents (Carrera, Polymer Chemistry: An Introduction, Fourth ed., Marcel Dekker, Inc. 1999). Particle size and shape, as well as derived properties like specific surface and particle packing, are the most significant factors affecting the mechanical characteristics of a compound. The polymerizable compositions are usually cured by free radical polymerization, which may be initiated using visible light irradiation (often referred to as "visible light curing" or simply "light curing") or by an oxidation-reduction reaction (sometimes called "self-curing"). Although compositions are known having acceptable compressive or flexural strength, see e.g. Klee et al., New Monomers and Polymers for Dental Applications (Warsaw Conference Transactions, 2000), such compositions also have one or more undesirable qualities.

For example, WO 98/36729, the contents of which are incorporated herein by reference, discloses polymerizable compositions for forming dental materials, comprising a polymerizable resin selected from the group consisting of a methacryloyl terminated hyperbranched polymer, a polymerizable monomer which was specially synthesized by inventors, a filler, and at least one polymerization initiator, sensibilizer or stabilizer. These compositions are reported to yield dental materials with a shrinkage of less than 1.5% when polymerized under pressure but with a shrinkage at the range of 1.98% to 2.89% when polymerized without pressure. The material stiffens upon application of shear stress or pressure and does not relax within a predetermined working time, due to its rheopex rheologic behavior. Furthermore, the compressive strength of the materials obtained is less than 250 MPa.

Another example of the difficulty in developing polymerizable dental compositions having desired qualities is illustrated by U.S. Patent No. 5,886,064, the contents of which are incorporated herein by reference. It is known in the art to increase the amount of inert filler so as to increase the strength of the cured composition, but often increasing the filler content leads to loss of moldability of the composition, which makes placing it and forming it into the proper shape in the mouth of the patient difficult. To address this difficulty, US 5,886,064, which is incorporated herein by reference, discloses a polymerizable composition which becomes flowable under compressive or shear stress. The inventors state that the composition can be packed in similar manner to amalgam and is particularly suitable as dental material or for the production of a dental material. This is achieved in US 5,886,064 by combining in the composition claimed therein at least one polymerizable monomer and/or oligomer, a polymerization initiator, at least one filler, and a dendrimer selected from the group consisting of a propylenimine, a polyether, a polythioether, a polyphenylenamide, and a polyphenylene ester dendrimer. The composition contains at least 70 wt.% of filler and 0.5 to 28 wt.% of dendrimer, and becomes flowable under pressure and/or shear stress. The composition demonstrates compressive strength of around only 170 MPa and rather high values of shrinkage.

Dendritic molecules, such as those used in US 5,886,064, axe per se are known in the art. For example, WO 93/14147, the contents of which are incorporated herein by reference, relates to dendrimers whose branches are formed by vinyl cyanide units, and to processes for their production. These dendrimers are suitable inter alia for mixing with thermoplastic polymers or polymeric compositions. Dendrimers with polymerizable groups or highly-filled mixtures are not mentioned. WO 93/17060, the contents of which are incorporated herein by reference, relates to dendritic macromolecules based on polyesters, which are characterized by a highly-branched (hyper-branched) structure rather than ideally branched dendrimer structure, and to processes for their production. The dendritic macromolecules are disclosed in WO 93/17060 as being suitable inter alia as a component for polymerizable compositions, although only liquid varnishes are described in WO 93/17060, while filler-containing compositions are not disclosed.

WO 99/16810 and the corresponding U.S. Patents Nos. 6,392,006 and

6,387,496, the contents of all of which are incorporated herein by reference, disclose inter alia hyperbranched molecules which are branched polymers containing ester groups and at least one amide group in the backbone, having hydroxyalkylamide end groups and having a weight average molecular mass of >800 g/mol, as well as such polymers which are entirely or partly modified. It is stated that these branched polymers may be obtained by reaction of a cyclic anhydride and an alkanolamine to form a β-hydroxyalkylamide, after which a polyesteramide is obtained through polycondensation. The branched polymers are reported to be useful in thermosetting powder-paint compositions.

U.S. Patent No. 6,093,777, the contents of which are incorporated herein by reference, describes a partially or fully cured thermosetting product, which includes a cured and molded product of a thermosetting composition. The composition includes 70%) to 99%o by weight of at least one thermosetting resin or compound and 1% to 30%) by weight of at least one toughening agent. The toughening agent is at least one hyperbranched dendritic macromolecule formed of ester units, optionally in combination with ether units. Thermoplastic products are not mentioned.

An elusive goal for the designers of dental composites, adhesives or other dental materials formed by polymerizing a polymerizable composition remains the obtaining of composites, adhesives or the like having high compression strength but which as a result of the polymerization process shrink little in comparison to the polymerizable composition prior to polymerization, i.e. dental composites, adhesives or other dental materials having high compression strength but which occupy nearly the same amount of space as the compositions from which the dental materials are formed, expressed quantitatively as low shrinkage values. Preferably such dental materials would also have other desirable properties, such as low water sorption, and the compositions from which they are formed would have a working time (sometimes called "initial hardening time", i.e. the period of time, measured from the start of mixing and in the absence of activating radiation, until a penetrator of a given load and dimensions is unable to penetrate to within 0.1 mm of the bottom of a sample of cement 5 mm thick) between 1.5 and 4 minutes, setting time (the period of time, measured from the start of mixing and in the absence of activating radiation, until the composition has set) below 5 minutes, and T_{e p} (maximal heat release temperature achieved by release of heat during polymerization) of about 41°C or lower, preferably 40°C or lower. However, to date, polymerizable compositions produced in accordance with prior art methods, including those produced in accordance with the aforementioned US 5,886,064, have not succeeded in yielding dental materials having the desired combination of compressive strength and low shrinkage.

Summary of the Invention

It would be desirable to have a polymerizable composition for use in dentistry which, upon polymerization, provides dental materials such as dental composites which combine high compressive strength with low shrinkage; or which may also serve as adhesives.

