DE20304797U1 - Addition-curing silicone impression materials with high final hardness - Google Patents

Description

Addition-curing silicone impression materials with high

Final hardness

The invention relates to addition-curing silicone impression materials based on polyorganosiloxanes, which achieve a high final hardness and are particularly suitable as dental materials.

In the dental field, i.e. in dental and dental technology applications, it is often desirable to use materials with a high final hardness. For example, hard materials are used as temporary and permanent filling materials, crown and bridge materials, cements and preferably as materials for bite registration.

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The bite registration materials mentioned as preferred are used by the dentist to fix the correct position of the upper and lower jaws in relation to each other. This position of the upper and lower jaws in relation to each other is then transferred to the model in the dental laboratory. This model is the basis for further work in the dental laboratory, and the requirements for the precision of this model are correspondingly high.

The following requirements apply to a bite registration material:

1) High final hardness and low elasticity The final hardness essentially determines the precision of a bite registration, because this high final hardness prevents vertical and horizontal displacements when transferring to the model in the dental laboratory. Further processing of the bite registration with the milling machine and scalpel is also simplified by the high final hardness.

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2) Long processing time with a short overall residence time in the patient’s mouth

The processing time should be long enough to cover the patient's entire row of teeth with the material and still achieve a uniform bite registration (at least 3 0 seconds). The time of maximum intercuspation should also be as short as possible to avoid displacement of the jaw during the setting phase. The total time the material remains in the patient's mouth from the start of mixing should not exceed 90 seconds.

3) Fracture behaviour

Excess material should be able to be broken off in the patient's mouth in order to check the correct bite registration.

4) Ease of use

Dosing and mixing should be as easy as possible for the dentist and should not require a great deal of effort. In particular, the material should be thixotropic to prevent it from flowing down the row of teeth, but it should be able to flow easily under the delivery pressure.

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5) Dimensional stability

The bite registration material should be dimensionally stable, i.e. not shrink, in order to enable the precise repositioning of the upper and lower jaw after transport from the dental practice to the dental laboratory.

6) Storage stability

The desired properties of a bite registration material should remain stable over a longer period of time.

For example, DE 4 122 310/EP 0 522 341 discloses a transparent silicone impression material that can be used as a bite registration material and achieves a final hardness of over 7 0 Shore A by using short-chain, vinyl-terminated polyorganosiloxanes of the general formula CH ₂ = CH-SiR ₂ O-(SiR ₂ O) _n -SiR ₂ -CH=CH ₂ with n=10-20 and by adding a new compound made of vinyl-terminated polyorganosiloxane and reinforcing filler. However, such a material is unsuitable for producing a precise bite registration due to its elastic properties and insufficient final hardness.

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EP O 894 117 describes the production of addition-curing silicone impression materials with a very high final hardness in the Shore D range and with a very high modulus of elasticity. A very short-chain, vinyl-stopped polyorganosiloxane of the general formula CH ₂ = CH-SiR ₂ O-(SiR ₂ O) _n -SiR ₂ -CH=CH ₂ with n=21-69 is used in combination with a vinyl-rich QM resin and reinforcing fillers. In addition to the high final hardness, the total residence time in the patient's mouth of 90 seconds is advantageous.

WO 99/09934 presents hardenable materials for dental applications that combine a very high final hardness with short setting times. A new class of compounds is used, the silane dendrimers, which, despite the high content of functional groups, are said to have the two positive properties mentioned for dental materials. The disadvantage is that the synthesis of the dendrimers is very complex. Larger quantities of these compounds, which are required for the production of dental impression materials, especially for very hard bite registration materials, have to be produced in a very complex manner.

