LU84482A1 - COMPOSITE DENTAL PROSTHESIS COMPRISING A PART OF FLEXIBLE POLYURETHANE AND A PART OF A RIGID POLYMER - Google Patents

Description

4 i s Composite dental prosthesis comprising a part in flexible polyurethane and a part in a rigid polymer.

The present invention relates to the field of dental prostheses and more particularly dentures 5 prepared from polyurethane elastomers and rigid polymers such as rigid acrylic resins and rigid epoxy resins.

It has been proposed to manufacture dentures having a flexible layer in contact with the gums and other parts of the mouth so as to relieve tissue. These flexible layers were composed of acrylic resins, silicones and similar rubbery materials. However, with aging, these flexible layers tend to harden and give off unwanted odors. In addition, some decomposition of the polymer may also occur, probably as a result of an oxidation process as well as fluctuations in the pH in the mouth. To overcome these drawbacks, U.S. Patents Nos. 4,024,636 and 4,080,412, both issued to 2o Colpitts et al., And both incorporated herein by reference, describe dentures in in which the teeth are anchored in a gum element comprising a part holding the teeth, made from a non-hydrophilic rigid polyurethane elastomer having a hardness not less than Shore D4O approximately, and an engaging part in the mouth , manufactured from a non-hydrophilic flexible polyurethane elastomer having a hardness not greater than Shore A65 approximately, integrally and chemically bonded in a unit mass. The patent of the United States of America NO. 4,024,637, issued to Colpitts, which is also incorporated herein by reference, describes a denture in which teeth made of non-hydrophilic rigid polyurethane elastomer are included in a non-hydrophilic flexible polyurethane elastomer and chemically related to that -this. As preferred non-hydrophilic elastomers, mention will be made of those formed from isocyanate-terminated prepolymers which are crosslinked or cured by mixing with a crosslinker> 2 and heating, so as to effect curing. Isocyanate-terminated prepolymers suitable for the preparation of rigid non-hydrophilic polyurethane elastomers are prepared by reacting poly ether-, diol s or triols with aliphatic or cycloaliphatic or aralkyl di-polyisocyanates in proportions such that there are groups NCO free. The prepolymers are then cured or crosslinked with a diol, polyol, alkanolamine, diamine or polyol containing a tertiary amine, or mixtures thereof. The diol or polyol is advantageously a polyether diol or a polyol or a hydroxyl-terminated polymer.

To improve the resistance of polyurethane dentures to mechanical deformation or bending under the conditions prevailing in the mouth, United States Patent No. 4,225,696 issued to Colpitts et al., Which is also incorporated in the present specification by way of reference, replaces the aliphatic, cycloaliphatic or aralkyl di- or polyisocyanates mentioned above with aromatic polyisocyanates in which the isocyanate groups are directly linked to the aromatic ring, for example 2,4-tolylene diisocyanate (TDI), isomeric mixtures of TDI, 3,3'-tolidene 4,4-diisocyanate (T0DI), 3,3'-dimethyl-diphenylmethane 4,4'-diisocyanate, diphenylmethane 4,4'-25 diisocyanate (MDI), mixtures of MDI and MDI adducts, etc. The polyurethane obtained can be transformed into the flexible part / engaging in the mouth, of a denture whose part engaging in the teeth is a relatively rigid polymer. The rigid polymer may 5 ° be a rigid polyurethane prepared in accordance with one

any of the aforementioned Colpitts et Coll patents or may be any of the rigid polymers used to date in the manufacture of dentures. As is well known, acrylics, a class of relatively rigid resins, have been used for years in manufacturing / L

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3 of prosthodontic appliances and would be prime candidates for the preparation of polyurethane / rigid polymer composite dentures, in accordance with the indications of US Patent No. 4,225,696 issued to Colpitts 5 et al. However, however interesting an improvement such as these composite dentures is, their polyurethane constituents, which, as indicated above, are prepared from an aromatic isocyanate such as TDI, TODI or MDI, are relatively photosensitive and capable of '' be degraded by actinic radiation. The likely explanation for this behavior is that when an isocyanate group reacts with water, it forms a urea group, which, in the case of aromatic isocyanates, is relatively stable chemically, but sensitive to light.