There is thus provided, in accordance with a preferred embodiment of the present invention, a polymerizable composition which comprises at least one polymerizable monomer, a polymerization initiator, at least one filler, and a polymerizable resin comprising a thermoplastic resin and a dendritic molecule, and optionally a cross-linker, wherein said composition contains at least about 40-95 wt.% of the filler, and from about 0.1 to about 10.0 wt.% of the dendritic molecule.

hi a preferred embodiment of the invention, the polymerizable monomer is chosen from the group consisting of mono- and multifunctional acrylates or methacrylates, preferably methyl methacrylate, triethylene glycol dimethacrylate, 2- hydroxyethyl methacrylate, hexanediol methacrylate, or dodecanediol dimethacrylate. hi one preferred embodiment of the invention, the monomer is substantially the only monomer present, i another preferred embodiment of the invention, the monomer is present as part of a mixture of monomers. The monomer is polymerizable by free radical polymerization. In one preferred embodiment of the invention, the free radical polymerization may be initiated by visible light radiation. In another preferred embodiment of the invention, the free radical polymerization may be initiated by an oxidation-reduction reaction, preferably by reaction of an amine with a peroxide. In a preferred embodiment of the invention, the monomer contains one or more functional groups selected from the group consisting of urethane, amine, acrylic, carboxylic, amide and hydroxyl. In a preferred embodiment of the invention, the at least one monomer is present in the composition in an amount of between about 12 and about 20 wt.%. In a preferred embodiment of the invention, the thermoplastic resin is chosen from the group consisting of bisphenol-A-dimethacrylate, bisphenylglycidyl methacrylate, mono- and multi-functional aliphatic and aromatic urethane acrylate oligomers, epoxy-acrylate oligomers and urethano-acrylate oligomers. Preferably, units of which the thermoplastic resin is composed have an average molecular weight (MW) of between about 500 and about 3000. hi one preferred embodiment of the invention, the thermoplastic resin comprises substantially only one type of oligomer. In another preferred embodiment of the invention, the thermoplastic resin comprises a mixture of oligomers. In one preferred embodiment of the invention, the free radical polymerization may be initiated by visible light radiation, another preferred embodiment of the invention, the free radical polymerization may be initiated by an oxidation-reduction reaction, preferably by reaction of an amine with a peroxide, h a preferred embodiment of the invention, the thermoplastic resin contains one or more functional groups selected from the group consisting of urethane, amine, acrylic, amide, and hydroxyl. hi a preferred embodiment of the invention, the thermoplastic resin is present in the composition in an amount of between about 10 and about 18 wt.%.

a preferred embodiment of the invention, the dendritic molecule is a dendrimer. In a preferred embodiment, the dendrimer has from about 1 to about 20 generations, hi a preferred embodiment of the invention, the terminal units of the dendrimer contain functional groups which can react with functional groups on the monomer, the thermoplastic resin or the cross-linker, hi a preferred embodiment of the invention, the dendrimer has a molecular weight between about 1,500 and about 25,000.

h another preferred embodiment of the invention, the dendritic molecule is a hyperbranched molecule. In a preferred embodiment, the hyperbranched moledule has from about 1 to about 20 generations, h a preferred embodiment, the hyperbranched molecule has at least one terminal unit which can react with a functional group on at least one of the monomer, the thermoplastic resin or the crosslinker. hi a preferred embodiment of the invention, the hyperbranched molecule contains functional groups selected from the group consisting of hydroxyl, amine, carboxylic, ester, amide, sulfide, carboxylate, fatty acid and any reactive functional group. In a preferred embodiment of the invention, the hyperbranched molecule has a molecular weight between about 1,500 and about 25,000. a preferred embodiment of the invention, the composition comprises an oxidizing initiator selected from the group consisting of benzoyl peroxide, lauryl peroxide, benzoin, benzophenone, alpha-diketones. hi a preferred embodiment, the oxidizing initiator is present in an amount of between about 0.3 and 1.5 wt.%. A preferred oxidizing initiator for use in self-cured polymerization is benzoyl peroxide. A preferred oxidizing initiator for use in photopolymerization is camphor quinone.

In a preferred embodiment of the invention, the composition also comprises a reducing initiator selected from the group consisting of tertiary amines. Reducing initiators are preferably used as reducing agents in combination with oxidizing initiators such as benzoyl peroxide, lauryl peroxide, or -diketones, to effect more rapid generation of radicals. Preferred reducing initiators for self-cured polymerization are N,N-dimethyl-p-toluidine and N,N-dimethyl-sym-xylidine. Preferred reducing initiators for use in photopolymerization are ethyl-4-dimethyl- aminobenzoate and diethyl-aminoethyl methacrylate. Preferably, the ratio of photoiniator to amine is about 1 :1.

In a preferred embodiment of the invention, the composition comprises a cross-linker. The inclusion of a cross-linker is especially preferable when the composition will be polymerized to function as an adhesive, h a preferred embodiment, the cross-linker contains functional groups which can cross-link one or more of the monomer, oligomer (thermoplastic resin) and dendritic molecule. In a preferred embodiment, the cross-linker contains functional groups selected from the group consisting of hydroxyl and acrylic, h a preferred embodiment, the cross linker is selected from the group consisting of multifunctional acrylates, preferably tri- or tetrafunctional acrylates. h a preferred embodiment, the cross linker is present in the composition in an amount of between about 0.5 and 2.0 wt.%.

In a preferred embodiment of the invention, the filler is selected from the group consisting of quartz, silica-glass containing at least one of the group consisting of strontium, barium, zinc, boron and yttrium, aluminoborosilicate glass, and colloidal silica. Preferably, the filler is in the form of particles, preferably having an average diameter of between about 30 nm and 30μm. one preferred embodiment of the invention the filler particles are coated with a coupling agent to bond to the resin matrix, preferably with a coating containing silyl groups (sometimes referred to as "silanized" filler, as is known in the art), h another preferred embodiment of the invention the filler particles are uncoated. In another preferred embodiment, prior to mixing in the composition of the invention the filler particles are optionally treated with hyperbranched polymers or dendrimers in order to enhance interfacial adhesion to the resin matrix. In a preferred embodiment of the invention, the filler contains matter which is radiopaque.

There is also provided, in accordance with a preferred embodiment of the present invention, a process for forming a dental material, comprising the steps of (a) providing a polymerizable composition which upon curing yields a dental material having a compressive strength of at least 250 MPa, preferably at least 300 MPa, as determined by ISO 9917 and exhibits linear shrinkage of less than 2%, preferably less than 1.5%, as determined in vitro using a self-developed methodology described below, the composition comprising at least one polymerizable monomer, a polymerization initiator, at least one filler, and a polymerizable resin comprising a thermoplastic resin and a dendritic molecule, and optionally a cross-linker, wherein said composition contains at least about 40-95 wt.% of the filler, and from about 0.1 to about 10.0 wt.% of the dendritic molecule and (b) polymerizing said composition, whereby to obtain a dental material having a compressive strength of at least 250 MPa, preferably 300 MPa, and exhibits linear shrinkage of less than about 2.0%, preferably less than about 1.5%.

hi a preferred embodiment of the invention, the material formed exhibits a water sorption of less than about 40 μg/mm³, preferably less 'than about 24 μg/mm³ as determined by the method of ISO 4049:2000(E)

i one preferred embodiment of the invention, the material formed is a dental composite. In another preferred embodiment of the invention, the material formed is a dental adhesive.

