IE64694B1

IE64694B1 - Hydrophilised impression compositions

Info

Publication number: IE64694B1
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: 1995-08-23
Also published as: ES2056547T3; EP0480238B1; PT99157A; DE4031759A1; EP0480238A1; DE59102244D1; JPH04272960A; PT99157B; IE913497A1; ATE108643T1; DK0480238T3; JP3073285B2

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

- 1 The present invention relates to hydrophilized, polysiloxane-based impression and duplicating compositions which are used, in particular, in the dental sector and to a process for their preparation.

In particular, the present invention relates to additioncrosslinking 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-vulcanizing two-component silicone rubber systems (RTV) in which the base paste containing the crosslinking agent is mixed with a catalyst paste and crosslinked at room temperature.

Systems of this type are known per se (cf., for exasqple, 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, the compositions are supplied in various viscoeity grades, for example kneadable, high-viscosity compositions for spoon application and medium- and low-viscosity compositions preferably for spray application.

On use, equivalent amounts of the base and catalyst 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 spraying and/or by impression spoon. After crosslinking 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 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 slurry due to incompatibility of the surface media; this results in a defective plaster model.

These defect sources can be substantially eliminated by hydrophilizing the silicone impression compositions. Thus, US 4,691,039 and US 4,752,633 describe ethoxylated siloxanes, and US 4,657,959 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 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, such as CaSO4*l/2 H20, CaCl2, K2SO4, 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 platinum black. The latter functions as a hydrogen adsorber, since reaction of the SiH group-containing crosslinking agent with the OH groups of the hydrophilizing agent during casting of the crosslinked impression using the aqueoue plaster slurry can produce hydrogen, and these gas bubbles result in a defective plaster model.

The present invention relates to hydrophilized additioncrosslinking silicone impression cosqpositions containing additives of selected ethoxylated fatty alcohols which. 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 hydrophilized, polysiloxane-based impression compositions which undergo addition-crosslinking at ambient temperature and contain (a) organopolysiloxanes containing at least two vinyl groups in the molecule, (b) optionally organopolysiloxanes containing no reactive groups, (c) organohydridopolysiloxanes containing two or more Si-H groups in the molecule, (d) a catalyst, (e) fillers and optionally further conventional additives, auxiliaries and dyes, (f) specific alkoxylated fatty alcohol and/or a methylated or an acylated alkoxylated fatty alcohol, characterized in that they contain no platinum black.

Both the base paste and the catalyst paste are prepared 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 simple preliminary experiments.

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

• Specific examples of hydropbilizing agents according to the invention are: Ci2H25O- (CH2-CH2-O) 5ch3C13H27° (CH2-CH2-O) 6CH3C14H29°" 7CH3 C12H2SO-(CH2-CH2-O)5H CI3H27°- (CH2-CH2-O) 6H C14H29°- (CH2-CH2-O)7H C12H25O-(CH2-CH2-O)5-CO-CH3C13H27°- (CH2-CH2-O) 6-CO-CH3 C14H2gO-(CH2-CH2-O)7-CO-CH3 and mixtures thereof These hydropbilizing agents are added either to the base paste alone or proportionately to the base paste and the catalyst paste, in amounts of 0.3 to 5.0% by weight, preferably 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, on at least two silicon atoms and having a viscosity in the range from 500 to 200,000 mPa*s at 20°C, depending on the desired viscosity of the formulated pastes.

A The silicone oils (b) are trimethylsiloxy-terminated polydimethylsiloxanes having a viscosity of from 50 to 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 prepared 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 3,775,352 and US Patent 3,814,730, are highly suitable.

Fillers (e) are taken to mean quartz sand, cristobalite sand, calcium sulphate, calcium carbonate, diatomaceous earth, precipitated and pyrogenically prepared silica with an uncharged or charged surface.

Dyes are employed to differentiate between the base paste and catalyst paste and to monitor mixing. Inorganic and organic coloured pigments are usually enpioyed.

In the freshly mixed pasty state, the hydrophilized impression compositions according to the invention have good affinity for the moist enamel and the moist gums. Zn addition, the crosslinked impressions can be cast with the agueous plaster slurry in the usual time of 30 minutes after removal of the impression from the mouth 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 lowand high-viscosity and kneadable impression compositions and of low-viscosity duplicating compositions. The parts indicated are parts by weight.

