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Patent US5830951 - Polyvinylsiloxane impression material - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsImproved two component polymerizable polyorganosiloxane compositions are described, particularly for use in making dental impressions, having improved tear strength and wettability. Improved tear strength results from inclusion of a quadri-functional polysiloxane having a vinyl content of 0.16 to 0.24...http://www.google.com/patents/US5830951?utm_source=gb-gplus-sharePatent US5830951 - Polyvinylsiloxane impression materialAdvanced Patent SearchPublication numberUS5830951 APublication typeGrantApplication numberUS 08/767,134Publication dateNov 3, 1998Filing dateDec 19, 1996Priority dateApr 13, 1995Fee statusLapsedAlso published asDE69733361D1, DE69733361T2, EP0946128A2, EP0946128B1, WO1998026748A2, WO1998026748A3Publication number08767134, 767134, US 5830951 A, US 5830951A, US-A-5830951, US5830951 A, US5830951AInventorsJurgen Hans FiedlerOriginal AssigneeDentsply Detrey G.M.B.H.Export CitationBiBTeX, EndNote, RefManPatent Citations (71), Non-Patent Citations (2), Referenced by (28), Classifications (24), Legal Events (6) External Links: USPTO, USPTO Assignment, EspacenetPolyvinylsiloxane impression material
US 5830951 AAbstract
1. A dental impression material having low viscosity comprising from about 45 to about 55 percent by weight based upon 100 percent by weight of the impression material of a base paste comprising:a1. from about 1 to about 10 percent by weight based upon 100 percent by weight of the impression material base paste of a linear dimethylvinyl terminated polydimethylsiloxane, a2. from about 8 to about 20 percent by weight based upon 100 percent by weight of the impression material base paste of a linear dimethyl-(H-methyl)-siloxane copolymer with a terminated component selected from trimethylsilyl or dimethylhydrosilyl, a3. from about 15 to about 25 percent by weight based upon 100 percent by weight of the impression material base paste of a dimethylvinylsilyl terminated polydimethylsiloxane, wherein said dimethylvinylsilyl terminated polydimethylsiloxane contains 15-25% by weight highly dispersed SiO2 based upon 100% by weight of said dimethylvinylsilyl terminated polydimethylsiloxane, a4. from about 50 to about 60 percent by weight based upon 100 percent by weight of the impression material base paste of a low molecular weight QM-resin, said QM-resin being homogeneously soluble in a1 and comprising SiO4/2, RO1/2, and R3 SiO1/2 wherein R represents n-alkyl, phenyl or vinyl and has an alkoxy group content from less than 4 mmol/g, a5. a water scavenger for adsorption, a6. from about 0 to about 10 percent by weight based upon 100 percent by weight of the impression material base paste of a linear dimethyl-(vinylmethyl)-siloxane copolymer with dimethylvinylsilyl termination, a7. dipolar surfactant to improve wetting properties, and optionally a8. pigments,and from about 45 to about 55 percent by weight based upon 100 percent by weight of the impression material of a catalyst paste composition comprising b1. from about 1 to about 5 percent by weight based upon 100 percent of the catalyst paste of a linear dimethylvinyl terminated polydimethylsiloxane, b2. from about 30 to about 35 percent by weight based upon 100 percent by weight of the catalyst paste of a dimethylvinylsilyl terminated polydimethylsiloxane, wherein said dimethylvinylsilyl terminated polydimethylsiloxane contains 20-35% highly disperse SiO2 based upon 100% by weight of said dimethylvinylsilyl terminated polydimethylsiloxane, b3. from about 55 to about 70 percent by weight based upon 100 percent by weight of the catalyst paste of a low molecular weight QM-resin, said QM-resin being homogeneously soluble in a1 and comprising SiO4/2, RO1/2, and R3 SiO1/2 wherein R represents n-alkyl, phenyl or vinyl and has an alkoxy group content from less than 4 mmol/g, b4. from about 0 to about 10 percent by weight based upon 100 percent by weight of the catalyst paste of a linear dimethyl-(vinylmethyl)-siloxane copolymer with dimethylvinylsilyl termination, b5. from about 0.5 to about 1.5 percent by weight based upon 100 percent by weight of the catalyst paste of a Pt-catalyst prepared from H2 PtCl6 and tetramethyldivinyldisiloxane b6. short chained dimethylvinylsilyl terminated polydimethylsiloxanes, b7. H2 -adsorbent, and optionally b8. pigments. 2. A material according to claim 1 wherein the dimethylvinylsilyl terminated polydimethylsiloxanes has the chemical formula ##STR6## wherein n is an integer of from about 50 to about 1300.
3. A material according to claim 1 having wetting characteristics specified by a contact angle to water below about 45�.
This is a Continuation-in-Part of U.S. Pat. application Ser. No. 08/490,690, filed Apr. 13, 1995, now U.S. Pat. No. 5,661,222.
Voigt et al in EP 0 522 341 Al describes very short processing times of 35-45 seconds for forming dentition bite registration devices, utilizing a "QM" resin as a means of speeding and increasing cross-linking. These resins comprise as Q, the quadri-functional SiO4/2 and as M, building blocks such as monofunctional units R3 SiO1/2 wherein R is vinyl, methyl, ethyl or phenyl, or similar tri or bi-functional units. voigt notes that an elastomer with small elastic deformation having a higher tenacity and hardness results. However, such material lacks flexibility, having a low strain value, and is unsuitable for impression taking. The increased cross-linking rate of the QM resin also results in very limited processing times that are unsatisfactory.