There is also provided, in accordance with a preferred embodiment of the present invention, a dental material having a compressive strength of at least about 200 MPa, preferably at least about 250 MPa as determined by the method of ISO 9917 and linear shrinkage of less than about 2%, preferably less than about 1.5%, the dental material being the result of polymerization of a composition comprising at least one polymerizable monomer, a polymerization initiator, at least one filler, and a polymerizable resin comprising a thermoplastic resin and a dendritic molecule, and optionally a cross-linker, wherein said composition contains at least about 40-95 wt.% of the filler, and from about 0.1 to about 10.0 wt.% of the dendritic molecule. There is also provided, in accordance with a preferred embodiment of the invention, a primer for pre-treating a tooth or other dental surface prior to application of an adhesive to said dental surface, comprising a solvent acceptable for use in dentistry and between about 1-30 wt.% of a hyperbranched dendritic macromolecule having a core which is built up by polycondensation so that the hyperbranched molecule has functional groups, for example, hydroxyl units in the terminal units and has amide nitrogen atoms as branching points.

There is also provided, in accordance with a preferred embodiment of the invention, a process for pre-treating a tooth or other dental surface prior to application of an adhesive to said tooth or dental surface, comprising (a) providing a solution comprising a solvent acceptable for use in dentistry and between about 1-30 wt.% of a hyperbranched dendritic macromolecule having a core which is built up by polycondensation of cyclic anhydrides with diisopropanolamine, so that the hyperbranched molecule has hydroxyl units in the terminal units and has amide nitrogen atoms as branching points, and (b) applying said solution to said tooth or other dental surface.

There is also provided, in accordance with a preferred embodiment of the invention, a dental filler material comprising at least one member of the group consisting of quartz, silica-glass containing at least of the group consisting of strontium, barium, zinc, boron and yttrium, aluminoborosilicate glass, and colloidal silica, the dental filler material comprising particles which have been coated with at least one dendritic molecule as described above. In a preferred embodiment of the invention, the dendritic molecule is a hyperbranched dendritic macromolecule having a core which is built up by polycondensation of one or more cyclic anhydrides with one or more alkanolamines, preferably diisopropanolamine, so that the hyperbranched molecule has hydroxyl units in the terminal units and has amide nitrogen atoms as branching points, hi apreferred embodiment of the invention, the filler particles have been coated by immersing the particles in a solution containing at least one dendritic molecule in order to enhance interfacial adhesion to the resin matrix. In a preferred embodiment of the invention, the filler contains matter which is radiopaque. h a preferred embodiment of the invention, the filler particles are between about 30 nm and 30 μm average diameter.

Detailed Description of Preferred Embodiments

In preferred embodiments, the present invention provides polymerizable compositions which yield dental materials having improved compressive strength and shrinkage properties vis-a-vis dental materials known in the prior art. In additional preferred embodiments of the invention, the dental materials may be formulated to have additional improved properties, such as water sorption or bonding to tooth substrates as expressed in measured shear bond strength.

A common feature to all the preferred embodiments of the present invention is the incorporation into the polymerizable composition of an amount of a dendritic polymer which upon curing is effective to impart to the composition, in conjunction with the other components in the composition, the desired properties of compressive strength and shrinkage.

Dendritic polymers per se and their preparation are known in the art. Dendritic polymers can be generally classified in two types: dendrimers and hyperbranched polymers. Dendritic polymers are based on AB_X monomers, where A is one type of group, B is another type of group, and x is an integer. As shown in Scheme 1, dendrimers consist of several layers of monomers built up around a core. Each layer is referred to as a "generation". Scheme 1 depicts a dendrimer in which the core is monomer B₃ and the remaining layers are all formed from AJB₂ monomers. However, as is known in the art, each generation of a dendrimer may be built up from different monomers. Often, the groups B are functional or polymerizable groups such as amines, carboxylic acid derivatives (esters, amides), (meth)acrylic, alfyl, styryl, vinyl, vinyloxy, vinylamine, etc., so that the outermost layer of the dendrimer contains many of these fimctional groups symmetrically spaced with respect to one another.

During the process of dendrimer formation, the functional groups B of the most recently added generation react with the groups A of the monomers to link the monomer to the dendrimer and thus add another generation. Points of such linkage are depicted in Scheme 1 by "•". Because of the regular, symmetrical nature of dendrimers, dendrimers are more difficult to produce and more expensive than hyperbranched polymers (see below).

SCHEME 1

Hyperbranched polymers, like dendrimers, may also be built from AB_X monomers. The most significant structural difference between hyperbranched polymers and dendrimers is that dendrimers have substantially no unreacted functional groups on the interior of the dendrimer, whereas hyperbranched polymers contain such functional groups in the interior. This difference can be seen by comparison of Scheme 1 with Scheme 2.

SCHEME 2

Hyperbranched polymers are thus generally less symmetrical than dendrimers, and for this reason commercially available hyperbranched polymers, such as Dendrepox™ polyamides from Epox Ltd. (U.S. Patent No. 6,288,208), tend to cost much less than commercially available dendrimers. However, because of the greater uniformity and symmetry of dendrimers, dendrimers may be formed with discrete domains having different properties. For example, a dendrimer may be designed to have large hydrophobic cavities in its interior and a hydrophilic outer surface, or vice versa. Although hyperbranched polymers may be designed to have different domains, this boundary between such domains will generally not be as discrete in hyperbranched polymers as in dendrimers.

Dendrimers and hyperbranched polymers may be synthesized in several different ways, the most commonly used being classical condensation reactions. These reactions are conducted either in bulk or in solution where the AB_x-monomers self-condense, or in combination with a core monomer B_y.

As shown in Scheme 3, dendritic polymers may be thought of as being composed of three types of repeating units: dendritic units, which are AB_X monomers fully incorporated into the polymer; terminal units in which all the B groups are unreacted, and linear units have at least one but fewer than all the B groups unreacted.

