IE913497A1

IE913497A1 - Hydrophilised impression compositions

Info

Publication number: IE913497A1
Application number: IE349791A
Authority: IE
Inventors: Reiner Voigt; Peter Schwabe; Gottfried Knispel; Roland Flindt
Original assignee: Bayer Ag
Priority date: 1990-10-06
Filing date: 1991-10-04
Publication date: 1992-04-08
Also published as: EP0480238A1; DK0480238T3; ES2056547T3; JPH04272960A; DE59102244D1; ATE108643T1; EP0480238B1; IE64694B1; PT99157B; PT99157A; JP3073285B2; DE4031759A1

Abstract

The present invention relates to hydrophilic polysiloxane-based impression or duplicating compositions which are used, in particular, in dentistry, and to a process for the preparation thereof.

Description

IE 913497 The present invention relates to hydrophilised, poly-siloxane-based impression and duplicating compositions which are used, in particular, in the dental sector, and ,to a process for the preparation thereof.

In particular, the present invention relates to addition-cross linking vinylsilicone pastes for the production of accurate impressions of jaws with teeth, with some teeth and without teeth, and of plaster models. These pastes are cold-vulcanising two-component silicone rubber 10 systems (room temperature vulcanising (RTV)), in which the base paste is mixed with a catalyst paste and cross-linked at room temperature.

Systems of this type are known per se (cf., for example, R. G. Graig, Restorative Dental Materials, The C. V.

Moosbe Company, St. Louis, 1980, pp. 195 ff.).

In general, these compositions comprise a base paste containing a silicone oil, filler and crosslinking agents, and a catalyst paste comprising silicone oil, filler and catalyst. For the various impression methods, 20 the compositions are supplied in various viscosity grades, for example kneadable and high-viscosity compositions for tray applications and medium- and 1ow-viscosity compositions preferably for syringe applications.

On use, equivalent amounts of the base and catalyst Le A 27 766 - 1ft- IE 913497 pastes, preferably 1:1 by weight or volume, are mixed to give a homogeneous composition and applied to the part of the jaw from which the impression is to be taken by syringing and/or by impression tray. After crosslinking 5 by means of a polyaddition reaction, the rubber-like impression is removed from the patient's mouth and subsequently cast using an aqueous slurry of modelling plaster. After the plaster has hardened, a precise reproduction of the jaw situation is attained.

Although the addition-crosslinking silicone impression compositions have excellent dimensional stability, they are, however, hydrophobic. Thus, application of the mixed impression composition to the moist surface of teeth and gums can result in prevention of flow or, in periodontal 15 pockets, can result, due to residual fluid, in unsatisfactory expulsion thereof, so that the crosslinked impression contains defects. On the other hand, it is possible for air bubbles to be trapped when casting the hydrophobic silicone impression using the aqueous plaster 20 slurry due to incompatibility of the surface media; this results in a defective plaster model.

These defect sources can be substantially eliminated by hydrophilising the silicone impression compositions. Thus, US 4,691,039 and US 4,752,633 describe ethoxylated 25 siloxanes, and US 4,657,953 polyether silicones and fluorine-containing silicone compounds, as additives to the silicone compositions. According to DE-A-3,721,784, water-soluble and sparingly soluble proteins can be Le A 27 766 - 2 - IE 913497 employed in combination with ethoxylated siloxanes, fatty alcohols, fatty acids, esters and beeswax derivatives and fluorine-containing compounds. EP-A-0 231 420 describes the addition of water-absorbent/water-adsorbent fillers, 5 such as CaSOA· 1/2 H20, CaCl2, K2SO*, zeolite and molecular sieves in combination with silicopolyethers. US 4,782,101 and EP-A-0 268 347 indicate addition-crosslinking silicone impression compositions which contain, as additives, polyol fatty acid esters and ethoxylated esters and 10 platinum black. The latter functions as a hydrogen adsorber, since reaction of the SiH group-containing crosslinking agent with the OH groups of the hydrophi-lising agent during casting of the crosslinked impression using the aqueous plaster slurry can produce hydrogen, 15 and these gas bubbles result in a defective plaster model.

The present invention relates to hydrophilised additioncrosslinking silicone impression compositions containing additives of selected ethoxylated fatty alcohols which, 20 even without addition of water-soluble or sparingly soluble proteins or water-adsorbent/water-absorbent fillers, have a markedly reduced water wetting angle and give a defect-free plaster model without the addition of platinum black.