Consequently, it is desirable to provide a denture which has a flexible element which engages in the mouth for the comfort of the wearer and which is at the same time resistant to bending and to photodegradation.

In accordance with the present invention there is provided a composite dental prosthesis, which comprises a portion holding the teeth made from a rigid non-polyurethane polymer having a hardness not less than about Shore D40, chemically integrally bonded to a portion mouth-engaging agent made from a flexible, non-hydrophilic polyurethane elastomer having a hardness of not more than about Shore A65, this polyurethane being the product of the reaction of a polyether polyol and a di- or aliphatic, cycloaliphatic or aralkyl polyisocyanate wherein the isocyanate groups are directly bonded to the aliphatic, cycloaliphatic or alkyl portions thereof.

The dental prostheses of the present invention have significant advantages over all polyurethane dentures. About 40% of partial or full dentures / 35 currently produced have acrylic teeth. Being given that it is difficult, in practice, to obtain a good chemical bond between the acrylic teeth and the polyurethane, the possibilities only of debris (coming from food, drinks, tobacco, etc.) infiltrate into crevices 5 between the teeth and the polyurethane are much larger than in the case of acrylic teeth linked to a part retaining the acrylic teeth. And, like rigid acrylics as a class, are generally very stable in flexion, and are superior in this respect to all polyurethane dentures, the part of which engages in the mouth is prepared with an aliphatic, cycloaliphatic di- or polyisocyanate. or aralkyl, it is particularly advantageous to combine the flexible polyurethanes relatively sensitive to bending, but resistant to the photo-degradation previously described, with acrylics or, for this question, with any other non-polyurethane polymers resistant to bending, such as rigid epoxy resins. The resistance of these polyurethanes to degradation under the influence of actinic radiation is probably due to the fact that, unlike aromatic urea groups, the aliphatic urea groups of these polyurethanes (insofar as they are formed by reaction of certain isocyanate groups with water) tend to react with each other to form biuret, which is considerably more resistant to light than aromatic urea groups which do not react appreciably to give biuret. Another advantage of these polyurethanes over those prepared with aromatic isocyanates is the reduced incidence of the formation of urea / biuret groups. More of the available isocyanate groups of an aliphatic isocyanate will react with the hydroxyl groups of the polyether polyol to form the desired urethane bonds (which provide chemical resistance) than would be with an aromatic isocyanate. f / t 1> 5

The teeth-retaining portion of the composite denture of the invention can be prepared from any of the known and conventional rigid acrylic resins used in the manufacture of dentures, for example those having a hardness of at least Shore D40 and up to Shore DI00.

The expression "acrylic resin" here includes homopoly-mothers of acrylic esters and acrylic amides corresponding to the general formula:

R1 O

10 1 11 CH2 = C - C - XR2 in which X is O or NH, is H or a methyl group and R is any one of various groups including aliphatic, cycloaliphatic, alkaryl, aralkyl, alkoxy, aryloxy, glycidyl groups , etc., and co-polymers of these esters / amides with other acrylic esters / amides and / or with one or more other ethylenically copolymerizable unsaturated monomers such as acrylonitrile, butadiene, styrene, vinyl acetate, etc. Poly (methyl methacrylate) is a particularly preferred resin for the part retaining the teeth of the composite denture of the invention, because the monomer is readily available, its cost is low and its use is common in dentistry. The techniques by which acrylic resins can be transformed into dentures and partial dentures are well known, see for example US Pat. Nos. 3,251,910 and 3,258,509, issued to Barnhar, both of which are incorporated into the present document for reference.

