Patent Application
20090098503
The invention relates to foam-generating, hardening compositions for forming impressions of surfaces, as well as impression trays for use therewith.
Irreversible plastic impression materials, such as alginates, polysulfides, C- or A-silicones, or polyethers are based on two components which must be homogenized and reacted with one another, before the impression is formed, by a complex process either by hand or by using static or dynamic, hand-operated or electrically driven mixing systems, for example mixing systems presently used in dentistry.
DE 19505896A1 (corresponding to U.S. Pat. No. 6,040,354) discloses a readily mixable impression material with high texture definition. Desirable is the consistency of whipping cream, i.e., the material should be easily deformable, but still firm. DE 19505896A1 proposes formation of a micro-fine crystal mesh in the pastes. These are free of bubbles.
Foamed silicone materials or silicone materials containing foaming agents are known in the art.
DE3210094 is directed to in situ formation of hollow microspheres in silicone impression materials by using foaming agents.
DE4029888A1 (corresponding to U.S. Pat. No. 5,256,726) discloses reactive systems which are potentially useful as impression materials for the preparation of polyurethanes, which may be provided as foams. However, the disclosure does not suggest a connection between forming an impression and foam. It therefore remains an open question if the foamed variant is recommended or suitable as material for a forming impressions.
DE10100736C2 is directed to a release agent based on organosilicone, wherein bubbles are formed by using a propellant. However, this material is not employed for forming impressions.
U.S. Pat. No. 4,677,139 is directed to a foam composition for use in dentistry, for example as wound dressing or compression dressing, or more particularly for temporarily separating the gum from the tooth, for example to facilitate obtaining impressions or in gum surgery.
Another material is the product Magic Foamcord, distributed by the company Coltène/Whaledent Inc. The material is used for sulcus expansion, but not for impressions, and also does not contain a foaming agent (EP1603480A1).
With this product, the surface making contact (the sulcus) is expanded by the expanding material. This characteristic distinguishes over a foam for making impressions of surfaces, because the foam must not alter the surface structure; otherwise, the accuracy of the impression would be adversely affected. Moreover, unlike the present invention, the product Magic Foamcord expands only through reaction with water, or humidity in the air, which expands its lumen through the foaming action.
DE10108038C1 (corresponding to U.S. 2004/007291) and -9C1 describe isocyanate-free, foamable mixtures with foaming agents. The application is limited to the production of industrial spray foams for construction projects and for device insulation. The non-toxic material is particularly recommended for minimizing the risk to non-commercial users.
It is an object of the present invention to provide a composition which obviates the need for using manually operated and/or electrically driven mixing systems and which can in addition also produce a foam structure.
A further object is to provide an impression tray for use with the composition of the invention.
The present invention is directed to a foam-generating, self-supportingly hardening composition for forming impressions of biological surfaces, in particular a dental composition, preferably containing a foaming agent, based on isocyanates, which react, for example, with mono-functional and multi-functional amines and/or with materials containing hydroxyl groups by forming urethane or urea, or A-silicones, or C-silicones or polyethers, or one or more alpha-silanes, or mixtures of thereof.
Advantageous embodiments are:
The invention also relates to an impression of biological surfaces made from such impression material, in particular a human impression, such as a dental impression, with a foam having closed pores.
Particularly suitable are materials based on a tri-, di- or mono-alkoxy-alpha-silane (e.g., an alpha-amino-trimethoxy-silane).
The preferably employed alpha-silanes are commercially available, for example, from the company Wacker. They are presently used in building foams, for example for attaching door components and for insulation. The foams have significantly lower toxicity than conventional isocyanate-based foams.
The hardening foam according to the invention has the following advantages:
a and b show an embodiment with two-chamber pressurized cartridges and the corresponding impression tray;
a and b show an embodiment with two-chamber pressurized cartridges having different foaming agent fractions.
The impression tray of the invention includes passageways 1 for supplying and discharging the foam. Also visible is the circular dam 2 for sealing the transition tray/gum.
In another embodiment, the impression tray may be provided with a stronger dam 3 facing the throat.
Suitable materials for the foam according to the invention are, for example, systems based on isocyanate which react, for example, with mono- and multi-functional amines and/or compounds having hydroxyl groups by forming urethane or urea, also A- or C-silicone and polyether, or mixtures thereof. Particularly suited are materials based on a tri-, di- or mono-alkoxy-α-silane (e.g., an α-amino-trimethoxy-silane).
The preferably employed alpha-silanes are available, for example, from the company Wacker. They are presently used in building foams, for example for attaching door components and for insulation. The foams have a significantly lower toxicity than conventional isocyanate-based foams.
A foam can be formed by selecting a suitable primary packing material which introduces, for example in the mixing device, into the impression material gases, which provide the material with a foam-like structure after the material exits the mixing device.
Preferably, foaming agents such as nitrogen or carbon dioxide, low-molecular hydrocarbons, such as pentane, butane, propane and mixtures thereof, or gas-forming chemicals, such as sodium bicarbonate with citric acid, are used which are directly added either to the base component, or to the catalyst component, or to both components.