A number of improvements of polyorganosiloxane impression materials focus upon adding a surfactant component to the dental impression material in order to reduce the hydrophobic nature of the polysiloxanes and make the composition more hydrophilic. Thus, Bryan et al in U.S. Pat. No. 4,657,959 describes adding an ethoxylated nonionic surface active agent containing siloxane or perfluoroalkyl solubilizing groups to achieve a three minute water contact angle below about 65�. While surfactants including hydrocarbyl groups, for rendering the surfactant soluble or dispersible in silicone prepolymer, are mentioned, including ethyleneoxy groups, the results achieved appeared to be less than optimal.
As stated above, all silicone material are known to have highly hydrophobic properties. Therefore, these materials are usually not able to wet the surface of the teeth properly, especially under moist conditions. Hydrophilic properties can be achieved in a silicone with the addition of dipoler surfactants. These additives are usually not soluble in the silicone matrix, but rather form an emulsion together with the silicon system. The Theological properties of such materials are characterized by a typical non-Newtonian flow behavior with a high yield stress and a highly sheer stress-dependent viscosity. Non-dipolar surfactants include for example, polyether modified silicones, and do not build proper micelles. The resulting emulsions are therefore not stable and tend to separate. However, the resulting multiple phase systems have a high yield stress which avoids the flow on the tooth surface when no or low stress is applied. Hydrophilic silicones therefore usually have poor flow characteristics under low stress.
Conventional "light bodies" formed from a two component system are usually applied in one of two forms. The first is a handmixed form in the case when the two components have to be mixed by hand. Second is an automixed form when the two components have to be released through a static mixer out of a cartridge. In both cases, the mixablility of the two components are strongly influenced by the rheological properties of the individual components making up the light body. Especially in the most common automixed form, the force to release the material out of the cartridge is influenced by the yield stress of the pastes.
Because of the Theological sub-structures, most conventional hydrophilic silicones have high yield stresses. To take advantage of low forces for releasing the material, large static mixers have to be employed. This leads to a high rate of waste because much of the material often remains in the mixer. Therefore, it is desired to achieve a low yield stress of both the single paste component and the mix in order to minimize the force which is necessary to remove the paste from the cartridge.
With conventional light body formulations a high stress has to be applied to obtain a flow of the impression material into the sulcus and into the other details of the preparation. Low viscosity type materials ("light bodies") are therefore always used in combination with a high viscosity type material in the so called "putty/wash" technique or in the "double mix" technique. To improve the mixablility of the putties, the viscosity of these products must be low. Even in the case where machine mixed heavy bodies are used the stress for releasing is limited by the technical properties of the machine. Higher viscosities lead to longer release times. In cases where these so-called soft putties or heavy bodies are used together with low viscosity silicones, the high yield stress and the highly stressed viscosity of the light body causes problem because it is impossible to generate sufficient pressure by the unset soft putty or heavy body during the taking of the impression. Therefore, a flow into the details of the preparation is not guaranteed. This problem is even more evident when the low viscosity material has a high yield stress.
In addition, the hydrophilic components to improve the wetting properties of the silicone tend to create a new problem. This problem is a stability problem of the cross linking SiH-components against moisture because these functional groups are sensitive against hydrolysis reactions especially under basic conditions. Therefore, it is a preferred embodiment of the present invention to add a water absorbing inorganic filler such as calcium sulfate hemihydrate, anhydrous calcium sulfate, calcium cloride, and the like and adsorbing compounds such as zeoliths, molecular sieves and other similar adsorbing and absorbing compounds.
A preferred QM resin comprises a polyorganosiloxane comprising units of SiO4/2 and units of R1 R2 2 SiO1/2 wherein R1 is unsaturated, preferably vinyl and R2 is alkyl, aryl, etc., such as methyl, ethyl, phenyl, etc. More preferably, the QM resin comprises the formula: ##STR1##
The retarder component of the composition is a low molecular weight, vinyl functional fluid that is a linear or cyclic polysiloxane in an amount of at least about 0.030 weight percent of said composition. Preferably, the retarder component comprises: a fluid 1,3-divinyl, tetramethyldisiloxane, in an amount of about 0.030 to 0.12 weight percent of said composition.
FIG. 3 is a graph showing the difference in the charcteristics of the base and catalyst components of the present invention.
FIG. 5 is a graph representing the development of viscosity during the setting reaction of the material accorindg to the invention by a time sweep with an oscillation rheometer.
The QM resin provides a vinyl concentration in the dispersions with the vinyl-terminated polydivinylsiloxanes of at least about 0.16 m-mole/g. Preferably the vinyl concentration is 0.16-0.24 m-mole/g. The amount of QM resin is preferably about 20-25% by weight of the dispersion. Such dispersions are sold by Miles, Inc. of Pittsburg, Pennsylvania. Other QM resin formulations may be used, including those that are "neat" or dispersed in carriers other than the preferred fluid polydivinylsiloxane.
A key element of the invention is a retarder component that delays onset of polymerization of the QM resin/dispersion such that sufficient working times to employ the composition are provided. It functions, as it is consumed, to offset what would otherwise be a too rapid polymerization. The preferred retarder fluid in the preferred impression material of interest is 1,3 divinyltetramethyldisiloxane at a sufficient concentration level to perform its retarding functions, which is in at least about 0.03 weight percent of the composition, preferably within a range of about 0.03 to 0.12 weight percent. This preferred amount is in contrast with the lower amounts of 0.0015-0.020 weight percent typically employed in PVS systems to stabilize compositions. Other suitable retarders are any low molecular weight, vinyl functional material that would be initially consumed in the polymerization, to delay hardening suitably and as desired, including linear and cyclic polysiloxanes.