Rigid epoxy resins, for example those having a Shore hardness of at least D40 and up to about Shore DI00, which can be used as a denture retainer, are a well known class of thermosetting resins. As resins representative of these, mention will be made of those derived from /) / 35 _. //.

bisphenol A and 1 epichlorohydrin, hardened with various ^ // 6! polyamines, and special epoxy resins such as cresol novolac epoxy resins, epoxy I phenyl novolac resins, resins derived from bisphenol F, resins derived from polynuclear phenol-glycidyl ether,! 5 cycloaliphatic epoxy resins, aromatic and heterocyclic glycidyl amine resins, tetraglycidylmethylenedianiline-derived resins, triglycidyl-p-aminophenol-derived resins, triazine-based resins and hydantoin epoxy resins. Details of | 10 formulation of polymer forming compositions! rigid epoxides and the conditions under which they undergo polymerization are well known to those skilled in the art and are fully described in the literature, see for example Kirk-Othmer Encyclopedia of Chemical Technology, third edition, Vol. 9, pp. 274 et seq., John Wiley & Sons, Inc. which is incorporated herein for reference. The polyether polyols which can be used to prepare the part of flexible polyurethane which engages in the mouth of the composite denture of the invention can be chosen from any one of the polyether polyols used up to now for the preparation of polyurethanes. These polyols have two and preferably three or more hydroxyl groups. Among the polyether polyols which can be used, mention will be made of poly (oxypropylene) glycols, poly (oxypropylene) poly (oxyethylene) glycols, poly (1,4-oxypropylene) glycols and graft copolymers of poly (oxypropylene ) (polyoxyethylene) glycols with acrylonitrile or mixtures of acrylonitrile and styrene. The equivalent mass of these polyether diols can; 30 to 20 to 1,000, a preferred range being 200 to 400. The polyol can be made up of simple polyols such as glycerol, trimethylolpropane, 1,2,6-hexanetriol, or pentaerythritol, or it can be made up of polyether triols such as poly (oxypropyled) adducts! Or poly (oxyethylene) of the above polyols. The equivalent massψΥ i 7 of the polyether polyols can be between 100 and 800, a preferred range being from 100 to 500. It should also be noted that various combinations of the diols and polyols can be used.

The polyisocyanates used for the preparation of flexible polyurethane elastomers may contain isocyanate groups directly linked to their aliphatic parts. As nonlimiting examples thereof, mention may be made of 4,4'-dicyclohexylmethane diisocyanate, isophorone 10 diisocyanate, 2,2 / 4-trimethyl-1/6-hexane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate , "dimeryl" diisocyanate, methylcyclohexyl diisocyanate and the reaction product of 3 moles of hexamethylene diisocyanate with one mole of water (Desmodur N triisocyanate).

The ratio of NCO to OH in the preparation of the flexible isocyanate-terminated prepoly mother can be between 1.75 and 2.5, a preferred range being 2.0 to 2.25. Flexible isocyanate-terminated prepolymers should have a free NCO content of about 3.5 to 5.5 percent, preferably 3.7 to 4.7 percent.

To cure (crosslink) the prepolymers, the preferred polyols are polyols containing tertiary amines, such as the adducts of poly (oxypropylene) or poly (oxyethylene) diamines or triamines such as ethylene diamine, diethylene triamine, tolylene diamine, phenylenediamine, or aniline, or any diols, polyols or their mixtures. They are advantageously polyols of relatively low molecular weight such as those obtained by condensation of propylene oxide with ethylenediamine or pentaerythritol to a molecular weight of approximately 500, or trimethyloi-propane or any which other base compound up to a molecular weight of 2500.