In order to achieve the desired high final hardness, the following solutions are always used in the above-mentioned patent documents and thus according to the state of the art:

- Increasing the filler content of the masses

- Use of reinforcing fillers or compounds containing such fillers

- Increasing the functionality of the reactive components of the masses

- Reduction of the chain length of the reactive components of the masses

By increasing the filler content and by using reinforcing fillers and compounds made from polyorganosiloxanes and reinforcing fillers, the mechanical properties of the cured silicone materials are improved, especially the elasticity of the material is increased. This is a disadvantage for the preferred use of silicone impression material for bite registration because of possible vertical and horizontal shifts during repositioning in the dental laboratory. In addition, such raw materials are known to increase the viscosity

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of silicone impression materials, so that the force required to convey the material from the commonly used double cartridge systems with static mixer becomes very high. When choosing the appropriate mixing cannula to convey the material, the user is therefore limited to the larger mixing cannulas with a larger volume.

The use of vinyl-containing polyorganosiloxanes, which have not only terminal but also lateral functionalities, i.e. vinyl groups, can increase the final hardness of the silicone impression materials, but they have the major disadvantage that they also contain vicinal, i.e. neighboring vinyl groups. It is known from the state of the art that vicinal vinyl groups inhibit the reaction time of the hydrosilylation reaction under precious metal catalysis. However, the bite registration materials should be characterized by a maximum residence time of the material in the patient's mouth of 90 seconds. This goal is not achieved in this way.

Very short-chain vinyl-terminated polyorganosiloxanes of the general formula CH ₂ = CH-SiR ₂ O-(SiR ₂ O) _n -SiR ₂ -CH=CH ₂

with &eegr;=0-6 and R= identical or different monovalent, unsaturated, optionally substituted hydrocarbons (mostly methyl groups) are known from DE-A-2 646 726 as inhibitors for regulating the crosslinking speed in the reaction of addition-curing silicone materials. Even with very short-chain functional polyorganosiloxanes, a very high final hardness can be achieved, but this is done at the expense of an undesirable extension of the setting time and thus the total time the material remains in the patient's mouth when used as a bite registration material.

Dental impression materials and bite registration materials based on polyorganosiloxanes have been known for many years (see, for example, R.G.Craig: Restorative Dental Materials, CV. Moosbe-Comp. , St. Louis 1980). According to the state of the art, the composition of these materials essentially consists of the following raw materials:

a) Organopolysiloxanes with two or more vinyl groups in the molecule (terminal and/or pendant) and viscosities in the range of 100-350,000 mPas

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b) Organopolysiloxanes of the general formula CH ₂ = CH-SiR ₂ O-(SiR ₂ O) _n -SiR ₂ -CH=CH ₂ with R= identical or different monovalent, unsaturated, optionally substituted hydrocarbons (mostly methyl groups) n= 10-69

c) Low molecular weight vinyl and ethoxy group-containing QM resins

d) Catalysts to accelerate addition crosslinking (hydrosilylation)

e) Organohydrogenpolysiloxanes with at least two SiH groups in the molecule

f) Reinforcing fillers

g) Non-reinforcing fillers
h) Dyes

i) Inhibitors

According to the state of the art, such addition-curing materials consist of two components (A and B components or also called catalyst and base components), which must be stored separately and, after homogeneous mixing (mixing ratio usually 1:1), crosslink in a noble metal-catalyzed hydrosilylation reaction. The homogeneous mixture of the two components

is done either by strand length dosing and manual mixing or via a double cartridge system with static mixer.

Such a double cartridge system is available from the company Mixpack, for example, and contains two separate chambers, each with a volume of 25 ml. Differently sized mixing cannulas are available as static mixers for the different viscosities and consistencies of the silicone impression materials. The bite registration materials available on the market are - for the reasons described above - of such a high viscosity that they can only be conveyed using a large mixing cannula without too much effort.

The aim of this invention is therefore to provide addition-curing 2-component silicone impression materials for use in the dental field, preferably for use as

To provide bite registration materials that combine the following advantageous properties:

- Achieving a high final hardness in the Shore D range and a high elastic modulus

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- easy processing for the user in terms of viscosity and thixotropy

- easy conveying and homogeneous mixing of the material from the commercially available double cartridge systems, also through smaller mixing cannulas than previously available on the market, thus also saving material

- faster setting behavior, the total time the material remains in the patient's mouth should be a maximum of seconds, preferably a maximum of 80 seconds from the start of mixing. The processing time should still be at least 3 0 seconds

- easy to work with a milling machine and scalpel, targeted breaking off of the material in the patient's mouth should be possible

- good storage stability in standard hand packaging.