The present invention accordingly provides hydrophilised, polysiloxane-based impression compositions which undergo addition-crosslinking at ambient temperature and contain Le A 27 766 - 3 - IE 913497 (a) organopolysiloxanes containing at least two vinyl groups in the molecule, (b) optionally organopolysiloxanes containing no reactive groups, 5 (c) organohydridopolysiloxanes containing two or more Si-H groups in the molecule, (d) a catalyst, (e) fillers and optionally further conventional additives, auxiliaries and colorants, 10 characterised in that they contain, (f) as hydrophilising agent, a specific ethoxylated fatty alcohol and/or a methylated or an acyl a ted ethoxylated fatty alcohol.

Both the base paste and the catalyst paste are prepared 15 by mixing the appropriate components (a) to (f), it being possible for the base paste to contain all the constituents apart from (d) and for the catalyst paste to contain all the constituents apart from (c). The optimum recipe for the desired application can be determined by 20 simple preliminary experiments.

The specific alkoxylated fatty alcohols and acylated alkoxylated fatty alcohols employed according to the invention as hydrophilising agent (f) are straight-chain or branched alcohols having 10 to 16, preferably 12 to 25 14, carbon atoms which have been reacted with 2 to 10 mol of alkylene oxide, preferably with 2 to 10 mol of ethylene oxide or propylene oxide, particularly preferably with 4 to 7 mol of ethylene oxide, and then optionally Le A 27 766 - 4 - IE 91349/ esterified with a C2- to C4-monocarboxylic acid, preferably acetic acid.

Specific examples of hydrophilising agents according to the invention ares 5 C12H250-(CH2-CH2-0)5CH3 C13H270-(CH2-CH2-0)6CH3 C14H290- (CH2-CH2-0) 7ch3 Ci2H250-(CH2CH2-0)5H Ci3H270-(CH2-CH2-0)6H 10 C14H290-(CH2-CH2-0)7H c12h25o- (CH2-CH2-0) 5-co-ch3 Ci3H270- (CH2-CH2-0) 6-co-ch3 c14h29o-( CHz-CH2-0) 3-co-ch3 and mixtures thereof.

These hydrophilising agents are added either to the base paste alone or proportionately to the base paste and the catalyst paste, in amounts of from 0.3 to 5.0% by weight, preferably from 0.5 to 3.0% by weight, based on the total mixture of base paste and catalyst paste.

The following materials are suitable as starting materials for the compositions according to the invention: The silicone oil (a) is a polydimethylsiloxane containing unsaturated hydrocarbon groups, preferably vinyl groups, 25 on at least two silicon atoms and having a viscosity in Le A 27 766 - 5 - t IE 913497 the range from 500 to 200,000 mPa-s at 20eC, depending on the desired viscosity of the formulated pastes.

The silicone oils (b) are trimethylsiloxy-terminated polydimethylsiloxanes having a viscosity of from 50 to 5 2000 mPa-s at 20*C.

The crosslinking agent (c) is a polydimethylsiloxane which contains hydrogen atoms on at least two silicon atoms in its molecule.

The catalyst (d) is preferably a platinum complex pre-10 pared from hexachloroplatinic(IV) acid. These compounds are also known per se. Other platinum compounds which accelerate the addition-crosslinking reaction are also suitable. For example, platinum-siloxane complexes, as described, for example, in US Patent 3,715,334, US Patent 15 3,775,352 and US Patent 3,814,730, are highly suitable.

Fillers (e) are taken to mean finely ground quartz, cristobal ite , calcium sulphate, calcium carbonate, diatoma-ceous earth, precipitated and pyrogenic silica with an untreated or treated surface.

Colorants are employed to differentiate between the base paste and catalyst paste and to monitor mixing. Inorganic and organic colour pigments are usually employed.

In the freshly mixed pasty state, the hydrophilised impression compositions according to the invention have Le A 27 766 - 6 - it good affinity for the moist enamel and the moist gums. In addition, the crosslinked impressions can be cast with the aqueous plaster slurry in the usual time of 30 minutes after removal of the impression from the mouth 5 of the patient, without evolution of hydrogen causing a defective plaster model.