Another preferred curing or crosslinking agent is a hydroxyl terminated prepolymer. These prepolymers are prepared essentially in the same manner as isocyanate-terminated prepolymers, but the ratio is such that they contain free and unreacted hydroxyl groups. The same diols and polyols and isocyanates can be used although it is preferred that the prepolymer has a functionality greater than 2, which can be obtained by using a polyol having a functionality greater than 2 and / or an isocyanate having a functionality greater than 2 2. The isocyanate is advantageously 2,2,4-10 trimethyl-1,6-hexane diisocyanate, hexamethylene diiso-cyanate or Desmodur N. (trade name).

The OH / NCO ratio in the hydroxyl-terminated prepolymers can advantageously be in the same range as the NCO / OH ratio in the isocyanate-terminated prepolymers. Note, however, that, given the fact that the crosslinking agent can consist of one or more diols or polyols (no isocyanate), the final OH / NCO ratio is infinite.

Another preferred curing or crosslinking agent is a prepolymer-polyol blend. It is thus possible to mix a polyurethane prepolymer having neither a free NCO group nor a free OH group, with a polyol, advantageously with a polyol having a functionability greater than 2, to form a prepolymer-polyol mixture. When such a mixture is mixed with an isocyanate-terminated prepolymer, in an NCO / OH ratio greater than 1, the crosslinking is carried out both by an NCO-OH reaction and by an NCO-urethane reaction.

To bond the rigid polymer component to the flexible polyurethane component, one or both of the adjoining surfaces are coated with a primer formula prepared by mixing a polyisocyanate with a polyol, and then joining the two components. After hardening of the flexible elastomer formula, a denture is obtained in which the rigid and flexible elements / 25 are permanently linked to each other / 9

To accelerate the formation of prepolymers or the hardening of prepolymers with crosslinking agents, metal catalysts such as tin catalysts, such as 5-dibutyltin dilaurate and stannous octanoate, can be used.

In the following flexible polyurethane resin formulas (all parts are by weight) given by way of illustration of the invention, ingredients whose properties are given in the table below have been used. 10 I. PREPARATION OF PREPOLYMERS (Constituents A)

FORM I

Polymeg 10001, 4 moles x 976 = 3904

Polymeg 20002, 1 mole x 1998 = 1998

Hylène W "1, 10 moles x 262 = 2620 15 Dibutyltin dilaurate (catalyst) _1.7 8523.7

Equivalent mass for an NCO 852.4

Poly (oxytetramethylene) glycol; molecular weight 976 2 20 Poly (oxytetamethylene) glycol; molecular weight 1998 3 4,4'-dicyclohexylmethane diisocyanate PROCEDURE OF PREPARATION Polymeg 1000 and Polymeg 2000 are introduced into the reactor and the mixture is heated to 70 ° C. Moisture is removed therefrom in vacuo for two to three hours until the bubbles stop.

Then apply a blanket of dry nitrogen and cool the mixture to 50 ° C, then add the Hylene. The reaction mixture is stirred at 10Q-120 rpm for at least 30 minutes and monitored, as a slightly exothermic reaction may occur. The reactor temperature is maintained at 65-70 ° C. The catalyst is added in successive portions to accelerate the reaction. After three hours, the NCO content is checked using the n-dibutylamine titration method. The NCO content must be / 10 of the order of 4.8%. Here as elsewhere, the variation can be + 5 percent.

When this content of free NCO is reached, the contents of the reactor are cooled, and it is packaged in lined containers of 3.78 liters or 1.14 liters. Dry nitrogen is used to maintain an inert atmosphere in the containers which are then hermetically sealed.

FORM 2

Polymeg 1000, 2 moles x 976 = 1952 ^ Polymeg 2000, 1 mole x 1998 = 1998

Hylène W, 6 moles x 262 = 1572

Dibutyltin dilaurate (catalyst) _1.1 5523.1

Equivalent mass for an NCO 920.5 15

The preparation procedures are the same as for Formula 1. The content of free NCO in the prepolymer must be 4.5%.