Terminal unit

SCHEME 3

Using this terminology, one way of quantitatively characterizing dendritic polymers is by their "degree of branching" (DB), which may be expressed as:

Σ dendritic units + Σ terminal units _DB = Σ linear units + Σ dendritic units + Σ terminal units

The DB for a dendrimer is equal to 1. (See Malmstrom et al., Hyperbranched Polymers: A Review, J.M.S.-Rev. Macromol. Chem. Phys., C37(3), 555-579 (1997)). Hyperbranched polymers constructed from the same monomers but having different DB values are correlated with higher solubility and lower melt viscosity for the sample with the greatest DB. In the practice of the present invention, the group B on the outermost layer/generation of the dendritic polymer is preferably a group B that can react or cross-link with the at least one monomer and/or the thermoplastic resin. Thus, for example, suitable combinations of monomers, thermoplastic resins and terminal groups B are mono- and multifunctional acrylates or methacrylates such as methyl methacrylate, triethylene glycol dimethacrylate, 2-hydroxyethyl methacrylate, hexanediol methacrylate, dodecanediol dimethacrylate, as the monomer, bisphenol- A- dimethacrylate, bisphenylglycidyl methacrylate, mono- and multi-functional aliphatic and aromatic urethane acrylate oligomers, epoxy-acrylate oligomers and urethano- acrylate oligomers, preferably having MW between 500 and 3000 as the thermoplastic resin, and dendritic molecules having functional groups selected from the group consisting of hydroxyl, amine, carboxylic, ester, amide, sulfide, carboxylate and fatty acid as the terminal groups. It has been found that when the dendritic molecule used is a dendrimer, it is preferable for the dendrimer to have between about 3 and about 770 terminal groups, and/or to contain between about 0 and 8 generations (wherein the central AB_X molecule constitutes the zeroeth generation, see Mark et al., Eds., Encyclopedia of Polymer Science and Engineering, 2^nd Ed., Index Volume, John Wiley & Sons, 1990). Preferably, when the dendritic molecule used is a hyperbranched polymer, the hyperbranched polymer has a degree of branching between about 0.4 and about 0.9. hi preferred embodiments of the invention, the interior the dendritic molecule is built up from units containing hydroxyl or amine groups.

In view of the foregoing, it will be appreciated that not all combinations of monomers, thermoplastic resins and dendritic polymers are suitable for use in accordance with the present invention. For example, US 5,886,064 discloses polymerizable compositions for use in dentistry which incorporate a polymerizable monomer or oligomer, at least 70 wt.% filler, and a dendrimer. However, as shown at Table 1 in column 9 of US 5,886,064, the dental materials obtained by curing of the compositions disclosed therein have compressive strengths of about 200 MPa or lower. Dental materials prepared in accordance with the present invention have significantly higher compressive strengths.

In accordance with a preferred embodiment of the present invention, the dendritic polymers used in the practice of the present invention have a molecular weight of between about 1,500 and about 25,000. Preferably the dendritic polymer constitutes between about 0.1 and about 10.0 wt.% of the composition. Examples of pairs of initiators suitable for use in accordance with the present invention are benzoyl peroxide, camphor quinone as oxidizing initiators and amines, preferably N,N-dimethyl-p-toluidine, ethyl-4-dimethylaminobenzoate and their derivatives, as reducing initiators. When cross-linkers are used, these are preferably molecules capable of cross-linking the groups B on the terminii of the dendritic molecules with the thermoplastic resin and/or the at least one monomer. Preferably, the initiator and cross-linker are each independently present in an amount of between about 0.3 and about 1.5 wt.%.

Examples of fillers suitable for use in accordance with the present invention are silanized glass and other dental fillers as are well known in the art, such as, quartz, silica-glass containing at least one of strontium, barium, zinc, boron, and yttrium, aluminoborosilicate glass, and colloidal silica. Preferably, the fillers are coated with a dendritic molecule, preferably the same dendritic molecule used in the remainder of the composition of the invention. The fillers preferably have an average particle size of between about 30 nm and about 30 μm, and may be present a mixture of particles having a range of sizes.

It has been found that dental materials prepared in accordance with the present invention exhibit low shrinkage, generally below about 2.0%) and preferably below about 1.5 %, measured by the method described below. At the same time, and in contrast to dental materials known in the prior art, including those prior art dental materials prepared from mixtures of monomers and/or oligomers and dendritic polymers, the dental materials obtained in accordance with the present invention also exhibit good compressive strength, generally at least about 250 MPa and preferably at least about 300 MPa.

one preferred embodiment of the present invention, a tooth or other dental surface to which an adhesive is to be applied may be pre-treated with a dendritic polymer as described above. Such application may be made, for example, by contacting the tooth or dental surface with a solution containing from about 1 to about 30%o dendritic polymer in a dentally acceptable solvent, such as ethanol or another alcohol or propylene glycol or another glycol.

Examples of some preferred embodiments of the invention will now be illustrated through the following illustrative and non-limitative examples.

Example 1 - Composition without dendritic molecule for use as core build-up material

A highly filled dental cement is formed from a composition consisting of two parts, mixture A (Base) and mixture B (Catalyst), which are mixed in equal amounts and oxidatively polymerized.

Mixture A: To a mixture of 1.4000 g of bisphenylglycidylmethacrylate (Bis-GMA), 1.7 mg 2,6-di-tert-butyl-4-methylphenol (BHT) and 1.5000 g 2- hydroxyethylmethacrylate (HEMA) were added 0.0400g of N,N-dimethyl-p-toluidine and 7.0583 g of silanised glass filler at room temperature. This mixture was then ground.

Mixture B: To a mixture of 1.3400 g of bisphenylglycidylmethacrylate (Bis-GMA), 2.0 mg BHT and 1.3080 g tetraethylglycidylmethacrylate (TEGDMA) were added 0.0400 g of benzoyl peroxide and 7.3100 g of silanised glass filler at room temperature. This mixture was then ground.

Mixtures A and B were stored separately for at least 24 hours at room temperature prior to use.

A dental cement was prepared by polymerizing a mixture consisting of 2.500 g of Mixture A and 2.500 g of Mixture A. The compressive strength of the resulting cement was determined using a Lloyd Mechanical Tester LR10K in accordance with ISO 9917 (as published My 1, 1998). The crosshead speed was 0.5 mm min. Ten specimens were tested. All specimens were kept at room temperature for 1 h following setting of the material and then immersed in water at (37°±1)° C for 24 h prior to measurement. The dental cement obtained was found to have a compressive strength of 253.0±20.0 MPa.

The value of water sorption, Wsp in micrograms per cubic millimeter of resulting material was calculated according to ISO 4049:2000(E). Five specimens were prepared. It was found that the value of water sorption for the material obtained was within ISO 4049:2000(E) requirements.