Exainple l (Comparison) A base paste is prepared in a kneader by mixing 290 parts of vinyl-terminated polydime thylsiloxane having a vis6 cosity of 10,000 mPa-s at 23 °C, 180 parts of SiH groupcontaining 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 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 viscosity of 5000 mPa*s at 23°C, 525 parts of fine quartz sand and 10 parts of hydrogenated castor oil having a melting point of 85°C. The paste is heated to a temperature of 95°C 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 invention) The composition and preparation of the two pastes is as in Example 1. The following additives are «dm-i ypH with each 1000 parts of the base paste: Example 2 10 parts c12h25o (ch2-ch2o) 5h 3 10 n -c12H25° (ch2-ch20) 5co-ch3 4 10 ItC13H27° (CH2-CH2O) 6H 5 20 NC13H27° (CH2-CH2O) gH 6 10 nC13H27° (CH2 -CH2O) 5CO-CH3 7 20 N C13H27O (CH2-CH2O) eC0-CH3 8 (Comparison) 10 NCSH19 -C6H4-° (CH2-CH2O) 10H Applicational testing: The prerequisite for the serviceability of the impression compositions is that they satisfy the requirements of the 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 the plaster model with the crosslinked impression compositions. The last two methods are described below: Testing of the scrape strength; g of base and 10 g of catalyst paste are mixed homogeneously within 30 seconds at 23°C and 50% relative 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 silicone disc is then covered with a plastic ring 'of the same diameter and a height of 2 cm, which is filled with an agueoue 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 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 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 reproducible with a maximum uncertainty of 15 μια.

The means of the trace widths are given in /xm. Each mean is based on three measurements on three adjacent traces. The mean and maximum standard deviation of the means are 8 μια and 22 /xm respectively.

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

Measurement of the wetting angle; g of base paste and 20 g of catalyst paste are mixed 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 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 a video system, the dynamic wetting 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 angle of the last 10 measurements is given (time range from about 11-15 seconds).

Results: Ex. Hydrophilizing agent Plaster test Scrape strength Trace width (μπι) Wetting angle t=l sec. t=13 sec 1 None 322±17 99±2 100±3 2 1% c12h25o (ch2-ch2o) 5h 357±17 74±4 44±2 5 3 1% C12H25O(CH2-CH2O)5-CO-CH3 364±17 77±3 45±2 4 1% c13h27o (ch2-ch2o) 6h 331±13 79±5 62±3 5 2% C13H27O2-CH2O) 6h 344±17 58±2 33±3 6 1% C13H27O(CH2-CH2O) 6-co-ch3 348±13 72±3 53±2 7 2%C13H27°iCH2CH2°^6COCH3 363±13 61±4 40±l 10 8 1%C9H19-C6H4-° (CH2-CH2o) io« 490±14 84±3 48±4

Claims

Claims:

1. Addition-crosslinking silicone impression comv positions containing: (a) organopolysiloxanes containing at least two i vinyl groups in the molecule, (b) optionally organopolysiloxanes containing no reactive groups, (c) organopolysiloxanes containing two or more Si-H groups in the molecule, (d) a catalyst, (e) fillers and optionally further conventional additives, auxiliaries and dyes, (£) a C 10 - to C 16 -fatty alcohol which has been alkoxylated by 2 to 10 alkoxy units and may < optionally be methylated or acylated characterized in that they contain no platinum black.

2. Silicone impression compositions according to Claim 1, characterized in that the straight-chain and branched fatty alcohols (f) are C 10 - to C 16 alcohols which have been reacted with from 2 to 10 mol of ethylene oxide or propylene oxide and have optionally been esterified by means of a C 2 - to C 4 monocarboxylic acid.

3. Silicone impression compositions according to Claim 1, characterized in that the straight-chain or branched fatty alcohols (f) are C 12 -C 14 - fatty alcohols which have been reacted with from 4 to 7 mol of ethylene oxide and have optionally been esterified by means of acetic acid.

4. Silicone impression conq>ositions according to Claims 1 and 2, characterized in that component (f) is added in amounts of 0.3 to 5.0 per cent by weight, based on the total mixture. Silicone impression compositions according to Claims 1 to 4, for use for casting teeth, mucous membranes and models. Process for the preparation of platinum black-free addition-crosslinking silicone impression compositions containing (a) organopolysiloxanes containing at least two vinyl groups in the molecule, (b) optionally organopolysiloxanes containing no reactive groups, (c) organopolysiloxanes containing two or more Si-H groups in the molecule, (d) a catalyst, (e) fillers and optionally further conventional additives, auxiliaries and dyes, (f) a C 10 - to C ie -fatty alcohol which has been alkoxylated by 2 to 10 alkoxy units and may optionally be methylated or acylated characterized in that a base paste A is prepared by mixing all or some of each of constituents (a) to (f), with the exception of (d), a catalyst paste B is prepared by mixing all or some of each of constituents (a) to (£), with the exception of (c), and equivalent amounts of A and B are mixed with one another to prepare the ready-for-use impression compositions. An addition-crosslinking silicone impression composition according to Claim 1, substantially as hereinbefore described and exemplified. A process for the preparation of an addition-crosslinking silicone impression composition according to Claim 1, substantially as hereinbefore described and exemplified. An addition-crosslinking silicone impression composition according to Claim 1, whenever prepared by a process claimed in Claim 6 or 8.