Ion leachable composite material

The invention relates to composite materials based on one or more nonacidic, nonionic, hydrophilic crosslinking monomer and one or more nonacidic, nonionic, hydrophilic dilution monomers with a viscosity <1 Pas, which are particularly suitable as dental materials.

Dental materials that are able to release ions in the oral cavity, such as fluoride, calcium or hydroxide ions, are finding increasing interest due to their remineralizing, bioactive and cariostatic effects.

Restaurati ve dental materials that have a caries-inhibiting effect due to the content of fluoride sources, such as special chlorhexidine-fluoride compounds, are known, for example, from U. Salz, Phillip Journal 14 (1997) 296.

Further examples of ion-releasing dental materials are glass ionomer cements and compomers, the organic matrix of which is at least partially composed of acidic monomers, oligomers or polymers (AD Wilson, JW McLean, Glasionomer Cement, Quintessence Publishers, Chicago 1988; J. Nicholson, M. Anstice, Trends Polym. Sci. <b>2</b> (1994) 272; R. Hickel, L. Kremers, C. Haffner, quintessence<b>47</b> (1996) 1581).

Glass ionomer cements are water-containing, two-component cements based on polymeric organic acids such as poly (acrylic acid) and powdery, solid bases such as calcium fluorine aluminum silicate glasses. The cement is cured by ionic reaction between polymer-bound COOH groups and the calcium or aluminum ions emerging from the filler, so that the components of the glass ionomer cement can only be mixed shortly before use. This is cumbersome and, in addition, the inclusion of air is usually unavoidable, which has an adverse effect on the strength of the material. Because of their poor flexural strength, glass ionomer cements are not suitable for occlusion-bearing fillings.

Compositions which are composed of polymerizable acid monomers and ion-releasing glass particles are referred to as compomers. These are water-free one-component systems that harden through radical polymerisation of the monomer matrix. A slight acid-base reaction only occurs when water is added to the filling via saliva. The uncured materials are sensitive to moisture and the uncontrolled contact with water, for example during manufacture or storage, leads to premature curing, which renders the material unusable. Compomers are more resilient than glass ionomer cements, but often show less ion release.

Both glass ionomer cements and compomers generally have a high ion-releasing capacity if the matrix of the materials has a sufficient hydrophilic character which promotes water absorption. In the case of glass ionomer cements, the matrix is ​​formed by polyalkenoic acids, while monomers containing carboxylic acid are used as matrix materials in the case of compomers. However, since a high water content or a high water absorption adversely affects the mechanical properties of polymers, it was previously not possible to produce materials with a high ion-releasing ability, which at the same time show a high mechanical strength.

EP 0 449 399 B1 discloses, as underfill materials, suitable composites based on ion-releasing fillers and a mixture of conventional dental monomers, such as, for example, the dimethacrylate of ethoxylated bisphenol-A, a hydrophobic dimethacrylate, with the urethane dimethacrylate made of 2-hydroxyethyl methacrylate and 2,2,4- Trimethylhexamethylene diisocyanate, which does not contain acidic monomers, but only has a low ion release.

The invention has for its object to provide composite materials with a high ion-releasing ability and high mechanical strength, which are stable in storage in the uncured state even under humid conditions and whose mechanical properties are not significantly impaired by water accumulation after curing.

This object is achieved by composite materials based on polymerizable monomers, which are characterized in that the material is a mixture of<ul id="ul0001" list-style="none" compact="compact"><li>(a) at least one non-acidic, nonionic, hydrophilic crosslinking monomer,</li><li>(b) at least one non-acidic, non-ionic, hydrophilic dilution monomer with a viscosity &lt;1 Pas and</li><li>(c) contains at least one ion-releasing filler.</li></ul>

Crosslinking monomers are those monomers which contain at least two, preferably 2 to 4, polymerizable groups per monomer molecule.

The monomers are hydrophilic, ie they are capable of hydrophilic interactions with the filler. Monomers are preferred which contain one or more, preferably 1 to 2 urethane and / or OH groups, preferably OH groups. It has also been found that these groups promote ion transport and release.

Nonacidic compounds are understood to mean monomers which do not carry any strongly acidic groups such as carboxyl, phosphoric acid, phosphonic acid, phosphinic acid or sulfonic acid groups and which preferably also do not carry any weakly acidic groups such as phenolic OH groups or SH groups or CH-acidic groups such as Contain β-diketone or β-diketoester groups.

For the purposes of this invention, nonionics are monomers which contain no ionic groups such as cationic ammonium or sulfonium groups or anionic acid residue groups of the strongly acidic groups mentioned above.