The compositions of the present invention also include a filler, preferably a mixture of hydrophobic fillers. A wide variety of inorganic, hydrophobic fillers may be employed such as silicas, aluminas, magnesias, titanias, inorganic salts, metallic oxides and glasses. It is preferred, however, that forms of silicone dioxides be employed. In accordance with the present invention, it has been found to be preferable to employ mixtures of silicone dioxides, including those derived form: crystalline silicone dioxide, such as pulverized quartz (4-6μ); amorphous silicone dioxides, such as a diatomaceous earth (4-7μ); and silanated fumed silica, such as Cab-o-Sil TS-530 (160-240 m2 /g), manufactured by Cabot Corporation. The sizes and surface areas of the foregoing materials are controlled to control the viscosity and thixotropicity of the resulting compositions. Some or all of the foregoing hydrophobic fillers may be superficially treated with one or more silanating or "keying" agents, as known to those of ordinary skill in the art. Such silanating may be accomplished through use of known halogenated silanes or silazides. The fillers are present, preferably, in amounts of from about 15 to about 45 weight percent of the composition, forming an impression composition that is polymer rich and, thus, having improved flow properties. The fillers, more preferably, are about 35-40 weight percent of the composition. A preferred filler mixture for a higher viscosity formulation includes 14-24 weight percent crystalline silicone dioxide, 3-6 weight percent amorphous silicone dioxide and 4-8 weight percent silanated fumed silicone dioxide. A most preferred filler is about 19% cristobalite at about 4-6μparticle diameter, about 4% diatomaceous earth at about 4-7μparticle diameter and about 6% silanated fumed silica at about 160-240 m2 /g.
A chemical system may be employed to diminish the presence or degree of hydrogen outgassing which may be typically generated as a result of the vinyl polymerization. The composition thus may comprise a finely divided platinum metal that scavenges for and takes up such hydrogen. The Pt metal may be deposited upon a substantially insoluble salt having a surface area of between about 0.1 and 40m2 /g. Suitable salts are barium sulphate, barium carbonate and calcium carbonate of suitable particle sizes. Other substrates include diatomaceous earth, activated alumina, activated carbon and others. The inorganic salts are especially preferred to lend improved stability to the resulting materials incorporating them. Dispersed upon the salts is about 0.2 to 2 parts per million of platinum metal, based upon the weight of the catalyst component. It has been found that employment of the platinum metal dispersed upon inorganic salt particles substantially eliminates or diminishes hydrogen outgassing during curing of dental silicones.
The surfactant of the invention may be of cationic, anionic, amphoteric or nonionic type. A key criteria for selection is that the Hydrophobic Liphophilic Balance (HLB) value (described by Gower, "Handbook of Industrial Surfactants", 1993) must be in the range of 8-11. As is well-known, the higher the HLB the more hydrophobic is the substance. In addition, the pH of the surfactant must be in the 6-8 range to prevent side reactions that may be detrimental the polymerization of the impression. A preferred surfactant is nonionic, having an HLB value of 10.8 comprising nonylphenoxypoly(ethyleneoxy) ethanol, sold by Rhone-Poulenc of Cranbury, NJ as Igepal CO-530. In comparison it is noted above with respect to Bryan et al, in U.S. '959 that Igepal CO-630, having an HLB of 13.0, differing in structure from CO-530 wherein the number of repeating units in CO-630 is 9 and those of CO-530 is 6, is not effective, demonstrating the criticality of the HLB limitation. The amount of surfactant used to render the composition hydrophilic is based on the rate of wetting. The desired contact angle at three (3) minutes is less than about 50�.
______________________________________             BASE   CATALYST______________________________________Organohydrogen Polysiloxane               9.00     0.00(5000-7000 cps) QM resin dispersion               19.62    23.95(45000-60000 cps) QM resin dispersion               34.59    42.89Cristobalite        19.01    19.06Diatomaceious earth 6.53     6.41Cab-O-Sil TS-530    6.53     6.00Pigments Predispersed in               0.65     0.25Divinyl PolysiloxaneTitanium Oxide Pigment               0.07     0.07Surfactant (Igepal CO-530)               4.00     0.00Plasticizer         0.00     0.50Platinum Catalyst   0.00     0.641,3-Divinyldimethyidisiloxane               0.00     0.07Finely divided Platinum metal               0.00     0.16on Calcium Carbonate               100.00   100.00______________________________________
______________________________________             BASE   CATALYST______________________________________Organohydrogen Polysiloxane               9.00     0.00(5000-7000 cps) QM resin dispersion               20.18    31.71(45000-60000 cps) QM resin dispersion               35.61    35.23Cristobalite        19.74    20.67Diatomaceious earth 4.30     4.28Cab-O-Sil TS-530    6.45     6.42Pigments Predispersed in               0.65     0.25Divinyl PolysiloxaneTitanium Oxide Pigment               0.07     0.07Surfactant (Igepal CO-530)               4.00     0.00Plasticizer         0.00     0.50Platinum Catalyst   0.00     0.641,3-Divinyldimethyidisiloxane               0.00     0.07Finely divided Platinum metal               0.00     0.16on Calcium Carbonate               100.00   100.00______________________________________
______________________________________             BASE   CATALYST______________________________________Organohydrogen Polysiloxane               10.00    0.00(5000-7000 cps) QM resin dispersion               14.73    26.91(45000-60000 cps) QM resin dispersion               43.80    43.80Cristobalite        17.00    17.40Diatomaceious earth 5.00     5.00Cab-O-Sil TS-530    5.00     5.00Pigments Predispersed in               0.40     0.50Divinyl PolysiloxaneTitanium Oxide Pigment               0.07     0.07Surfactant (Igepal CO-530)               4.00     0.00Plasticizer         0.00     0.50Platinum Catalyst   0.00     0.651,3-Divinyldimethyidisiloxane               0.00     0.07Finely divided Platinum metal               0.00     0.10on Calcium Carbonate               100.00   100.00______________________________________
______________________________________             BASE   CATALYST______________________________________Organohydrogen Polysiloxane               10.00    0.00(5000-7000 cps) QM resin dispersion               