The examples below illustrate the invention, the recipes of the medium-viscosity, addition-crosslinking silicone impression compositions also being representative of low-10 and high-viscosity and kneadable impression compositions and of low-viscosity duplicating compositions. The parts indicated are parts by weight.

Example 1 (Comparison) A base paste is prepared in a kneader by mixing 290 parts 15 of vinyl-terminated polydimethylsiloxane having a viscosity of 10,000 mPa-s at 23eC, 180 parts of SiH group-containing polydimethylsiloxane having a viscosity of 300 mPa-s at 23*C, 515 parts of fine quartz sand, 10 parts of hydrogenated castor oil having a melting point 20 of 85*C and 5 parts of inorganic coloured pigment. During the mixing process, the paste is warmed to a temperature of 95*C and subsequently cooled to room temperature.

The catalyst paste is prepared in a kneader by mixing 463 parts of vinyl-terminated polydimethylsiloxane having a 25 viscosity of 5000 mPa-s at 23°C, 525 parts of fine quartz sand and 10 parts of hydrogenated castor oil having a Le A 27 766 - 7 - IE 913497 melting point of 85eC. The paste is heated to a temperature of 95eC with mixing, cooled to room temperature and subsequently mixed with 2 parts of a complex of platinum and divinyltetramethyldisiloxane.

Examples 2-7 (according to the inventionϊ The composition and preparation of the two pastes is as in Example 1. The following additives are admixed with each 1000 parts of the base paste: Example 2 10 parts C12H250(CH2-CH20)5H 3 10 C12H250(CH2-CH20)5C0-CH3 4 10 C13H270(CH2-CH20)6H 20 C13H270(CH2-CH20)eH 6 10 C13H270(CH2-CH20)6C0-CH3 15 7 20 C13H270(CH2-CH20)6C0-CH3 8 (Comparison) 10 " CeH^-CgH^-OiCI^-CHaO^oH Applications! testing: The prerequisite for the serviceability of the impression compositions is that they satisfy the requirements of the 20 ISO 4823 standard and specification No. 19 of the American Dental Association. In addition, the wetting angle is determined as evidence of the hydrophilicity effect and the scrape strength of the plaster test specimens are determined as evidence of compatibility of 25 the plaster model with the crosslinked impression Le A 27 766 - 8 - IE 91349# compositions. The last two methods are described below: Testing of the scrape strength: 10 g of base paste and 10 g of catalyst paste are mixed homogeneously within 30 seconds at 23eC and 50% relative 5 atmospheric humidity on a mixing block using a spatula and transferred into a grooved block (DIN 13913, Figure 3). The crosslinked silicone disc is removed 15 minutes after commencing mixing and is stored at 23 °C and 50% relative atmospheric humidity for 30 minutes. The sili-10 cone disc is then covered with a plastic ring of the same diameter and a height of 2 cm, which is filled with an aqueous plaster slurry (100 g of Geostone*/23 g of water) and covered with a glass plate. After one hour from mixing the plaster in vacuo, the plaster test specimen is 15 separated from the silicone plate.

In order to simulate scraping with a modelling instrument, a steel ring having a diameter of 4.3 mm and a V-shaped blade is drawn with the ring vertical for 4.8 mm over the plaster surface at a speed of 26 mm/min under 20 loads of 70 g (100 g weight) and 35 g (50 g weight), producing an arc-shaped trace. The width of the trace (chord) is measured under oblique-incident light under a stereomicroscope at a magnification of 20 times using a screw micrometer eyepiece. The measurements are repro-25 ducible with a maximum uncertainty of 15 μπι.

The means of the trace widths are given in μπι. Each mean Le A 27 766 - 9 - IE 913497 is based on three measurements on three adjacent traces. The mean and maximum standard deviation of the means are 8 μΐη and 22 μπι respectively.

Products are regarded as scrape-resistant if the trace 5 widths for both loads are < 300 μπι. Products characterised as "non-scrape-resistant" are those whose trace widths under weight of 100 g is > 400 μΐη.

Measurement of the wetting angle: 20 g of base paste and 20 g of catalyst paste are mixed 10 homogeneously for 30 seconds at 23°C and 50% relative atmospheric humidity on a mixing block using a spatula, packed into a plastic surround measuring 9 x 5 x 0.5 cm bonded to a glass plate, and covered with a polyester film. After 15 minutes from commencing mixing, the 15 crosslinked silicone plate was removed. After storage for 24 hours at 23°C and 50% relative atmospheric humidity, a water drop was placed on the side of the silicone plate facing the glass, and the wetting angle was determined.