Preferred crosslinking monomers are 2,2-bis-4- (3-methacryloxy-2-hydroxypropyl) -phenylpropane) (bis-GMA), ie the reaction product of glycidyl methacrylate and bisphenol-A (containing OH groups), and 7,7,9 Trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diyl-dimethacrylate (UDMA), ie the urethane dimethacrylate from 2 mol of 2-hydroxyethyl methacrylate (HEMA) and 1 mol of 2.2 , 4-trimethylhexamethylene diisocyanate (containing urethane groups). In addition, reaction products of glycidyl methacrylate with other bisphenols, such as bisphenol-B (2,2'-bis (4-hydroxyphenyl) butane), bisphenol-F (2,2'-methylenediphenol) or 4,4'-dihydroxydiphenyl , and reaction products of 2 mol of HEMA or 2-hydroxypropyl (meth) acrylate, preferably with 1 mol of known diisocyanates, such as, for example, hexamethylene diisocyanate, m-xylylene diisocyanate or tolylene diisocyanate, are preferred as crosslinking monomers.

Dilution monomers are monomers with a viscosity of &lt;1 Pas, preferably &lt;100 mPas, which are suitable for diluting the generally highly viscous crosslinking monomer and thus allow the production of composites with a high filler content. The viscosity data refer to a temperature of 23 ° C. The viscosity is determined using a plate or rotary viscometer in accordance with DIN 53018.

The dilution monomers also contain at least two, preferably two to three polymerizable groups and at least one, preferably 1 to 2 OH and / or urethane groups, preferably OH groups. They are non-ionic and non-acidic compounds.

A particularly preferred dilution monomer is glycerol dimethacrylate (GDMA). Other preferred dilution monomers can be prepared by reacting low-viscosity di- or triepoxides, such as, for example, ethylene glycol diglycidyl ether, glycerol triglycidyl ether or trimethylolpropane triglycidyl ether with (meth) acrylic acid. Furthermore, the reaction products of 2 or 3 mol of methacrylic acid with glycerol triglycidyl ether or trimethylolpropane triglycidyl ether are further preferred. “Low viscosity” means substances with a viscosity of &lt;200 mPas, preferably &lt;100 mPas (23 ° C.).

Preferred groups capable of polymerization are methacrylic and / or acrylic groups, in particular methacrylic groups, both for crosslinking and for diluting monomers.

To produce composite materials, crosslinking and dilution monomers are mixed with fillers, initiators for radical polymerization and, if necessary, other auxiliaries. One-component composite materials, ie composite materials that contain all the necessary components, are preferred.

The composite materials according to the invention preferably have the following composition:<ul id="ul0002" list-style="none"><li>(a) 1 to 40% by weight, particularly preferably 10 to 30% by weight and very particularly preferably 15 to 25% by weight of crosslinking monomer,</li><li>(b) 2 to 40% by weight, particularly preferably 2 to 30% by weight and very particularly preferably 5 to 20% by weight of dilution monomer;</li><li>(c) 30.0 to 94.0 weight percent filler;</li><li>(d) 0.01 to 5% by weight, particularly preferably 0.1 to 2.0% by weight, of an initiator for free-radical polymerization and, if appropriate, further auxiliaries.</li></ul>

The filler content depends largely on the intended use of the composite material and is preferably 30 to 60% by weight, particularly preferably 40 to 60% by weight in the case of fastening cements and 60 to 94% by weight, preferably 70 to 85 in the case of filling composites % By weight.

The composite materials preferably contain at least 5% by weight, particularly preferably at least 10% by weight, of monomers containing hydroxyl groups, ie monomers with at least one hydroxyl group per monomer molecule.

The uncured materials can contain up to 1.0% by weight of water without the storage stability of the materials or the mechanical properties of the cured materials being impaired. This considerably facilitates both the manufacture and the processing of the materials by the dentist or dental technician.

The materials according to the invention preferably contain a maximum of 2% by weight of monofunctional monomers, ie monomers with only one unsaturated, polymerizable group, such as 2-hydroxyethyl (meth) acrylate.

The known initiators for cold, hot and photo curing are suitable as initiators for radical polymerization. Suitable initiators are described, for example, in the Encyclopedia of Polymer Science and Engineering, Vol. 13, Wiley-Intersci. Pub., New York etc. 1988, pp. 754 ff.

Preferred initiators are azo compounds such as azobis (isobutyronitrile) (AIBN) or azobis (4-cyanvaleric acid) or peroxides such as dibenzoyl peroxide, dilauroyl peroxide, tert-butyl peroctoate, tert-butyl perbenzoate or di (tert-butyl) peroxide.

Particularly suitable initiators for hot curing are benzpinacol and 2,2'-di (C₁-C₈-alkyl) benzpinacols.