Linear polymerization shrinkage was determined in vitro using a self- developed methodology based on the description of the AcuVol (Bisco Inc., USA) as described in Labella et al., Dental Materials 15 (1999) 128-137 and Choi & Suh,

"Single versus Multi-view Measurements of Volumetric Shrinkage by AcuVol, available at http://www.bisco.com/rd. Glass tubes of 5.0 mm diameter and 6.5 mm height were filled with uncured composite material. Samples (n=3) were placed on a black pedestal and were imaged by a digital camera (Nikon Coolpix 900) against a black background while illuminated by a white light source. Computer hardware and corresponding software were employed for the acquisition and processing of images. The measurements were taken in a single-view mode. The height of the uncured samples was measured 2 min after they were placed on the pedestal. Additional series of images were acquired for the cured material at 10 min, 30 min, and 60 min commencement of the test, as well as after immersion in water at 37(±1)°C for 24 hours. The value of linear shrinkage (%) was calculated (Standard Deviation is ± 0.7%)). The material obtained was found have linear shrinkage of 2.4%.

Example 2

The procedure of Example 1 was followed, except that in each of mixtures A and B, 0.01 g of Bis-GMA (representing 0.1 wt.% of the total weight of each mixture) was replaced with a dendripolyamide oligomer based on a six-valent semi-flexible core (Molecular Weight 12,100; H-functionality size 45 mole^-1; H-functionality type as Versamide 125). The compressive strength of the resulting cement was found to be in the range of 150.0 ± 20.0 MPa. Water sorption determined as described in Example 1 was at the range of 16.0±2.0 μg/mm³. The result complies with ISO 4049:2000(E) requirements.

Linear shrinkage determined as described in Example 1 was in the range of ±3.6%. Example 3

The procedure of Example 1 was followed, except that in each of mixtures A and B, 0.01 g of Bis-GMA (representing 0.1 wt.% of the total weight of each mixture) was replaced with a hyperbranched polyesteramide according to WO 99/16810 (U.S. Patents Nos. 6,387,496 and 6,392,006) having 8 terminal hydroxyl functional groups (MW 1,500). The compressive strength of the resulting cement was found to be in the range of 303.7 ± 20.0 MPa. Water sorption, determined as described in Example 1, was found to be within ISO 4049:2000(E) requirements.

Linear shrinkage determined as described in Example 1 was ±0.8%. Example 4

The procedure of Example 3 was followed, except that 0.03 g of the same hyperbranched polyesteramide used in Example 3 (representing 0.3 wt.% of the total weight of each mixture) was used in each of Mixtures A and B. The compressive strength of the resulting cement was found to be in the range of 386.0 ± 20.0 MPa. Water sorption, determined as described in Example 1, was found to be within ISO 4049:2000(E) requirements. Linear shrinkage determined as described in Example 1 was ±1.5%.

Example 5

The procedure of Example 3 was followed, except that 0.05 g of the hyperbranched polyesteramide (representing 0.5 wt.%) of the total weight of each mixture) was used in each of Mixtures A and B. The compressive strength of the resulting cement was found to be in the range of 227.0 ± 20.0 MPa. Water sorption determined as described in Example 1 was at the range of 16.0±2.0 μg/mm³. The result complied with ISO 4049:2000(E) requirements.

Linear shrinkage detemiined as described in Example 1 was in the range ±2.3%.

Example 6

The procedure of Example 1 was followed, except that in each of mixtures A and B, 0.05 g of Bis-GMA (representing 0.5 wt.%> of the total weight of each mixture) was replaced with a dendripolyamide oligomer with a four-valent semi-flexible core (Molecular Weight 6,500; H-functionality size 30 mole^-"1; H-functionality type as Versamide 125). The compressive strength of the resulting cement was found to be in the range of 201.0 ± 20.0 MPa. Water sorption determined as described in Example 1 was at the range of 30.0±2.0 μg/mm³. The result complies with ISO 4049:2000(E) requirements. Linear shrinkage determined as described in Example 1 was at the range ±2.4%.

Example 7 - Core Composite (BJM) - commercial core build-up material

Two mixtures, Mixture A and Mixture B, were prepared as follows: Mixture A: To a mixture of 1.3600 g of bisphenylglycidylmethacrylate (Bis-GMA), 1.7 mg 2,6-di-tert-butyl-4-methylphenol (BHT), 0.0300 g hyperbranched polyesteramide according to WO 99/16810 (U.S. Patents Nos. 6,387,496 and 6,392,006) and having 8 terminal hydroxyl functional groups (MW 1,500) and 1.5700 g of 2-hydroxyethylmethacrylate (HEMA) were added 0.0400g of N,N-dimethyl-p- toluidine and 6.9983 g of filler containing a mixture of colloidal silica, silanised glass, borosilicate glass and fluorine-releasing filler at room temperature. The Core Composite composition consists of the same components as the model one, but the filler level is different for two parts of composition and contains silanized glass, colloidal silica, borosilicate glass mixture, and fluorine-releasing filler. The changes in filler content were dictated by aesthetic demands and desired additional properties: easy handling, thermal conductivity, fluorine-release etc. This mixture of components was then ground to form Mixture A.

Mixture B: To a mixture of 1.3400 g of Bis-GMA, 1.3 mg BHT, 0.0270 g hyperbranched polyesteramide according to WO 99/16810 (U.S. Patents Nos. 6,387,496 and 6,392,006) having 8 terminal hydroxyl functional groups (MW 1,500) and 1.3000 g of tetraethylglycidylmethacrylate (TEGDMA) were added 0.0400 g of benzoyl peroxide and 7.2917 g of filler containing a mixture colloidal silica, silanised glass, borosilicate glass and fluorine-releasing filler at room temperature. This mixture of components was ground to form Mixture B.

Mixtures A and B were stored separately for at least 24 hours at room temperature prior to use, and then 2.5 g of Mixture A was mixed with 2.5 of Mixture B and allowed to cure for 10 minutes.

The dental material obtained after curing was found to have a compressive strength of 250.0 ± 20.0 MPa, linear shrinkage of 1.50 ± 0.50 %, and water sorption 23.8 μg/mm³.

Example 8

A comparison between the dental material obtained in Example 4 and core build-up materials prepared from commercially available compositions was carried out under identical conditions. The results of physical and mechanical evaluations, measured as described above, are summarized in Table 1 : Table 1. Comparison of main physico-mechanical properties of composites

The value of water sorption, Ws_P in micrograms per cubic millimeter of resulting material was calculated according to ISO 4049:2000(E). Linear shrinkage was determined using the method described in Example 1 above.