The foaming agent and the propellant nay also be separated in multi-chamber containers, whereby the characteristic material properties can be precisely adjusted for a particular application.
Particularly preferred embodiments of the invention will now be described with reference to the following examples Parts and percentages refer to weight unless indicated otherwise:
An impression material consisting of
a) a base paste of an A-silicone impression material with a typical commercially used composition, in this case the commercial product Flexitime Correct Flow1 (Charge 250327) from the company Haraeus Kulzer GmbH, and Note: 1 The impression material Flexitime is a two-phase, addition-cross-linked, polyvinyl siloxane (see 3.3). it consists of a high-viscosity (Heavy-Tray) and a low-viscosity (Correct Flow) phase. In the Heavy-Tray-phase, the base paste and the reactor paste are mixed in the so-called Penta-Mixer. The Correct-Flow-phase is mixed with a mixing cannula and dispenser and applied manually. The curing time of the phases is 3.5-5 minutes. In the addition-cross-linked silicones (A-silicones) the base component includes linear chains with vinyl end groups. The reactor component is composed of organo-hydrogen-siloxanes. Organic platinum compounds function as catalyst. When the two components are mixed, ethyl bridges are formed, without producing low-molecular, volatile substances (poly-addition).
b) a catalyst paste of the commercial product Flexitime Correct Flow (Charge 250334), is filled into two-chamber pressurized gas cartridges. In this example, the propellant is pentane (see
The handling time of the impression material is significantly reduced compared to a manually operated impression gun in which a 50 ml solid cartridge is inserted. The impression material can hence be applied with significantly improved dosing and better placement, because the mixing nozzle does not move back and forth as a result of a manual pumping motion.
Surprisingly, unlike the conventional material supplied from a solid cartridge and mixed with a static mixer, the formed silicone has a foam structure. The Shore A hardness is thereby reduced by about 10 units to 36 units (measured 10 minutes after the start of the mixing process). The processing time and curing time of this A-silicone are similar to those of the conventional product. The pores in the cured impression material are located almost entirely inside the hardened material, whereas the surface of the impression is almost bubble-free and extremely uniform.
An impression material consisting of
a) a base paste of an A-silicone impression material with a typical commercially used composition, in this case the commercial product Flexitime Correct Flow (Charge 250327) from the company Haraeus Kulzer GmbH, and
b) a catalyst paste of the commercial product Flexitime Correct Flow (Charge 250334), is filled into two-chamber pressurized gas cartridges. In this example, the propellant is pentane; in addition, 5% pentane are added to the base paste as foaming agent and internal propellant (see
The handling time of the impression material is significantly reduced compared to a manually operated impression gun in which a 50 ml solid cartridge is inserted. The impression material can hence be applied with significantly improved dosing and better placement, because the mixing nozzle does not move back and forth as a result of a manual pumping motion.
As expected, unlike the conventional material supplied from a solid cartridge and mixed with a static mixer, the formed silicone has a foam structure. The Shore A hardness is thereby reduced by about 19 units to 27 units (measured 10 minutes following the start of the mixing process). It can be visually observed that the volume of the impression material increases continually by about 10 to 15% until the time of setting, thus exhibiting the desired foaming pressure commensurate with the intended application. The processing time and curing time of this A-silicone are similar to those of the conventional product. The pores in the cured impression material are in this case also located almost entirely inside the hardened material, whereas the surface of the impression is almost bubble-free and extremely uniform.
Due to its high elasticity and damping characteristic, a silicone material similar to the present structure appears to be suitable as a mouth guard for sports activities.
An impression material consisting of
a) a base paste of an A-silicone impression material with a typical commercially used composition, in this case the commercial product Flexitime Correct Flow (Charge 250327) from the company Haraeus Kulzer GmbH, and
b) a catalyst paste of the commercial product Flexitime Correct Flow (Charge 250334),
is filled into two-chamber pressurized gas cartridges.
In this example, the propellant is pentane. In addition, 2% pentane are added to the catalyst paste as foaming agent and internal propellant (see
The handling time of the impression material is significantly reduced compared to a manually operated impression gun in which a 50 ml solid cartridge is inserted. The impression material can hence be applied with significantly improved dosing and better placement, because the mixing nozzle does not move back and forth as a result of a manual pumping motion.
As expected, unlike the conventional material supplied from a solid cartridge and mixed with a static mixer, the formed silicone has a foam structure. The Shore A hardness is thereby reduced by about 17 units to 29 units. It can be visually observed that the volume of the impression material increases continually by about 10 to 15% until the time of setting, thus exhibiting the desired foaming pressure commensurate with the intended application. The processing time and curing time of this A-silicone are similar to those of the conventional product. The pores in the cured impression material are in this case also located almost entirely inside the hardened material, whereas the surface of the impression is almost bubble-free and extremely uniform.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2007 016 791.3 | Apr 2007 | DE | national |