Suitable photoinitiators for the UV or visible range are described by JP Fouassier, JF Rabek (ed.), Radiation Curing in Polymer Science and Technology, Vol. II, Elsevier Applied Science, London and New York 1993, pages 155 to 237. Preferred photoinitiators are benzoin ethers, dialkylbenzyl ketals, dialkoxyacetophenones, acylphosphine oxides, α-diketones such as 10-phenanthrenequinone, diacetyl, furil, anisil, 4,4'-dichlorobenzil and 4,4'-dialkoxybenzil and camphorquinone.

Dibenzoyl peroxide, camphorquinone and acylphosphine oxides are preferred for the production of dental materials.

Suitable fillers are all known ion-releasing fillers for the production of glass ionomer cements. Approx²⁺-, F^-- and / or OH^-ion-releasing fillers, as described in the abovementioned documents or in DE 39 41 629 and US Pat. No. 4,814,362.

Particularly preferred fillers are glass powder of fluoroaluminosilicate glasses with an average particle size of 0.05 to 15 μm, preferably 0.5 to 5.0 μm, which contain silicon oxide, aluminum oxide and calcium oxide as main components (cf. AD Wilson, JW McLean, glass ionomer cement, Quintessence Verlags GmbH, Berlin 1988, pages 21 ff.).

Preferred glasses are made by melting 25 to 45% by weight of SiO₂, 15 to 40 wt .-% Al₂O₃, 0 to 10 wt .-% AlF₃, 0 to 30 wt% CaO, 0 to 10 wt% Na₂0.0 to 15 wt% CaF₂, 0 to 15 wt% NaF and 0 to 25 wt% AlPO₄ receive.

A particularly preferred glass has the following composition: 25% by weight SiO₂, 16.2% by weight of Al₂O₃, 8.8 wt% AlF₃, 12.8 wt% NaF, 13.0 wt% CaF₂ and 24.2 wt% AlPO₄.

Dental materials that release calcium hydroxide or fluoride have proven themselves in dentistry. The controlled release of calcium hydroxide and fluoride promotes the formation of secondary dentin and an alkalizing effect on the pulp, which protects it against acids and bacterial attacks.

However, fillers that release alkaline ions are not compatible with acidic monomers and cause the matrix to spontaneously harden. One-component, calcium hydroxide-releasing composites are therefore either not stable or show only a low ion release when using non-acidic monomers.

The monomers used according to the invention contain no acidic groups and can therefore be combined with alkaline fillers without any problems. For the first time, they allow the production of one-component, calcium hydroxide-releasing composites with a high ion-releasing capacity.

Alkaline fillers include fillers with alkaline components such as CaO, Ca (OH)₂ or Na₂O understood, which show an alkaline reaction in connection with water.

Preferred alkaline fillers are calcium hydroxide, calcium oxide and especially calcium hydroxide-releasing glasses, ie glasses with a high calcium oxide content.

Glasses with a CaO content of at least 20% by weight, preferably 40 to 75% by weight and in particular 45 to 60% by weight are preferred.

A preferred glass powder with a high calcium oxide content is described in EP 0 449 399 B1 and contains 40 to 75% by weight, preferably 45 to 60% by weight calcium oxide, 5 to 30% by weight, preferably 15 to 28% by weight. % Boron oxide and 5 to 35 wt .-%, preferably 10 to 30 wt .-% silicon dioxide. The average particle size (weight average) of the glass powder is between 1 and 100 μm, preferably 10 and 30 μm.

Further preferred are transparent glasses with high calcium and fluorine ion release, which contain the following components: <tables id="tabl0001" num="0001"><table frame="all"><tgroup cols="2" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><thead valign="top"><row rowsep="1"><entry namest="col1" nameend="col1" align="center">component</entry><entry namest="col2" nameend="col2" align="center">% By weight</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">SiO₂</entry><entry namest="col2" nameend="col2" align="char" char=",">24.0 to 56.0</entry></row><row><entry namest="col1" nameend="col1" align="left">CaO</entry><entry namest="col2" nameend="col2" align="char" char=",">26.0 to 57.0</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">F</entry><entry namest="col2" nameend="col2" align="char" char=",">4.0 to 14.0.</entry></row></tbody></tgroup></table></tables>