FORM 3 20

Polymeg 2000, 1 mole x 1998 = 1998

Polymeg 1000, 1 mole x 976 = 976

Hylène W, 4 moles x 262 - 1048 4022

Equivalent mass for an NCO 1005.5 25

The preparation procedures are the same as for formula 1. The content of free NCO must be 4.18% ·.

FORM 4

Polymeg 2000 = 1198 30

Polymeg 1000 s 488

Hylène W - 786

Dibutyltin dilaurate (catalyst) _0 / 76 3,272.76 /

Equivalent mass for an NCO 1190 sJ

35/11 PROCEDURE OF PREPARATION The poly (oxytetramethylene) glycols, Polymeg 2000 and Polymeg 1000 are introduced into the reactor and the humidity is removed under vacuum for two to three hours 5 by gentle stirring at 60-120 t / min at 70 ° C.

The mixture of dehumidified glycol is cooled to 50 ° C., a blanket of dry nitrogen is applied and diiso-cyanate (Hylene W) is added. The catalyst is added in successive portions to accelerate the reaction.

The reactor charge must be exothermic. Reagent temperatures should not be allowed to exceed 75 ° C. After 2 to 3 hours of reaction, the NCO content must be checked by the n-dibutylamine titration method. The NCO content must be around 3.3%. If an NCO content greater than 3.7% is found, the treatment should be continued for an additional hour at 70 ° C after the addition of a small amount (0.005%) of the catalyst.

The above flexible isocyanate terminated prepolymers are practically linear.

20 PREPARATION OF CROSSLINKERS (COMPONENTS B) FORM 5

Pluracol 3551 100 g

TiO2 (rutile) 0.2 g

Dibutyltin dilaurate (catalyst) as required 25 _.

100.2

Equivalent mass for a hydroxyl 125.1 Derived from the reaction of ethylenediamine with poly (oxypropylene), molecular mass 490.

PROCEDURE OF PREPARATION All the pigments are dispersed in 5% of the total polyol, Pluracol 355. For the dispersion, one can use a ball mill or a roller mill or any / 35 high speed and high mill dispersion. / / 12

Then, the rest of the polyol, Pluracol 355, is stirred there.

The mixture is then degassed and the moisture is removed by applying a vacuum and gently heating to 60-70 ° C.

The catalyst must be added before application.

^ The amount of catalyst depends on the type of isocyanate-terminated prepolymer to be used. Usually 0.15 to 0.35% catalyst is added, depending on the total weight of the polymer and the type of polymer and reactant groups.

10 FROMULE 6 1,4-butanediol 450

Pluracol PeP 550 * 500

Ti02 1 g

Dibutyietin dilaurate (catalyst) as required 15,951

Equivalent mass for a hydroxyl 68.0 * Addition product to poly (oxypropylene) of pentaerythritol having a molecular mass of approximately 500.

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PREPARATION PROCEDURE

All the pigments are dispersed in 5% of the polyols; then the rest of the polyols are mixed with the pigment dispersion. Moisture is then removed from the mixture by applying a vacuum and gently heating to 60-70 ° C.

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The catalyst must be added before application.

The amount of catalyst depends on the type of isocyanate-terminated prepolymer that can be used.

Usually, in the rigid elastomer formula, the amount of catalyst is in the range of 0.15 to 0.25 and, for the flexible elastomer formula, in the range / of 0.30 to 0, 35% 9 35 13 FORMULA 7

Pluracol Pep 550 500 g

Ti02 0/5 500.5 5 Equivalent mass for a hydroxyl 125.1

The preparation procedure is similar to that of formula 6.