Example 9 - Liquid Dental Adhesive without dendritic polymer

A liquid, light-curable dental adhesive was prepared by mixing 2.100 g of tetraethylglycidylmthacrylate (TEGDMA), 2.700 g 2-hydroxyethyimethacrylate (HEMA), 4.200 g urethane di-methacrylate oligomer, 0.500 g phosphonate as a bonding agent, 0.446g triacrylate monomer as a cross-linking agent, 0.025 g ethyl-4- dimethylaminobenzoate (EDB) as a polymerization accelerator, and 0.029 g camphor quinone as a polymerization initiator and exposing to light of 450-500 nm wavelength, as described below.

The shear bond strength (SBS) between this light-cured adhesive and dentin was determined using a Lloyd Mechanical tester LR10K and a "Bencore Multi-T" Model 800-827-7540 testing device for dental restorative materials. The test was conducted using bovine teeth which were first potted in poly-methyl methacrylate and then ground and polished to expose dentine. Dentine surfaces were acid treated for 20 seconds and water rinsed. Excess moisture was blotted from the surface. The surface appeared visibly moist. 37%₀ phosphoric acid was used to condition the dentin surface. A micro-brush was used to place ample amounts of the uncured adhesive to the surface. After 20 seconds the surface was air dried for 5 seconds and then light cured for 10 seconds. A second application of the adhesive was carried out by air- drying and light curing for 10 seconds. A gelatin capsule technique in accordance with M.A. Latta, "A Laboratory Evaluation of the Shear Bond Strength of Resibond and Prime and Bond 21. to Dentin", Creighton University, Omaha, Nebraska, was used for testing the shear bond strength: gelatine capsule 4.5 mm in diameter were approximately 2/3 filled with a composite ("Lumifil anterieur" resin based light- activated dental restorative material, R&S, 13 rue. Jean Lolive, 93605 Aulnay, France, then cured in an Astralis 7 curing unit ("Vivadent") for one minute and/or in an Apollo 95E unit using the plasma lamp (Dental Medical Diagnostic Systems, Inc.) for ten seconds. Additional composite was added to slightly overfill the capsules. The capsules were firmly seated against the bonding sites and excess resin removed. The specimens were additionally light cured for 20 second. Then, gelatine capsules with composite resin were bonded to the tooth surface. After bonding and curing the sample, specimens were placed in water at 37°C for 24 hours. The shear bond strength (SBS) of the dental adhesive was found to be 6.3 ± 2.0 MPa.

Example 10 - Liquid Dental Adhesive with dendritic polymers

The procedure of Example 6 was repeated, except that 0.020 g (0.2 wt.%) of a hyperbranched polyesteramide according to WO 99/16810 (U.S. Patents Nos.

6,387,496 and 6,392,006) having 8 terminal hydroxyl functional groups (MW 1,500) was added to the adhesive composition. The shear bond strength (SBS), measured as in Example 6, was 10.5 ± 2.0 MPa.

Example 11

The procedure of Example 7 was repeated, except that 0.065 g (0.65 wt.%) of the hyperbranched polyesteramide was added to the adhesive composition. The shear bond strength (SBS) was found to be 11.6 ± 2.0 MPa.

Example 12

The procedure of Example 7 was repeated, except that 0.150 g of the hyperbranched polyesteramide was added to the adhesive composition. The shear bond strength (SBS) was found to be 10.7 ± 2.0 MPa.

Example 13 The procedure of Example 10 was repeated, except that 0.020 g of dendripolyamide oligomer with a six-valent semi-flexible core (Molecular Weight

12,100; H-functionality size 45 mole ^l; H-functionality type as Versamide 125) were added to the adhesive composition. The shear bond strength (SBS) measured as in Example 10 was found to be 5.5 ± 2.0 MPa.

Example 14 - Filled Dental Adhesive Composition without dendritic polymer

Dental adhesives maybe used for final cementation of crowns and bridges, for inlays and onlays, for posts and cores, for ceramic crowns and Maryland bridges, or for bonding metal, plastic or ceramic orthodontic attachments to teeth. Adhesives may also be used for amalgam restoration, veneering of alloys, and for the implantation of prostheses. This and the following two examples compare dental adhesives prepared without and with dendritic molecules. The adhesives are "dual curable", i.e. polymerization may be initiated by combining the two component mixtures A and B of the adhesive, but the rate polymerization can be increased by exposing the combined components to light.

Two mixtures, Mixture A and Mixture B, were prepared as follows:

Mixture A: To a mixture of 1.240 g 2-hydroxyethylmethacrylate (HEMA), 3.660 g urethane di-methacrylate oligomer and 0.200 g triacrylate monomer cross-linking agent were added 0.030 g N,N-dihydroxyethyl-p-toluidine (DHEPT), 0.030 g camphor quinone, 0.030 g ethyl-4-dimethylaminobenzoate (EDB), and 4.810 g strontium-alumino-fluoro-silicate glass at room temperature. These components were then mixed to form Mixture A.

Mixture B: To a mixture of 2.200 g bisphenylglycidylmethacrylate (Bis-GMA), 0.200 g of triacrylate monomer cross-linking agent and 1.700 g tetraethylglycidylmethacrylate (TEGDMA) were added 0.080 g benzoyl peroxide, 0.200 g aromatic acrylate monomer derivative coupling agent and 5.620 g strontium- alumino-ffuoro-silicate glass at room temperature. These components were then mixed to form Mixture B.

Mixtures A and B were stored separately for 24 hours at room temperature, and then 2.5 g of Mixture A was mixed with 2.5 g of Mixture B and allowed to cure for 1 hour. Shear bond strength (SBS) to a cobalt-nickel alloy, Rexillium™, which is commonly used in the practice of tooth repair, was measured in manner analogous to the measurement of shear bond strength to bovine dentin described in Example 6. Tests were conducted using Rexillium™ discs first potted in poly-methyl methacrylate and then ground and polished to expose smooth surface. Compressive strength was measured using the technique described in Example 1.

The dental material obtained after curing was found to have a shear bond strength of 3.4 ± 1.3 MPa and a compressive strength of 222.0 ± 20.0 MPa.