The transparent glasses used according to the invention preferably additionally contain at least one of the following components <tables id="tabl0002" num="0002"><table frame="all"><tgroup cols="2" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><thead valign="top"><row rowsep="1"><entry namest="col1" nameend="col1" align="left">component</entry><entry namest="col2" nameend="col2" align="left">% By weight</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" /></row><row><entry namest="col1" nameend="col1" align="left">N / A₂O</entry><entry namest="col2" nameend="col2" align="left">1.0 to 9.0</entry></row><row><entry namest="col1" nameend="col1" align="left">B₂O₃</entry><entry namest="col2" nameend="col2" align="left">1.0 to 14.0</entry></row><row><entry namest="col1" nameend="col1" align="left">MgO</entry><entry namest="col2" nameend="col2" align="left">1.0 to 14.0</entry></row><row><entry namest="col1" nameend="col1" align="left">SrO</entry><entry namest="col2" nameend="col2" align="left">1.0 to 12.0</entry></row><row><entry namest="col1" nameend="col1" align="left">ZnO</entry><entry namest="col2" nameend="col2" align="left">1.0 to 7.0</entry></row><row><entry namest="col1" nameend="col1" align="left">Al₂O₃</entry><entry namest="col2" nameend="col2" align="left">0.5 to 5.0</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">ZrO₂</entry><entry namest="col2" nameend="col2" align="left">0.5 to 4.0.</entry></row></tbody></tgroup></table></tables>

Preferred quantity ranges exist for the individual components of the transparent glasses. These can be chosen independently and are as follows<tables id="tabl0003" num="0003"><table frame="all"><tgroup cols="2" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><thead valign="top"><row rowsep="1"><entry namest="col1" nameend="col1" align="left">component</entry><entry namest="col2" nameend="col2" align="left">% By weight</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" /></row><row><entry namest="col1" nameend="col1" align="left">SiO₂</entry><entry namest="col2" nameend="col2" align="left">30.0 to 54.0, especially 36.0 to 54.0</entry></row><row><entry namest="col1" nameend="col1" align="left">CaO</entry><entry namest="col2" nameend="col2" align="left">32.0 to 50.0</entry></row><row><entry namest="col1" nameend="col1" align="left">F</entry><entry namest="col2" nameend="col2" align="left">5.0 to 12.0</entry></row><row><entry namest="col1" nameend="col1" align="left">N / A₂O</entry><entry namest="col2" nameend="col2" align="left">1.0 to 8.0</entry></row><row><entry namest="col1" nameend="col1" align="left">B₂O₃</entry><entry namest="col2" nameend="col2" align="left">1.0 to 12.0</entry></row><row><entry namest="col1" nameend="col1" align="left">MgO</entry><entry namest="col2" nameend="col2" align="left">1.0 to 10.0</entry></row><row><entry namest="col1" nameend="col1" align="left">SrO</entry><entry namest="col2" nameend="col2" align="left">1.0 to 10.0</entry></row><row><entry namest="col1" nameend="col1" align="left">ZnO</entry><entry namest="col2" nameend="col2" align="left">1.0 to 5.0</entry></row><row><entry namest="col1" nameend="col1" align="left">Al₂O₃</entry><entry namest="col2" nameend="col2" align="left">0.5 to 4.0</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">ZrO₂</entry><entry namest="col2" nameend="col2" align="left">0.5 to 4.0.</entry></row></tbody></tgroup></table></tables>

Particularly preferred quantitative ranges of the components of the transparent glass, which can be selected independently of one another, are as follows <tables id="tabl0004" num="0004"><table frame="all"><tgroup cols="2" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><thead valign="top"><row rowsep="1"><entry namest="col1" nameend="col1" align="left">component</entry><entry namest="col2" nameend="col2" align="left">% By weight</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" /></row><row><entry namest="col1" nameend="col1" align="left">SiO₂</entry><entry namest="col2" nameend="col2" align="left">45.0 to 54.0</entry></row><row><entry namest="col1" nameend="col1" align="left">CaO</entry><entry namest="col2" nameend="col2" align="left">35.0 to 50.0</entry></row><row><entry namest="col1" nameend="col1" align="left">F</entry><entry namest="col2" nameend="col2" align="left">6.0 to 12.0</entry></row><row><entry namest="col1" nameend="col1" align="left">N / A₂O</entry><entry namest="col2" nameend="col2" align="left">4.0 to 7.0</entry></row><row><entry namest="col1" nameend="col1" align="left">B₂O₃</entry><entry namest="col2" nameend="col2" align="left">1.0 to 12.0</entry></row><row><entry namest="col1" nameend="col1" align="left">MgO</entry><entry namest="col2" nameend="col2" align="left">1.0 to 10.0</entry></row><row><entry namest="col1" nameend="col1" align="left">SrO</entry><entry namest="col2" nameend="col2" align="left">1.0 to 10.0</entry></row><row><entry namest="col1" nameend="col1" align="left">ZnO</entry><entry namest="col2" nameend="col2" align="left">1.0 to 5.0</entry></row><row><entry namest="col1" nameend="col1" align="left">Al₂O₃</entry><entry namest="col2" nameend="col2" align="left">0.5 to 4.0</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">ZrO₂</entry><entry namest="col2" nameend="col2" align="left">0.5 to 4.0.</entry></row></tbody></tgroup></table></tables>

All the amounts of the components of the transparent fluorine-containing glasses indicated above and in the description and the claims below are to be understood as values ​​which were obtained as follows. The amounts of the oxides were determined by quantitative determination of the corresponding cations, ie Si, Ca, Na, B, Mg, Sr, Zn and Al, by means of X-ray fluorescence analysis and conversion of the values ​​obtained into the amounts of corresponding oxides. The content of a cation is thus used to infer the content of the corresponding oxides. In contrast, the amount of F^- determined directly by means of an electrode selective for fluoride ions after the glass had been subjected to a soda-potash digestion.