FORMULA 8 10 Pluracol TP 440 420 g

Butanediol 450 g

Ti02 1 g

Dibutyltin dilaurate (catalyst) as required 871

Equivalent mass for a hydroxyl 67

The preparation procedure is similar to that of formula 6 FORMULA 9 20 Desmodur N - triisocyanate1 478

Polymeg 650 2112 2, Pluracol TP 1540 750

Ti02 5.0

Yellow lacquer No. 6 3.0 25 Lake red No. 3 1.8

Lake blue No. 1 0.2 3350.0

Equivalent mass for a hydroxyl 668 30 1 (three molecules of hexamethylene diisocyanate reacted with one molecule of water) 2

Addition pipe of trimethylolpropane to poly (oxypro-poly), Molecular mass 1500.

PREPARATION PROCEDURE

Poly (oxytetramethylene) glycol is introduced into a reactor / 14 and the moisture is removed therefrom under vacuum for 2 to 3 hours by gentle stirring at 60-120 rpm at 70 ° C. Then the vacuum is broken under dry nitrogen and the dry nitrogen cover is kept for the duration of the reaction.

Desmodur N-triisocyanate is introduced therein with stirring and reacted with glycol until the NCO content is reduced to zero. Then mix the Pluracol TP 1540.

The pigments are dispersed in a small amount of triol, Pluracol TP 1540, and they are mixed therein with the entire prepolymer-polyol mixture.

II. PREPARATION OF FLEXIBLE POLYURETHANE RESINS

EXAMPLE 1

Component A, formula 1, 100 parts 15 Component B, formula 5, 13.6 parts

Catalyst, stannous octoate, 8 drops NCO / OH - 1.08 to 1

Components A and B are degassed and dehumidified for at least one hour at 60 ° C, then they are mixed.

20 gently with the catalyst and placed in a preheated vacuum oven for 1 to 2 minutes. They are then cast in a preheated denture mold containing a rigid non-hydrophilic polyurethane elastomer previously cast as described above and they are kept in an oven 25 at 90 ° C. for 3 hours. Then remove the dentures from the mold and finish by removing the sprues and burrs and polishing it if necessary.

EXAMPLE 2

Component A, formula 2, 100 parts 20 Component B, formula 6, 7 parts

Catalyst, dibutyltin dilaurate, 12 drops NCO / OH = 1.05 to 1.

EXAMPLE 3 /

Component A, formula 3, 100 parts / 25 Component B, formula 6, 6.44 parts / // 15

Catalyst, dibutyltin dilaurate, 16 drops NCO / OH = 1.05 to 1.

The compositions of Examples 2 and 3 are degassed, the moisture is removed, they are mixed, poured and hardened as in Example 1.

EXAMPLE 4

Component A, formula 9, 100 parts

Constituent B, formula 11, 56.2 parts

Catalyst, stannous octoate, 0.32 10 NCO / OH = 1.05 to 1.

Components A and B must be heated to around 60 ° C and degassed and dehumidified under vacuum before mixing. Then we have to add the catalyst. The mixture should be poured into a preheated mold and heated with a mold release agent. The elastomer must be cured in an oven at 95 ° C for 2 hours.

IV. MANUFACTURE OF THE COMPOSITE DENTURE EXAMPLE 5

In this example, a rigid acrylic denture 20 preformed supplied by a dental laboratory or by a dentist is provided with a part engaging in the mouth prepared with a flexible polyurethane elastomer such as any one of those described in strips. examples 1 to 4 above.

The rigid acrylic denture is placed in a balloon so that the lower part of the denture is flush with the balloon. The coating material is then introduced into the balloon to the bottom of the balloon. When the coating material has hardened, a release agent is applied to all surfaces, i.e. to the coating, the denture, and the teeth. When the release agent is dried (in about 5 minutes), additional coating material is applied to cover the whole. dentures. The balloon is then completely closed by adjusting it / 35. We separate the balloon and remove iQy / fJv

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16 t dentures. The dentures are then ground to make room for the part that engages in the mouth of the flexible polyurethane elastomer.