19.40    32.37(45000-60000 cps) QM resin dispersion               36.03    36.03Cristobalite        20.00    20.00Diatomaceious earth 5.00     5.00Cab-O-Sil TS-530    5.00     5.00Pigments Predispersed in               1.50     0.00Divinyl PolysiloxaneTitanium Oxide Pigment               0.07     0.07Surfactant (Igepal CO-530)               3.00     0.00Plasticizer         0.00     0.50Platinum Catalyst   0.00     1.001,3-Divinyldimethyidisiloxane               0.00     0.03Finely divided Platinum metal               0.00     0.00on Calcium Carbonate               100.00   100.00______________________________________
______________________________________             BASE   CATALYST______________________________________Organohydrogen Polysiloxane               11.00    0.00(5000-7000 cps) QM resin dispersion               14.36    28.44(45000-60000 cps) QM resin dispersion               43.07    42.64Cristobalite        17.00    17.19Diatomaceious earth 5.00     4.95Cab-O-Sil TS-530    5.00     4.95Pigments Predispersed in               1.50     0.00Divinyl PolysiloxaneTitanium Oxide Pigment               0.07     0.07Surfactant (Igepal CO-530)               3.00     0.00Plasticizer         0.00     0.49Platinum Catalyst   0.00     1.131,3-Divinyldimethyidisiloxane               0.00     0.06Finely divided Platinum metal               0.00     0.09on Calcium Carbonate               100.00   100.00______________________________________
______________________________________             BASE   CATALYST______________________________________Organohydrogen Polysiloxane               9.52     0.00(5000-7000 cps) QM resin dispersion               11.19    27.91(45000-60000 cps) QM resin dispersion               38.07    38.21Cristobalite        22.84    21.21Diatomaceious earth 5.71     5.73Cab-O-Sil TS-530    5.71     5.73Pigments Predispersed in               1.58     0.00Divinyl PolysiloxaneTitanium Oxide Pigment               0.13     0.13Surfactant (Tergitol 15-S-3)               4.76     0.00Plasticizer         0.48     0.48Platinum Catalyst   0.00     0.481,3-Divinyldimethyidisiloxane               0.00     0.05Finely divided Platinum metal               0.00     0.08on Calcium Carbonate               100.00   100.00______________________________________
______________________________________             BASE   CATALYST______________________________________Organohydrogen Polysiloxane               9.52     0.00(5000-7000 cps) QM resin dispersion               11.19    27.91(45000-60000 cps) QM resin dispersion               38.07    38.21Cristobalite        22.84    21.21Diatomaceious earth 5.71     5.73Cab-O-Sil TS-530    5.71     5.73Pigments Predispersed in               1.58     0.00Divinyl PolysiloxaneTitanium Oxide Pigment               0.13     0.13Surfactant (Igepal CO-630)               4.76     0.00Plasticizer         0.48     0.48Platinum Catalyst   0.00     0.481,3-Divinyldimethyidisiloxane               0.00     0.05Finely divided Platinum metal               0.00     0.08on Calcium Carbonate               100.00   100.00______________________________________
______________________________________             BASE   CATALYST______________________________________Organohydrogen Polysiloxane               9.52     0.00(5000-7000 cps) QM resin dispersion               11.19    27.91(45000-60000 cps) QM resin dispersion               38.07    38.21Cristobalite        22.84    21.21Diatomaceious earth 5.71     5.73Cab-O-Sil TS-530    5.71     5.73Pigments Predispersed in               1.58     0.00Divinyl PolysiloxaneTitanium Oxide Pigment               0.13     0.13Surfactant (Igepal CO-210)               4.76     0.00Plasticizer         0.48     0.48Platinum Catalyst   0.00     0.481,3-Divinyldimethyidisiloxane               0.00     0.05Finely divided Platinum metal               0.00     0.08on Calcium Carbonate               100.00   100.00______________________________________
______________________________________             BASE   CATALYST______________________________________Organohydrogen Polysiloxane               9.52     0.00(5000-7000 cps) QM resin dispersion               11.19    27.91(45000-60000 cps) QM resin dispersion               38.07    38.21Cristobalite        22.84    21.21Diatomaceious earth 5.71     5.73Cab-O-Sil TS-530    5.71     5.73Pigments Predispersed in               1.58     0.00Divinyl PolysiloxaneTitanium Oxide Pigment               0.13     0.13Surfactant (Igepal CO-430)               4.76     0.00Plasticizer         0.48     0.48Platinum Catalyst   0.00     0.481,3-Divinyldimethyidisiloxane               0.00     0.05Finely divided Platinum metal               0.00     0.08on Calcium Carbonate               100.00   100.00______________________________________
______________________________________             BASE   CATALYST______________________________________Organohydrogen Polysiloxane               9.52     0.00(5000-7000 cps) QM resin dispersion               11.19    27.91(45000-60000 cps) QM resin dispersion               38.07    38.21Cristobalite        22.84    21.21Diatomaceious earth 5.71     5.73Cab-O-Sil TS-530    5.71     5.73Pigments Predispersed in               1.58     0.00Divinyl PolysiloxaneTitanium Oxide Pigment               0.13     0.13Surfactant (Igepal CO-530)               4.76     0.00Plasticizer         0.48     0.48Platinum Catalyst   0.00     0.481,3-Divinyldimethyidisiloxane               0.00     0.05Finely divided Platinum metal               0.00     0.08on Calcium Carbonate               100.00   100.00______________________________________
Equal parts of the base and catalyst components are mixed and the samples or specimen is placed in a specimen mold having an I-shaped cavity that is 1.5 mm thick, 20 mm�11 mm, with top arms of 8 mm depth and center I portion 5 mm wide. The filled mold is clamped between two stainless steel plates and the assembly is placed in a 32� C. water bath. At six minutes from start of mix, the assembly is removed from the bath. The mold is unclamped, the specimen is removed from the mold and any flash is removed from the specimen. At 10 minutes from start of mix the specimen is clamped into the specimen test grips of an Instron Model 1123 in the extension mode. The Instron is attached to a Microcon II micropressor that has been programmed to calculate the tear strength psi!,% elongation, and modulus of elasticity. At 11 minutes, the specimen is stressed by the Instron at a rate of 10 mm/min. until the specimen reaches peak failure. (The maximum load is set to 5 kg.) This is repeated for five specimens and then statistically evaluated results are reported, as shown in Table I.