Due to the high F content of the transparent glasses, fluorides such as CaF are formed to a noticeable extent₂, in the glass. Therefore the calculated oxide content and therefore the absolute oxygen content of the glass are too high and the sum of the components exceeds 100%. The proportion exceeding 100% is therefore shown as so-called "fluorine-equivalent oxygen". This is customary for fluoride-containing silicate glasses and is described in detail, for example, in J. Lange "Raw Materials in the Glass Industry", German publisher for basic material industry, Leipzig, Stuttgart (1993), pp. 221-223.

It is common practice in glass production to add small amounts of fluoride as a flux in order to improve the melting behavior of the respective glass. However, these small amounts of fluorine do not significantly change the overall structure of the glasses.

In contrast, a high fluorine content of at least 4.0% by weight is built into the transparent glass used according to the invention, which changes the basic structure of the glass significantly compared to corresponding glasses which are free of fluorine or have only low fluorine contents due to the flux used. Due to this high proportion of fluorine and the simultaneous incorporation of further network converter ions, such as Ca.²⁺ or Na⁺ there is a strong degradation of the SiO₄-Tetrahedron network structure of the glass. The result is a glass structure that can no longer be explained with classic network theory. The glass structure is approaching a new glass structure called "invert glass structure". An inverted glass is a glass that has less than 50 mol% of network former.

As a result of the changed structure, above all the refractive index of the glass changes, and surprisingly it is also possible to release fluorine ions while simultaneously releasing calcium ions from the glass. When the composite material is used in the dental field, the desired alkaline effect can be produced in the oral cavity by the calcium ions together with carbonate in the saliva and the known remineralizing effect by the fluorine ions. Calcium ions also promote the remineralization process.

Furthermore, the high fluoride content of the glass brings about a sharp reduction in its refractive index to values ​​below 1.60 and preferably below 1.56. The organic matrix of the composite material formed by curing the polymerizable monomer has a very similar refractive index, which is why the entire composite material can also be translucent or even transparent. This is of course of particular advantage if the composite material is to be used for the production of visible dental restorations, which should naturally have similar optical properties to translucent natural dental material.

To produce the transparent glass used according to the invention, corresponding raw materials, in particular oxides, carbonates and fluorides, are mixed and melted into a glass at temperatures of in particular 1000 to 1600 ° C. The resulting glass melt is then quenched by pouring it into water. The transparent glass frit obtained is then ground, dried and can then be combined with polymerizable monomer to form the polymerizable composite material according to the invention.

The glass is usually used as a powder, the average size of the particles usually being 1 to 100 μm and preferably 10 to 30 μm based on the number of particles.

The above-mentioned ion-releasing fillers can be combined with other fillers, the proportion of the ion-releasing fillers being at least 5% by weight, preferably 15 to 70% by weight.

Amorphous, spherical materials based on mixed oxides of SiO are particularly suitable as further filler components₂, ZrO₂ and / or TiO₂ with an average average particle size of 0.005 to 2.0 µm, preferably 0.1 to 1 µm, as disclosed for example in DE-PS 32 47 800, microfine fillers, such as pyrogenic silica or precipitated silica, and macro or mini Fillers such as quartz, glass ceramic or glass powder with an average particle size of 0.01 to 20 μm, preferably 0.5 to 5 μm, and radiopaque fillers such as ytterbium fluoride. Mini-fillers are fillers with a particle size of 0.5 to 1.5 µm and macro-fillers are fillers with a particle size of 10 to 20 µm.

In addition, the compositions according to the invention can, if necessary, contain further auxiliaries, in particular stabilizers, UV absorbers, dyes, pigments and / or lubricants. Stabilizers are understood to mean those substances which prevent premature polymerization and thus above all increase the storage stability of monomer mixtures and composites without, however, impairing the properties of the cured materials. Preferred stabilizers are hydroquinone monomethyl ether (MEHQ) and 2,6-di-tert-butyl-4-methylphenol (BHT).

It has surprisingly been found that the simultaneous use of the above-mentioned crosslinking and diluting monomers enables compositions with a high ion-releasing ability to be obtained which, in the uncured state, are stable in storage even under moist conditions and whose mechanical properties are not significantly impaired by water accumulation. The monomer mixtures according to the invention can be processed without problems with alkaline fillers to form one-component composites.