After receiving a conventional full acrylic denture 5 with a new impression taken by the dentist, a plaster model is prepared in accordance with conventional dental laboratory procedures. The plaster model is then sealed (that is, a coating is placed on all exposed surfaces of the plaster except the bottom 10). The dentures are then placed in a balloon so that the lower part of the dentures is flush with the balloon. A coating material is then introduced into the balloon, flush with the top of the balloon. When the coating material has hardened, a release agent is applied to all surfaces (i.e., the coating, the denture and the teeth).

When the primer or release agent has dried (in about 5 minutes), additional coating material is added to cover the entire denture. The balloon is then completely sealed by fitting a lid to it. We separate the balloon and remove the dentures.

The dentures are then ground to make room for the flexible polyurethane elastomer. A sealant is again applied to all of the newly exposed plaster surfaces. After grinding the dentures, the dentures are washed with isopropanol or anhydrous ethanol to remove grinding residue and air dried. A denture is applied to all surfaces *, on which the flexible elastomer must adhere, for example 7.8 g of PeP 550 30 (a polyether polyol from BASF Wyandotte having an average molecular weight of approximately 600 and an index hydroxyl of 448, and which is based on oxyalkylated pentaerythritol with propylene oxide) mixed with 7.3 g of Hylene W (4,4'-dicyclohexylmethane diisocyanate, from DuPont), We remove from .. / 35 plaster model filling material. * 17 new mold release product is applied to the mold and the plaster model to allow air drying (in about 5 minutes). The denture coated with the primer is then inserted into the mold cavity. A flexible polyurethane formula is introduced into the mold cavity and the low points of the plaster mold. The complete assembly of the mold is placed in a clamp and the pinched mold is heated in an oven heated to 85 ° C. After about 3 hours, the assembly is removed from the oven and cooled until it can be comfortably touched. The mold is opened and the dentures are removed from the covering material and the plaster model. The dentures are then deburred, polished, etc., to obtain the finished product. / / · '15 / /

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Claims (7)

1. Composite prosthesis comprising a part holding the teeth made from a rigid non-polyurethane polymer, having a hardness not less than about Shore D40, 5 chemically bonded in an integral manner to a part which occurs in the mouth, made from from an elastomer of flexible non-hydrophilic polyurethane having a hardness not greater than Shore A65 approximately, this polyurethane being the product of the reaction of a polyether polyol and an aliphatic, cycloaliphatic or aralkyl di- or polyisocyanate which isocyanate groups are directly linked to these aliphatic, cycloaliphatic or alkyl parts. 2. Prosthesis according to claim 1, characterized in that the rigid polymer is a rigid acrylic polymer or a rigid epoxy polymer. 3. Prosthesis according to claim 2, characterized in that the rigid acrylic polymer or the rigid epoxy polymer has a hardness up to Shore D100. 4. Prosthesis according to claim 1, characterized in that the di- or the polyisocyanate is chosen from 4,4'-dicyclohexylmethane diisocyanate, isophorone diiso-cyanate, 2,2,4-trimethyl-l, 6-hexane diisocyanate, hexamethylene diisocyanate, xylylene diisocianate, dimeryl diisocyanate, methylcyclohexyl diisocyanate and the reaction product of 3 moles of hexamethylene diisocyanate with one mole of water. 5. Prosthesis according to claim 1, characterized in that the polyether polyol is a polyether diol, triol, or tetrol having an equivalent mass of 100 to 800. 6. Prosthesis according to claim 5, characterized in that the polyol is derived from pentaerythritol or glycerol oxyalkylated by ethylene oxide, propylene oxide or, a mixture of the latter. / 7. Prosthesis according to claim 1, characterized ^ / -4 * 19 J "in that the rigid polymer is chemically bonded integrally to the polyurethane elastomer with a primer based on polyurethane. Drawings: ........ pages pages including ....... 4 ........ guard pope ....... 43 ".. paaos do description .... ...... pages of claims ......... Δ ...... descriptive abstract Luxembourg, 2 2 NOV, 1982 The representative: /) / c — t ^ harles München