Wetting contact angles are measured for each Example as follows. One gram (1g) of base and one gram (1g) of catalyst paste are mixed together until uniform (˜30 seconds). A one-half gram (0.5g) of mixed paste is placed between two sheets of polyethylene (Dentsilk) and pressed flat using a glass plate, about 2-3 mm thick. The specimen is allowed to stand undisturbed until set (˜15 minutes). The polyethylene sheets are removed, being careful not to touch the surface of the specimen, and the specimen placed on the table of a gynometer, a well known device for measuring contact angles. The eyepiece recticle is adjusted to the horizontal and vertical planes of the specimen surface and stop watch is started as a drop of water is dropped onto the specimen surface. At 1.5 minutes to 3.5 minutes, the inside contact angle, in degrees, of the water/specimen interface is measured using the gynometer scale, recorded for the specimen and reported in Table I hereinbelow.
TABLE I__________________________________________________________________________PROPERTIES OF EXAMPLES    ExamplesProperty 1   2   3   4   5   6  7  8  9  10__________________________________________________________________________Work Time (min)    3   3   3   2   3   4.25                           2.50                              3.33                                 3.18                                    2.50Set      6   6   6   4   6   9  5  7  7  5.75% Deformation    0.5 0.25            0.45                0.3 1.9 4.25                           1.7S                              2.25                                 23 1.65% Strain 2.75        3.15            3.25                2.75                    3.5 NA NA NA NA NAConsistency (mm)    33  34  36  32  38  33 29 32 31 30Contact Angle with    30  35  38  37  42  28 52 56 42 31water at 3 min. (�)Tear Strength PSI    277 277 295 289 216 NA NA NA NA NA__________________________________________________________________________
______________________________________               BASE  CATALYST______________________________________Organohydrogen Polysiloxane                 8.0     --(5000-7000 cps) QM resin dispersion                 28.7    39.6(45000-60000 cps) QM resin dispersion                 12.3    16.7Cristobalite          32.0    39.6Diatomaceious earth   --      --Cab-O-Sil TS-530      3       3Pigments Predispersed in Divinyl Polysiloxane                 1       --Titanium Oxide Pigment                 --      --Surfactant (Igepal CO-530)                 7.5     --Plasticizer           --      --Platinum Catalyst     --      0.361,3-Divinyldimethyidisiloxane                 --      0.11Finely divided Platinum metal                 --      0.60on Calcium CarbonateDried Calcium Sulfate 5.0     --Organic Pigments      2.5     --Total                 100.00  100.00______________________________________
______________________________________               BASE  CATALYST______________________________________Organohydrogen Polysiloxane                 9.0     0(5000-7000 cps) QM resin dispersion                 13.2    29.6(45000-60000 cps) QM resin dispersion                 47.27   47.27Cristobalite          14.0    14.0Diatomaceious earth   4       4Cab-O-Sil TS-530      4       4Pigments Predispersed in Divinyl Polysiloxane                 1       --Titanium Oxide Pigment                 0.035   0.035Surfactant (Igepal CO-530)                 5       --Plasticizer           --      --Platinum Catalyst     --      0.281,3-Divinyldimethyidisiloxane                 --      0.014Finely divided Platinum metal                 --      0.8on Calcium CarbonateDried Calcium Sulfate --      --Organic Pigments      2.5     --Total                 100.00  100.00______________________________________
______________________________________               BASE  CATALYST______________________________________Organohydrogen Polysiloxane                 7.5     0(5000-7000 cps) QM resin dispersion                 35.56   44.89(45000-60000 cps) QM resin dispersion                 11.84   14.97Cristobalite          29      31.63Diatomaceious earth   0       --Cab-O-Sil TS-530      3       3Pigments Predispersed in Divinyl Polysiloxane                 0.9     --Titanium Oxide Pigment                 --      --Surfactant (Igepal CO-530)                 5       --Plasticizer           --      --Platinum Catalyst     --      0.551,3-Divinyldimethyidisiloxane                 --      0.056Finely divided Platinum metal                 --      0.5on Calcium CarbonateDried Calcium Sulfate 5       5Organic Pigments      2.2     0Total                 100.00  100.00______________________________________
TABLE II______________________________________      ExamplesProperty     12          13      14______________________________________Work Time (min)        2.92        3.33    3.50Set Time (min)        5.67        7.25    7.00% Deformation        0.45        1.85    1.20% Strain     3.9         6.0     4.2Consistency (mm)        40          41      40Contact Angle with        33          50      40water at 3 min. (�)Tear Strength (PSI)        200         166     220______________________________________