This goal is achieved with an addition-curing 2-component silicone impression material with the following composition, whereby surprisingly the use of very short-chain, terminal-functional polyorganosiloxanes and reinforcing fillers can be completely dispensed with. All information is in percent by weight based on the total mass of the material (i.e. catalyst and base component).

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a) 1-90 wt.% preferably 5-20 wt.% organopolysiloxanes with two terminal vinyl groups

b) 1-90 wt.%, preferably 5-20 wt.%, low molecular weight QM resin containing vinyl and ethoxy groups

c) 1-10 wt.% organohydrogenpolysiloxanes with at least two SiH groups in the molecule

d) 0.005-2 wt.% preferably 0.01-1 wt.% catalysts to accelerate the hydrosilylation reaction

e) 1-90 wt.% preferably 20-70 wt.% non-reinforcing fillers

f) 0-10 wt.% moisture binder

g) 0-10 wt.% other additives and auxiliaries h) 0-2 wt.% preferably 0.5-1 wt.% dyes i) 0-1 wt.% preferably 0-0.1 wt.% inhibitors

The organopolysiloxanes a) are known vinyl-terminated polydimethylsiloxanes with viscosities in the range of 100-165,000 mPas, preferably in the range of 200-10,000 mPas.

The QM resins b) according to the invention are described in W.NoIl, Chemistry and Technology of Silicones, Verlag Chemie, Weinheim, 2nd edition 1968 and contain as Q units the tetrafunctional SiO _4/2 and as M building blocks the

monofunctional R ₃ SiO _1/2 , where R can be vinyl, methyl, ethyl, phenyl. Furthermore, trifunctional RSiO _3/2 can be present as T units and the difunctional R ₂ SiO ₂₇₂ can be present as D units. The QM resins used have viscosities of 150-65,000 mPas, preferably 150-3,000 mPas and vinyl contents of 0.2-8 mmol/g, preferably 0.2-2 mmol/g.

The compounds according to c) contain reactive SiH groups which build up the polymer in an addition reaction with the compounds a) and b) under noble metal catalysis. The compounds used are polymethylhydrogensiloxanes with a SiH content in the range from 0.5 to 15 mmol/g, preferably from 2-10 mmol/g. The noble metal catalyst d) is preferably a platinum complex; platinum-siloxane complexes, as already described in US-A-3,715,334, US-A-3,775,352 and US-A-3,814,730, are particularly suitable. The non-reinforcing fillers according to e) have a BET surface area of up to 50m ² /g, these include quartz, cristobalite, diatomaceous earth, kieselguhr, calcium carbonates, talc, zeolites, sodium aluminum silicates, metal oxide and glass powder. These fillers can be hydrophobized by surface treatment.

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According to the state of the art, zeolites, anhydrous aluminium sulphate, molecular sieves, diatomaceous earth and blue gels can be used as moisture binders.

The other additives and auxiliaries g) are surfactants, emulsifiers, stabilizers, thixotropic agents and hydrogen absorbers. The dyes h), which can be used to distinguish between the base and catalyst components and to control the homogeneity of the mixture, are inorganic and/or organic color pigments that can also be used dissolved in polyorganosiloxanes or other solvents.

To control the reactivity, it may be necessary to use inhibitors i). Such inhibitors are known and are described, for example, in US-A-3,933,880. These are usually acetylenically unsaturated alcohols or vinyl-containing, aliphatic or cyclic poly-, oligo-, and disiloxanes.

The masses are preferably formulated in two components to ensure storage stability.

The entire content of noble metal catalyst d) is in the catalyst component, the entire content of SiH compound c) is in the second component, the base component, which is spatially separated from the first component. By mixing the two components, the masses harden in an addition reaction known as hydrosilylation.

The volume ratios of the two components can be 10:1 to 1:10. Volume mixing ratios of 1:1, 4:1 and 5:1 (base to catalyst component) are particularly preferred.