Example 15 - Filled Dental Adhesive Composition with dendritic polymer

The procedure of Example 10 was repeated, except that 0.100 g (1.0 wt.%) of a hyperbranched polyesteramide according to WO 99/16810 (U.S. Patents Nos. 6,387,496 and 6,392,006) built up by condensation of cyclic anhydrides and diisopropanol amine, as described in the aforementioned patents, and having 8 terminal hydroxyl functional groups (MW 1,500) was added to each of Mixtures A and B. The shear bond strength (SBS) measured as in Example 10 was 6.5 ± 1.3 MPa and compressive strength measured as in Example 1 was 117.0 ± 20.0 MPa.

Example 16

The procedure of Example 11 was repeated, except that 0.150 g (1.5 wt.%) of the hyperbranched polyesteramide was added to each of Mixtures A and B. SBS was found to be 5.0 ± 1.3 MPa and compressive strength found to be 96.0 ± 20.0 MPa.

It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the present invention includes both combinations and subcombinations of the features described hereinabove as well as modifications and variations thereof which would occur to a person of skill in the art upon reading the foregoing description and which are not in the prior art.

Claims

1. A polymerizable composition which comprises at least one polymerizable monomer, a polymerization initiator, at least one filler, a polymerizable resin comprising a thermoplastic resin, and a dendritic material, wherein said composition contains about 40-95 wt.% of said filler, and from about 0.1 to about 10.0 wt.% of said dendritic material.

2. A polymerizable composition according to claim 1 and further comprising a cross-linker.

3. A polymerizable composition according to claim 1 or 2 wherein the polymerizable monomer is chosen from the group consisting of mono- and multifunctional acrylates and methacrylates.

4. A polymerizable composition according to claim 3 wherein said polymerizable monomer is selected from the group consisting of methyl methacrylate, triethylene glycol dimethacrylate, 2-hydroxyethyl methacrylate, hexanediol methacrylate and dodecanediol dimethacrylate.

5. A polymerizable composition according to any one of claims 1 to 4 wherein said monomer is substantially the only monomer present.

6. A polymerizable composition according to any one of claims 1 to 4 wherein said monomer is present as part of a mixture of monomers.

7. A polymerizable composition according to any one of claims 1 to 6 wherein said monomer is polymerizable by free radical polymerization.

8. A polymerizable composition according to claim 7 wherein said free radical polymerization may be initiated by visible light radiation.

9. A polymerizable composition according to claim 7 wherein said free radical polymerization may be initiated by an oxidation-reduction reaction.

10. A polymerizable composition according to claim 9 wherein said oxidation- reduction reaction is the reaction of an amine with a peroxide.

11. A polymerizable composition according to any one of claims 1 to 10 wherein said monomer contains one or more functional groups selected from the group consisting of urethane, amine, acrylic, carboxylic, amide and hydroxyl.

12. A polymerizable composition according to any one of claims 1 to 11 wherein said at least one monomer is present in the composition in an amount of between about 12 and about 20 wt.%.

13. A polymerizable composition according to any one of claims 1 to 12 wherein said theraioplastic resin is chosen from the group consisting of bisphenol- A- dimethacrylate, bisphenylglycidyl methacrylate, mono- and multi-functional aliphatic and aromatic urethane acrylate oligomers, epoxy-acrylate oligomers and urethano- acrylate oligomers.

14. A polymerizable composition according to any one claims 1 to 13 wherein said thermoplastic resin is composed of units having an average molecular weight (MW) of between about 500 and about 3000.

15. A polymerizable composition according to any one of claims 1 to 14 wherein said thermoplastic resin comprises substantially one type of oligomer.

16. A polymerizable composition according to any one of claims 1 to 14 wherein said thermoplastic resin comprises a mixture of oligomers.

17. A polymerizable composition according to any one of claims 1 to 16 wherein said thermoplastic resin is composed of units which are polymerizable by free radical polymerization.

18. A polymerizable composition according to claim 17 wherein said free radical polymerization may be initiated by visible light radiation.

19. A polymerizable composition according to claim 17 wherein said free radical polymerization may be initiated by an oxidation-reduction reaction.

20. A polymerizable composition according to claim 19 wherein said oxidation- reduction reaction is the reaction of an amine with a peroxide.

21. A polymerizable composition according to any one of claims 1 to 20 wherein said thermoplastic resin contains one or more functional groups selected from the group consisting of urethane, amine, acrylic, amide, and hydroxyl.

22. A polymerizable composition according to any one of claims 1 to 21 wherein said thermoplastic resin is present in the composition in an amount of between about 10 and about 18 wt.%.

23. A polymerizable composition according to any one of claims 1 to 22 wherein said dendritic molecule is a dendrimer.

24. A polymerizable composition according to claim 23 wherein said dendrimer has from about 1 to about 20 generations.

25. A polymerizable composition according to claim 23 or 24 wherein said dendrimer has functional groups which can react with functional groups on said monomer, said thermoplastic resin or said cross-linker.

26. A polymerizable composition according to any one of claims 23 to 25 wherein said dendrimer has a molecular weight between about 1,500 and about 25,000.

27. A polymerizable composition according to any one of claims 1 to 22 wherein said dendritic molecule is a hyperbranched molecule.

28. A polymerizable composition according to claim 27 wherein said hyperbranched molecule has from about 1 to about 20 generations.

29. A polymerizable composition according to claim 27 or 28 wherein said hyperbranched molecule has at least one terminal unit which can react with a functional group on at least one of said monomer, said thermoplastic resin and said crosslinker.

30. A polymerizable composition according to any one of claims 27 to 29 wherein said hyperbranched molecule has hydroxyl imits in the terminal units and has amide nitrogen atoms as branching points.

31. A polymerizable composition according to any one of claims 27 to 30 wherein said hyperbranched molecule has at least one mono- or polymeric branching chain extender which is bonded to said core and contains at least three reactive groups.

32. A polymerizable composition according to any one of claims 27 to 31 wherein said hyperbranched molecule contains functional groups selected from the group consisting of hydroxyl, amine, carboxylic, ester, amide, sulfide, carboxylate, anhydride and fatty acid.

33. A polymerizable composition according to any one of claims 27 to 32 wherein said hyperbranched molecule has a molecular weight between about 1,500 and about 25,000.

34. A polymerizable composition according to any one of claims 1 to 33 wherein said composition comprises an oxidizing initiator selected from the group consisting of benzoyl peroxide, lauryl peroxide, benzoin, benzophenone, and -diketones.

35. A polymerizable composition according to claim 34 wherein said oxidizing initiator is present in an amount of between about 0.3 and 1.5 wt.%.