a4. from about 50 to about 60 percent by weight based upon 100 percent by weight of the base paste of low molecular weight QM-resins optionally containing functional groups reactive in the hydrosilylation reaction and ethoxy groups and being homogeneously soluble in al and including SiO4/2, RO1/2 and R3 SiO1/2 in which R represents n-alkyl, phenyl or vinyl and has an alkoxy group content from less than 4 mmol/g,
b1 . from about 1 to about 5 percent by weight based upon 100 percent by weight of the catalyst paste of linear dimethylvinyl terminated polydimethylsiloxanes,
b2. from about 30 to about 35 percent by weight based upon 100 percent by weight of the catalyst paste of dimethylvinylsilyl terminated polydimethylsiloxanes containing 20-35% highly disperse SiO2 b3. from about 55 to about 70 percent by weight based upon 100 percent by weight of the catalyst paste of low molecular weight QM-resins optionally containing functional groups reactive in the hydrosilylation reaction and ethoxy groups and being homogeneously soluble in al and comprises SiO4/2, RO1/2, and R3 SiO1/2 in which R represents n-alkyl, phenyl or vinyl and has an alkoxy group content from less than 4 mmol/g
b4. from about 0 to about 10 percent by weight based upon 100 percent by weight of the catalyst paste of linear dimethyl-(vinylmethyl)-siloxane copolymers with dimethylvinylsilyl termination's ,
b5. from about 0.5 to about 1.5 percent by weight based upon 100 percent by weight of the catalyst paste of Pt-catalyst prepared from H2 PtCl6 and tetramethyldivinyldisiloxane
b7. H2 -adsorbent; and optionally
All "%" and "percent" are by weight. A low viscosity type dental impression material is provided having the flow characteristics under clinical conditions combined with a high tear strength to maintain the subgingival undercuts. "Low" viscosity as used herein means that of type 3 accordingly to ISO 4823. These characteristics are demonstrated by the following physical parameter:
h.sub. 200 Pa! =5.0-15.0 Pas for single pastes
h.sub. 200 Pa! =15.0-25.0 Pas for the mix
and a yield stress of: θ.sub. 0-10 Pa! less than about 5.0 Pa contact angle: less than about 45� tear strength: greater than about 1.5 MPa
Wherein al and bi are characterised as vinyl terminated dimethyl polysiloxanes according to the formula ##STR3## specified with a viscosity in the range of 0.2-200 Pas at 20� C. and vinyl content of 0.01-0.5 mval/g. The letter "n" represents an integer of from 50 to about 1300, although this is not an absolute limitation of the invention. The component a2 is characterised as an organpolysiloxane according to the formula ##STR4## having at least three Si-bonded hydrogen atoms per molecule. Suitably, this organopolysiloxanes contain 2.0-8.5 mval/g of active SiH-units.
The components a4 and b3 are characterised in that they contain tetrafunctional SiO4/2 as Q-moieties and monofnctional R3 SiO1/2 as M-units, in which R can be alkyl aryl or alkenyl most preferably methyl or vinyl. Moreover, trifunctional RSiO3/2 (silsesquioxane-units or T-units) and R2 SiO2/2 as D-units can be present wherein the content of these QM-units has to be higher than about 10%.
The components a6 and b6 are characterised as the product of a copolymerization reaction of dimethyl-dihalogenosilanes or dimethyldialkoxysilanes with methylvinyl dihalogenosilanes or methylvinyl dialkoxysilanes leading to a copolymer according to the formula ##STR5## with wherein R is as above preferably a vinyl giving a vinyl content of 0.5-3.0 mval/g, and a viscosity of η(20� C.)=200 mPas-10,000 mPas. One preferred R group is (CH2)3 --O-- CH2 CH2 --O!x --CH3 where x is an integer of from about 2 to about 10.
Component a7 is characterised as nonylphenoxy poly(ethyleneoxy)-ethanol, and b5 is characterised as the product of the reaction of hydrous chloroplatinic acid with tetramethyldivinyldisiloxane.
Component b7 is characterised as highly disperse platinum or palladium on charcoal, calciumsulfate, alumina or zeoliths.
In the disucssion to follow reference will be made to FIGS. 3-4 as were briefly discussed hereinabove. In FIG. 3, the x-axis shows the frequency omega in 1/s, and the two y-axis show the shear stress G'(left y-axis) in Pascal (Pa) and the viscosity n' in Pascal seconds (Pas) (left y-axis). In FIG. 4, the x-axis is time in seconds (s). The y-axis is again the shear strees G in Pa on the left y-axis. On the right y-axis, there are two parameters, the viscosity n' in kPas and the loss angle. The shear modulus G' of a fluid system is split into two parts. The storage modulus G' represents the elastic properties of the system, whereas the loss modulus G" represents the viscous properties. The loss angle, delta, represents the angle between G' and G" in the triangle developed by the axis, G' and G". FIG. 5 has the same x and y axis as FIG. 4.
Furthermore, in FIG. 3, the letter "A" represents the shear modulus G'; the letter "B" represents delta or the loss angle between G' and G"; and "C" represents n', the viscosity in Pas. In FIG. 4, the small circle graphical information represents delta; the letter "V" in a circle represents the viscosity; the astrics represent the shear stress G; the small squares represent the storage modulous G'; and the diamond shape represents information for the loss modulous G".