The following examples illustrate the invention in more detail. All parts given are parts by weight.

example 1

In a mixing vessel, 113 parts of vinyl-terminated polydimethylsiloxane with a viscosity of 200 mPas, 85 parts of a polydimethylsiloxane containing both terminal and pendant vinyl groups, 113 parts of a compound of polyorganosiloxane and hydrophobic pyrogenic

Silica, 11 parts of a platinum catalyst and 480 parts of a surface-treated cristobalite are introduced and mixed homogeneously for 30 minutes. The mixture is then degassed for 15 minutes in a vacuum.

Example 2

77 parts of vinyl-terminated polydimethylsiloxane with a viscosity of 200 mPas, 49 parts of a polyorganosiloxane containing both terminal and pendant vinyl groups, 100 parts of a compound of polyorganosiloxane and hydrophobicized pyrogenic silica, 94 parts of a SiH crosslinker with an SiH content of 9.3 mmol/g, 3 parts of dye and 480 parts of a surface-treated cristobalite are placed in a mixing vessel and mixed homogeneously for 30 minutes. The mixture is then degassed for 15 minutes in a vacuum.

Example 3

50 parts of the catalyst component described in Example 1 and 50 parts of the base component described in Example 2 are pumped from a double cartridge and mixed homogeneously using a static mixer. Pumping from the double cartridge requires a great deal of force.

receives a cured molded body with a final hardness of 88 Shore A. The &Egr;-modulus is determined in accordance with EN ISO 178 in a bending test at 16 MPa (dimensions of the test specimens 25 mm, 5 mm, 5 mm, cuboid).

Example 4

77 parts of vinyl-terminated polydimethylsiloxane with a viscosity of 200 mPas, 26 parts of a polydimethylsiloxane containing both terminal and pendant vinyl groups, 326 parts of a compound of polyorganosiloxane and hydrophobicized pyrogenic silica, 9 parts of a platinum catalyst and 11 parts of a surface-treated silica with a BET surface area of 170-200m ² /g are placed in a mixing vessel and mixed homogeneously for 30 minutes. The mixture is then degassed for 15 minutes in a vacuum.

Example 5

In a mixing vessel, 70 parts of vinyl-terminated polydimethylsiloxane with a viscosity of 200 mPas, 24 parts of a polydimethylsiloxane containing both terminal and pendant vinyl groups, 300 parts of a compound of polyorganosiloxane and hydrophobicized pyrogenic silica, 39 parts of a SiH crosslinker with

a SiH content of 7.3 mmol/g, 1 part dye and parts of a surface-treated silica with a BET surface area of 170-200m ² /g and mixed homogeneously for 30 minutes. The mixture is then degassed for 15 minutes in a vacuum.

Example 6

50 parts of the catalyst component described in Example 4 and 50 parts of the base component described in Example 5 are pumped from a double cartridge and mixed homogeneously using a static mixer. Pumping from the double cartridge requires a great deal of force. The product contains a cured molded body with a final hardness of 66 Shore A. The modulus of elasticity is determined in accordance with EN ISO 17 8 in a bending test at approx. 5 MPa (dimensions of the test bodies 25 mm, 5 mm, 5 mm, cuboid).

Example 7 (according to the invention)

In a mixing vessel, 75 parts of vinyl-terminated polydxmethylsiloxane with a viscosity of 200 mPas, parts of a QM quartz containing vinyl and ethoxy groups with a viscosity of 2,000 mPas and a vinyl content of 1.4 mmol/g, 214 parts of a

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surface-treated cristobalite, 44 parts calcium carbonate, 5 parts of a platinum catalyst, 1 part of a zeolite and 1 part of a polyether siloxane as a thixotropic agent and mixed homogeneously for 30 minutes. The mixture is then degassed for 15 minutes in a vacuum.