By means of the video system, the dynamic wetting 20 behaviour of liquids on solid substrates can be measured directly and evaluated. 49 wetting angle measurements are carried out for 15 seconds. The initial wetting angle was defined as the wetting angle value after 1 second (mean of 3 values). After 13 seconds, the mean of the wetting 25 angle of the last 10 measurements is given (time range from about 11-15 seconds).

Le A 27 766 - 10 - IE 913497 Results r Ex. Hydrophilising agent Plaster test Wetting angle Scrape strength Trace width (μια) t=l sec. t=13 sec. 5 _ 1 None 322117 9912 10013 2 1% £^50 (0^-0^0)^ 357117 7414 4412 3 1% (^50^-0^)5-00-0¼ 364117 7713 4512 4 1% C^TO^-Oy^eH 331113 7915 6213 10 5 2% Ο^τΟ^-Ο^βΗ 344117 5812 3313 6 1% 0^/3((^-0^0)6-00-0¼ 348113 72+3 5312 7 2% 0^/3(0^-0^0)6-00-0¼ 363113 6114 4011 8 1% CgH^-CgH^-OiC^-a^hoH 490114 8413 4814 Le A 27 766 - 11 -

Claims

1. Addition-crosslinking silicone impression compositions containing: (a) organopolysiloxanes containing at least two 5 vinyl groups in the molecule, (b) optionally organopolysiloxanes containing no reactive groups, (c) organopolysiloxanes containing two or more Si-H groups in the molecule, 10 (d) a catalyst, (e) fillers and optionally further conventional additives, auxiliaries and colorants, characterised in that they contain, (f) as hydrophilising agent, an optionally acylated

2. 15 C10— to C16-fatty alcohol which is alkoxylated with 2 to 10 alkoxy units.

3. 2. Silicone impression compositions according to Claim 1, characterised in that the hydrophilising agents are straight-chain or branched C10- to C16-fatty 20 alcohols which have been reacted with from 2 to 10 mol of ethylene oxide or propylene oxide and optionally methylated or esterified with a C£- to C^-monocarboxy1i c acid.

4. 3. Silicone impression compositions according to Claim 25 1, characterised in that the hydrophilising agents are straight-chain or branched C12- to C14-fatty alcohols which have been reacted with from 4 to Le A 27 766 - 12 - IE 913497 7 mol of ethylene oxide and optionally methylated or esterified with acetic acid.

5. 4. Silicone impression compositions according to Claims 1 and 2, characterised in that the hydrophilising 5 agents are added in amounts of from 0.3 to 5.0 per cent by weight, based on the total mixture.

6. 5. Silicone impression compositions according to Claims 1 to 4, for use for making dental, mucous membrane and model impressions.

7. 6. Process for the preparation of addition-crosslinking silicone impression compositions containing (a) organopolysiloxanes containing at least two vinyl groups in the molecule, (b) optionally organopolysiloxanes containing no 15 reactive groups, (c) organopolysiloxanes containing two or more Si-H groups in the molecule, (d) a catalyst, (e) fillers and optionally further conventional 20 additives, auxiliaries and colorants and (f) as hydrophilising agent, an optionally acylated C10- to C16-fatty alcohol which is alkoxylated with 2 to 10 alkoxy units, characterised in that a base paste A is prepared by 25 mixing, optionally part amounts of, constituents (a) to (f) with the exception of (d), a catalyst paste B is prepared by mixing constituents (a) to (f), Le A 27 766 - 13 - IE 913497 with the exception of any part amounts of (c), and the ready-for-use impression composition is prepared by mixing equivalent amounts of A and B with one another.

8. 7. An addition-crossiinking silicone impression composition according to Claim 1, substantially as hereinbefore described and exemplified.

9. 8. A process for the preparation of an addition-crosslinking silicone impression composition according to Claim 1, substantially as hereinbefore described and exemplified.

10. 9. An addition-crosslinking silicone impression composition according to Claim 1, whenever prepared by a process claimed in Claim 6 or 8. Dated this the 4th day of October, 1991 F. R. KELLY & CO. BY: ---"EXECUTIVE

11. 27. Clyde RBallsbridge, Dublin 4 AGENTS FOR THE APPLICANTS Le A 27 766 - 14 -