The catalyst paste according to the invention even with an aerosil content of 10% shows nearly Newtonian flow characteristics with constant viscosity of 10.0 Pas and no yield stress or thixotropic effect. The rheological properties of the single pastes according to the invention have been measured by a frequency sweep with an oscillation rheometer (CS-50 Fa. Bohlin) . FIG. 3 shows the difference between the non Newtonian flow characteristics of the Base and the quasi-Newtonian behaviour of the Catalyst.
The thixotropy of a base paste according to the invention can be shown by a time sweep measured with oscillation rheometer under non-disordering conditions. The sample was placed on the plate of a cone/plate measuring system. After lowering the upper plate a boost stress of 200 Pa was applied on the material for a period of 5 sec. to disturb the Theological substructure responsible for the yield stress. The relaxation of the elastic properties was measured by oscillation with a frequency of 1 Hz and a deformation of 0.0005 radian in periods of 10 sec. As can be seen in the graph of FIG. 4 at the beginning of the measurement the loss modulus (G") is higher than the storage modulus (G') and the paste behaves as a liquid. After the relaxation time of ca. 600 seconds (sec.) the substructure is rebuilt and the material shows elastic behaviour. By side of the typical relaxation time the gel point, when G"=G' is characteristic for the thixotropic behaviour of non Newtonian fluids. The time tg (usm) for reaching this gel point is at least 90 sec. for a base paste according to the invention.
The material according to the invention has been developed preferably for the application as a dental cartridge material. Because of the Theological properties of the material according to the invention only very low forces are necessary to release the material out of the cartridge. Therefore very small static mixers can be used to release the material according to invention out of the cartridge, resulting in a minimal rate of waste and a large reduction of costs for the user. By "low viscosity" herein, it is meant that according to ISO 4823.
To investigate the development of viscosity during the setting reaction of the material according to the invention a sample (Example B) was measured in a time sweep with an oscillation-rheometer (Fig. 5) . The material was released out of a cartridge (as used in dental applications) immediately on the plate of a cone/plate measuring system and the measurement was started 10 sec. after release. The first value of viscosity was registrated 15 sec. after release. The measurement was carried out under non disordering conditions with a frequency of 1 Hz, a deformation of 0.001 radians and a measuring period of 10 sec. Under these conditions the rheological substructures are not disturbed by the torque of the oscillation (as it can be shown in a amplitude sweep of both single pastes). As shown in FIG. 5 the viscosity rises very fast in the first period of the reaction. This effect can by explained by relaxation of the shear stress caused by the release out of the cartridge (thixotropic effect). At the beginning of the setting reaction the loss angle δ is higher than about 45�. That means at this time the material has no yield stress. As a liquid the material is able to flow on the surface of the teeth at low shear stress even under the influence from gravity, when it is syringed out of the cartridge.
Important for the kinetics of the setting reaction is at first the gel time tg (set material) and second the setting time tc. The gel time tg (set material) is reached when the loss angle δ=arctan(G"/G') has the maximum value. In cases when there is no maximum for the loss angle (when δ>45�) the gel time is reached when the loss angle passes 45� (G'=G") . The setting time is reached when the storage modulus G' has reached its plateau.
In the examples A and B according to the invention the formed network is partly interpenetrated by the existing network of QM-resins. This allows additional network strength. These QM-resins are characterised in that they contain tetrafunctional SiO4/2 as Q-moieties and monofunctional R3 SiO1/2 as M-units, in which R can be alkyl, aryl or alkenyl most preferably methyl or vinyl. Moreover, trifunctional RSiO3/2 (silsesquioxane-units or T-units) and R2 SiO2/2 as D-units can be present. The content of these QM-resins is preferably higher than about 10%. A lower content as in the case of Example E is not sufficient to increase the tear strength.
Adding a filler to reinforce the mechanical strength is not necessary in the case of a material according to the invention. The fillers used are only necessary to adjust the Theological properties and to adsorb moisture from the surfactant or environment. Even with a filler content of less than 15% by weight the material according to the invention (Examples A, B and D) has a higher tear strength than conventional highly filled light bodies (filler content greater than 40% by weight, Example F). In combination with a high strain in compression the improved mechanical strength is able to maintain the subgingival undercuts.
To improve the wetting properties a high amount of surfactant has been added to the material according to the invention in order to achieve a very low contact angle to water. The surfactants are the same as earlier described. Surprisingly these high amounts of surfactant lead to only a very low yield stress of less than 5 Pa in the case of the base paste (Examples A, B and D). Conventional light bodies (Example F) have higher yield stresses with even lower content of surfactant. As it is seen in FIG. 3 this low yield stress of the base paste does not lead to a yield stress of the syringed material. It is caused by a Theological substructure, which is disturbed by shear stress during releasing out of the cartridge.
(all %'s are by weight)
7.5mval/g)
2:66.5% dimethylvinyl terminated polydimethylsiloxane containing QM-resins.
0.07W Pt/CaCO3
0.20W Pigment
6.0% dimethylvinyl terminated dimethyl(methylvinyl)-siloxane copolymers (viscosity 5.0 Pas)
1.0% dimethylvinyl terminated dimethyl(methylvinyl)-siloxane copolymers (viscosity 0.2 Pas)
10.0% dimethylvinyl terminated polydimethylsiloxane containing methylsilesquisiloxane resins. 32.00% dimethylvinyl terminated polydimethylsiloxanes containing high disperse SiO2 0.4% Pt-catalyst
10.0% dimethylvinyl terminated polydimethylsiloxanes containing high disperse SiO2 8.4% W crosslinking H-Silicones (SiH-content 4.3 mval/g)
Determination of Theological parameters for the examples according to the invention was as follows.