The invention is explained in more detail below on the basis of exemplary embodiments.

<b>Examples 1 to 5</b>

As starting materials for the production of hydrophilic composites, monomer mixtures with the compositions given in Table 1 were produced and then further processed into the one-component composite pastes shown in Table 2. <tables id="tabl0005" num="0005"><table frame="all"><title>Table 1</title><tgroup cols="6" colsep="1" rowsep="1"><colspec colnum="1" colname="col1" colwidth="26.25mm" /><colspec colnum="2" colname="col2" colwidth="26.25mm" /><colspec colnum="3" colname="col3" colwidth="26.25mm" /><colspec colnum="4" colname="col4" colwidth="26.25mm" /><colspec colnum="5" colname="col5" colwidth="26.25mm" /><colspec colnum="6" colname="col6" colwidth="26.25mm" /><thead valign="top"><row rowsep="1"><entry namest="col1" nameend="col6" align="center"><b>Composition of the monomer mixtures</b></entry></row><row><entry namest="col1" nameend="col1" rowsep="0" align="center">Monomer</entry><entry namest="col2" nameend="col6" align="center">Mixture (in mass.%)</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" /><entry namest="col2" nameend="col2" align="center">1</entry><entry namest="col3" nameend="col3" align="center">2^*)</entry><entry namest="col4" nameend="col4" align="center">3</entry><entry namest="col5" nameend="col5" align="center">4^*)</entry><entry namest="col6" nameend="col6" align="center">5^*)</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="center">Bis-GMA¹⁾</entry><entry namest="col2" nameend="col2" align="center">39,0</entry><entry namest="col3" nameend="col3" align="center">42,0</entry><entry namest="col4" nameend="col4" align="center">42,0</entry><entry namest="col5" nameend="col5" align="center">42,0</entry><entry namest="col6" nameend="col6" align="center">42,0</entry></row><row><entry namest="col1" nameend="col1" align="center">UDMA²⁾</entry><entry namest="col2" nameend="col2" align="center">30,0</entry><entry namest="col3" nameend="col3" align="center">37,1</entry><entry namest="col4" nameend="col4" align="center">27,8</entry><entry namest="col5" nameend="col5" align="center">27,8</entry><entry namest="col6" nameend="col6" align="center">27,8</entry></row><row><entry namest="col1" nameend="col1" align="center">GDMA³⁾</entry><entry namest="col2" nameend="col2" align="center">30,0</entry><entry namest="col3" nameend="col3" align="center">-</entry><entry namest="col4" nameend="col4" align="center">29,4</entry><entry namest="col5" nameend="col5" align="center">-</entry><entry namest="col6" nameend="col6" align="center">-</entry></row><row><entry namest="col1" nameend="col1" align="center">TEGDMA⁴⁾</entry><entry namest="col2" nameend="col2" align="center">-</entry><entry namest="col3" nameend="col3" align="center">20,1</entry><entry namest="col4" nameend="col4" align="center">-</entry><entry namest="col5" nameend="col5" align="center">29,4</entry><entry namest="col6" nameend="col6" align="center">-</entry></row><row><entry namest="col1" nameend="col1" align="center">HEMA⁵⁾</entry><entry namest="col2" nameend="col2" align="center">-</entry><entry namest="col3" nameend="col3" align="center">-</entry><entry namest="col4" nameend="col4" align="center">-</entry><entry namest="col5" nameend="col5" align="center">-</entry><entry namest="col6" nameend="col6" align="center">29,4</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="center">Initiator / additives⁶⁾</entry><entry namest="col2" nameend="col2" align="center">1,0</entry><entry namest="col3" nameend="col3" align="center">0,8</entry><entry namest="col4" nameend="col4" align="center">0,8</entry><entry namest="col5" nameend="col5" align="center">0,8</entry><entry namest="col6" nameend="col6" align="center">0,8</entry></row></tbody></tgroup><tgroup cols="6" colsep="0" rowsep="0"><colspec colnum="1" colname="col1" colwidth="26.25mm" /><colspec colnum="2" colname="col2" colwidth="26.25mm" /><colspec colnum="3" colname="col3" colwidth="26.25mm" /><colspec colnum="4" colname="col4" colwidth="26.25mm" /><colspec colnum="5" colname="col5" colwidth="26.25mm" /><colspec colnum="6" colname="col6" colwidth="26.25mm" /><tbody valign="top"><row><entry namest="col1" nameend="col6" align="justify">^*) Comparative example</entry></row><row><entry namest="col1" nameend="col6" align="justify">¹⁾ Bisphenol A glycidyl methacrylate (Essehem)</entry></row><row><entry namest="col1" nameend="col6" align="justify">²⁾ 7,7,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diyl-dimethacrylate (from Ivoclar)</entry></row><row><entry namest="col1" nameend="col6" align="justify">³⁾ Glycerol dimethacrylate (from Röhm)</entry></row><row><entry namest="col1" nameend="col6" align="justify">⁴⁾ Triethylene glycol dimethacrylate (Esschem)</entry></row><row><entry namest="col1" nameend="col6" align="justify">⁵⁾ 2-hydroxyethyl methacrylate (from Röhm)</entry></row><row><entry namest="col1" nameend="col6" align="justify">⁶⁾ Initiator: camphorquinone; accelerator: N- (2-cyanoethyl) -N-methylaniline; inhibitor; hydroquinone monomethyl ether</entry></row></tbody></tgroup></table></tables><tables id="tabl0006" num="0006"><table frame="all"><title>Table 2</title><tgroup cols="6" colsep="1" rowsep="1"><colspec colnum="1" colname="col1" colwidth="26.25mm" /><colspec colnum="2" colname="col2" colwidth="26.25mm" /><colspec colnum="3" colname="col3" colwidth="26.25mm" /><colspec colnum="4" colname="col4" colwidth="26.25mm" /><colspec colnum="5" colname="col5" colwidth="26.25mm" /><colspec