36. A polymerizable composition according to claim 35 wherein said oxidizing initiator is benzoyl peroxide.

37. A polymerizable composition according to any one of claims 34 to 36 wherein said composition also comprises, in addition to the oxidizing initiator, a reducing initiator selected from the group consisting of tertiary amines.

38. A polymerizable composition according to claim 37 wherein said reducing initiator is selected from the group consisting of N,N-dimethyl-p-toluidine and N,N- dimethyl-sym-xylidine.

39. A polymerizable composition according to claim 37 wherein said reducing initiator is selected from the group consisting of ethyl-4-dimethyl-aminobenzoate and diethyl-aminoethyl methacrylate.

40. A polymerizable composition according to any one of claims 37 to 39 wherein the ratio of said oxidizing initiator to amine is about 1:1.

41. A polymerizable composition according to any one of claims 1 to 40 wherein said composition comprises a cross-linker.

42. A polymerizable composition according to claim 41 wherein said cross-linker contains functional groups which can cross-link one or more of said monomer, oligomer (thermoplastic resin) and dendritic molecule.

43. A polymerizable composition according to claim 41 or 42 wherein said cross- linker contains functional groups selected from the group consisting of hydroxyl and acrylic.

44. A polymerizable composition according to any one of claims 41 to 43 wherein said cross linker is selected from the group consisting of multifunctional acrylates,

45. A polymerizable composition according to claim 44 wherein said acrylates are tri- or tetrafunctional acrylates.

46. A polymerizable composition according to any one of claims 41 to 45 wherein said cross linker is present in the composition in an amount of between about 0.5 and 2.0 wt.%.

47. A polymerizable composition according to any one of claims 1 to 46 wherein said filler is selected from the group consisting of quartz, silica-glass containing at least one of the group consisting of strontium, barium, zinc, boron and yttrium, aluminoborosilicate glass, and colloidal silica.

48. A polymerizable composition according to claim 47 wherein said filler is in the form of particles.

49. A polymerizable composition according to claim 48 wherein said particles of filler have an average diameter of between about 30 nm and 30μm.

50. A polymerizable composition according to claim 48 or 49 wherein said filler particles are coated with a coupling agent to bond to the resin matrix.

51. A polymerizable composition according to claim 50 wherein said coupling agent contains silyl groups (i.e. "silanized" filler).

52. A polymerizable composition according to any one of claims 47 to 49 wherein said filler particles are uncoated.

53. A polymerizable composition according to claim 48 or 49 wherein said filler particles are treated with hyperbranched polymers or dendrimers in order to enhance interfacial adhesion to the resin matrix prior to being mixed into said composition.

54. A polymerizable composition according to any one of claims 47 to 53 wherein said filler contains matter which is radiopaque.

55. A process for forming a dental material, comprising the steps of

(a) providing a polymerizable composition which upon curing yields a dental material having a compressive strength of at least 250 MPa as determined by ISO 9917 and exhibits linear shrinkage of less than 2% as determined in vitro, the composition comprising at least one polymerizable monomer, a polymerization initiator, at least one filler, a polymerizable resin comprising a thermoplastic resin, and a dendritic molecule, wherein said composition contains about 40-95 wt.% of said filler, and from about 0.1 to about 10.0 wt.%) of said dendritic molecule, and (b) polymerizing said composition, whereby to obtain a dental material having a compressive strength of at least 200 MPa and exhibits linear shrinkage of less than about 2.0%.

56. A process according to claim 55, wherein said composition upon curing yields a dental material having compressive strength of at least 300 MPa.

57. A process according to claim 55 or 56, wherein said composition upon curing yields a dental material having linear shrinkage of less than about 1.5%.

58. A process according to any one of claims 55 to 57, wherein said composition further comprises a cross-linker.

59. A process according to any one of claims 55 to 58, wherein the material formed exhibits a water sorption of less than about 40 μg/mm³, as deteraiined by the method of ISO 4049:2000(E)

60. A process according to claim 59, wherein the material formed exhibits a water

3 sorption of less than about 24 μg/mm .

61. A process according to any one of claims 55 to 58, wherein the material formed is a dental composite.

62. A process according to any one of claims 55 to 58, wherein the material formed is a dental adhesive.

63. A dental material having a compressive strength of at least about 250 MPa as deteπnined by the method of ISO 9917 and linear shrinkage of less than about 2%, the dental material being the result of polymerization of a composition comprising at least one polymerizable monomer, a polymerization initiator, at least one filler, and a polymerizable resin comprising a thermoplastic resin and a dendritic molecule, wherein said composition contains about 40-95 wt.% of said filler, and from about 0.1 to about 10.0 wt.% of said dendritic molecule.

64. A dental material according to claim 63 having a compressive strength of at least about 300 MPa.

65. A dental material according to claim 63 or 64 having a linear shrinkage of less than about 1.5%

66. A dental material according to any one of claims 63 to 65 wherein said composition further comprises a cross-linker.

67. A primer for pre-treating a tooth or other dental surface prior to application of an adhesive to said dental surface, comprising a solvent acceptable for use in dentistry and between about 1-30 wt.% of a hyperbranched dendritic macromolecule which is a branched condensation polymer containing ester groups and at least one amide group in the polymer backbone, having at least one hydroxyalkyl amide end group.

68. A process for pre-treating a tooth or other dental surface prior to application of an adhesive to said tooth or dental surface, comprising (a) providing a solution comprising a solvent acceptable for use in dentistry and between about 1-30 wt.% of a hyperbranched dendritic macromolecule which is a branched condensation polymer containing ester groups and at least one amide group in the polymer backbone, having at least one hydroxyalkyl amide end group, and (b) applying said solution to said tooth or other dental surface.

69. A dental filler material comprising at least one member of the group consisting of quartz, silica-glass containing at least of the group consisting of strontium, barium, zinc, boron and yttrium, aluminoborosilicate glass, and colloidal silica, the dental filler material comprising particles which have been coated with at least one dendritic molecule.

70. A dental filler material according to claim 69 wherein said dendritic molecule is a hyperbranched dendritic macromolecule which is a branched condensation polymer containing ester groups and at least one amide group in the polymer backbone, having at least one hydroxyalkyl amide end group.

71. A dental filler material according to any one of claims 69 to 70 wherein the filler particles have been coated by immersing said particles in a solution containing said at least one dendritic molecule in order to enhance interfacial adhesion to the resin matrix.

72. A dental filler material according to any one of claims 69 to 71 wherein the filler contains matter which is radiopaque.

73. A dental filler material according to any one of claims 69 to 72 wherein the filler particles are between about 30 nm and 30 μm average diameter.