In pastes containing a surfactant (base-pastes) a Theological substructure is built up by the dipolar molecules of the surfactant. At a stress below the yield stress, these micelles together with the filler build up a solid structure. The system behaves quasi-elastically characterised by linear shear-stress/stress-modulus relation. When the shear stress increases the viscosity of the material reaches a maximum and the yield stress is passed over, the substructures are disturbed and the system behaves as a non-Newtonian fluid. The yield stress has been measured with a shear stress slope of 0-100 Pa in a time of 120 seconds. It is noted that this parameter is strongly dependent on the stress/time slope, a steeper slope will result in a lower yield stress. Because of this, the rheological parameters of such systems are usually measured under definite stress situations.
Most often the reorganization of the disturbed substructures is combined with a relaxation time. In such thixotropic systems even the stress history of the system has to be taken into account by the measurement of all Theological parameters. Therefore the material is put on the plate of a cone/plate measuring system 20 minutes (min) before measuring the yield stress. The viscosity is measured in the creep test immediately after putting the material on the measuring system in the case of the single pastes and after a period of 30 sec in the case of the mixed material
The setting time tc, is measured in a time sweep on a Rotation/Oscillation-Rheometer (CS-50 Fa. Bohlin) in the oscillation mode. The measurement has to be carried out under non-destructive conditions. These conditions can be realised by measuring inside of the linear viscoelastic range of both the set and unset material. Optimal conditions for the setting reaction of addition curing silicones are a frequency of 1 Hz and a deformation of 0.001. The setting time is read when the shear modulus G*=G'+G" has reached the plateau. The setting time has clinical relevance for the dentist because this period of time is identical with the minimal removal time.
TABLE III__________________________________________________________________________physical parametersExample    Example A            Example B                  Example C                        Example D                              Example E                                    Example F__________________________________________________________________________viscosity A      10.4 Pas            10.1 Pas                  8.18 Pas                        7.37 Pas                              2.39 Pas                                    42.2 PasB          13.3 Pas            13.3 Pas                  10.4 Pas                        9.01 Pas                              8.15 Pas                                    67.2 Pasmix        21.2 Pas            21.1 Pas    16.8 Pas    76.8 Pasyield stress (base)      2.13 Pa     2.63 Pa                        2.61 Pa                              3.44 Pacontact angle to water      42.7�            38.3�                  44.8�                        43.7�                              40.2�                                    ca. 45�strain in compression      8.0%  6.43% 7.33% 5.23% 6.93% 3.5-5.0%tear strength      1.61 MPa            1.74 MPa                  0.85 MPa                        1.54 MPa                              0.68  1.5-3.0working time (ADA 19)      106 s 140 s 120 s 104 s 153 s 120-150 scompression set      0.30% 0.25% 0.15% 0.33% 0.28% &lt;0.5%(ADA 19)setting time tc      300 s 300 s 305 s 325 s       &lt;300 s__________________________________________________________________________
TABLE IV__________________________________________________________________________   Example A         Example B               Example C                     Example D                           Example E                                 Example F__________________________________________________________________________min. viscosity &#951;*   39 Pas         35 Pas               11 Pas                     45 Pas                           16 Pas                                 140 Pasgel time tg (usm)   101 s 101 s *     30 s  11 s  24.5__________________________________________________________________________ *The basepaste of Example C shows a very long gel time in the time sweep. This formulation has a very week rheological substructure which is disturbed under the measuring conditions (1.0 Hz, 0.0005 radian). It tend to separate under the influence from gravity. Therefore the measurement o the thixotropic effects are without any physical relevance.
Together with the gel time the min. viscosity η* after disturbing the Theological structure is important for the flow characteristics of the material. Only in the examples according to the invention (Example A, B and D) a long gel time is combined with a low viscosity.
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KgDental Impression Masses, Hardened Products Produced from them, and Use of Surfactants for the Production of Dental Impression MassesUS20110160332 *Mar 11, 2011Jun 30, 20113M EspeCurable silicone impression materials with high tear strength and low consistencyDE19915004A1 *Apr 1, 1999Oct 5, 2000Espe Dental AgSilicone-based molding materials used for preparing dental molds include polyalkylene oxide compound to improve rigidity of molding material* Cited by examinerClassifications U.S. Classification525/478, 264/16, 433/214, 524/493, 528/31, 523/109, 524/588, 106/38.22, 528/32, 106/35, 528/15, 528/39International ClassificationC08L83/04, A61K6/10Cooperative ClassificationC08G77/70, C08G77/18, C08L83/04, A61K6/10, C08G77/12, C08G77/20, C08G77/80, C08G77/44European ClassificationA61K6/10, C08L83/04Legal EventsDateCodeEventDescriptionApr 11, 1997ASAssignmentOwner name: DENTSPLY DETREY G.M.B.H., GERMANYFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:FIEDLER, JURGEN HANS;REEL/FRAME:008452/0016Effective date: 19970327May 2, 2002FPAYFee paymentYear of fee payment: 4May 21, 2002REMIMaintenance fee reminder mailedMay 24, 2006REMIMaintenance fee reminder mailedNov 3, 2006LAPSLapse for failure to pay maintenance feesJan 2, 2007FPExpired due to failure to pay maintenance feeEffective date: 20061103RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services