colnum="6" colname="col6" colwidth="26.25mm" /><thead valign="top"><row rowsep="1"><entry namest="col1" nameend="col6" align="center"><b>Composition of the composite pastes</b></entry></row><row><entry namest="col1" nameend="col1" rowsep="0" align="left">component</entry><entry namest="col2" nameend="col6" align="center">Composite (in% by mass)</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" /><entry namest="col2" nameend="col2" align="center">1</entry><entry namest="col3" nameend="col3" align="center">2^*)</entry><entry namest="col4" nameend="col4" align="center">3</entry><entry namest="col5" nameend="col5" align="center">4^*)</entry><entry namest="col6" nameend="col6" align="center">5^*)</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">Monomer mixture₁₎</entry><entry namest="col2" nameend="col2" align="center">22,0</entry><entry namest="col3" nameend="col3" align="center">22,1</entry><entry namest="col4" nameend="col4" align="center">22,3</entry><entry namest="col5" nameend="col5" align="center">22,3</entry><entry namest="col6" nameend="col6" align="center">22,3</entry></row><row><entry namest="col1" nameend="col1" align="left">Alkali glass, sil.²⁾</entry><entry namest="col2" nameend="col2" align="center">48,0</entry><entry namest="col3" nameend="col3" align="center">52,2</entry><entry namest="col4" nameend="col4" align="center">-</entry><entry namest="col5" nameend="col5" align="center">-</entry><entry namest="col6" nameend="col6" align="center">-</entry></row><row><entry namest="col1" nameend="col1" align="left">SP-2034, sil.³⁾</entry><entry namest="col2" nameend="col2" align="center">11,0</entry><entry namest="col3" nameend="col3" align="center">-</entry><entry namest="col4" nameend="col4" align="center">60,1</entry><entry namest="col5" nameend="col5" align="center">60,1</entry><entry namest="col6" nameend="col6" align="center">60,1</entry></row><row><entry namest="col1" nameend="col1" align="left">YbF₃ ⁴⁾</entry><entry namest="col2" nameend="col2" align="center">12,0</entry><entry namest="col3" nameend="col3" align="center">10,0</entry><entry namest="col4" nameend="col4" align="center">11,6</entry><entry namest="col5" nameend="col5" align="center">11,6</entry><entry namest="col6" nameend="col6" align="center">11,6</entry></row><row><entry namest="col1" nameend="col1" align="left">Aerosil-OX-50®, silanized⁵⁾</entry><entry namest="col2" nameend="col2" align="center">4,0</entry><entry namest="col3" nameend="col3" align="center">3,8</entry><entry namest="col4" nameend="col4" align="center">-</entry><entry namest="col5" nameend="col5" align="center">-</entry><entry namest="col6" nameend="col6" align="center">-</entry></row><row><entry namest="col1" nameend="col1" align="left">Sphärosil® sil.⁶⁾</entry><entry namest="col2" nameend="col2" align="center">-</entry><entry namest="col3" nameend="col3" align="center">-</entry><entry namest="col4" nameend="col4" align="center">6,0</entry><entry namest="col5" nameend="col5" align="center">6,0</entry><entry namest="col6" nameend="col6" align="center">6,0</entry></row><row><entry namest="col1" nameend="col1" align="left">HDK-2000⁷⁾</entry><entry namest="col2" nameend="col2" align="center">3,0</entry><entry namest="col3" nameend="col3" align="center">2,4</entry><entry namest="col4" nameend="col4" align="center">-</entry><entry namest="col5" nameend="col5" align="center">-</entry><entry namest="col6" nameend="col6" align="center">-</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">Ba glass sil. (GM 27884)⁸⁾</entry><entry namest="col2" nameend="col2" align="center">-</entry><entry namest="col3" nameend="col3" align="center">9,5</entry><entry namest="col4" nameend="col4" align="center">-</entry><entry namest="col5" nameend="col5" align="center">-</entry><entry namest="col6" nameend="col6" align="center">-</entry></row></tbody></tgroup><tgroup cols="6" colsep="0" rowsep="0"><colspec colnum="1" colname="col1" colwidth="26.25mm" /><colspec colnum="2" colname="col2" colwidth="26.25mm" /><colspec colnum="3" colname="col3" colwidth="26.25mm" /><colspec colnum="4" colname="col4" colwidth="26.25mm" /><colspec colnum="5" colname="col5" colwidth="26.25mm" /><colspec colnum="6" colname="col6" colwidth="26.25mm" /><tbody valign="top"><row><entry namest="col1" nameend="col6" align="justify">¹⁾ the monomer mixtures listed in Table 1 were used, composite 1 is based on monomer mixture 1, etc.</entry></row><row><entry namest="col1" nameend="col6" align="justify">²⁾ silanized alkaline glass with 47.4% by weight SiO_2, 39.8% by weight CaO, 8.4% by weight Na₂O, 7.6 wt% F^-</entry></row><row><entry namest="col1" nameend="col6" align="justify">³⁾ silanized glass ionomer-fluor-calcium-aluminum-silicate glass, average grain size 1.6 µm</entry></row><row><entry namest="col1" nameend="col6" align="justify">⁴⁾ Ytterbium fluoride (Rhone-Poulenc)</entry></row><row><entry namest="col1" nameend="col6" align="justify">⁵⁾ silanized pyrolysis silica (from Degussa) primary particle size 40 nm, BET surface 50 m²/G</entry></row><row><entry namest="col1" nameend="col6" align="justify">⁶⁾ silanized SiO₂-ZrO₂-Mixed oxide (Tokoyama Soda), secondary grain size &lt;7 µm</entry></row><row><entry namest="col1" nameend="col6" align="justify">⁷⁾ finely divided precipitated silica (from Wacker)</entry></row><row><entry namest="col1" nameend="col6" align="justify">⁸⁾ silanized barium aluminosilicate glass powder (Schott), proportion with a grain size &lt;7 µm: 99%</entry></row></tbody></tgroup></table></tables>