Example 8 (according to the invention)

26 parts of vinyl-terminated polydimethylsiloxane with a viscosity of 200 mPas, parts of a QM quartz containing vinyl and ethoxy groups with a viscosity of 2,000 mPas and a vinyl content of 1.4 mmol/g, 198 parts of a surface-treated cristobalite, 70 parts of calcium carbonate, 59 parts of a SiH crosslinker mixture with an average SiH content of 7.8 mmol/g, 7 parts of a dye, 1 part of a zeolite, 1 part of a polyethersiloxane as a thixotropic agent and 0.1 part of an inhibitor mixture are placed in a mixing vessel and mixed homogeneously for 30 minutes. The mixture is then degassed in a vacuum for 15 minutes.

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Example 9 (according to the invention)
50 parts of the catalyst component according to the invention described in Example 7 and 50 parts of the base component according to the invention described in Example 8 are pumped from a double cartridge and mixed homogeneously using a static mixer. Pumping from the double cartridge requires only a small amount of force and is also possible using smaller mixing cannulas. A cured molded body is obtained with a final hardness of 51 Shore D. The ε-modulus is determined in a bending test based on EN ISO 178 to be 12 6 MPa (dimensions of the test bodies 25 mm, 5 mm, 5 mm, cuboid).

Example 10 (comparative example )

A commercially available addition-curing silicone material for bite registration is mixed from the double cartridge using a static mixer according to the manufacturer's instructions. The required force is great. A hardened molded body is obtained with a final hardness of 43 Shore D. The ε-modulus is determined in a bending test based on EN ISO 178 at 61 MPa (dimensions of the test bodies 25 mm, 5 mm, 5 mm, cuboid).

Example 11 (comparative example)

A second commercially available addition-curing silicone material for bite registration is mixed from the double cartridge using a static mixer according to the manufacturer's instructions. The required force is great. A hardened molded body is obtained with a final hardness of 45 Shore D. The modulus of elasticity is determined in MPa in a bending test based on EN ISO 17 8 (dimensions of the test bodies 25 mm, 5 mm, 5 mm, cuboid).

It is clear from the above examples that the addition-curing silicone impression material according to the invention, which is preferably used for bite registration, is clearly superior to commercially available materials in terms of its properties that are important for use as a bite registration - final hardness, ε-modulus and ease of delivery from double cartridges. The results are summarized again in Table 1.

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Table 1

Example hardness Total setting B-Module in Fundability i t No. time at 37° C Based on from double EN ISO 178 cartridge- {Bending test) Systems with static mixer 3 88 Shore A 100 seconds 16 MPa difficult eligible 6 66 Shore A 100 seconds 5MPa difficult eligible 9(invented 51 Shore D 8 0 seconds 126MPa difficult dungsge eligible according to) 10 43 Shore D 90 seconds 61 MPa difficult eligible 11 45 Shore D 90 seconds 59 MPa difficult eligible

Claims (3)

1. Addition-curing silicone impression materials based on polyorganosiloxanes, which achieve a high final hardness and are particularly suitable as dental materials, in particular addition-curing 2-component silicone impression material with the following composition: a) 1-90 wt.%, preferably 5-20 wt.% organopolysiloxanes with two terminal vinyl groups b) 1-90 wt.%, preferably 5-20 wt.% low molecular weight QM resin containing vinyl and ethoxy groups c) 1-10 wt.% organohydrogenpolysiloxanes with at least two SiH groups in the molecule d) 0.005-2 wt.%, preferably 0.01-1 wt.% catalysts to accelerate the hydrosilylation reaction e) 1-90 wt.%, preferably 20-70 wt.% non-reinforcing fillers f) 0-10 wt.% moisture binder g) 0-10 wt.% other additives and auxiliaries h) 0-2 wt.%, preferably 0.5-1 wt.% dyes i) 0-1 wt.%, preferably 0-0.1 wt.% inhibitors. 2. Addition-curing 2-component silicone impression material according to claim 1, characterized in that the catalyst component (first component) comprises the entire content of noble metal catalyst and the base component (second component), which is spatially separated from the first component, comprises the entire content of SiH compound. 3. Addition-curing impression material according to one of claims 1 or 2, characterized in that the volume ratio of the two components (base component: catalyst component) is 10:1 to 1:10, preferably 1:1, 4:1 or 5:1.