Test specimens were formed from the composite pastes in accordance with ISO standard 4049 (1988), hardened by irradiation with light at a wavelength of 400-500 nm (2 × 3 minutes) and their mechanical properties were then determined.

To determine the fluoride release capacity, hardened test specimens (diameter = 20 mm, H = 1.5 mm) were stored in 30 ml buffer solution at 37 ° C in a shaker and the amount of fluoride released was measured with a fluorine electrode after certain time intervals.

The results summarized in Table 3 show that the hydrophilic composite 1, which contains no acidic or ionic monomer components, releases about ten times more fluoride ions within 28 days than Compoglass®, a commercially available compomer based on COOH-acidic monomers (filler: SP-2034 and YbF₃). The fluoride ion release of composite 1 is therefore of the same order of magnitude as that of glass ionomer cements (see, for example, Vivaglass®, glass ionomer cement based on polyacrylic acid, filler: SP-2034 and YbF₃).

Composite 1, however, has significantly better mechanical properties and a higher water resistance than the compomer and the glass ionomer cement. Even storing it in water for six days and then boiling it for 24 hours hardly affects the mechanical properties.

Unhardened composite 1 was stable in storage under moist conditions (90% atmospheric humidity) over the investigation period of 8 weeks.

If the hydrophilic GDMA in composite 1 is replaced by the hydrophobic TEGDMA (composite 2), a significantly lower fluoride release is measured, although composite 2 contains a larger proportion of alkali glass instead of SP-2034, which shows a significantly higher fluoride release than SP-2034.

Composite 3 contains only SP-2034 as an ion-releasing filler. Its fluoride release is comparable to that of Compoglass®, however, in contrast to Compoglass®, Composite 3 is stable in storage even in humid conditions in the uncured state.

In composite 4, GDMA was replaced by TEGDMA. As in the case of composites 1 and 2, this exchange significantly reduces the fluoride release.

In composite 5, the hydrophilic but monofunctional HEMA was used instead of GDMA. Composite 5 shows a significantly higher fluoride release than composite 4, but the mechanical properties after water accumulation are unsatisfactory.<tables id="tabl0007" num="0007"><img file="EP0923926A2_D0001.tif" /></tables>